We compute numerically the Lorentzian Engle-Pereira-Rovelli-Livine spinfoam propagator on a 4-simplex, by adapting the Lefschetz thimble and Markov chain Monte-Carlo methods to oscillatory spinfoam integrals. Our method can compute any spinfoam observables at relatively large spins. We obtain the numerical results of the propagators at different spins and demonstrate their consistency with the expected spinfoam semiclassical behavior in the large spin limit. Our results exhibit significant quantum corrections at smaller spins. Our method is reliable and thus can be employed to discover the semiclassical and quantum behaviors of the spinfoam model.

The space-based gravitational wave detector LISA will observe mergers of massive black hole binary systems (MBHBs) to cosmological distances, as well as inspiralling stellar-origin (or stellar-mass) binaries (SBHBs) years before they enter the LIGO/Virgo band. Much remains to be explored for the parameter recovery of both classes of systems. Previous MBHB analyses relied on inspiral-only signals and/or a simplified Fisher matrix analysis, while SBHBs have not yet been extensively analyzed with Bayesian methods. We accelerate likelihood computations by (i) using a Fourier-domain response of the LISA instrument, (ii) using a reduced order model for nonspinning waveforms that include a merger-ringdown and higher harmonics, and (iii) setting the noise realization to zero and computing overlaps in the amplitude/phase representation. We present the first simulations of Bayesian inference for the parameters of massive black hole systems including consistently the merger and ringdown of the signal, as well as higher harmonics. We clarify the roles of LISA response time and frequency dependencies in breaking degeneracies and illustrate how degeneracy breaking unfolds over time. We also find that restricting the merger-dominated signal to its dominant harmonic can make the extrinsic likelihood very degenerate. Including higher harmonics proves to be crucial to breaking degeneracies and considerably improves the localization of the source, with a surviving bimodality in the sky position. We also present simulations of Bayesian inference for the extrinsic parameters of SBHBs, and show that although unimodal, their posterior distributions can have non-Gaussian features.

Isolated neutron stars are prime targets for continuous-wave (CW) searches by ground-based gravitational-wave interferometers. Results are presented from a CW search targeting ten pulsars. The search uses a semicoherent algorithm, which combines the maximum-likelihood $\mathcal{F}$-statistic with a hidden Markov model (HMM) to efficiently detect and track quasi-monochromatic signals which wander randomly in frequency. The targets, which are associated with TeV sources detected by the High Energy Stereoscopic System (H.E.S.S.), are chosen to test for gravitational radiation from young, energetic pulsars with strong $\gamma$-ray emission, and take maximum advantage of the frequency tracking capabilities of HMM compared to other CW search algorithms. The search uses data from the second observing run of the Advanced Laser Interferometer Gravitational-Wave Observatory (aLIGO). It scans $1-\mathrm{Hz}$ sub-bands around $f_{*}$, $4f_{*}/3$, and $2f_{*}$, where $f_{*}$ denotes the star’s rotation frequency, in order to accommodate a physically plausible frequency mismatch between the electromagnetic and gravitational-wave emission. The 24 sub-bands searched in this study return 5,256 candidates above the Gaussian threshold with a false alarm probability of 1% per sub-band per target. Only 12 candidates survive the three data quality vetoes which are applied to separate non-Gaussian artifacts from true astrophysical signals. CW searches using the data from subsequent observing runs will clarify the status of the remaining candidates.

The short distance behavior of dark matter (DM) at galaxy scales exhibits several features not explained by the typical cold dark matter with velocity-independent cross section. We discuss a particle physics model with a hidden sector interacting feebly with the visible sector where a dark fermion self-interacts via a dark force with a light dark photon as the mediator. We study coupled Boltzmann equations involving two temperatures, one for each sector. We fit the velocity-dependent DM cross section to the data from scales of dwarf galaxies to clusters consistent with relic density constraint.

We present the first lattice QCD determination of the ${\mathrm{\Lambda }}_b\to {\mathrm{\Lambda }}^{*}(1520)$ vector, axial vector, and tensor form factors that are relevant for the rare decays ${\mathrm{\Lambda }}_b\to {\mathrm{\Lambda }}^{*}(1520){\ell }^{+}{\ell }^{-}$. The lattice calculation is performed in the ${\mathrm{\Lambda }}^{*}(1520)$ rest frame with nonzero ${\mathrm{\Lambda }}_b$ momenta, and is limited to the high-$q^2$ region. An interpolating field with covariant derivatives is used to obtain good overlap with the ${\mathrm{\Lambda }}^{*}(1520)$. The analysis treats the ${\mathrm{\Lambda }}^{*}(1520)$ as a stable particle, which is expected to be a reasonable approximation for this narrow resonance. A domain-wall action is used for the light and strange quarks, while the $b$ quark is implemented with an anisotropic clover action with coefficients tuned to produce the correct $B_s$ kinetic mass, rest mass, and hyperfine splitting. We use three different ensembles of lattice gauge-field configurations generated by the RBC and UKQCD collaborations, and perform extrapolations of the form factors to the continuum limit and physical pion mass. We give Standard-Model predictions for the ${\mathrm{\Lambda }}_b\to {\mathrm{\Lambda }}^{*}(1520){\ell }^{+}{\ell }^{-}$ differential branching fraction and angular observables in the high-$q^2$ region.

Recent lattice QCD calculations strongly indicate that the chiral crossover of QCD at zero baryon chemical potential (${\mu }_B$) is a remnant of the second order chiral phase transition. Universal properties of this second order phase transition can be mapped to QCD temperature $T$ and ${\mu }_B$ using nonuniversal parameters determined by lattice QCD recently. Motivated by these results, first, we discuss the analytic structure of the partition function in the QCD crossover regime—the so-called Yang-Lee edge singularity—solely based on universal properties. Next, utilizing the lattice QCD results for nonuniversal parameters we map this singularity to the real $T$ and complex ${\mu }_B$ plane, leading to the determination of the radius of convergence in ${\mu }_B$ in the QCD crossover regime. These universality- and QCD-based results provide tight constraints on the range of validity of the lattice QCD calculations at ${\mu }_B>0$. Implication of this result on the location of the conjectured QCD critical point is discussed.

We numerically solve for $2+1$ asymptotically Lifshitz universal horizon solutions in Hořava-Lifshitz gravity for dynamical exponents $z=2$ through $z=16$. We find that for all $z$ there is a thermodynamical first law. Furthermore, we find that the energy-entropy relation or Smarr formula expected for a thermal state in a two-dimensional Lifshitz field theory, $E=\frac{2}{z+2}TS$, is also satisfied for universal horizons, including the correct $z$ scaling.

One approach to defining dynamics for quantum gravity in a naturally timeless setting is to select a suitable matter degree of freedom as a “clock” before quantization. This idea of deparametrization was recently introduced in group field theory leading to a Hamiltonian formulation in which states or operators evolve with respect to the clock given by a free massless scalar field, similar to what happens in deparametrized models in quantum cosmology. Here we extend the construction of Hamiltonian group field theory to models with multiple scalar matter fields, encountering new features and technical subtleties compared with the previously studied case. We show that the effective cosmological dynamics for these more general models reduce to the Friedmann dynamics of general relativity with multiple scalar fields in the limit of large volume, if suitable (nongeneric) initial conditions are chosen. At high energy, we find corrections to the classical Friedmann equations whose form is similar to what is found in loop quantum cosmology. These corrections lead to generic singularity resolution by a bounce. For generic initial conditions, the effective cosmological dynamics treat the clock field and other matter fields differently, in disagreement with the Friedmann dynamics of general relativity. We speculate on a possible interpretation in terms of inhomogeneities.

The open question of whether a Kerr black hole can become tidally deformed or not has profound implications for fundamental physics and gravitational-wave astronomy. We consider a Kerr black hole embedded in a weak and slowly varying, but otherwise arbitrary, multipolar tidal environment. By solving the static Teukolsky equation for the gauge-invariant Weyl scalar ${\psi }_0$ and by reconstructing the corresponding metric perturbation in an ingoing radiation gauge, for a general harmonic index $\ell$, we compute the linear response of a Kerr black hole to the tidal field. This linear response vanishes identically for a Schwarzschild black hole and for an axisymmetric perturbation of a spinning black hole. For a nonaxisymmetric perturbation of a spinning black hole, however, the linear response does not vanish, and it contributes to the Geroch-Hansen multipole moments of the perturbed Kerr geometry. As an application, we compute explicitly the rotational black hole tidal Love numbers that couple the induced quadrupole moments to the quadrupolar tidal fields, to linear order in the black hole spin, and we introduce the corresponding notion of a tidal Love tensor. Finally, we show that those induced quadrupole moments are closely related to the well-known physical phenomenon of tidal torquing of a spinning body interacting with a tidal gravitational environment.

Available laser technology is opening the possibility of testing QED experimentally in the so-called strong-field regime. This calls for developing theoretical tools to investigate strong-field QED processes in electromagnetic fields of complex spacetime structure. Here, we propose a scheme to compute electron wave functions in tightly focused laser beams by taking into account exactly the complex spacetime structure of the fields. The scheme is solely based on the validity of the Wentzel-Kramers-Brillouin (WKB) approximation and the resulting wave functions, unlike previously proposed ones [Phys. Rev. Lett. 113, 040402 (2014)], do not rely on approximations on the classical electron trajectory. Moreover, a consistent procedure is indicated to take into account higher-order quantum effects within the WKB approach depending on higher-and-higher powers of the Planck constant. In the case of a plane-wave background field the found wave functions exactly reduce to the Volkov states, which are then written in a new and fully quasiclassical form. Finally, by using the leading-order WKB wave functions to compute the probabilities of nonlinear Compton scattering and nonlinear Breit-Wheeler pair production, it is explicitly shown that, if additionally the energies of the charges are sufficiently large that the latter are not significantly deflected by the field, the corresponding Baier’s formulas are exactly reproduced for an otherwise arbitrary classical electron/positron trajectory.

We study the prospect for discovering the $cg\to b{H}^{+}\to bA{W}^{+}$ process at the LHC. Induced by the top-flavor changing neutral Higgs coupling ${\rho }_{tc}$, the process may emerge if $m_{H^{+}}>m_A+m_{W^{+}}$, where $H^{+}$ and $A$ are charged and $CP$-odd Higgs bosons in the general two Higgs doublet model (g2HDM). We show that the $cg\to b{H}^{+}\to bA{W}^{+}$ process can be discovered at LHC run 3, while the full run 2 data at hand can constrain the parameter space significantly by searching for the same-sign dilepton final state. The process has unique implications on the hint of $gg\to A\to t\overline{t}$ excess at $m_A\approx 400\mathrm{GeV}$ reported by CMS. When combined with other existing constraints, the $cg\to b{H}^{+}\to bA{W}^{+}$ process can essentially rule out the g2HDM explanation of such an excess.

Pionless effective field theory in a finite volume (${\mathrm{FVEFT}}_{\cancel{\pi }}$) is investigated as a framework for the analysis of multinucleon spectra and matrix elements calculated in lattice QCD (LQCD). By combining ${\mathrm{FVEFT}}_{\cancel{\pi }}$ with the stochastic variational method, the spectra of nuclei with atomic number $A\in \{2,3\}$ are matched to existing finite-volume LQCD calculations at heavier-than-physical quark masses corresponding to a pion mass $m_{\pi }=806\mathrm{MeV}$, thereby enabling infinite-volume binding energies to be determined using infinite-volume variational calculations. Based on the variational wave functions that are constructed in this approach, the finite-volume matrix elements of various local operators are computed in ${\mathrm{FVEFT}}_{\cancel{\pi }}$ and matched to LQCD calculations of the corresponding QCD operators in the same volume, thereby determining the relevant one- and two-body effective field theory counterterms and enabling an extrapolation of the LQCD matrix elements to infinite volume. As examples, the scalar, tensor, and axial matrix elements are considered, in addition to the magnetic moments and the isovector longitudinal momentum fraction.

Recently unpolarized and polarized $J/\psi (\mathrm{\Upsilon })$ production at the Electron-Ion Collider (EIC) has been proposed as a new way to extract two poorly known color-octet NRQCD long-distance matrix elements: $⟨0|{\mathcal{O}}_8^{J/\psi }({}^1{S}_0)|0⟩$ and $⟨0|{\mathcal{O}}_8^{J/\psi }({}^3{P}_0)|0⟩$. The proposed method is based on a comparison to open heavy-quark pair production ideally performed at the same kinematics. In this paper we analyze this proposal in more detail and provide predictions for the EIC based on the available determinations of the color-octet matrix elements. We also propose two additional methods that do not require comparison to open heavy-quark pair production.

In recent years, evidence for lepton flavor universality violation beyond the Standard Model has been accumulated. In this context, a singly charged $SU(2{)}_L$ singlet scalar (${\varphi }^{\pm }$) is very interesting, as it can only have flavor off-diagonal couplings to neutrinos and charged leptons therefore necessarily violating lepton flavor (universality). In fact, it gives a (necessarily constructive) tree-level effect in $\ell \to {\ell }^{\prime }\nu \nu$ processes, while contributing to charged lepton flavor violating only at the loop level. Therefore, it can provide a common explanation of the hints for new physics in $\tau \to \mu \nu \nu /\tau (\mu )\to e\nu \nu$ and of the Cabibbo Angle Anomaly. Such an explanation predicts $\mathrm{Br}[\tau \to e\gamma ]$ to be of the order of a few times ${10}^{-11}$, while $\mathrm{Br}[\tau \to e\mu \mu ]$ can be of the order of ${10}^{-9}$ for order one couplings and therefore in the reach of forthcoming experiments. Furthermore, we derive a novel coupling-independent lower limit on the scalar mass of $\approx 200\mathrm{GeV}$ by recasting LHC slepton searches. In the scenario preferred by low energy precision data, the lower limit is even strengthened to $\approx 300\mathrm{GeV}$, showing the complementary between LHC searches and flavor observables. Furthermore, we point out that this model can be tested by reinterpreting dark matter monophoton searches at future $e^{+}{e}^{-}$ colliders.

We report measurements of the branching fractions of singly Cabibbo-suppressed decays ${\mathrm{\Lambda }}_c^{+}\to p\eta$ and ${\mathrm{\Lambda }}_c^{+}\to p{\pi }^0$ using the full Belle data sample corresponding to an integrated luminosity of $980.6{\mathrm{fb}}^{-1}$. The data were collected by the Belle detector at the KEKB $e^{+}{e}^{-}$ asymmetric energy collider. A clear ${\mathrm{\Lambda }}_c^{+}$ signal is seen in the invariant mass distribution of $p\eta$. The fitted number of signal events of the ${\mathrm{\Lambda }}_c^{+}\to p\eta$ process is $7734\pm 263$; from this, we measure the ratio of branching fractions $\mathcal{B}({\mathrm{\Lambda }}_c^{+}\to p\eta )/\mathcal{B}({\mathrm{\Lambda }}_c^{+}\to p{K}^{-}{\pi }^{+})=[2.258\pm 0.077(\mathrm{stat})\pm 0.122(\mathrm{syst})]\times {10}^{-2}$, from which we infer the branching fraction $\mathcal{B}({\mathrm{\Lambda }}_c^{+}\to p\eta )=[1.42\pm 0.05(\mathrm{stat})\pm 0.11(\mathrm{syst})]\times {10}^{-3}$. In addition, no significant signal for ${\mathrm{\Lambda }}_c^{+}\to p{\pi }^0$ is found, so an upper limit on the branching fraction of $\mathcal{B}({\mathrm{\Lambda }}_c^{+}\to p{\pi }^0)<8.0\times {10}^{-5}$ at a 90% credibility level is set, more than 3 times better than the best current upper limit.

S-wave states of charmonium and bottomonium are described using bottom-up AdS/QCD. We propose a holographic model that unifies the description of masses and decay constants, leading to a precise match with experimental data on heavy quarkonia. Finite temperature effects are considered by calculating the current-current spectral functions of heavy vector mesons. The identification of quasiparticle states as Breit-Wigner resonances in the holographic spectral function was made. We develop a prescription to subtract background contributions from the spectral function to isolate the Breit-Wigner peak. The quasi-particle holographic thermal evolution is described, allowing us to estimate the melting temperature for vector charmonia and bottomonia. Our holographic model predicts that $J/\mathrm{\Psi }$ melts at 415 MeV $(\sim 2.92T_c)$ and $\mathrm{\Upsilon }$ melts at 465 MeV $(\sim 3.27T_c)$.

The zeroth law of thermodynamics involves a transitivity relation (pairwise between three objects) expressed either in terms of “equal temperature” (ET), or “in equilibrium” (EQ) conditions. In conventional thermodynamics conditional on vanishingly weak system-bath coupling these two conditions are commonly regarded as equivalent. In this work we show that for thermodynamics at strong coupling they are inequivalent: namely, two systems can be in equilibrium and yet have different effective temperatures. A recent result [J.-T. Hsiang and B. L. Hu, Phys. Rev. D 103, 065001 (2021) for Gaussian quantum systems shows that an effective temperature $T^{*}$ can be defined at all times during a system’s nonequilibrium evolution, but because of the inclusion of interaction energy, after equilibration the system’s $T^{*}$ is slightly higher than the bath temperature $T_{\mathrm{B}}$, with the deviation depending on the coupling. A second object coupled with a different strength with an identical bath at temperature $T_{\mathrm{B}}$ will not have the same equilibrated temperature as the first object. Thus $ET\ne EQ$ for strong coupling thermodynamics. We then investigate the conditions for dynamical equilibration for two objects 1 and 2 strongly coupled with a common bath $B$, each with a different equilibrated effective temperature. We show this is possible, and prove the existence of a generalized fluctuation-dissipation relation under this configuration. This affirms that in equilibrium is a valid and perhaps more fundamental notion which the zeroth law for quantum thermodynamics at strong coupling should be based on. Only when the system-bath coupling becomes vanishingly weak that “temperature” appearing in thermodynamic relations becomes universally defined and makes better physical sense.

We consider the photonic vortical effect, i.e., the difference of the flows of left- and right-handed photons along the vector of angular velocity in rotating photonic medium. Two alternative frameworks to evaluate the effect are considered, both of which have already been tried in the literature: first, the standard thermal field theory and, alternatively, Hawking-radiation-type derivation. In our earlier attempt to compare the two approaches, we found a crucial factor of 2 difference. Here, we revisit the problem, paying more attention to details of infrared regularizations. We find out that introduction of an infinitesimal mass of the vector field brings the two ways of evaluating the chiral vortical effect into agreement with each other. Some implications, on both the theoretical and phenomenological sides, are mentioned.