The 100 most-cited articles in Physical review. D/Physical review. D., 2017

Many aspects of the large-scale structure of the Universe can be described successfully using cosmological models in which $27\ifmmode\pm\else\textpm\fi{}1%$ of the critical mass-energy density consists of cold dark matter (CDM). However, few---if any---of the predictions of CDM models have been successful on scales of $\ensuremath{\sim}10\text{ }\text{ }\mathrm{kpc}$ or less. This lack of success is usually explained by the difficulty of modeling baryonic physics (star formation, supernova and black-hole feedback, etc.). An intriguing alternative to CDM is that the dark matter is an extremely light ($m\ensuremath{\sim}{10}^{\ensuremath{-}22}\text{ }\text{ }\mathrm{eV}$) boson having a de Broglie wavelength $\ensuremath{\lambda}\ensuremath{\sim}1\text{ }\text{ }\mathrm{kpc}$, often called fuzzy dark matter (FDM). We describe the arguments from particle physics that motivate FDM, review previous work on its astrophysical signatures, and analyze several unexplored aspects of its behavior. In particular, (i) FDM halos or subhalos smaller than about…

The space-based Laser Interferometer Space Antenna (LISA) will be able to observe the gravitational-wave signals from systems comprised of a massive black hole and a stellar-mass compact object. These systems are known as extreme-mass-ratio inspirals (EMRIs) and are expected to complete $\ensuremath{\sim}1{0}^{4}--1{0}^{5}$ cycles in band, thus allowing exquisite measurements of their parameters. In this work, we attempt to quantify the astrophysical uncertainties affecting the predictions for the number of EMRIs detectable by LISA, and find that competing astrophysical assumptions produce a variance of about three orders of magnitude in the expected intrinsic EMRI rate. However, we find that irrespective of the astrophysical model, at least a few EMRIs per year should be detectable by the LISA mission, with up to a few thousands per year under the most optimistic astrophysical assumptions. We also investigate the precision with which LISA will be able to extract the parameters of these sources. We find that typical fractional statistical errors with which the intrinsic parameters…

We improve the accuracy of the effective-one-body (EOB) waveforms that were employed during the first observing run of Advanced LIGO for binaries of spinning, nonprecessing black holes by calibrating them to a set of 141 numerical-relativity (NR) waveforms. The NR simulations expand the domain of calibration toward larger mass ratios and spins, as compared to the previous EOBNR model. Merger-ringdown waveforms computed in black-hole perturbation theory for Kerr spins close to extremal provide additional inputs to the calibration. For the inspiral-plunge phase, we use a Markov-chain Monte Carlo algorithm to efficiently explore the calibration space. For the merger-ringdown phase, we fit the NR signals with phenomenological formulae. After extrapolation of the calibrated model to arbitrary mass ratios and spins, the (dominant-mode) EOBNR waveforms have faithfulness---at design Advanced-LIGO sensitivity---above 99% against all the NR waveforms, including 16 additional waveforms used for validation, when maximizing only on initial phase and time. This implies a negligible loss in event…

Using data on the Lyman-\ensuremath{\alpha} spectra obtained by the X-shooter and HIRES/MIKE spectrographs, bounds on warm dark matter are computed using state-of-the-art analysis. This places a new best lower limit of 5.3 keV on the mass of thermal relic dark matter.

We show a simple, systematic and direct approach to decoupling gravitational sources in general relativity. As a direct application, a robust and simple way to generate anisotropic solutions for self-gravitating systems from perfect fluid solutions is presented.

Gravitational-wave observation together with a large number of electromagnetic observations shows that the source of the latest gravitational-wave event, GW170817, detected primarily by advanced LIGO, is the merger of a binary neutron star. We attempt to interpret this observational event based on our results of numerical-relativity simulations performed so far, paying particular attention to the optical and infrared observations. We finally reach a conclusion that this event is described consistently by the presence of a long-lived hypermassive or supramassive neutron star as the merger remnant because (i) significant contamination by lanthanide elements along our line of sight to this source can be avoided by the strong neutrino irradiation from it and (ii) it could play a crucial role in producing an ejecta component of appreciable mass with fast motion in the postmerger phase. We also point out that (I) the neutron-star equation of state has to be sufficiently stiff (i.e., the maximum mass of cold spherical neutron stars, ${M}_{\mathrm{max}}$, has to be appreciably higher than…

We revisit the cosmological and astrophysical constraints on the fraction of the dark matter in primordial black holes (PBHs) with an extended mass function. We consider a variety of mass functions, all of which are described by three parameters: a characteristic mass and width and a dark matter fraction. Various observations then impose constraints on the dark matter fraction as a function of the first two parameters. We show how these constraints relate to those for a monochromatic mass function, demonstrating that they usually become more stringent in the extended case than the monochromatic one. Considering only the well-established bounds, and neglecting the ones that depend on additional astrophysical assumptions, we find that there are three mass windows, around $5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}16}{M}_{\ensuremath{\bigodot}}$, $2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}14}{M}_{\ensuremath{\bigodot}}$ and $25--100{M}_{\ensuremath{\bigodot}}$, where PBHs can constitute all the dark matter. However, if one includes all the bounds, PBHs can…

The LIGO observation of black hole merger has revivified interest in the idea whether primordial black holes might comprise some or all of the dark matter. The authors scrutinize the impact of primordial black holes on the CMB, analytically calculating spherical accretion onto black holes. The paper provides stringent constraints on models purporting to connect dark matter to primordial black holes.

The authors present the largest numerical simulations to date of first order phase transitions in the early universe, in order to explore the shape of acoustically generated gravitational waves and forecast the prospects for detection with LISA. The latter, a space-based gravitational wave observatory due to launch in about a decade, is an ideal instrument to observe gravitational wave signals from phase transitions in the electroweak era, corresponding to roughly 10 pico-seconds after the big bang.

We determine a new set of parton distribution functions (ABMP16), the strong coupling constant ${\ensuremath{\alpha}}_{s}$ and the quark masses ${m}_{c}$, ${m}_{b}$ and ${m}_{t}$ in a global fit to next-to-next-to-leading order (NNLO) in QCD. The analysis uses the $\overline{\mathrm{MS}}$ scheme for ${\ensuremath{\alpha}}_{s}$ and all quark masses and is performed in the fixed-flavor number scheme for ${n}_{f}=3$, 4, 5. Essential new elements of the fit are the combined data from HERA for inclusive deep-inelastic scattering (DIS), data from the fixed-target experiments NOMAD and CHORUS for neutrino-induced DIS, data from Tevatron and the LHC for the Drell-Yan process and the hadro-production of single-top and top-quark pairs. The theory predictions include new improved approximations at NNLO for the production of heavy quarks in DIS and for the hadro-production of single-top quarks. The description of higher twist effects relevant beyond the leading twist collinear factorization approximation is refined. At NNLO, we obtain the value…

Primordial black holes (PBHs) have long been a candidate for the elusive dark matter (DM), and remain poorly constrained in the $\ensuremath{\sim}20--100\text{ }\text{ }{M}_{\ensuremath{\bigodot}}$ mass range. PBH binaries were recently suggested as the possible source of LIGO's first detections. In this paper, we thoroughly revisit existing estimates of the merger rate of PBH binaries. We compute the probability distribution of orbital parameters for PBH binaries formed in the early Universe, accounting for tidal torquing by all other PBHs, as well as standard large-scale adiabatic perturbations. We then check whether the orbital parameters of PBH binaries formed in the early Universe can be significantly affected between formation and merger. Our analytic estimates indicate that the tidal field of halos and interactions with other PBHs, as well as dynamical friction by unbound standard DM particles, do not do significant work on nor torque PBH binaries. We estimate the torque due to baryon accretion to be much weaker than previous calculations, albeit possibly large enough to…

We calculated the QCD equation of state using Taylor expansions that include contributions from up to sixth order in the baryon, strangeness and electric charge chemical potentials. Calculations have been performed with the Highly Improved Staggered Quark action in the temperature range $T\ensuremath{\in}[135\text{ }\text{ }\mathrm{MeV},330\text{ }\text{ }\mathrm{MeV}]$ using up to four different sets of lattice cutoffs corresponding to lattices of size ${N}_{\ensuremath{\sigma}}^{3}\ifmmode\times\else\texttimes\fi{}{N}_{\ensuremath{\tau}}$ with aspect ratio ${N}_{\ensuremath{\sigma}}/{N}_{\ensuremath{\tau}}=4$ and ${N}_{\ensuremath{\tau}}=6\ensuremath{-}16$. The strange quark mass is tuned to its physical value, and we use two strange to light quark mass ratios ${m}_{s}/{m}_{l}=20$ and 27, which in the continuum limit correspond to a pion mass of about 160 and 140 MeV, respectively. Sixth-order results for Taylor expansion coefficients are used to estimate truncation errors of the fourth-order expansion. We show that truncation errors are small for baryon chemical potentials less…

We describe a stream-based analysis pipeline to detect gravitational waves from the merger of binary neutron stars, binary black holes, and neutron-star--black-hole binaries within $\ensuremath{\sim}1$ min of the arrival of the merger signal at Earth. Such low-latency detection is crucial for the prompt response by electromagnetic facilities in order to observe any fading electromagnetic counterparts that might be produced by mergers involving at least one neutron star. Even for systems expected not to produce counterparts, low-latency analysis of the data is useful for deciding when not to point telescopes, and as feedback to observatory operations. Analysts using this pipeline were the first to identify GW151226, the second gravitational-wave event ever detected. The pipeline also operates in an offline mode, in which it incorporates more refined information about data quality and employs acausal methods that are inapplicable to the online mode. The pipeline's offline mode was used in the detection of the first two gravitational-wave events, GW150914 and GW151226, as well as the…

The answer is yes. We indeed find that interacting dark energy can alleviate the current tension on the value of the Hubble constant ${H}_{0}$ between the cosmic microwave background anisotropies constraints obtained from the Planck satellite and the recent direct measurements reported by Riess et al. 2016. The combination of these two data sets points toward a nonzero dark matter-dark energy coupling $\ensuremath{\xi}$ at more than two standard deviations, with $\ensuremath{\xi}=\ensuremath{-}0.2{6}_{\ensuremath{-}0.12}^{+0.16}$ at 95% C.L., i.e. with a moderate evidence for interacting dark energy with an odds ratio of $6\ensuremath{\mathbin:}1$ respect to a non interacting cosmological constant. However the ${H}_{0}$ tension is better solved when the equation of state of the interacting dark energy component is allowed to freely vary, with a phantomlike equation of state $w=\ensuremath{-}1.185\ifmmode\pm\else\textpm\fi{}0.064$ (at 68% C.L.), ruling out the pure cosmological constant case, $w=\ensuremath{-}1$, again at more than two standard deviations. When Planck data are…

We employ a mathematical framework based on rational approximants in order to calculate the pseudoscalar-pole piece of the hadronic light-by-light contribution to the anomalous magnetic moment of the muon, ${a}_{\ensuremath{\mu}}^{\mathrm{HLbL};P}$. The method is systematic and data based, profiting from over 13 different collaborations, and able to ascribe, for the first time, a systematic uncertainty which provides for the model independence. As a result, we obtain ${a}_{\ensuremath{\mu}}^{\mathrm{HLbL};P}=94.3(5.3)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}$, whose uncertainty is well below the one foreseen at future experiments measuring the $({g}_{\ensuremath{\mu}}\ensuremath{-}2)$.

Using some of the latest cosmological data sets publicly available, we derive the strongest bounds in the literature on the sum of the three active neutrino masses, ${M}_{\ensuremath{\nu}}$, within the assumption of a background flat $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ cosmology. In the most conservative scheme, combining Planck cosmic microwave background temperature anisotropies and baryon acoustic oscillations (BAO) data, as well as the up-to-date constraint on the optical depth to reionization ($\ensuremath{\tau}$), the tightest 95% confidence level upper bound we find is ${M}_{\ensuremath{\nu}}<0.151\text{ }\text{ }\mathrm{eV}$. The addition of Planck high-$\ensuremath{\ell}$ polarization data, which, however, might still be contaminated by systematics, further tightens the bound to ${M}_{\ensuremath{\nu}}<0.118\text{ }\text{ }\mathrm{eV}$. A proper model comparison treatment shows that the two aforementioned combinations disfavor the inverted hierarchy at $\ensuremath{\sim}64%\text{ }\text{ }\text{ }\mathrm{C}.\mathrm{L}.$ and $\ensuremath{\sim}71%\text{ }\text{…

In classical general relativity (GR), an observer falling into an astrophysical black hole is not expected to experience anything dramatic as she crosses the event horizon. However, tentative resolutions to problems in quantum gravity, such as the cosmological constant problem, or the black hole information paradox, invoke significant departures from classicality in the vicinity of the horizon. It was recently pointed out that such near-horizon structures can lead to late-time echoes in the black hole merger gravitational wave signals that are otherwise indistinguishable from GR. We search for observational signatures of these echoes in the gravitational wave data released by the advanced Laser Interferometer Gravitational-Wave Observatory (LIGO), following the three black hole merger events GW150914, GW151226, and LVT151012. In particular, we look for repeating damped echoes with time delays of $8M\mathrm{log}M$ ($+\text{spin}$ corrections, in Planck units), corresponding to Planck-scale departures from GR near their respective horizons. Accounting for the ``look elsewhere'' effect…

We study in detail sub-GeV dark matter scattering off electrons in xenon, including the expected electron recoil spectra and annual modulation spectra. We derive improved constraints using low-energy XENON10 and XENON100 ionization-only data. For XENON10, in addition to including electron-recoil data corresponding to about 1--3 electrons, we include for the first time events corresponding to about 4--7 electrons. Assuming the scattering is momentum independent (${F}_{\mathrm{DM}}=1$), this strengthens a previous cross-section bound by almost an order of magnitude for dark matter masses above 50 MeV. The available XENON100 data corresponds to events with about 4--50 electrons, and leads to a constraint that is comparable to the XENON10 bound above 50 MeV for ${F}_{\mathrm{DM}}=1$. We demonstrate that a search for an annual modulation signal in upcoming xenon experiments (XENON1T, XENONnT, LZ) could substantially improve the above bounds even in the presence of large backgrounds. We also emphasize that in simple benchmark models of sub-GeV dark matter, the dark matter-electron…

Jet energy scale measurements and their systematic uncertainties are reported for jets measured with the ATLAS detector using proton-proton collision data with a center-of-mass energy of $\sqrt{s}=13\text{ }\text{ }\mathrm{TeV}$, corresponding to an integrated luminosity of $3.2\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ collected during 2015 at the LHC. Jets are reconstructed from energy deposits forming topological clusters of calorimeter cells, using the anti-${k}_{t}$ algorithm with radius parameter $R=0.4$. Jets are calibrated with a series of simulation-based corrections and in situ techniques. In situ techniques exploit the transverse momentum balance between a jet and a reference object such as a photon, $Z$ boson, or multijet system for jets with $20<{p}_{\mathrm{T}}<2000\text{ }\text{ }\mathrm{GeV}$ and pseudorapidities of $|\ensuremath{\eta}|<4.5$, using both data and simulation. An uncertainty in the jet energy scale of less than 1% is found in the central calorimeter region ($|\ensuremath{\eta}|<1.2$) for jets with $100<{p}_{\mathrm{T}}<500\text{ }\text{…

We study the direct detection prospects for a representative set of simplified models of sub-GeV dark matter (DM), accounting for existing terrestrial, astrophysical and cosmological constraints. We focus on dark matter lighter than an MeV, where these constraints are most stringent, and find three scenarios with accessible direct detection cross sections: (i) DM interacting via an ultralight kinetically mixed dark photon, (ii) a DM subcomponent interacting with nucleons or electrons through a light scalar or vector mediator, and (iii) DM coupled with nucleons via a mediator heavier than $\ensuremath{\sim}100\text{ }\text{ }\mathrm{keV}$.

We extend the semianalytic technique of Iyer and Will for computing the complex quasinormal frequencies of black holes, $\ensuremath{\omega}$, by constructing the Pad\'e approximants of the (formal) series for ${\ensuremath{\omega}}^{2}$. It is shown that for the (so-far best documented) quasinormal frequencies of the Schwarzschild and Reissner-Nordstr\"om black holes the Pad\'e transforms ${P}_{6}^{6}$ and ${P}_{7}^{6}$ are, within the domain of applicability, always in excellent agreement with the numerical results. We argue that the method may serve as a black box with the ``potential'' $Q(x)$ as an input and the accurate quasinormal modes as the output. The generalizations and modifications of the method are briefly discussed as well as the preliminary results for other classes of black holes.

The four-dimensional (4D) Lorentz group $SL(2,\mathbb{C})$ acts as the two-dimensional (2D) global conformal group on the celestial sphere at infinity where asymptotic 4D scattering states are specified. Consequent similarities of 4D flat space amplitudes and 2D correlators on the conformal sphere are obscured by the fact that the former are usually expressed in terms of asymptotic wave functions which transform simply under spacetime translations rather than the Lorentz $SL(2,\mathbb{C})$. In this paper we construct on-shell massive scalar wave functions in 4D Minkowski space that transform as $SL(2,\mathbb{C})$ conformal primaries. Scattering amplitudes of these wave functions are $SL(2,\mathbb{C})$ covariant by construction. For certain mass relations, we show explicitly that their three-point amplitude reduces to the known unique form of a 2D CFT primary three-point function and compute the coefficient. The computation proceeds naturally via Witten-like diagrams on a hyperbolic slicing of Minkowski space and has a holographic flavor.

We show that quasi-parton distribution functions (quasi-PDFs) may be treated as hybrids of PDFs and primordial rest-frame momentum distributions of partons. This results in a complicated convolution nature of quasi-PDFs that necessitates using large ${p}_{3}\ensuremath{\gtrsim}3\text{ }\text{ }\mathrm{GeV}$ momenta to get reasonably close to the PDF limit. As an alternative approach, we propose using pseudo-PDFs $\mathcal{P}(x,{z}_{3}^{2})$ that generalize the light-front PDFs onto spacelike intervals and are related to Ioffe-time distributions $\mathcal{M}(\ensuremath{\nu},{z}_{3}^{2})$, the functions of the Ioffe time $\ensuremath{\nu}={p}_{3}{z}_{3}$ and the distance parameter ${z}_{3}^{2}$ with respect to which it displays perturbative evolution for small ${z}_{3}$. In this form, one may divide out the ${z}_{3}^{2}$ dependence coming from the primordial rest-frame distribution and from the problematic factor due to lattice renormalization of the gauge link. The $\ensuremath{\nu}$ dependence remains intact and determines the shape of PDFs.

Within the standard three-neutrino framework, the absolute neutrino masses and their ordering (either normal, NO, or inverted, IO) are currently unknown. However, the combination of current data coming from oscillation experiments, neutrinoless double beta ($0\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$) decay searches, and cosmological surveys, can provide interesting constraints for such unknowns in the sub-eV mass range, down to $O({10}^{\ensuremath{-}1})\text{ }\text{ }\mathrm{eV}$ in some cases. We discuss current limits on absolute neutrino mass observables by performing a global data analysis that includes the latest results from oscillation experiments, $0\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$ decay bounds from the KamLAND-Zen experiment, and constraints from representative combinations of Planck measurements and other cosmological data sets. In general, NO appears to be somewhat favored with respect to IO at the level of $\ensuremath{\sim}2\ensuremath{\sigma}$, mainly by neutrino oscillation data (especially atmospheric), corroborated by cosmological…

Certain models with rank-3 tensor degrees of freedom have been shown by Gurau and collaborators to possess a novel large $N$ limit, where ${g}^{2}{N}^{3}$ is held fixed. In this limit the perturbative expansion in the quartic coupling constant, $g$, is dominated by a special class of ``melon'' diagrams. We study ``uncolored'' models of this type, which contain a single copy of real rank-3 tensor. Its three indices are distinguishable; therefore, the models possess $O(N{)}^{3}$ symmetry with the tensor field transforming in the tri-fundamental representation. Such uncolored models also possess the large $N$ limit dominated by the melon diagrams. The quantum mechanics of a real anticommuting tensor therefore has a similar large $N$ limit to the model recently introduced by Witten as an implementation of the Sachdev-Ye-Kitaev (SYK) model which does not require disorder. Gauging the $O(N{)}^{3}$ symmetry in our quantum mechanical model removes the nonsinglet states; therefore, one can search for its well-defined gravity dual. We point out, however, that the model possesses a vast number…

Ultralight bosons can induce superradiant instabilities in spinning black holes, tapping their rotational energy to trigger the growth of a bosonic condensate. Possible observational imprints of these boson clouds include (i) direct detection of the nearly monochromatic (resolvable or stochastic) gravitational waves emitted by the condensate, and (ii) statistically significant evidence for the formation of ``holes'' at large spins in the spin versus mass plane (sometimes also referred to as ``Regge plane'') of astrophysical black holes. In this work, we focus on the prospects of LISA and LIGO detecting or constraining scalars with mass in the range ${m}_{s}\ensuremath{\in}[{10}^{\ensuremath{-}19},{10}^{\ensuremath{-}15}]\text{ }\text{ }\mathrm{eV}$ and ${m}_{s}\ensuremath{\in}[{10}^{\ensuremath{-}14},{10}^{\ensuremath{-}11}]\text{ }\text{ }\mathrm{eV}$, respectively. Using astrophysical models of black-hole populations calibrated to observations and black-hole perturbation theory calculations of the gravitational emission, we find that, in optimistic scenarios, LIGO could observe a…

We study solutions of the Klein-Gordon, Maxwell, and linearized Einstein equations in ${\mathbb{R}}^{1,d+1}$ that transform as $d$-dimensional conformal primaries under the Lorentz group $SO(1,d+1)$. Such solutions, called conformal primary wavefunctions, are labeled by a conformal dimension $\mathrm{\ensuremath{\Delta}}$ and a point in ${\mathbb{R}}^{d}$, rather than an on-shell ($d+2$)-dimensional momentum. We show that the continuum of scalar conformal primary wavefunctions on the principal continuous series $\mathrm{\ensuremath{\Delta}}\ensuremath{\in}\frac{d}{2}+i\mathbb{R}$ of $SO(1,d+1)$ spans a complete set of normalizable solutions to the wave equation. In the massless case, with or without spin, the transition from momentum space to conformal primary wavefunctions is implemented by a Mellin transform. As a consequence of this construction, scattering amplitudes in this basis transform covariantly under $SO(1,d+1)$ as $d$-dimensional conformal correlators.

We discuss a supersymmetric generalization of the Sachdev-Ye-Kitaev (SYK) model. These are quantum mechanical models involving $N$ Majorana fermions. The supercharge is given by a polynomial expression in terms of the Majorana fermions with random coefficients. The Hamiltonian is the square of the supercharge. The $\mathcal{N}=1$ model with a single supercharge has unbroken supersymmetry at large $N$, but nonperturbatively spontaneously broken supersymmetry in the exact theory. We analyze the model by looking at the large $N$ equation, and also by performing numerical computations for small values of $N$. We also compute the large $N$ spectrum of ``singlet'' operators, where we find a structure qualitatively similar to the ordinary SYK model. We also discuss an $\mathcal{N}=2$ version. In this case, the model preserves supersymmetry in the exact theory and we can compute a suitably weighted Witten index to count the number of ground states, which agrees with the large $N$ computation of the entropy. In both cases, we discuss the supersymmetric generalizations of the Schwarzian…

Astrophysical black holes arise either from the collapse of stars or through previous binary black hole mergers. What can we say about the populations of ''first generation'' and ''second generation'' black holes participating in binary mergers? This paper shows how one can test models of these populations using gravitational wave astronomy of binary mergers.

The authors calculate the tidal Love numbers (TLN), which encode the effect of rapidly changing gravitational fields on deformable, self-gravitating objects, for various exotic compact objects. They have found a universal logarithmic dependence of the TLNs close to black holes and use this to propose future gravitational wave measurements of TLNs, which would provide a test for general relativity in the strong field regime.

For primordial black holes (PBH) to be the dark matter in single-field inflation, the slow-roll approximation must be violated by at least $\mathcal{O}(1)$ in order to enhance the curvature power spectrum within the required number of $e$-folds between cosmic microwave background scales and PBH mass scales. Power spectrum predictions which rely on the inflaton remaining on the slow-roll attractor can fail dramatically leading to qualitatively incorrect conclusions in models like an inflection potential and misestimate the mass scale in a running mass model. We show that an optimized temporal evaluation of the Hubble slow-roll parameters to second order remains a good description for a wide range of PBH formation models where up to a $1{0}^{7}$ amplification of power occurs in 10 $e$-folds or more.

The process of superradiance can extract angular momentum and energy from astrophysical black holes (BHs) to populate gravitationally bound states with an exponentially large number of light bosons. We analytically calculate superradiant growth rates for vectors around rotating BHs in the regime where the vector Compton wavelength is much larger than the BH size. Spin-1 bound states have superradiance times as short as a second around stellar BHs, growing up to a thousand times faster than their spin-0 counterparts. The fast rates allow us to use measurements of rapidly spinning BHs in x-ray binaries to exclude a wide range of masses for weakly coupled spin-1 particles, $5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}14}\ensuremath{-}2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}\text{ }\text{ }\mathrm{eV}$; lighter masses in the range $6\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}20}\ensuremath{-}2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}17}\text{ }\text{ }\mathrm{eV}$ start to be constrained by supermassive BH spin measurements at a lower…

Stellar-mass primordial black holes (PBH) have been recently reconsidered as a dark matter (DM) candidate after the aLIGO discovery of several binary black hole (BH) mergers with masses of tens of ${M}_{\ensuremath{\bigodot}}$. Matter accretion on such massive objects leads to the emission of high-energy photons, capable of altering the ionization and thermal history of the universe. This, in turn, affects the statistical properties of the cosmic microwave background (CMB) anisotropies. Previous analyses have assumed spherical accretion. We argue that this approximation likely breaks down and that an accretion disk should form in the dark ages. Using the most up-to-date tools to compute the energy deposition in the medium, we derive constraints on the fraction of DM in PBH. Provided that disks form early on, even under conservative assumptions for accretion, these constraints exclude a monochromatic distribution of PBH with masses above $\ensuremath{\sim}2\text{ }\text{ }{M}_{\ensuremath{\bigodot}}$ as the dominant form of DM. The bound on the median PBH mass gets more stringent if…

SuperCDMS SNOLAB will be a next-generation experiment aimed at directly detecting low-mass particles (with masses $\ensuremath{\le}10\text{ }\text{ }\mathrm{GeV}/{\mathrm{c}}^{2}$) that may constitute dark matter by using cryogenic detectors of two types (HV and iZIP) and two target materials (germanium and silicon). The experiment is being designed with an initial sensitivity to nuclear recoil cross sections $\ensuremath{\sim}1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}43}\text{ }\text{ }{\mathrm{cm}}^{2}$ for a dark matter particle mass of $1\text{ }\text{ }\mathrm{GeV}/{\mathrm{c}}^{2}$, and with capacity to continue exploration to both smaller masses and better sensitivities. The phonon sensitivity of the HV detectors will be sufficient to detect nuclear recoils from sub-GeV dark matter. A detailed calibration of the detector response to low-energy recoils will be needed to optimize running conditions of the HV detectors and to interpret their data for dark matter searches. Low-activity shielding, and the depth of SNOLAB, will reduce most backgrounds, but…

We interpret the recent hints for lepton flavor universality violation in rare $B$ meson decays. Based on a model-independent effective Hamiltonian approach, we determine regions of new physics parameter space that give a good description of the experimental data on ${R}_{K}$ and ${R}_{{K}^{*}}$, which is in tension with Standard Model predictions. We suggest further measurements that can help narrowing down viable new physics explanations. We stress that the measured values of ${R}_{K}$ and ${R}_{{K}^{*}}$ are fully compatible with new physics explanations of other anomalies in rare $B$ meson decays based on the $b\ensuremath{\rightarrow}s\ensuremath{\mu}\ensuremath{\mu}$ transition. If the hints for lepton flavor universality violation are the first signs of new physics, perturbative unitarity implies new phenomena below a scale of $\ensuremath{\sim}100\text{ }\text{ }\mathrm{TeV}$.

The measured $\overline{B}\ensuremath{\rightarrow}{D}^{(*)}l\overline{\ensuremath{\nu}}$ decay rates for light leptons ($l=e$, $\ensuremath{\mu}$) constrain all $\overline{B}\ensuremath{\rightarrow}{D}^{(*)}$ semileptonic form factors, by including both the leading and $\mathcal{O}({\mathrm{\ensuremath{\Lambda}}}_{\mathrm{QCD}}/{m}_{c,b})$ subleading Isgur-Wise functions in the heavy quark effective theory. We perform a novel combined fit to the $\overline{B}\ensuremath{\rightarrow}{D}^{(*)}l\overline{\ensuremath{\nu}}$ decay distributions to predict the $\overline{B}\ensuremath{\rightarrow}{D}^{(*)}\ensuremath{\tau}\overline{\ensuremath{\nu}}$ rates and determine the Cabibbo-Kobayashi-Maskawa matrix element $|{V}_{cb}|$. Most theoretical and experimental papers have neglected uncertainties in the predictions for form factor ratios at order ${\mathrm{\ensuremath{\Lambda}}}_{\mathrm{QCD}}/{m}_{c,b}$, which we include. We also calculate $\mathcal{O}({\mathrm{\ensuremath{\Lambda}}}_{\mathrm{QCD}}/{m}_{c,b})$ and $\mathcal{O}({\ensuremath{\alpha}}_{s})$ contributions to semileptonic…

Are there ways to set model-independent bounds on decaying dark matter via signatures in the Cosmic Microwave Background? The authors propose a method which achieves this goal for a large class of dark matter scenarios.

The vector leptoquark representation, ${U}_{\ensuremath{\mu}}=(3,1,2/3)$, was recently identified as an exceptional single mediator model to address experimental hints on lepton flavor universality violation in semileptonic $B$-meson decays, both in neutral ($b\ensuremath{\rightarrow}s\ensuremath{\mu}\ensuremath{\mu}$) and charged ($b\ensuremath{\rightarrow}c\ensuremath{\tau}\ensuremath{\nu}$) current processes. Nonetheless, it is well known that massive vectors crave an ultraviolet (UV) completion. We present the first full-fledged UV complete and calculable gauge model which incorporates this scenario while remaining in agreement with all other indirect flavor and electroweak precision measurements, as well as, direct searches at high-${p}_{T}$. The model is based on a new non-Abelian gauge group spontaneously broken at the TeV scale, and a specific flavor structure suppressing flavour violation in $\mathrm{\ensuremath{\Delta}}F=2$ processes while inducing sizeable semileptonic transitions.

We demonstrate a new method of extracting parton distributions from lattice calculations. The starting idea is to treat the generic equal-time matrix element $\mathcal{M}(P{z}_{3},{z}_{3}^{2})$ as a function of the Ioffe time $\ensuremath{\nu}=P{z}_{3}$ and the distance ${z}_{3}$. The next step is to divide $\mathcal{M}(P{z}_{3},{z}_{3}^{2})$ by the rest-frame density $\mathcal{M}(0,{z}_{3}^{2})$. Our lattice calculation shows a linear exponential ${z}_{3}$-dependence in the rest-frame function, expected from the $Z({z}_{3}^{2})$ factor generated by the gauge link. Still, we observe that the ratio $\mathcal{M}(P{z}_{3},{z}_{3}^{2})/\mathcal{M}(0,{z}_{3}^{2})$ has a Gaussian-type behavior with respect to ${z}_{3}$ for 6 values of $P$ used in the calculation. This means that $Z({z}_{3}^{2})$ factor was canceled in the ratio. When plotted as a function of $\ensuremath{\nu}$ and ${z}_{3}$, the data are very close to ${z}_{3}$-independent functions. This phenomenon corresponds to factorization of the $x$- and ${k}_{\ensuremath{\perp}}$-dependence for the TMD…

In the next few years, Advanced LIGO (aLIGO) may see gravitational waves (GWs) from thousands of black hole (BH) mergers. This marks the beginning of a new precision tool for physics. Here we show how to search for new physics beyond the standard model using this tool, in particular the QCD axion in the mass range ${\ensuremath{\mu}}_{a}\ensuremath{\sim}{10}^{\ensuremath{-}14}$ to ${10}^{\ensuremath{-}10}\text{ }\text{ }\mathrm{eV}$. Axions (or any bosons) in this mass range cause rapidly rotating BHs to shed their spin into a large cloud of axions in atomic Bohr orbits around the BH, through the effect of superradiance (SR). This results in a gap in the mass vs spin distribution of BHs when the BH size is comparable to the axion's Compton wavelength. By measuring the spin and mass of the merging objects observed at LIGO, we could verify the presence and shape of the gap in the BH distribution produced by the axion. The axion cloud can also be discovered through the GWs it radiates via axion annihilations or level transitions. A blind monochromatic GW search may reveal up to…

We construct perturbative classical solutions of the Yang-Mills equations coupled to dynamical point particles carrying color charge. By applying a set of color to kinematics replacement rules first introduced by Bern, Carrasco and Johansson, these are shown to generate solutions of $d$-dimensional dilaton gravity, which we also explicitly construct. Agreement between the gravity result and the gauge theory double copy implies a correspondence between non-Abelian particles and gravitating sources with dilaton charge. When the color sources are highly relativistic, dilaton exchange decouples, and the solutions we obtain match those of pure gravity. We comment on possible implications of our findings to the calculation of gravitational waveforms in astrophysical black hole collisions, directly from computationally simpler gluon radiation in Yang-Mills theory.

In this work, we propose the modeling of static wormholes within the $f(R,T)$ extended theory of gravity perspective. We present some models of wormholes, which are constructed from different hypotheses for their matter content, i.e., different relations for their pressure components (radial and lateral) and different equations of state. The solutions obtained for the shape function of the wormholes obey the necessary metric conditions. They show a behavior similar to those found in previous references about wormholes, which also happens to our solutions for the energy density of such objects. We also apply the energy conditions for the wormholes' physical content.

We construct closed-form gravitational waveforms (GWs) with tidal effects for the coalescence of binary neutron stars. The method relies on a new set of eccentricity-reduced and high-resolution numerical relativity (NR) simulations and is composed of three steps. First, tidal contributions to the GW phase are extracted from the time-domain NR data. Second, those contributions are employed to fix high-order coefficients in an effective and resummed post-Newtonian expression. Third, frequency-domain tidal approximants are built using the stationary phase approximation. Our tidal approximants are valid from the low frequencies to the strong-field regime. They can be analytically added to any binary black hole GW model to obtain a binary neutron star waveform, either in the time or in the frequency domain. This work provides simple, flexible, and accurate models ready to be used in both searches and parameter estimation of binary neutron star events.

We consider gravitational wave production by bubble collisions during a cosmological first-order phase transition. In the literature, such spectra have been estimated by simulating the bubble dynamics, under so-called thin-wall and envelope approximations in a flat background metric. However, we show that, within these assumptions, the gravitational wave spectrum can be estimated in an analytic way. Our estimation is based on the observation that the two-point correlator of the energy-momentum tensor $⟨T(x)T(y)⟩$ can be expressed analytically under these assumptions. Though the final expressions for the spectrum contain a few integrations that cannot be calculated explicitly, we can easily estimate it numerically. As a result, it is found that the most of the contributions to the spectrum come from single-bubble contribution to the correlator, and in addition the fall-off of the spectrum at high frequencies is found to be proportional to ${f}^{\ensuremath{-}1}$. We also provide fitting formulas for the spectrum.

Primordial black holes (PBHs) are one of the candidates to explain the gravitational wave (GW) signals observed by the LIGO detectors. Among several phenomena in the early universe, cosmic inflation is a major example to generate PBHs from large primordial density perturbations. In this paper, we discuss the possibility to interpret the observed GW events as mergers of PBHs that are produced by cosmic inflation. The primordial curvature perturbation should be large enough to produce a sizable amount of PBHs, and thus we have several other probes to test this scenario. We point out that the current pulsar timing array (PTA) experiments already put severe constraints on GWs generated via the second-order effects, and that the observation of the cosmic microwave background puts severe restriction on its $\ensuremath{\mu}$ distortion. In particular, it is found that the scalar power spectrum should have a very sharp peak at $k\ensuremath{\sim}1{0}^{6}\text{ }\text{ }{\mathrm{Mpc}}^{\ensuremath{-}1}$ to fulfill the required abundance of PBHs while evading constraints from the PTA…

We investigate constraints on scalar dark matter (DM) by analyzing the Lyman-$\ensuremath{\alpha}$ forest, which probes structure formation at medium and small scales, and also by studying its cosmological consequences at high and low redshift. For scalar DM that constitutes more than 30% of the total DM density, we obtain a lower limit $m\ensuremath{\gtrsim}{10}^{\ensuremath{-}21}\text{ }\text{ }\mathrm{eV}$ for the mass of scalar DM. This implies an upper limit on the initial field displacement (or the decay constant for an axion-like field) of $\ensuremath{\phi}\ensuremath{\lesssim}{10}^{16}\text{ }\text{ }\mathrm{GeV}$. We also derive limits on the energy scale of cosmic inflation and establish an upper bound on the tensor-to-scalar ratio of $r<{10}^{\ensuremath{-}3}$ in the presence of scalar DM. Furthermore, we show that there is very little room for ultralight scalar DM to solve the ``small-scale crisis'' of cold DM without spoiling the Lyman-$\ensuremath{\alpha}$ forest results. The constraints presented in this paper can be used for testing generic theories that contain…

The authors present new state-of-the-art six-loop perturbative results for renormalization group (RG) functions in a four-dimensional O(n) symmetric scalar quantum field theory. They also outline a procedure to obtain critical exponents, which can be applied to the corresponding two and three-dimensional theories as well.

We do a start-to-finish calculation of the stochastic gravitational wave background to be expected from cosmic strings. We start from a population of string loops taken from simulations, smooth these by Lorentzian convolution as a model of gravitational backreaction, calculate the average spectrum of gravitational waves emitted by the string population at any given time, and propagate it through a standard model cosmology to find the stochastic background today. Except for modeling back reaction as smoothing, we take into account all known effects, including changes in the number of cosmological relativistic degrees of freedom at early times and the possibility that some energy is in rare bursts that we might never have observed.

Following a new microlensing constraint on primordial black holes (PBHs) with $\ensuremath{\sim}1{0}^{20}--1{0}^{28}\text{ }\text{ }\mathrm{g}$ [H. Niikura et al., arXiv:1701.02151.], we revisit the idea of PBH as all dark matter (DM). We have shown that the updated observational constraints suggest the viable mass function for PBHs as all DM to have a peak at $\ensuremath{\simeq}1{0}^{20}\text{ }\text{ }\mathrm{g}$ with a small width $\ensuremath{\sigma}\ensuremath{\lesssim}0.1$, by imposing observational constraints on an extended mass function in a proper way. We have also provided an inflation model that successfully generates PBHs as all DM fulfilling this requirement.

Isolated objects in asymptotically flat spacetimes in general relativity are characterized by their conserved charges associated with the Bondi-Metzner-Sachs (BMS) group. These charges include total energy, linear momentum, intrinsic angular momentum and center-of-mass location, and, in addition, an infinite number of supermomentum charges associated with supertranslations. Recently, it has been suggested that the BMS symmetry algebra should be enlarged to include an infinite number of additional symmetries known as super-rotations. We show that the corresponding charges are finite and well defined, and can be divided into electric parity ``super center-of-mass'' charges and magnetic parity ``superspin'' charges. The supermomentum charges are associated with ordinary gravitational-wave memory, and the super center-of-mass charges are associated with total (ordinary plus null) gravitational-wave memory, in the terminology of Bieri and Garfinkle. Superspin charges are associated with the ordinary piece of spin memory. Some of these charges can give rise to black hole hair, as…

Tests of lepton-universality as rate ratios in $b\ensuremath{\rightarrow}s\ensuremath{\ell}\ensuremath{\ell}$ transitions can be predicted very accurately in the Standard Model. The deficits with respect to expectations reported by the LHCb experiment in muon-to-electron ratios of the $B\ensuremath{\rightarrow}{K}^{(*)}\ensuremath{\ell}\ensuremath{\ell}$ decay rates thus point to genuine manifestations of lepton nonuniversal new physics. In this paper, we analyze these measurements in the context of effective field theory. First, we discuss the interplay of the different operators in ${R}_{K}$ and ${R}_{{K}^{*}}$ and provide predictions for ${R}_{{K}^{*}}$ in the Standard Model and in new-physics scenarios that can explain ${R}_{K}$. We also provide approximate numerical formulas for these observables in bins of interest as functions of the relevant Wilson coefficients. Secondly, we perform frequentist fits to ${R}_{K}$ and ${R}_{{K}^{*}}$. The Standard Model disagrees with these measurements at $3.7\ensuremath{\sigma}$ significance. We find excellent fits in scenarios with…

We investigate the observational constraints on an interacting vacuum energy scenario with two different neutrino schemes (with and without a sterile neutrino) using the most recent data from cosmic microwave background (CMB) temperature and polarization anisotropy, baryon acoustic oscillations (BAO), type Ia supernovae from JLA sample and structure growth inferred from cluster counts. We find that inclusion of the galaxy clusters data with the minimal data combination $\mathrm{CMB}+\mathrm{BAO}+\mathrm{JLA}$ suggests an interaction in the dark sector, implying the decay of dark matter particles into dark energy, since the constraints obtained by including the galaxy clusters data yield a non-null and negative coupling parameter between the dark components at 99% confidence level. We deduce that the current tensions on the parameters ${H}_{0}$ and ${\ensuremath{\sigma}}_{8}$ can be alleviated within the framework of the interacting as well as noninteracting vacuum energy models with sterile neutrinos.

We construct an updated and extended compilation of growth-rate data based on recent redshift-space distortion measurements. The data set consists of 34 data points and includes corrections for model dependence. In order to minimize overlap and maximize the independence of the data points, we also construct a subsample of this compilation (a ``gold'' growth data set) which consists of 18 data points. We test the consistency of this data set with the best-fit $\mathrm{Planck}15/\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ parameters in the context of General Relativity using the evolution equation for the growth factor $\ensuremath{\delta}(a)$ with a $w\mathrm{CDM}$ background. We find tension at the $\ensuremath{\sim}3\ensuremath{\sigma}$ level between the best-fit parameters $w$ (the dark energy equation of state), ${\mathrm{\ensuremath{\Omega}}}_{0m}$ (the matter density parameter), and ${\ensuremath{\sigma}}_{8}$ (the matter power spectrum normalization on scales $8{h}^{\ensuremath{-}1}\text{ }\text{ }\mathrm{Mpc}$) and the corresponding…

In Abbott et al. [Phys. Rev. X 6, 041014 (2016)], the properties of the first gravitational wave detected by LIGO, GW150914, were measured by employing an effective-one-body (EOB) model of precessing binary black holes whose underlying dynamics and waveforms were calibrated to numerical-relativity (NR) simulations. Here, we perform the first extensive comparison of such an EOBNR model to 70 precessing NR waveforms that span mass ratios from 1 to 5, dimensionless spin magnitudes up to 0.5, generic spin orientations, and length of about 20 orbits. We work in the observer's inertial frame and include all $\ensuremath{\ell}=2$ modes in the gravitational-wave polarizations. We introduce new prescriptions for the EOB ringdown signal concerning its spectrum and time of onset. For total masses between $10{\mathrm{M}}_{\ensuremath{\bigodot}}$ and $200{\mathrm{M}}_{\ensuremath{\bigodot}}$, we find that precessing EOBNR waveforms have unfaithfulness within about 3% to NR waveforms when considering the Advanced-LIGO design noise curve. This result is obtained without recalibration of the…

Gravitational wave astronomy provides an unprecedented opportunity to test the nature of black holes and search for exotic, compact alternatives. Recent studies have shown that exotic compact objects (ECOs) can ring down in a manner similar to black holes, but can also produce a sequence of distinct pulses resembling the initial ringdown. These ``echoes'' would provide definite evidence for the existence of ECOs. In this work we study the generation of these echoes in a generic, parametrized model for the ECO, using Green's functions. We show how to reprocess radiation in the near-horizon region of a Schwarzschild black hole into the asymptotic radiation from the corresponding source in an ECO spacetime. Our methods allow us to understand the connection between distinct echoes and ringing at the resonant frequencies of the compact object. We find that the quasinormal mode ringing in the black hole spacetime plays a central role in determining the shape of the first few echoes. We use this observation to develop a simple template for echo waveforms. This template preforms well over a…

Primordial black hole (PBH) mergers have been proposed as an explanation for the gravitational wave events detected by the LIGO collaboration. Such PBHs may be formed in the early Universe as a result of the collapse of extremely rare high-sigma peaks of primordial fluctuations on small scales, as long as the amplitude of primordial perturbations on small scales is enhanced significantly relative to the amplitude of perturbations observed on large scales. One consequence of these small-scale perturbations is generation of stochastic gravitational waves that arise at second order in scalar perturbations, mostly before the formation of the PBHs. These induced gravitational waves have been shown, assuming Gaussian initial conditions, to be comparable to the current limits from the European Pulsar Timing Array, severely restricting this scenario. We show, however, that models with enhanced fluctuation amplitudes typically involve non-Gaussian initial conditions. With such initial conditions, the current limits from pulsar timing can be evaded. The amplitude of the induced…

Recently, spin-one wave functions in four dimensions that are conformal primaries of the Lorentz group $SL(2,\mathbb{C})$ were constructed. We compute low-point, tree-level gluon scattering amplitudes in the space of these conformal primary wave functions. The answers have the same conformal covariance as correlators of spin-one primaries in a $2d$ CFT. The Britto--Cachazo--Feng--Witten (BCFW) recursion relation between three- and four-point gluon amplitudes is recast into this conformal basis.

We argue that the Lorentzian path integral is a better starting point for quantum cosmology than its Euclidean counterpart. In particular, we revisit the minisuperspace calculation of the Feynman path integral for quantum gravity with a positive cosmological constant. Instead of rotating to Euclidean time, we deform the contour of integration over metrics into the complex plane, exploiting Picard-Lefschetz theory to transform the path integral from a conditionally convergent integral into an absolutely convergent one. We show that this procedure unambiguously determines which semiclassical saddle point solutions are relevant to the quantum mechanical amplitude. Imposing ``no-boundary'' initial conditions, i.e., restricting attention to regular, complex metrics with no initial boundary, we find that the dominant saddle contributes a semiclassical exponential factor which is precisely the inverse of the famous Hartle-Hawking result.

A generic, noneccentric binary black hole (BBH) system emits gravitational waves (GWs) that are completely described by seven intrinsic parameters: the black hole spin vectors and the ratio of their masses. Simulating a BBH coalescence by solving Einstein's equations numerically is computationally expensive, requiring days to months of computing resources for a single set of parameter values. Since theoretical predictions of the GWs are often needed for many different source parameters, a fast and accurate model is essential. We present the first surrogate model for GWs from the coalescence of BBHs including all seven dimensions of the intrinsic noneccentric parameter space. The surrogate model, which we call NRSur7dq2, is built from the results of 744 numerical relativity simulations. NRSur7dq2 covers spin magnitudes up to 0.8 and mass ratios up to 2, includes all $\ensuremath{\ell}\ensuremath{\le}4$ modes, begins about 20 orbits before merger, and can be evaluated in $\ensuremath{\sim}50\text{ }\text{ }\mathrm{ms}$. We find the largest NRSur7dq2 errors to be comparable to the…

Using nonlinear evolution equations of QCD, we compute the von Neumann entropy of the system of partons resolved by deep inelastic scattering at a given Bjorken $x$ and momentum transfer ${q}^{2}=\ensuremath{-}{Q}^{2}$. We interpret the result as the entropy of entanglement between the spatial region probed by deep inelastic scattering and the rest of the proton. At small $x$ the relation between the entanglement entropy $S(x)$ and the parton distribution $xG(x)$ becomes very simple: $S(x)=\mathrm{ln}[xG(x)]$. In this small $x$, large rapidity $Y$ regime, all partonic microstates have equal probabilities---the proton is composed by an exponentially large number $\mathrm{exp}(\mathrm{\ensuremath{\Delta}}Y)$ of microstates that occur with equal and exponentially small probabilities $\mathrm{exp}(\ensuremath{-}\mathrm{\ensuremath{\Delta}}Y)$, where $\mathrm{\ensuremath{\Delta}}$ is defined by $xG(x)\ensuremath{\sim}1/{x}^{\mathrm{\ensuremath{\Delta}}}$. For this equipartitioned state, the entanglement entropy is maximal---so at small $x$, deep inelastic scattering probes a maximally…

The Daya Bay Collaboration reports precise measurements of the ${\ensuremath{\theta}}_{13}$ neutrino mixing angle and predicts the $\mathrm{\ensuremath{\Delta}}\phantom{\rule{0}{0ex}}{m}_{32}^{2}$ mass difference for both normal and inverted hierarchy scenarios. These values are based on comparing the detection of antineutrinos by ''near'' and ''far'' detectors of more than 2.5 million inverse beta-decay observations.

We consider gedanken experiments to destroy an extremal or nearly extremal Kerr-Newman black hole by causing it to absorb matter with sufficient charge and/or angular momentum as compared with energy that it cannot remain a black hole. It was previously shown by one of us that such gedanken experiments cannot succeed for test particle matter entering an extremal Kerr-Newman black hole. We generalize this result here to arbitrary matter entering an extremal Kerr-Newman black hole, provided only that the nonelectromagnetic contribution to the stress-energy tensor of the matter satisfies the null energy condition. We then analyze the gedanken experiments proposed by Hubeny and others to overcharge and/or overspin an initially slightly nonextremal Kerr-Newman black hole. Analysis of such gedanken experiments requires that we calculate all effects on the final mass of the black hole that are second-order in the charge and angular momentum carried into the black hole, including all self-force effects. We obtain a general formula for the full second order correction to mass,…

We present a measurement of the cosmic-ray $\mathrm{electron}+\mathrm{positron}$ spectrum between 7 GeV and 2 TeV performed with almost seven years of data collected with the Fermi Large Area Telescope. We find that the spectrum is well fit by a broken power law with a break energy at about 50 GeV. Above 50 GeV, the spectrum is well described by a single power law with a spectral index of $3.07\ifmmode\pm\else\textpm\fi{}0.02\phantom{\rule{0ex}{0ex}}(\mathrm{stat}+\mathrm{syst})\ifmmode\pm\else\textpm\fi{}0.04(\text{energy measurement})$. An exponential cutoff lower than 1.8 TeV is excluded at 95% CL.

We show that solving the flavor problem of the Standard Model with a simple $U(1{)}_{H}$ flavor symmetry naturally leads to an axion that solves the strong $CP$ problem and constitutes a viable Dark Matter candidate. In this framework, the ratio of the axion mass and its coupling to photons is related to the SM fermion masses and predicted within a small range, as a direct result of the observed hierarchies in quark and charged lepton masses. The same hierarchies determine the axion couplings to fermions, making the framework very predictive and experimentally testable by future axion and precision flavor experiments.

We examine how to construct a spatial manifold and its geometry from the entanglement structure of an abstract quantum state in Hilbert space. Given a decomposition of Hilbert space $\mathcal{H}$ into a tensor product of factors, we consider a class of ``redundancy-constrained states'' in $\mathcal{H}$ that generalize the area-law behavior for entanglement entropy usually found in condensed-matter systems with gapped local Hamiltonians. Using mutual information to define a distance measure on the graph, we employ classical multidimensional scaling to extract the best-fit spatial dimensionality of the emergent geometry. We then show that entanglement perturbations on such emergent geometries naturally give rise to local modifications of spatial curvature which obey a (spatial) analog of Einstein's equation. The Hilbert space corresponding to a region of flat space is finite-dimensional and scales as the volume, though the entropy (and the maximum change thereof) scales like the area of the boundary. A version of the $\mathrm{ER}=\mathrm{EPR}$ conjecture is recovered, in that…

Working in relativistic quantum field theory, we derive the quantization condition satisfied by coupled two- and three-particle systems of identical scalar particles confined to a cubic spatial volume with periodicity $L$. This gives the relation between the finite-volume spectrum and the infinite-volume $\mathbf{2}\ensuremath{\rightarrow}\mathbf{2}$, $\mathbf{2}\ensuremath{\rightarrow}\mathbf{3}$, and $\mathbf{3}\ensuremath{\rightarrow}\mathbf{3}$ scattering amplitudes for such theories. The result holds for relativistic systems composed of scalar particles with nonzero mass $m$, whose center of mass energy lies below the four-particle threshold, and for which the two-particle $K$ matrix has no singularities below the three-particle threshold. The quantization condition is exact up to corrections of the order $\mathcal{O}({e}^{\ensuremath{-}mL})$ and holds for any choice of total momenta satisfying the boundary conditions.

We consider a real scalar singlet field which provides a strong first-order electroweak phase transition via its coupling to the Higgs boson, and gives a $CP$ violating contribution on the top quark mass via a dimension-6 operator. We study the correlation between the baryon-to-entropy ratio produced by electroweak baryogenesis, and the gravitational wave signal from the electroweak phase transition. We show that future gravitational wave experiments can test, in particular, the region of the model parameter space where the observed baryon-to-entropy ratio can be obtained even if the new physics scale, which is explicit in the dimension-6 operator, is high.

Dijet events are studied in the proton-proton collision data set recorded at $\sqrt{s}=13\text{ }\text{ }\mathrm{TeV}$ with the ATLAS detector at the Large Hadron Collider in 2015 and 2016, corresponding to integrated luminosities of $3.5\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ and $33.5\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ respectively. Invariant mass and angular distributions are compared to background predictions and no significant deviation is observed. For resonance searches, a new method for fitting the background component of the invariant mass distribution is employed. The data set is then used to set upper limits at a 95% confidence level on a range of new physics scenarios. Excited quarks with masses below 6.0 TeV are excluded, and limits are set on quantum black holes, heavy ${W}^{\ensuremath{'}}$ bosons, ${W}^{*}$ bosons, and a range of masses and couplings in a ${Z}^{\ensuremath{'}}$ dark matter mediator model. Model-independent limits on signals with a Gaussian shape are also set, using a new approach allowing factorization of physics and detector…

The coalescence of compact objects is one of the most promising sources, as well as the source of the first detections, of gravitational waves for ground-based interferometric detectors, such as advanced LIGO and Virgo. Generically, compact objects in binaries are expected to be spinning with spin angular momenta misaligned with the orbital angular momentum, causing the orbital plane to precess. This precession adds rich structure to the gravitational waves, introducing such complexity that an analytic closed-form description has been unavailable until now. We here construct the first closed-form frequency-domain gravitational waveforms that are valid for generic spin-precessing quasicircular compact binary inspirals. We first construct time-domain gravitational waves by solving the post-Newtonian precession equations of motion with radiation reaction through multiple scale analysis. We then Fourier transform these time-domain waveforms with the method of shifted uniform asymptotics to obtain closed-form expressions for frequency-domain waveforms. We study the accuracy of these…

We consider light propagation in a nonmagnetized pressureless plasma around a Kerr black hole. We find the necessary and sufficient condition the plasma electron density has to satisfy to guarantee that the Hamilton-Jacobi equation for the light rays is separable, i.e., that a generalized Carter constant exists. For all cases where this condition is satisfied we determine the photon region; i.e., the region in the spacetime where spherical light rays exist. A spherical light ray is a light ray that stays on a sphere $r=\text{constant}$ (in Boyer-Lindquist coordinates). Based on these results, we calculate the shadow of a Kerr black hole under the influence of a plasma that satisfies the separability condition. More precisely, we derive an analytical formula for the boundary curve of the shadow on the sky of an observer that is located anywhere in the domain of outer communication. Several examples are worked out.

Numerical relativity is an essential tool in studying the coalescence of binary black holes (BBHs). It is still computationally prohibitive to cover the BBH parameter space exhaustively, making phenomenological fitting formulas for BBH waveforms and final-state properties important for practical applications. We describe a general hierarchical bottom-up fitting methodology to design and calibrate fits to numerical relativity simulations for the three-dimensional parameter space of quasicircular nonprecessing merging BBHs, spanned by mass ratio and by the individual spin components orthogonal to the orbital plane. Particular attention is paid to incorporating the extreme-mass-ratio limit and to the subdominant unequal-spin effects. As an illustration of the method, we provide two applications, to the final spin and final mass (or equivalently: radiated energy) of the remnant black hole. Fitting to 427 numerical relativity simulations, we obtain results broadly consistent with previously published fits, but improving in overall accuracy and particularly in the approach to extremal…

Motivated by recent developments in black hole thermodynamics, we investigate van der Waals phase transitions of charged black holes in massive gravity. We find that massive gravity theories can exhibit strikingly different thermodynamic behavior compared to that of Einstein gravity, and that the mass of the graviton can generate a range of new phase transitions for topological black holes that are otherwise forbidden.

There are at least two formation scenarios consistent with the first gravitational-wave observations of binary black hole mergers. In field models, black hole binaries are formed from stellar binaries that may undergo common envelope evolution. In dynamic models, black hole binaries are formed through capture events in globular clusters. Both classes of models are subject to significant theoretical uncertainties. Nonetheless, the conventional wisdom holds that the distribution of spin orientations of dynamically merging black holes is nearly isotropic while field-model black holes prefer to spin in alignment with the orbital angular momentum. We present a framework in which observations of black hole mergers can be used to measure ensemble properties of black hole spin such as the typical black hole spin misalignment. We show how to obtain constraints on population hyperparameters using minimal assumptions so that the results are not strongly dependent on the uncertain physics of formation models. These data-driven constraints will facilitate tests of theoretical models and help…

Dynamical dark energy has been recently suggested as a promising and physical way to solve the 3 sigma tension on the value of the Hubble constant ${H}_{0}$ between the direct measurement of Riess et al. (2016) (R16, hereafter) and the indirect constraint from cosmic microwave anisotropies obtained by the Planck satellite under the assumption of a $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ model. In this paper, by parametrizing dark energy evolution using the ${w}_{0}\ensuremath{-}{w}_{a}$ approach, and considering a 12 parameter extended scenario, we find that: (a) the tension on the Hubble constant can indeed be solved with dynamical dark energy, (b) a cosmological constant is ruled out at more than 95% c.l. by the $\mathrm{Planck}+\mathrm{R}16$ dataset, and (c) all of the standard quintessence and half of the ``downward going'' dark energy model space (characterized by an equation of state that decreases with time) is also excluded at more than 95% c.l. These results are further confirmed when cosmic shear, CMB lensing, or SN Ia luminosity distance data are also included. The…

Merging binary neutron stars (BNSs) represent the ultimate targets for multimessenger astronomy, being among the most promising sources of gravitational waves (GWs), and, at the same time, likely accompanied by a variety of electromagnetic counterparts across the entire spectrum, possibly including short gamma-ray bursts (SGRBs) and kilonova/macronova transients. Numerical relativity simulations play a central role in the study of these events. In particular, given the importance of magnetic fields, various aspects of this investigation require general relativistic magnetohydrodynamics (GRMHD). So far, most GRMHD simulations focused the attention on BNS mergers leading to the formation of a hypermassive neutron star (NS), which, in turn, collapses within few tens of ms into a black hole surrounded by an accretion disk. However, recent observations suggest that a significant fraction of these systems could form a long-lived NS remnant, which will either collapse on much longer time scales or remain indefinitely stable. Despite the profound implications for the evolution and the…

We address the evolution of heavy-quarkonium states in an expanding quark-gluon plasma by implementing effective field theory techniques in the framework of open quantum systems. In this setting we compute the nuclear modification factors for quarkonia that are $S$-wave Coulombic bound states in a strongly coupled quark-gluon plasma. The calculation is performed at an accuracy that is leading order in the heavy-quark density expansion and next-to-leading order in the multipole expansion. The quarkonium density-matrix evolution equations can be written in the Lindblad form, and, hence, they account for both dissociation and recombination. Thermal mass shifts, thermal widths and the Lindblad equation itself depend on only two nonperturbative parameters: the heavy-quark momentum diffusion coefficient and its dispersive counterpart. Finally, by numerically solving the Lindblad equation, we provide results for the $\mathrm{\ensuremath{\Upsilon}}(1S)$ and $\mathrm{\ensuremath{\Upsilon}}(2S)$ suppression.

The direct detection of gravitational waves (GWs) is an invaluable new tool to probe gravity and the nature of cosmic acceleration. A large class of scalar-tensor theories predicts that GWs propagate with velocity different than the speed of light, a difference that can be $\mathcal{O}(1)$ for many models of dark energy. We determine the conditions behind the anomalous GW speed, namely, that the scalar field spontaneously breaks Lorentz invariance and couples to the metric perturbations via the Weyl tensor. If these conditions are realized in nature, the delay between GW and electromagnetic signals from distant events will run beyond human time scales, making it impossible to measure the speed of GWs using neutron star mergers or other violent events. We present a robust strategy to exclude or confirm an anomalous speed of GWs using eclipsing binary systems, the electromagnetic phase of which can be exquisitely determined. The white dwarf binary $\mathrm{J}0651+2844$ is a known example of such a system that can be used to probe deviations in the GW speed as small as…

Assuming the existence of a local, analytic, unitary UV completion in a Poincar\'e invariant scalar field theory with a mass gap, we derive an infinite number of positivity requirements using the known properties of the amplitude at and away from the forward scattering limit. These take the form of bounds on combinations of the pole subtracted scattering amplitude and its derivatives. In turn, these positivity requirements act as constraints on the operator coefficients in the low energy effective theory. For certain theories these constraints can be used to place an upper bound on the mass of the next lightest state that must lie beyond the low energy effective theory if such a UV completion is to ever exist.

The chiral kinetic theory of Weyl fermions with collisions in the presence of weak electric and magnetic fields is derived from quantum field theories. It is found that the side-jump terms in the perturbative solution of Wigner functions play a significant role for the derivation. Moreover, such terms manifest the breaking of Lorentz symmetry for distribution functions. The Lorentz covariance of Wigner functions thus leads to modified Lorentz transformation associated with side-jump phenomena further influenced by background fields and collisions.

We present new $(3+1)\mathrm{D}$ numerical relativity simulations of the binary neutron star (BNS) merger and postmerger phase. We focus on a previously inaccessible region of the binary parameter space spanning the binary's mass ratio $q\ensuremath{\sim}1.00--1.75$ for different total masses and equations of state, and up to $q\ensuremath{\sim}2$ for a stiff BNS system. We study the mass ratio effect on the gravitational waves (GWs) and on the possible electromagnetic (EM) emission associated with dynamical mass ejecta. We compute waveforms, spectra, and spectrograms of the GW strain including all the multipoles up to $l=4$. The mass ratio has a specific imprint on the GW multipoles in the late-inspiral-merger signal, and it affects qualitatively the spectra of the merger remnant. The multipole effect is also studied by considering the dependency of the GW spectrograms on the source's sky location. Unequal mass BNSs produce more ejecta than equal mass systems with ejecta masses and kinetic energies depending almost linearly on $q$. We estimate luminosity peaks and light curves of…

We present measurements of a combination of the decay constants of the light pseudoscalar mesons and the gradient flow scale ${t}_{0}$, which allow us to set the scale of the lattices generated by CLS with $2+1$ flavors of nonperturbatively improved Wilson fermions. Mistunings of the quark masses are corrected for by measuring the derivatives of observables with respect to the bare quark masses.

Measurements of the ratio of $B\ensuremath{\rightarrow}{K}^{*}\ensuremath{\mu}\ensuremath{\mu}$ to $B\ensuremath{\rightarrow}{K}^{*}ee$ branching fractions, ${R}_{{K}^{*}}$, by the LHCb Collaboration strengthen the hints from previous studies with pseudoscalar kaons, ${R}_{K}$, for the breakdown of lepton universality, and therefore the Standard Model (SM), to $\ensuremath{\sim}3.5\ensuremath{\sigma}$. Complementarity between ${R}_{K}$ and ${R}_{{K}^{*}}$ allows us to pin down the Dirac structure of the new contributions to be predominantly SM-like chiral, with possible admixture of chirality-flipped contributions of up to $\mathcal{O}(\mathrm{few}10%)$. Scalar and vector leptoquark representations $({S}_{3},{V}_{1},{V}_{3})$ plus possible (${\stackrel{\texttildelow{}}{S}}_{2},{V}_{2}$) admixture can explain ${R}_{K,{K}^{*}}$ via tree-level exchange. Flavor models naturally predict leptoquark masses not exceeding a few TeV, with couplings to third-generation quarks at $O(0.1)$, implying that this scenario can be directly tested at the LHC.

By using the Gauss-Bonnet theorem, the bending angle of light in a static, spherically symmetric and asymptotically flat spacetime has been recently discussed, especially by taking account of the finite distance from a lens object to a light source and a receiver [Ishihara, Suzuki, Ono, Asada, Phys. Rev. D 95, 044017 (2017)]. We discuss a possible extension of the method of calculating the bending angle of light to stationary, axisymmetric and asymptotically flat spacetimes. For this purpose, we consider the light rays on the equatorial plane in the axisymmetric spacetime. We introduce a spatial metric to define the bending angle of light in the finite-distance situation. We show that the proposed bending angle of light is coordinate-invariant by using the Gauss-Bonnet theorem. The nonvanishing geodesic curvature of the photon orbit with the spatial metric is caused in gravitomagnetism, even though the light ray in the four-dimensional spacetime follows the null geodesic. Finally, we consider Kerr spacetime as an example in order to examine how the bending angle of light is computed…

We investigate the constraint ability of the gravitational wave (GW) as the standard siren on the cosmological parameters by using the third-generation gravitational wave detector: the Einstein Telescope. The binary merger of a neutron with either a neutron or black hole is hypothesized to be the progenitor of a short and intense burst of $\ensuremath{\gamma}$ rays; some fraction of those binary mergers could be detected both through electromagnetic radiation and gravitational waves. Thus we can determine both the luminosity distance and redshift of the source separately. We simulate the luminosity distances and redshift measurements from 100 to 1000 GW events. We use two different algorithms to constrain the cosmological parameters. For the Hubble constant ${H}_{0}$ and dark matter density parameter ${\mathrm{\ensuremath{\Omega}}}_{m}$, we adopt the Markov chain Monte Carlo approach. We find that with about 500--600 GW events we can constrain the Hubble constant with an accuracy comparable to Planck temperature data and Planck lensing combined results, while for the dark matter…

Semiconductors are by now well-established targets for direct detection of MeV to GeV dark matter via scattering off electrons. We show that semiconductor targets can also detect significantly lighter dark matter via an absorption process. When the dark matter mass is above the band gap of the semiconductor (around an eV), absorption proceeds by excitation of an electron into the conduction band. Below the band gap, multiphonon excitations enable absorption of dark matter in the 0.01 eV to eV mass range. Energetic dark matter particles emitted from the sun can also be probed for masses below an eV. We derive the reach for absorption of a relic kinetically mixed dark photon or pseudoscalar in germanium and silicon, and show that existing direct detection results already probe new parameter space. With only a moderate exposure, low-threshold semiconductor target experiments can exceed current astrophysical and terrestrial constraints on sub-keV bosonic dark matter.

Binary systems containing boson stars---self-gravitating configurations of a complex scalar field---can potentially mimic black holes or neutron stars as gravitational-wave sources. We investigate the extent to which tidal effects in the gravitational-wave signal can be used to discriminate between these standard sources and boson stars. We consider spherically symmetric boson stars within two classes of scalar self-interactions: an effective-field-theoretically motivated quartic potential and a solitonic potential constructed to produce very compact stars. We compute the tidal deformability parameter characterizing the dominant tidal imprint in the gravitational-wave signals for a large span of the parameter space of each boson star model, covering the entire space in the quartic case, and an extensive portion of interest in the solitonic case. We find that the tidal deformability for boson stars with a quartic self-interaction is bounded below by ${\mathrm{\ensuremath{\Lambda}}}_{\mathrm{min}}\ensuremath{\approx}280$ and for those with a solitonic interaction by…

Continuing work initiated in an earlier publication [A. Ishihara, Y. Suzuki, T. Ono, T. Kitamura, and H. Asada, Phys. Rev. D 94, 084015 (2016).], we discuss a method of calculating the bending angle of light in a static, spherically symmetric, and asymptotically flat spacetime, especially by taking into account the finite distance from a lens object to a light source and a receiver. For this purpose, we use the Gauss-Bonnet theorem to define the bending angle of light, such that the definition can be valid also in the strong deflection limit. Finally, this method is applied to Schwarzschild spacetime in order to discuss also possible observational implications. The proposed corrections for Sgr ${\mathrm{A}}^{*}$ for instance are able to amount to $\ensuremath{\sim}{10}^{\ensuremath{-}5}\text{ }\text{ }\mathrm{arcseconds}$ for some parameter range, which may be within the capability of near-future astronomy, while also the correction for the Sun in the weak-field limit is $\ensuremath{\sim}{10}^{\ensuremath{-}5}\text{ }\text{ }\mathrm{arcseconds}$.

We revisit the effective field theory of the standard model that is extended with sterile neutrinos, $N$. We examine the basis of complete and independent effective operators involving $N$ up to mass dimension seven (dim-7). By employing equations of motion, integration by parts, and Fierz and group identities, we construct relations among operators that were considered independent in the previous literature, and we find 7 redundant operators at dim-6, as well as 16 redundant operators and two new operators at dim-7. The correct numbers of operators involving $N$ are, without counting Hermitian conjugates, $16(L\ensuremath{\cap}B)+1(\overline{)L}\ensuremath{\cap}B)+2(\overline{)L}\ensuremath{\cap}\overline{)B})$ at dim-6 and $47(\overline{)L}\ensuremath{\cap}B)+5(\overline{)L}\ensuremath{\cap}\overline{)B})$ at dim-7. Here $L/B(\overline{)L}/\overline{)B})$ stands for lepton/baryon number conservation (violation). We verify our counting by the Hilbert series approach for ${n}_{f}$ generations of the standard model fermions and sterile neutrinos. When operators involving different…

We propose a unique stellar model under the $f(R,\mathcal{T})$ gravity by using the conjecture of Mazur-Mottola [P. Mazur and E. Mottola, Report No. LA-UR-01-5067, P. Mazur and E. Mottola, Proc. Natl. Acad. Sci. USA 101, 9545 (2004)] which is known as gravastar and a viable alternative to the black hole as available in literature. This gravastar is described by the three different regions, viz., (I) Interior core region, (II) Intermediate thin shell, and (III) Exterior spherical region. The pressure within the interior region is equal to the constant negative matter density which provides a repulsive force over the thin spherical shell. This thin shell is assumed to be formed by a fluid of ultrarelativistic plasma and the pressure, which is directly proportional to the matter-energy density according to Zel'dovich's conjecture of stiff fluid [Y. B. Zel'dovich, Mon. Not. R. Astron. Soc. 160, 1 (1972)], does counterbalance the repulsive force exerted by the interior core region. The exterior spherical region is completely vacuum and assumed to be de Sitter spacetime which can be…

The $6.8\ensuremath{\sigma}$ anomaly in excited $^{8}\mathrm{Be}$ nuclear decays via internal pair creation is fit well by a new particle interpretation. In a previous analysis, we showed that a 17 MeV protophobic gauge boson provides a particle physics explanation of the anomaly consistent with all existing constraints. Here we begin with a review of the physics of internal pair creation in $^{8}\mathrm{Be}$ decays and the characteristics of the observed anomaly. To develop its particle interpretation, we provide an effective operator analysis for excited $^{8}\mathrm{Be}$ decays to particles with a variety of spins and parities and show that these considerations exclude simple models with scalar particles. We discuss the required couplings for a gauge boson to give the observed signal, highlighting the significant dependence on the precise mass of the boson and isospin mixing and breaking effects. We present anomaly-free extensions of the Standard Model that contain protophobic gauge bosons with the desired couplings to explain the $^{8}\mathrm{Be}$ anomaly. In the first model,…

Proton decay is not allowed in the Standard Model but is a signature prediction of Grand Unified Theories (GUTs). The Super-Kamiokande Collaboration reports results from its rigorous search for proton decay in two channels. The non-observation of proton decay sets new lower bounds on the proton lifetime and imposes stringent constraints on possible GUT and other Beyond the Standard Model scenarios.

The standard black holes (BHs) in general relativity, as well as other ultracompact objects (with or without an event horizon) admit planar circular photon orbits. These light rings (LRs) determine several spacetime properties. For instance, stable LRs trigger instabilities and, in spherical symmetry, (unstable) LRs completely determine BH shadows. In generic stationary, axisymmetric spacetimes, nonplanar bound photon orbits may also exist, regardless of the integrability properties of the photon motion. We suggest a classification of these fundamental photon orbits (FPOs) and, using Poincar\'e maps, determine a criterion for their stability. For the Kerr BH, all FPOs are unstable (similar to its LRs) and completely determine the Kerr shadow. But in non-Kerr spacetimes, stable FPOs may also exist, even when all LRs are unstable, triggering new instabilities. We illustrate this for the case of Kerr BHs with Proca hair, wherein, moreover, qualitatively novel shadows with a cuspy edge exist, a feature that can be understood from the interplay between stable and unstable FPOs. FPOs are…

The conserved magnetic flux of $U(1)$ electrodynamics coupled to matter in four dimensions is associated with a generalized global symmetry. We study the realization of such a symmetry at finite temperature and develop the hydrodynamic theory describing fluctuations of a conserved 2-form current around thermal equilibrium. This can be thought of as a systematic derivation of relativistic magnetohydrodynamics, constrained only by symmetries and effective field theory. We construct the entropy current and show that at first order in derivatives, there are seven dissipative transport coefficients. We present a universal definition of resistivity in a theory of dynamical electromagnetism and derive a direct Kubo formula for the resistivity in terms of correlation functions of the electric field operator. We also study fluctuations and collective modes, deriving novel expressions for the dissipative widths of magnetosonic and Alfv\'en modes. Finally, we demonstrate that a nontrivial truncation of the theory can be performed at low temperatures compared to the magnetic field: this theory…

When binary systems of neutron stars merge, a very small fraction of their rest mass is ejected, either dynamically or secularly. This material is neutron-rich and its nucleosynthesis provides the astrophysical site for the production of heavy elements in the Universe, together with a kilonova signal confirming neutron-star mergers as the origin of short gamma-ray bursts. We perform full general-relativistic simulations of binary neutron-star mergers employing three different nuclear-physics equations of state (EOSs), considering both equal- and unequal-mass configurations, and adopting a leakage scheme to account for neutrino radiative losses. Using a combination of techniques, we carry out an extensive and systematic study of the hydrodynamical, thermodynamical, and geometrical properties of the matter ejected dynamically, employing the WinNet nuclear-reaction network to recover the relative abundances of heavy elements produced by each configurations. Among the results obtained, three are particularly important. First, we find that, within the sample considered here, both the…

The question of whether there exist bound states of two heavy quarks $Q=(c,b)$ and antiquarks $\overline{Q}=(\overline{c},\overline{b})$, distinct from a pair of quark-antiquark mesons, has been debated for more than forty years. We estimate masses of ${Q}_{1}{Q}_{2}{\overline{Q}}_{3}{\overline{Q}}_{4}$ resonant states ${X}_{{Q}_{1}{Q}_{2}{\overline{Q}}_{3}{\overline{Q}}_{4}}$ and suggest a means of producing and observing them. We concentrate on the $cc\overline{c}\overline{c}$ channel which is most easily produced and the $bb\overline{b}\overline{b}$ channel which has a better chance of being relatively narrow. We obtain $M({X}_{cc\overline{c}\overline{c}})=6,192\ifmmode\pm\else\textpm\fi{}25\text{ }\text{ }\mathrm{MeV}$ and $M({X}_{bb\overline{b}\overline{b}})=\phantom{\rule{0ex}{0ex}}18,826\ifmmode\pm\else\textpm\fi{}25\text{ }\text{ }\mathrm{MeV}$, for the ${J}^{PC}={0}^{++}$ states involving charmed and bottom tetraquarks, respectively. An experimental search for these states in the predicted mass range is highly desirable.

Recently, several $B$-physics experiments have reported an appreciable deviation from the standard model (SM) in the tree-level observables ${R}_{{D}^{(*)}}$; the combined weighted average now stands at $\ensuremath{\approx}4\ensuremath{\sigma}$. We first show the anomaly necessarily implies model-independent collider signals of the form $pp\ensuremath{\rightarrow}b\ensuremath{\tau}\ensuremath{\nu}$ that should be expeditiously searched for at ATLAS/CMS as a complementary test of the anomaly. Next we suggest a possible interconnection of the anomaly with the radiative stability of the standard model Higgs boson and point to a minimal effective supersymmetric scenario with $R$-parity violation as the underlying cause. We also comment on the possibility of simultaneously explaining the recently reported ${R}_{{K}^{(*)}}$ anomaly in this setup.

We derive an approximate analytical formula for the spectral density of the $q$-body Sachdev-Ye-Kitaev (SYK) model obtained by summing a class of diagrams representing leading intersecting contractions. This expression agrees with that of $Q$-Hermite polynomials, with $Q$ a nontrivial function of $q\ensuremath{\ge}2$ and the number of Majorana fermions $N$. Numerical results, obtained by exact diagonalization, are in excellent agreement with this approximate analytical spectral density even for relatively small $N\ensuremath{\sim}8$. For $N\ensuremath{\gg}1$ and not close to the edge of the spectrum, we find that the approximate analytical spectral density simplifies to ${\ensuremath{\rho}}_{\mathrm{asym}}(E)=\mathrm{exp}[2{\mathrm{arcsin}}^{2}(E/{E}_{0})/\mathrm{log}\ensuremath{\eta}]$, where $\ensuremath{\eta}(N,q)$ is the suppression factor of the contribution of intersecting Wick contractions relative to nested contractions and ${E}_{0}$ is the ground-state energy per particle. This spectral density reproduces the known result for the free energy in the large-$q$ and large-$N$…

In this paper we present results for the renormalization of gauge invariant nonlocal fermion operators which contain a Wilson line, to one-loop level in lattice perturbation theory. Our calculations have been performed for Wilson/clover fermions and a wide class of Symanzik improved gluon actions. The extended nature of such ``long-link'' operators results in a nontrivial renormalization, including contributions which diverge linearly as well as logarithmically with the lattice spacing, along with additional finite factors. On the lattice there is also mixing among certain subsets of these nonlocal operators; we calculate the corresponding finite mixing coefficients, which are necessary in order to disentangle individual matrix elements for each operator from lattice simulation data. Finally, extending our perturbative setup, we present nonperturbative prescriptions to extract the linearly divergent contributions.

A search for the solar neutrino effective magnetic moment has been performed using data from 1291.5 days exposure during the second phase of the Borexino experiment. No significant deviations from the expected shape of the electron recoil spectrum from solar neutrinos have been found, and a new upper limit on the effective neutrino magnetic moment of ${\ensuremath{\mu}}_{\ensuremath{\nu}}^{\mathrm{eff}}<{2.8\ifmmode\times\else\texttimes\fi{}10}^{\ensuremath{-}11}$ ${\ensuremath{\mu}}_{B}$ at 90% C.L. has been set using constraints on the sum of the solar neutrino fluxes implied by the radiochemical gallium experiments. Using the limit for the effective neutrino moment, new limits for the magnetic moments of the neutrino flavor states, and for the elements of the neutrino magnetic moments matrix for Dirac and Majorana neutrinos, are derived.

We present the results of a search for the rare decays $B\ensuremath{\rightarrow}h\ensuremath{\nu}\overline{\ensuremath{\nu}}$, where $h$ stands for ${K}^{+},{K}_{\mathrm{S}}^{0},\phantom{\rule{0ex}{0ex}}{{K}^{*}}^{+},{{K}^{*}}^{0},{\ensuremath{\pi}}^{+},{\ensuremath{\pi}}^{0},{\ensuremath{\rho}}^{+}$ and ${\ensuremath{\rho}}^{0}$. The results are obtained with $772\ifmmode\times\else\texttimes\fi{}{10}^{6}\text{ }\text{ }B\overline{B}$ pairs collected with the Belle detector at the KEKB ${e}^{+}{e}^{\ensuremath{-}}$ collider. We reconstruct one $B$ meson in a semileptonic decay and require a single $h$ meson but nothing else on the signal side. We observe no significant signal and set upper limits on the branching fractions. The limits set on the ${B}^{0}\ensuremath{\rightarrow}{K}_{\mathrm{S}}^{0}\ensuremath{\nu}\overline{\ensuremath{\nu}}$, ${B}^{0}\ensuremath{\rightarrow}{{K}^{*}}^{0}\ensuremath{\nu}\overline{\ensuremath{\nu}}$, ${B}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}\ensuremath{\nu}\overline{\ensuremath{\nu}}$,…