We study the asymptotically flat spacetime in Chern-Simons modified gravity and then gravitational memory effects are considered in this work. If the Chern-Simons scalar does not directly couple with the ordinary matter fields, there are also displacement, spin, and center-of-mass memory effects as in general relativity. This is because the term of the action that violates the parity invariance is linear in the scalar field but quadratic in the curvature tensor. This results in the parity violation occurring at the higher orders in the inverse luminosity radius. Although there exists the Chern-Simons scalar field, interferometers, pulsar timing arrays, and the Gaia mission are incapable of detecting its polarization, so the scalar field does not induce any new memory effects that can be detected by interferometers or pulsar timing arrays. The asymptotic symmetry group is also the extended Bondi-Metzner-Sachs group. The constraints on the memory effects excited by the tensor modes are obtained as well.

We present a deep-learning artificial intelligence model (AI) that is capable of learning and forecasting the late-inspiral, merger and ringdown of numerical relativity waveforms that describe quasicircular, spinning, nonprecessing binary black hole mergers. We used theNRHybSur3dq8 surrogate model to produce train, validation and test sets of $\ell =|m|=2$ waveforms that cover the parameter space of binary black hole mergers with mass ratios $q\le 8$ and individual spins $|s_{\{1,2\}}^z|\le 0.8$. These waveforms cover the time range $t\in [-5000\mathrm{M},130\mathrm{M}]$, where $t=0M$ marks the merger event, defined as the maximum value of the waveform amplitude. We harnessed the ThetaGPU supercomputer at the Argonne Leadership Computing Facility to train our AI model using a training set of 1.5 million waveforms. We used 16 NVIDIA DGX A100 nodes, each consisting of 8 NVIDIA A100 Tensor Core GPUs and 2 AMD Rome CPUs, to fully train our model within 3.5 h. Our findings show that artificial intelligence can accurately forecast the dynamical evolution of numerical relativity waveforms in the time range $t\in [-100\mathrm{M},130\mathrm{M}]$. Sampling a test set of 190,000 waveforms, we find that the average overlap between target and predicted waveforms is $\gtrsim 99\%$ over the entire parameter space under consideration. We also combined scientific visualization and accelerated computing to identify what components of our model take in knowledge from the early and late-time waveform evolution to accurately forecast the latter part of numerical relativity waveforms. This work aims to accelerate the creation of scalable, computationally efficient and interpretable artificial intelligence models for gravitational wave astrophysics.

This paper presents the Summed Parallel Infinite Impulse Response (SPIIR) pipeline used for public alerts during the third advanced LIGO and Virgo observation run (O3 run). The SPIIR pipeline uses infinite impulse response (IIR) filters to perform extremely low-latency matched filtering and this process is further accelerated with graphics processing units (GPUs). It is the first online pipeline to select candidates from multiple detectors using a coherent statistic based on the maximum network likelihood ratio statistic principle. Here we simplify the derivation of this statistic using the singular-value-decomposition (SVD) technique and show that single-detector signal-to-noise ratios from matched filtering can be directly used to construct the statistic. Coherent searches are in general more computationally challenging than coincidence searches due to extra search over sky direction parameters. The search over sky directions follows an embarrassing parallelization paradigm and has been accelerated using GPUs. The detection performance is reported using a segment of public data from LIGO-Virgo’s second observation run. We demonstrate that the median latency of the SPIIR pipeline is less than 9 seconds, and present an achievable road map to reduce the latency to less than 5 seconds. During the O3 online run, SPIIR registered triggers associated with 38 of the 56 nonretracted public alerts. The extreme low-latency nature makes it a competitive choice for joint time-domain observations, and offers the tantalizing possibility of making public alerts prior to the merger phase of binary coalescence systems involving at least one neutron star.

We study gravitational lensing by a generic extended mass distribution. For that, we consider the diffraction of electromagnetic waves by an extended, weakly aspherical, gravitating object. We account for the static gravitational field of such a lens by representing its exterior potential in the most generic form, expressed via an infinite set of symmetric trace free (STF) tensor multipole mass moments. This yields the most general form of the gravitational phase shift, which allows for a comprehensive description of the optical properties of a generic gravitational lens. We found that at each order of the STF moments, the gravitational phase shift is characterized by only two parameters: a magnitude and a rotation angle that characterize the corresponding caustics, which form in the point spread function of the lens. Both of these parameters are uniquely expressed in terms of the transverse-trace free (TT) projections of the multipole moments on the lens plane. Not only does this result simplify the development of physically consistent models of realistic lenses, it also drastically reduces the number of required parameters in the ultimate model. To help with the interpretation of the results, we established the correspondence of the gravitational phase shift expressed via the TT-projected STF multipole mass moments and its representation via spherical harmonics. For axisymmetric mass distributions, the new results are consistent with those that we obtained in previous studies. For arbitrary mass distributions, our results are novel and offer new insight into gravitational lensing by realistic astrophysical systems. These findings are discussed in the context of ongoing astrophysical gravitational lensing investigations as well as observations that are planned with the solar gravitational lens.

It is shown here that symmetric-hyperbolicity, which guarantees well-posedness, leads to a set of two inequalities for matrices whose elements are determined by a given theory. As a part of the calculation, carried out in a mostly covariant formalism, the general form for the symmetrizer, valid for a general Lagrangian theory, was obtained. When applied to nonlinear electromagnetism linearly coupled to curvature, the inequalities lead to strong constraints on the relevant quantities, which were illustrated with applications to particular cases. The examples show that nonlinearity leads to constraints on the field intensities, and nonminimal coupling imposes restrictions on quantities associated to curvature.

We dynamically evolve for the first time dark matter admixed neutron stars with fermionic dark matter. These systems are mixtures of the ordinary nuclear matter of a neutron star and dark matter. To perform our dynamical evolutions, we derive the equations of motion, in conservation form, for spherically symmetric systems with an arbitrary number of perfect fluids. Using finite volume and high-resolution shock-capturing methods, we dynamically evolve the two-fluid case, with the first fluid modeling ordinary matter and the second fluid modeling dark matter. We use our dynamical solutions to study nonlinear stability, radial oscillation frequencies, and a dynamical formation process.

The LISA mission will likely be a signal dominated detector, such that one challenge is the separation of the different astrophysical sources, and to distinguish between them and the instrumental noise. One of the goals of LISA is to probe the early Universe by detecting stochastic gravitational wave (GW) backgrounds. As correlation with other detectors is uncertain for LISA, discriminating such a GW background from the instrumental noise requires a good estimate of the latter. To this purpose, we have revisited time delay interferometry (TDI) to look for new TDI signal combinations that fulfill the laser frequency noise suppression requirements. We illustrate that it is possible to do a linear combination of these TDI channels to find special null combinations that suppress GWs and mainly carry information about instrumental noise. We find that there exist many null combinations that show different sensitivities to GWs, some of which seem more suitable than the traditional T combination for estimating test-mass (TM) acceleration noise. In an idealized LISA configuration, they are all sensitive to a particular linear combination of the six TMs acceleration, similar to a rigid rotation of the LISA triangle. In the following article, we illustrate what are the noise properties that can be extracted by monitoring these interferometry signals and discuss the implication of these findings for the detection of stochastic GW backgrounds.

A relativistic mean-field hadronic model with a dark matter (DM) particle coupled to nucleons including short-range correlations (SRC) is applied to study neutron stars (NS). The lightest neutralino is chosen as the dark particle candidate, which interacts with nucleons by the exchange of Higgs bosons. A detailed thermodynamical analysis shows that the contribution of the DM fermions to the energy density of the matter composed by these particles and nucleons is completely dominated by the DM kinetic terms. The model reproduces satisfactorily the constraints on the mass-radius diagram obtained from the analysis of the combined data from the NICER mission, LIGO collaboration, and mass measurements from radio observations. We show that the SRC balance the reduction of the neutron star mass due to the DM component, and because of that the model is able to present more massive NS. We also present a study of the effect, in the NS mass-radius profiles, of the uncertainties in some bulk parameters related to the hadronic sector. We find that it is possible to generate parametrizations, with DM content, compatible with the recent astrophysical constraints and with the uncertainty in the symmetry energy slope obtained from the results reported by the updated lead radius experiment (PREX-2).

We examine the gravitational wave frequencies from neutron stars during thermal evolution, adopting the relativistic Cowling approximation. We particularly focus on the neutron star models, in which the direct Urca (rapid cooling process) does not work, without the superfluidity and superconductivity. For such models, the cooling curve barely depends on the equation of state (EOS) and mass of the neutron star, while we show that the gravitational wave frequencies strongly depend on the both properties. Then, we find that the frequencies of the fundamental and the first pressure modes multiplied with the stellar mass are well expressed as a function of the stellar compactness almost independently of the EOS. We also find that the frequency of the first gravity mode in the later phase of the thermal evolution is strongly correlated with the stellar compactness. In addition, we derive the empirical formula, estimating the threshold mass for the onset of the direct Urca inside the neutron star as a function of the nuclear saturation parameter. This formula will give us a constraint on the neutron star properties, if it is observationally found that the direct Urca occurs (or does not work) inside the neutron star.

Atom interferometry is a powerful experimental technique that can be employed to search for the oscillation of atomic transition energies induced by ultralight scalar dark matter (ULDM). Previous studies have focused on the sensitivity to ULDM of km-length atom gradiometers, where atom interferometers are located at the ends of very long baselines. In this work, we generalize the treatment of the time-dependent signal induced by a linearly-coupled scalar ULDM candidate for vertical atom gradiometers of any length and find correction factors that especially impact the ULDM signal in short-baseline gradiometer configurations. Using these results, we refine the sensitivity estimates in the limit where shot noise dominates for AION-10, a compact 10 m gradiometer that will be operated in Oxford, and discuss optimal experimental parameters that enhance the reach of searches for linearly-coupled scalar ULDM. After comparing the reach of devices operating in broadband and resonant modes, we show that well-designed compact atom gradiometers are able to explore regions of dark matter parameter space that are not yet constrained.

We study the sea quark contributions to the electromagnetic form factors of $\mathrm{\Sigma }$ baryons with nonlocal chiral effective theory. Both octet and decuplet intermediate states are included in the one loop calculation. $G_{{\mathrm{\Sigma }}^{-}}^u$ and $G_{{\mathrm{\Sigma }}^{+}}^d$ could be priority observables for the examination of sea quark contributions to the baryon structure because these quantities are much larger than the strange form factors of nucleons. It will be less difficult for the lattice simulation to determine the sign of these pure sea quark contributions unambiguously. In ${\mathrm{\Sigma }}^0$, the light sea quark form factors $G_{{\mathrm{\Sigma }}^0}^u$ and $G_{{\mathrm{\Sigma }}^0}^d$ are identical. Since the light sea quark form factors in protons are different, it will be more meaningful to compare the lattice result of the light sea quark form factors in ${\mathrm{\Sigma }}^0$ with that obtained from an effective field theory.

We evaluate dissipative effects for a system consisting of a massive Dirac field confined between two walls, one of them oscillating, in $1+1$ dimensions. In the model that we consider, a dimensionless parameter characterizing each wall is tuned so that bag-boundary conditions are attained for a particular value. We present explicit results for the probability of creating a fermion pair, and relate the total probability to the imaginary part of the effective action.

The free energy density of $\mathcal{N}=4$ supersymmetric Yang-Mills theory in four space-time dimensions is derived through second order in the ’t Hooft coupling $\lambda$ at finite temperature using effective-field theory methods. The contributions to the free energy density at this order come from the hard scale $T$ and the soft scale $\sqrt{\lambda }T$. The effects of the scale $T$ are encoded in the coefficients of an effective three-dimensional field theory that is obtained by dimensional reduction at finite temperature. The effects of the electric scale $\sqrt{\lambda }T$ are taken into account by perturbative calculations in the effective theory.

The vectorlike quarks are predicted in many new physics scenarios beyond the Standard Model (SM) and could be seen potential signatures of new physics at the TeV energy scale. In this work, we study single production of exotic singlet and doublet vectorlike bottom quarks (VLQ-$B$) at future Compact Linear Collider (CLIC) via the process $e^{+}{e}^{-}\to B\overline{b}$ with the decay channel $B\to bZ$ and two types of modes: $Z\to {\ell }^{+}{\ell }^{-}$ and $Z\to \nu \overline{\nu }$. We calculate the cross sections of signal and relevant SM backgrounds. After a fast simulation of the signal and background events, the exclusion limit at 95% confidence level and $5\sigma$ discovery prospects on the parameters (the coupling strength ${\kappa }_B$ and the VLQ-$B$ mass) have been, respectively, presented at the future CLIC with center of mass energy $\sqrt{s}=3\mathrm{TeV}$ and integrated luminosity of $5{\mathrm{ab}}^{-1}$.

In this work, we adopt the ${}^3{P}_0$ model to investigate the strong decays of the low-lying doubly bottom baryons in the $j-j$ coupling scheme systematically. In this scheme, we construct the formulism of the ${}^3{P}_0$ model under the spectator assumption, and then the heavy diquark symmetry is preserved automatically. Our results show that some of the $\lambda$-mode ${\mathrm{\Xi }}_{bb}(1P)$ and ${\mathrm{\Omega }}_{bb}(1P)$ states are narrow, which have good potentials to be observed by future experiments. For the low-lying $\rho$-mode and $\rho \text{−}\lambda$ hybrid states, the Okubo-Zweig-Iizuka-allowed strong decays are highly suppressed and they should be extremely narrow. Future experiments can test our phenomenological predictions at the quark level.

We study double-spin asymmetries in Drell-Yan processes in which one initial hadron is transversely polarized and another one is longitudinally polarized. The complete part of the hadronic tensor relevant to asymmetries is derived. This part consists of twist-2 and twist-3 parton distributions and is gauge invariant. We construct some observables which can be used to extract these parton distributions from experimental measurements.

We present the results that form the basis for calculations of the unpolarized gluon parton distributions (PDFs) using the pseudo-PDF approach. We give the results for the most complicated box diagram both for gluon bilocal operators with arbitrary indices and for combinations of indices corresponding to three matrix elements that are most convenient to extract the twist-2 invariant amplitude. We also present detailed results for the gluon-quark transition diagram. The additional results for the box diagram and the gluon-quark contribution may be used for extractions of the gluon PDF from different matrix elements, with a possible cross-check of the results obtained in this way.

Recently, the LHCb Collaboration announced the discovery of the $T_{cc}^{+}$ tetraquark. Being merely a few hundred keV below the $D^{*+}{D}^0$ threshold, the $T_{cc}^{+}$ is expected to have a molecular component, for which there is a good separation of scales that can be exploited to make reasonably accurate theoretical predictions about this tetraquark. Independently of its nature, the most important decay channels will be $D^{+}{D}^0{\pi }^0$, $D^0{D}^0{\pi }^{+}$, and $D^{+}{D}^0\gamma$. Its closeness to threshold suggests that the mass and particularly the width of the $T_{cc}^{+}$ tetraquark depend on the resonance profile. While the standard Breit-Wigner parametrization generates a $T_{cc}^{+}$ that is too broad for current theoretical calculations to reproduce, a three-body unitarized Breit-Wigner shape reveals instead a decay width (${\mathrm{\Gamma }}_{\mathrm{pole}}=48\pm 2_{-12}^{+0}\mathrm{keV}$) consistent with theoretical expectations. Here, we consider subleading-order contributions to the decay amplitude, which, though having at most a moderate impact in the width, still indicate potentially significant differences with the experimental width that can be exploited to disentangle the nature of the $T_{cc}^{+}$. Concrete calculations yield ${\mathrm{\Gamma }}^{\mathrm{LO}}=49\pm 16\mathrm{keV}$ and ${\mathrm{\Gamma }}^{\mathrm{NLO}}=58_{-6}^{+7}\mathrm{keV}$, though we expect further corrections to the next-to-leading-order (NLO) decay widths from asymptotic normalization effects. We find that a detailed comparison of the NLO total and partial decay widths with experiment suggests the existence of a small (but distinguishable from zero) nonmolecular component of the $T_{cc}^{+}$.

We present a model for the vector and axial form factors of the transitions ${\overline{B}}^0\to D^{**}$ in good agreement with the presently available data and based on the present theoretical knowledge, combining (a) the safe lattice QCD predictions at $m_Q=\infty$ and $w=1$; (b) the predictions at general $w$ of a relativistic, covariant quark model at $m_Q=\infty$, including the well-tested Godfrey and Isgur spectroscopic model and which agrees with lattice QCD at $w=1$; (c) the constraint of Bjorken and Neubert relating semileptonic and class I nonleptonic decays, which shows that ${\overline{B}}^0\to D_0(2300{)}^{+}{\pi }^{-}$ strongly constrains ${\tau }_{1/2}(w)$ to be much smaller than ${\tau }_{3/2}(w)$, in agreement with the theoretical expectation; and (d) the general HQET expansion which constrains the $1/m_Q$ corrections (cf. Leibovich et al. Phys. Rev. Lett. 78, 3995 (1997)., denoted hereafter as LLSW). An important element in the understanding of data is the large contribution of virtual $D_V^{(*)}$ to the broad structures seen in SL decays at low $D^{(*)}\pi$ masses—which makes it difficult to isolate the broad resonances denoted as $D_{1/2}$ in the following.

In this work, we calculate the branching ratios of the color-allowed two-body nonleptonic decays of the bottom baryons, which include the ${\mathrm{\Xi }}_b\to {\mathrm{\Xi }}_c^{(*)}$ and ${\mathrm{\Omega }}_b\to {\mathrm{\Omega }}_c^{(*)}$ weak transitions by emitting a pseudoscalar meson (${\pi }^{-}$, $K^{-}$, $D^{-}$, and $D_s^{-}$) or a vector meson (${\rho }^{-}$, $K^{*-}$, $D^{*-}$, and $D_s^{*-}$). For achieving this aim, we adopt the three-body light-front quark model with the support of hadron spectroscopy, where the spatial wave functions of these heavy baryons involved in these weak decays are obtained by a semirelativistic potential model associated with the Gaussian expansion method. Our results show that these decays with the ${\pi }^{-}$, ${\rho }^{-}$, and $D_s^{(*)-}$-emitted mode have considerable widths, which could be accessible at the ongoing LHCb and Belle II experiments.