We study the gravitational-wave background from the observed cosmological quasar distribution. Using the DR9Q quasar catalogue from the ninth data release of the Sloan Digital Sky Survey (SDSS), we create a complete, statistically consistent sample of quasars from $z=0.3$ to 5.4. Employing the spectroscopic information from the catalogue we estimate the masses of the supermassive black holes hosted by the quasars in the sample, resulting in a log-normal distribution of mean ${10}^{8.32\pm 0.33}{M}_{\odot }$. The computation of the individual gravitational-wave strains relies on specific functional forms derived from simulations of gravitational collapse and mergers of massive black hole binaries. The background gravitational-wave emission is assembled by adding up the individual signals from each quasar modeled as plane waves whose interference can be constructive or destructive depending on the quasar evolutionary state. Our results indicate that the estimated gravitational-wave background discussed in this work could only be marginally detectable by LISA. This conclusion might change if more complete quasar catalogs than that provided by the SDSS become available.

We investigate the possibility that the dark matter abundance is sourced by the baryon/lepton asymmetry of the early Universe. It turns out that a Goldstone field of a global classically preserved symmetry in the Standard Model experiences a kick during a period of baryon/lepton number generation. This mechanism can be regarded as dynamical generation of initial conditions for misalignment yet the prediction for relic abundance presents an inverse dependence on the coupling in parallel with freeze-in vs freeze-out. We explore two realizations of this mechanism and show that in conjunction with leptogenesis, it is possible to identify a viable promising region of parameter space for dark matter production with mass 10 MeV–1 GeV and decay constant $f$ in the range of ${10}^{10}–{10}^{12}\mathrm{GeV}$.

The simulation of dense fermionic matters is a long-standing problem in lattice gauge theory. One hopeful solution would be the use of quantum computers. In this paper, digital quantum simulation is designed for lattice gauge theory at nonzero density. The quantum variational algorithm is adopted to obtain the ground state at nonzero density. A benchmark test is performed in the lattice Schwinger model.

We present measurements of partial branching fractions of inclusive semileptonic $B\to X_u{\ell }^{+}{\nu }_{\ell }$ decays using the full Belle dataset of $711{\mathrm{fb}}^{-1}$ of integrated luminosity at the $\mathrm{\Upsilon }(4S)$ resonance and for $\ell =e$, $\mu$. Inclusive semileptonic $B\to X_u{\ell }^{+}{\nu }_{\ell }$ decays are Cabibbo-Kobayashi-Maskawa (CKM) suppressed and measurements are complicated by the large background from CKM favored $B\to X_c{\ell }^{+}{\nu }_{\ell }$ transitions, which have a similar signature. Using machine learning techniques, we reduce this and other backgrounds effectively, while retaining access to a large fraction of the $B\to X_u{\ell }^{+}{\nu }_{\ell }$ phase space and high signal efficiency. We measure partial branching fractions in three phase-space regions covering about 31% to 86% of the accessible $B\to X_u{\ell }^{+}{\nu }_{\ell }$ phase space. The most inclusive measurement corresponds to the phase space with lepton energies of $E_{\ell }^B>1\mathrm{GeV}$, and we obtain $\mathrm{\Delta }\mathcal{B}(B\to X_u{\ell }^{+}{\nu }_{\ell })=(1.59\pm 0.07\pm 0.16)\times {10}^{-3}$ from a two-dimensional fit of the hadronic mass spectrum and the four-momentum-transfer squared distribution, with the uncertainties denoting the statistical and systematic error. We find $|V_{ub}|=(4.10\pm 0.09\pm 0.22\pm 0.15)\times {10}^{-3}$ from an average of four calculations for the partial decay rate with the third uncertainty denoting the average theory error. This value is higher but compatible with the determination from exclusive semileptonic decays within 1.3 standard deviations. In addition, we report charmless inclusive partial branching fractions separately for $B^{+}$ and $B^0$ mesons as well as for electron and muon final states. No isospin breaking or lepton flavor universality violating effects are observed.

We report the first search for the penguin-dominated process $B_s^0\to {\eta }^{\prime }{X}_{s\overline{s}}$ using a semi-inclusive method. A $121.4{\mathrm{fb}}^{-1}$ integrated luminosity $\mathrm{\Upsilon }(5S)$ data set collected by the Belle experiment, at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider, is used. We observe no statistically significant signal and, including all uncertainties, we set a 90% confidence level upper limit on the partial branching fraction at $1.4\times {10}^{-3}$ for $M(X_{s\overline{s}})\le 2.4\mathrm{GeV}/c^2$.

We present new results on the radiopurity of a 3.4-kg NaI(Tl) crystal scintillator operated in the SABRE proof-of-principle detector setup. The amount of potassium contamination, determined by the direct counting of radioactive ${}^{40}\mathrm{K}$, is found to be $2.2\pm 1.5\mathrm{ppb}$, lowest ever achieved for NaI(Tl) crystals. With the active veto, the average background rate in the crystal in the 1–6 keV energy region of interest (ROI) is $1.20\pm 0.05\mathrm{counts}/\mathrm{day}/\mathrm{kg}/\mathrm{keV}$, which is a breakthrough since the DAMA/LIBRA experiment. Our background model indicates that the rate is dominated by ${}^{210}\mathrm{Pb}$ and that about half of this contamination is located in the polytetrafluoroethylene reflector. We discuss ongoing developments of the crystal manufacture aimed at the further reduction of the background, including data from purification by zone refining. A projected background rate lower than $\sim 0.2\mathrm{counts}/\mathrm{day}/\mathrm{kg}/\mathrm{keV}$ in the ROI is within reach. These results represent a benchmark for the development of next-generation NaI(Tl) detector arrays for the direct detection of dark matter particles.

We compute the one-loop vacuum polarization energies of Abrikosov-Nielsen-Olesen vortices with topological charge $n$ in scalar electrodynamics, for the Bogomolny-Prasad-Sommerfeld case of equal gauge and scalar masses. This calculation allows us to investigate the relationship between the winding number and the quantum-corrected vortex energy, which in turn determines the stability of higher winding configurations against decay into configurations with unit winding. While the classical energy is proportional to $n$, we find that the vacuum polarization energy is negative and approximately proportional to $n-1$ with a small constant offset.

The gravitational waves emitted during the coalescence of binary black holes are an excellent probe to test the behavior of strong gravity. In this paper, we propose a new test called the merger-ringdown consistency test that focuses on probing the imprints of the dynamics in strong-gravity around the black-holes during the plunge-merger and ringdown phase. Furthermore, we present a scheme that allows us to efficiently combine information across multiple ringdown observations to perform a statistical null test of GR using the detected BH population. We present a proof-of-concept study for this test using simulated binary black hole ringdowns embedded in the next-generation ground-based detector noise. We demonstrate the feasibility of our test using a deep learning framework, setting a precedence for performing precision tests of gravity with neural networks.

In the present paper, the $3+1$ decomposition of the spacetime onto hypersurface(s) is analyzed and established for theories within the Palatini formalism by considering a general function of the Ricci scalar in the gravitational action. The corresponding Gauss-Codazzi relations are obtained, and the boundary term that has to be subtracted in the gravitational action is easily deduced. Then, these relations are applied to the so-called Arnowitt-Deser-Misner decomposition to describe the foliation of the spacetime onto hypersurfaces of constant time within these theories. Finally, the junction conditions are also obtained by using a decomposition in Gaussian normal coordinates, which coincide with the conditions deduced previously through different approaches.

In this study, a scalar field propagating in a higher-dimensional Reissner-Nordström-de Sitter black hole is investigated. Scalar fields are assumed to have nonminimal coupling to the brane or bulk scalar curvature. Five different definitions of black hole temperatures are discussed: temperature based on surface gravity, Bousso-Hawking temperature, and three effective temperatures. The greybody factors of minimally and nonminimally coupled scalar fields on the brane and in the bulk are examined under the effect of particle and spacetime properties. The energy emission spectra of black holes are determined at various temperatures for both the brane and bulk channels. The energy emission rates at the Bousso-Hawking temperature are found to be dominant over those at other temperatures. The energy emission curves are suppressed by the presence of coupling parameters. Finally, the bulk-over-brane emission ratios are calculated. Notably, bulk dominance becomes possible for a certain definition of the temperatures and regime of the cosmological constant.

We study the impact of cosmological scale modifications to general relativity on the dynamics of halos within voids by comparing N-body simulations incorporating Hu-Sawicki $f(R)$ gravity, with $|f_{R0}|={10}^{-6}$ and ${10}^{-5}$, to those of $\mathrm{\Lambda }\mathrm{CDM}$. By examining the radial velocity statistics within voids classified based on their size and density-profile, as “rising” ($R$-type) or “shell” ($S$-type), we find that halo motions in small $R$-type voids, with effective radius $<15\mathrm{Mpc}/h$, reveal distinctive differences between $f(R)$ and $\mathrm{\Lambda }\mathrm{CDM}$ cosmologies. To understand this observed effect, we study the linear and nonlinear fifth forces, and develop an iterative algorithm to accurately solve the nonlinear fifth force equation. We use this to characterize the Chameleon screening mechanism in voids and contrast the behavior with that observed in gravitationally collapsed objects. The force analysis underscores how smaller $R$-type voids exhibit the highest ratios of fifth force to Newtonian force, which source distinguishable differences in the velocity profiles and thereby provide rich environments in which to constrain gravity.

For photon virtualities of $Q^2\gtrsim 20{\mathrm{GeV}}^2$, the results of the (hard Pomeron) fit in the tensor-Pomeron model in terms of the variables, $Q^2$, and the virtual-photon-proton energy squared, $W^2$, provide empirical evidence for the validity of the color dipole picture (CDP). Consistency of the CDP with the perturbative QCD (pQCD) improved parton model implies the prediction of $C_2={\epsilon }_0\cong 0.30$ for the exponent $C_2$ of the energy-squared dependence in agreement with the results of the fits. For $Q^2\lesssim 20G{\mathrm{eV}}^2$, the CDP yields a parameter-free smooth transition from $Q^2\gtrsim 20{\mathrm{GeV}}^2$ to $Q^2=0$ photoproduction, in distinction from the tensor-Pomeron model that relies on the additional parameter quantifying the intercept of the soft-Pomeron trajectory.

We derive simple relations which express 2D light front force distributions in terms of 3D Breit frame pressure and shear force distributions. Mathematically the relations correspond to invertible Abel transformation and they establish one-to-one mathematical equivalence of 3D Breit frame force distributions and 2D light front ones. The beauty and simplicity of the Abel transformations allow us to derive a number of new relations for light front force distributions. Any knowledge (model calculation, experimental measurement, etc.) about pressure and shear force distributions in Breit frame can be unambiguously transformed into light front force distributions with the help of Abel transformation. Due to the positivity property of the Abel transformation we obtain an important result—the 2D local stability conditions are satisfied automatically if the corresponding 3D stability conditions are fulfilled. In this way we established not only mathematical equivalence of 2D and 3D forces distributions but also their physics equivalence in terms of stability. As an illustration of how the relations work, we calculated the light front force distributions for a large nucleus as a liquid drop, and for large $N_c$ nucleon as a chiral soliton.

We measure the inclusive semielectronic decay branching fraction of the $D_s^{+}$ meson. A double-tag technique is applied to $e^{+}{e}^{-}$ annihilation data collected by the BESIII experiment at the BEPCII collider, operating in the center-of-mass energy range 4.178–4.230 GeV. We select positrons from $D_s^{+}\to X{e}^{+}{\nu }_e$ with momenta greater than $200\mathrm{MeV}/c$ and determine the laboratory momentum spectrum, accounting for the effects of detector efficiency and resolution. The total positron yield and semielectronic branching fraction are determined by extrapolating this spectrum below the momentum cutoff. We measure the $D_s^{+}$ semielectronic branching fraction to be $(6.30\pm 0.13(\mathrm{stat}.)\pm 0.09(\mathrm{syst}.)\pm 0.04(\mathrm{ext}.))\%$, showing no evidence for unobserved exclusive semielectronic modes. We combine this result with external data taken from literature to determine the ratio of the $D_s^{+}$ and $D^0$ semielectronic widths, $\frac{\mathrm{\Gamma }(D_s^{+}\to X{e}^{+}{\nu }_e)}{\mathrm{\Gamma }(D^0\to X{e}^{+}{\nu }_e)}=0.790\pm 0.016(\mathrm{stat}.)\pm 0.011(\mathrm{syst}.)\pm 0.016(\mathrm{ext}.)$. Our results are consistent with and more precise than previous measurements.

The first law for entanglement entropy in CFT in an odd-dimensional asymptotically AdS black hole is studied by using the $\mathrm{AdS}/\mathrm{CFT}$ duality. The entropy of CFT considered here is due to the entanglement between two subsystems separated by the horizon of the AdS black hole, which itself is realized as the conformal boundary of a black droplet in even-dimensional global AdS bulk spacetime. In ($2+1$)-dimensional CFT, the first law is shown to be always satisfied by analyzing a class of metric perturbations of the exact solution of a 4-dimensional black droplet. In ($4+1$)-dimensions, the first law for CFT is shown to hold under the Neumann boundary condition at a certain bulk hypersurface anchored to the conformal boundary of the boundary AdS black hole. From the boundary view point, this Neumann condition yields there being no energy flux across the boundary of the boundary AdS black hole. Furthermore, the asymptotic geometry of a 6-dimensional small AdS black droplet is constructed as the gravity dual of our ($4+1$)-dimensional CFT, which exhibits a negative energy near the spatial infinity, as expected from vacuum polarization.

For a general renormalizable $\mathcal{N}=1$ supersymmetric gauge theory with a simple gauge group we verify the ultraviolet (UV) finiteness of the two-loop matter contribution to the triple gauge-ghost vertices. These vertices have one leg of the quantum gauge superfield and two legs corresponding to the Faddeev–Popov ghost and antighost. By an explicit calculation made with the help of the higher covariant derivative regularization we demonstrate that the sum of the corresponding two-loop supergraphs containing a matter loop is not UV divergent in the case of using a general $\xi$-gauge. In the considered approximation this result confirms the recently proved theorem that the triple gauge-ghost vertices are UV finite in all orders, which is an important ingredient of the all-loop perturbative derivation of the Novikov-Shifman-Vainshtein-Zakharov relation.

We present a new method of measuring the mass density along the line of sight, based on precise measurements of the variations of the times of arrival (TOAs) of electromagnetic signals propagating between two distant regions of spacetime. The TOA variations are measured between a number of slightly displaced pairs of points from the two regions. These variations are due to the nonrelativistic geometric effects (Rømer delays and finite distance effects) as well as the gravitational effects in the light propagation (gravitational ray bending and Shapiro delays). We show that from a sufficiently broad sample of TOA measurements we can determine two scalars quantifying the impact of the spacetime curvature on the light propagation, directly related to the first two moments of the mass density distribution along the line of sight. The values of the scalars are independent of the angular positions or the states of motion of the two clock ensembles we use for the measurement and free from any influence of masses off the line of sight. These properties can make the mass density measurements very robust. The downside of the method is the need for extremely precise signal timing.

We have recently derived a manifestly covariant evolution law, under the geometrical optics (or eikonal) approximation of the vacuum Maxwell equations, for the electric field along null geodesics in a general spacetime, relative to an arbitrary set of instantaneous observers [Phys. Rev. D 101, 081501(R) (2020)]. As one of its applications, we derive here the final detected intensity signal arising from a prototypical laser interferometric gravitational-wave (GW) Michelson-Morley detector, comoving with transverse-traceless (TT) observers, valid for both long and short GW wavelengths (as compared to the lengths of the interferometers arms). The motion of the test particles and light is described through the covariant kinematic and optical parameters. One of our main results is the presentation of the integrated null geodesic parametric equations exchanged between two TT observers in terms of explicitly observable quantities (laser initial frequency and positions of the observers) and the profile of the plane GW packet. This allows us to revisit the derivation of the consequential radar distance and Doppler shift, taking the opportunity to discuss some related subtle conceptual issues and how they might affect the interferometric process. Another achievement is the calculation of the electric field in each arm up to the detection event, for any relative orientations of the arms and the GW direction. The main quantitative result is the new expression for the final interference pattern, for normal GW incidence, which turns out to have three contributions: (i) the well-known traditional one due to the difference in optical paths, and two new ones due to (ii) the Doppler effect and (iii) the divergence of the laser beams. The quantitative relevance of the last two contributions is compared to the traditional one and shown to be negligible within the geometrical optics regime of light. Although in general further contributions from the nonparallel transport of the polarization vector are expected [cf. Phys. Rev. D 101, 081501(R) (2020)], again in the case of GW normal incidence, such a vector is indeed parallel transported, and those contributions are absent.

The space-based gravitational wave detector Laser Interferometric Space Antenna is expected to observe signals from a large population of compact object binaries, comprised predominantly of white dwarfs, in the Milky Way. Resolving individual sources from this population against its self-generated confusion noise poses a major data analysis problem. We present an iterative source estimation and subtraction method to address this problem based on the use of particle swarm optimization (PSO). In addition to PSO, a novel feature of the method is the cross-validation of sources estimated from the same data using different signal parameter search ranges. This is found to greatly reduce contamination by spurious sources and may prove to be a useful addition to any multisource resolution method. Applied to a recent mock data challenge, the method is able to find $O({10}^4)$ Galactic binaries across a signal frequency range of [0.1, 15] mHz and, for frequency $\gtrsim 4\mathrm{mHz}$, reduces the residual data after subtracting out estimated signals to the instrumental noise level.