We present a rapid parameter estimation framework for compact binary coalescence (CBC) signals observed by the LIGO-Virgo-KAGRA (LVK) detector network. The goal of our framework is to enable optimal source localization of binary neutron star (BNS) signals in low latency as well as improve the overall scalability of full CBC parameter estimation analyses. Our framework is based on the reduced order quadrature (ROQ) technique and resolves its shortcomings by utilizing multiple ROQ bases in a single parameter estimation run. We have also developed sets of compact ROQ bases for various waveform models, IMRPhenomD, IMRPhenomPv2, IMRPhenomPv2_NRTidalv2, and IMRPhenomXPHM. We benchmark our framework with hundreds of simulated observations of BNS signals by the LIGO-Virgo detector network and demonstrate that it provides accurate and unbiased estimates on BNS source location, with a median analysis time of 6 min. The median searched area is reduced by around 30% compared to estimates produced by BAYESTAR: from $21.8{\mathrm{deg}}^2$ to $16.6{\mathrm{deg}}^2$. Our framework also enables detailed parameter estimation taking into account gravitational-wave higher multipole moments, the tidal deformation of colliding objects, and detector calibration errors of amplitude and phase with the timescale of hours. Our rapid parameter estimation technique has been implemented in one of the LVK parameter estimation engines, BILBY, and is being employed by the automated parameter estimation analysis of the LVK alert system.

GW190521, the most massive binary black hole merger confidently detected by the LIGO-Virgo-KAGRA Collaboration, is the first gravitational-wave observation of an intermediate-mass black hole. The signal was followed approximately 34 days later by flare ZTF19abanrhr, detected in AGN $\mathrm{J}124942.3+344929$ by the Zwicky Transient Facility at the 78% spatial contour for GW190521’s sky localization. Using the GWTC-2.1 data release, we find that the association between GW190521 and flare ZTF19abanrhr as its electromagnetic counterpart is preferred over a random coincidence of the two transients with a log Bayes’ factor of 8.6, corresponding to an odds ratio of $\sim 5400:1$ for equal prior odds and $\sim 400:1$ assuming an astrophysical prior odds of $1/13$. Given the association, the multimessenger signal allows for an estimation of the Hubble constant, finding $H_0=102_{-25}^{+27}\mathrm{km}{\mathrm{s}}^{-1}{\mathrm{Mpc}}^{-1}$ when solely analyzing GW190521 and ${79.2}_{-9.6}^{+17.6}\mathrm{km}{\mathrm{s}}^{-1}{\mathrm{Mpc}}^{-1}$ assuming prior information from the binary neutron star merger GW170817, both consistent with the existing literature.

Two of the conditions that have been suggested to determine the lower boundary of the conformal window in asymptotically free gauge theories are the linear condition, ${\gamma }_{\overline{\psi }\psi ,\mathrm{IR}}=1$, and the quadratic condition, ${\gamma }_{\overline{\psi }\psi ,\mathrm{IR}}(2-{\gamma }_{\overline{\psi }\psi ,\mathrm{IR}})=1$, where ${\gamma }_{\overline{\psi }\psi ,\mathrm{IR}}$ is the anomalous dimension of the operator $\overline{\psi }\psi$ at an infrared fixed point in a theory. We compare these conditions as applied to an $\mathcal{N}=1$ supersymmetric gauge theory with gauge group $G$ and $N_f$ pairs of massless chiral superfields $\mathrm{\Phi }$ and $\tilde{\mathrm{\Phi }}$ transforming according to the respective representations $\mathcal{R}$ and $\overline{\mathcal{R}}$ of $G$. We use the fact that ${\gamma }_{\overline{\psi }\psi ,\mathrm{IR}}$ and the value $N_f=N_{f,\text{cr}}$ at the lower boundary of the conformal window are both known exactly for this theory. In contrast to the case with a nonsupersymmetric gauge theory, here we find that in higher-order calculations, the linear condition provides a more accurate determination of $N_{f,\text{cr}}$ than the quadratic condition when both are calculated to the same finite order of truncation in a scheme-independent expansion.

A modified neutrino sector could imprint a signature on precision measurements of the quark sector because many such measurements rely on the semileptonic decays of the charged currents. Currently, global fits of the determinations of the Cabibbo-Kobayashi-Maskawa (CKM) matrix elements point to a $3\sigma$-level deficit in the first-row CKM unitarity test, commonly referred to as the Cabibbo-angle anomaly. We find that a MeV sterile neutrino that mixes with the electron-type neutrino increases the extracted $|V_{ud}|$, accommodating the Cabibbo-angle anomaly. This MeV sterile neutrino affects the superallowed nuclear $\beta$ decays and neutron decay, but it barely modifies the other measurements of the CKM elements. While various constraints may apply to such a sterile neutrino, we present viable scenarios within an extension of the inverse seesaw model.

We show that bottom-strange production at a high-energy muon collider, ${\mu }^{+}{\mu }^{-}\to bs$, is a sensitive probe of new physics. We consider the full set of four-fermion contact interactions that contribute to this process at dimension 6, and discuss the complementarity of a muon collider and of the study of rare $B$ meson decays that also probe said new physics. If a signal were to be found at a muon collider, the forward-backward asymmetry of the $b$-jet provides diagnostics about the underlying chirality structure of the new physics. In the absence of a signal at a center of mass energy of 10 TeV, ${\mu }^{+}{\mu }^{-}\to bs$ can indirectly probe new physics at scales close to 100 TeV. We also discuss the impact that beam polarization has on the muon collider sensitivity performance.

We consider a ($2+1$)-dimensional modified electrodynamics endowed with terms that are either Lorentz invariant or Lorentz violating and involve an ever-increasing number of derivatives. Our construction relies on $U(1)$ gauge invariance, and the Abelian Chern-Simons term poses the starting point. The structure of the nonminimal Standard-Model Extension (SME) in ($3+1$) spacetime dimensions serves as an inspiration for our pursuit. For elaborate studies and applications we particularly focus on the second term of the operator series in the general framework, which is the first contribution with additional derivatives. The latter forms the essential ingredient for several models of modified planar electrodynamics to be examined. The propagators of the models constitute the foundation for us deriving the physical propagating modes as well as for drawing conclusions on unitarity in the quantum regime. We are also interested in identifying parameter regions of sub- and superluminal mode propagation and determining classical solutions of the field equations for the planar models introduced. Moreover, a duality between an extended Chern-Simons theory and a subset of the fermion sector coefficients in the nonminimal SME is pointed out as well. Finally, the integer quantum Hall effect is chosen as a test bed to demonstrate the applicability of our findings to real physical systems. Predictions on momentum- and direction-dependent corrections of the Hall resistivity are made at the level of effective field theory, which could be tested in experiments. Thus, the ($2+1$)-dimensional models proposed are potentially applicable to model electromagnetic phenomena in certain planar condensed-matter systems.

In the last decades, the Standard Model (SM) of particle physics has been extensively tested and confirmed, with the announced discovery of the Higgs boson in 2012 being the last missing puzzle piece. Even though since then the search for new particles and interactions has been further intensified, the experiments ATLAS and CMS at the Large Hadron Collider (LHC) at CERN did not find evidence for the direct production of a new state. However, in recent years, deviations between LHC data and SM predictions in multiple observables involving two or more leptons (electrons or muons) have emerged, the so-called “multilepton anomalies,” pointing towards the existence of a beyond the SM Higgs boson $S$. While from these measurements its mass cannot be exactly determined, it is estimated to lay in the range between 130 and 160 GeV. Motivated by this observation, we perform a search for signatures of $S$, by using existing CMS and ATLAS analyses. Combining channels involving the associate productions of SM gauge bosons ($\gamma \gamma$ and $Z\gamma$), we find that a simplified model with a new scalar with $m_S=151.5\mathrm{GeV}$ is preferred over the SM hypothesis by $4.3\sigma$ ($3.9\sigma$) locally (globally). On the face of it, this provides a good indication for the existence of a new scalar resonance $S$ decaying into photons, in association with missing energy, and allows for a connection to the long-standing problem of dark matter. Furthermore, because $S$ is always produced together with other particles, we postulate the existence of a second new (heavier) Higgs boson $H$ that decays into $S$ and propose novel searches to discover this particle, which can be performed by ATLAS and CMS.

In this study, we introduce a transformative, automated framework for classifying basis invariants in generic field theories. Utilizing a novel ring-diagram methodology accompanied by the well-known Cayley-Hamilton theorem, our approach uniquely enables the identification of basic invariants and their $CP$-property characterization. Critically, our framework also unveils previously concealed attributes of established techniques reliant on the Hilbert-Poincaré series and its associated Plethystic logarithm. This paradigm shift has broad implications for the deeper understanding and more accurate classification of $CP$ invariants in generic field theories.

We compute the low-lying spectrum of 4D SU(2) Yang-Mills in a finite volume using quantum simulations. In contrast to small-volume lattice truncations of the Hilbert space, we employ toroidal dimensional reduction to the “femtouniverse” matrix quantum mechanics model. In this limit the theory is equivalent to the quantum mechanics of three interacting particles moving inside a 3-ball with certain boundary conditions. We use the variational quantum eigensolver and quantum subspace expansion techniques to compute the string tension to glueball mass ratio near the small/large-volume transition point, finding qualitatively good agreement with large volume Euclidean lattice simulations.

Recently, a variety of quantum algorithms have been devised to estimate thermal averages on a genuine quantum processor. In this paper, we consider the practical implementation of the so-called Quantum-Quantum Metropolis Algorithm. As a test bed for this purpose, we simulate a basic system of three frustrated quantum spins and discuss its systematics, also in comparison with the Quantum Metropolis Sampling algorithm.

In the context of $N=1$ four-dimensional type-IIB supergravity theories, the $U$-dual completion arguments suggest including four $S$-dual pairs of fluxes in the holomorphic superpotential, namely the so-called $(F,H),(Q,P),(P^{\prime },Q^{\prime })$, and $(H^{\prime },F^{\prime })$. These can generically induce cubic polynomials for the complex-structure moduli as well as the Kähler moduli in the flux superpotential. In this article, we explore the insights of the four-dimensional nongeometric scalar potential in the presence of such generalized $U$-dual fluxes by considering an explicit type-IIB toroidal compactification model based on an orientifold of ${\mathbb{T}}^6/({\mathbb{Z}}_2\times {\mathbb{Z}}_2)$ orbifold. First, we observe that the flux superpotential induces a huge scalar potential having a total of 76,276 terms involving 128 flux parameters and 14 real scalars. Subsequently, we invoke a new set of (the so-called) “axionic fluxes” comprising of combinations of the standard fluxes and the RR axions, and it turns out that these axionic fluxes can be very useful in rewriting the scalar potential in a relatively compact form. In this regard, using the metric of the compactifying toroidal sixfold, we present a new formulation of the effective scalar potential, which might be useful for understanding the higher-dimensional origin of the various pieces via the so-called “dimensional-oxidation” process. We also discuss the generalized Bianchi identities and the tadpole cancellation conditions, which can be important while seeking the physical anti–de Sitter/de Sitter vacua in such models.

The fluid-gravity correspondence is a duality between anti–de Sitter Einstein gravity and a relativistic fluid living at the conformal boundary. We show that one can accommodate the causal first-order viscous hydrodynamics recently developed by Bemfica, Disconzi, Noronha, and Kovtun in this framework, by requiring a set of natural conditions for the geometric data at the horizon. The latter hosts an induced Carrollian fluid, whose equations of motion are shown to be tightly tied to the ones describing the fluid at the boundary. Functional expressions for the transport coefficients are found—with those associated to viscosity and heat flux uniquely determined—satisfying a set of known causality requirements for the underlying equations of motion.

It has been proposed that quantum complexity is dual to the volume of the extremal surface, the action of the Wheeler-DeWitt patch, and the spacetime volume of the patch. Recently, a generalized volume-complexity observable was formulated as an equivalently good candidate for the dual holographic complexity. This proposal is abbreviated as “$\text{complexity}=\text{anything}$.” This proposal offers greater flexibility in selecting extremal surfaces and evaluating physical quantities, e.g., volume or action, on these surfaces. In this study, we explore the $\text{complexity}=\text{anything}$ proposal for Gauss-Bonnet black holes in asymptotic anti–de Sitter space in various dimensions. We demonstrate that this proposal guarantees the linear growth of the generalized volume at late times, regardless of the coupling parameters for four-dimensional Gauss-Bonnet gravity. However, this universality does not hold for higher dimensions. Moreover, discontinuous deformations of the extremal surfaces emerge when multiple peaks exist in the effective potential, which is reminiscent of a phase transition. Additionally, we present constraints on the coupling parameters of five-dimensional models in order for the generalized volume to be a viable candidate for holographic complexity.

Hawking radiation is the proposed thermal black-body radiation of quantum nature emitted from a black hole. One common way to give an account of Hawking radiation is to consider a detector that follows a static trajectory in the vicinity of a black hole and interacts with the quantum field of the radiation. In the present work, we study the Hawking radiation perceived by a detector that follows a quantum superposition of static trajectories in Schwarzschild spacetime, instead of a unique well-defined trajectory. We analyze the quantum state of the detector after the interaction with a massless real scalar field. We find that for certain trajectories and excitation levels, there are nonvanishing coherences in the final state of the detector. We then examine the dependence of these coherences on the trajectories followed by the detector and relate them to the distinguishability of the different possible states in which the field is left after the excitation of the detector. We interpret our results in terms of the spatial distribution and propagation of particles of the quantum field.

This paper explores a complete representation of the Vaidya model, a radial flux of radiation in the eikonal approximation, used for modeling various phenomena in both classical and semiclassical general relativity and astrophysics. The majority of the applications of the Vaidya model have been formulated in an incomplete representation. A complete representation is obtained here by direct integration of the Einstein field equations. We present the methodology to obtain this complete representation, and its utility in the modeling of general relativistic phenomena.

Orbital eccentricity is a crucial physical effect to unveil the origin of compact-object binaries detected by ground- and spaced-based gravitational-wave (GW) observatories. Here, we perform for the first time a Bayesian inference study of inspiral-merger-ringdown eccentric waveforms for binary black holes with nonprecessing spins using two (instead of one) eccentric parameters: eccentricity and relativistic anomaly. We employ for our study the multipolar effective-one-body (EOB) waveform model SEOBNRv4EHM, and use initial conditions such that the eccentric parameters are specified at an orbit-averaged frequency. We show that this new parametrization of the initial conditions leads to a more efficient sampling of the parameter space. We also assess the impact of the relativistic-anomaly parameter by performing mock-signal injections, and we show that neglecting such a parameter can lead to significant biases in several binary parameters. We validate our model with mock-signal injections based on numerical-relativity waveforms, and we demonstrate the ability of the model to accurately recover the injected parameters. Finally, using standard stochastic samplers employed by the LIGO-Virgo-KAGRA Collaboration, we analyze a set of real GW signals observed by the LIGO-Virgo detectors during the first and third runs. We do not find clear evidence of eccentricity in the signals analyzed, more specifically we measure $e_{\mathrm{gw},10\mathrm{Hz}}^{\mathrm{GW}150914}=0.08_{-0.06}^{+0.09}$, $e_{\mathrm{gw},20\mathrm{Hz}}^{\mathrm{GW}151226}={0.04}_{-0.04}^{+0.05}$, and $e_{\mathrm{gw},5.5\mathrm{Hz}}^{\mathrm{GW}190521}=0.15_{-0.12}^{+0.12}$.

When particle dark matter is bound gravitationally around a massive black hole in sufficiently high densities, the dark matter will affect the rate of inspiral of a secondary compact object that forms a binary with the massive black hole. In this paper, we revisit previous estimates of the impact of dark-matter accretion by black-hole secondaries on the emitted gravitational waves. We identify a region of parameter space of binaries for which estimates of the accretion were too large (specifically, because the dark-matter distribution was assumed to be unchanging throughout the process, and the secondary black hole accreted more mass in dark matter than that enclosed within the orbit of the secondary). To restore consistency in these scenarios, we propose and implement a method to remove dark-matter particles from the distribution function when they are accreted by the secondary. This new feedback procedure then satisfies mass conservation, and when evolved with physically reasonable initial data, the mass accreted by the secondary no longer exceeds the mass enclosed within its orbital radius. Comparing the simulations with accretion feedback to those without this feedback, including feedback leads to a smaller gravitational-wave dephasing from binaries in which only the effects of dynamical friction are being modeled. Nevertheless, the dephasing can be hundreds to almost a thousand gravitational-wave cycles, an amount that should allow the effects of accretion to be inferred from gravitational-wave measurements of these systems.

Hierarchical mergers in a dense environment are one of the primary formation channels of the intermediate-mass black hole (IMBH) binary system. We expect that the resulting massive binary system will exhibit mass asymmetry. The emitted gravitational wave (GW) carries significant contributions from higher-order modes and hence complex waveform morphology due to the superposition of different modes. Further, IMBH binaries exhibit lower merger frequency and shorter signal duration in the LIGO detector, increasing the risk of them being misclassified as short-duration noisy glitches. Deep learning algorithms can be trained to discriminate noisy glitches from short GW transients. We present thames—a deep-learning-based end-to-end signal-detection algorithm for GW signals from quasicircular nearly edge-on, mass asymmetric IMBH binaries in advanced GW detectors. Our study shows that it outperforms matched-filter based pycbc searches for higher mass asymmetric, nearly edge-on IMBH binaries. The maximum gain in the sensitive volume-time product for mass ratio $q\in (5,10)$ is by a factor of 5.24 (2.92) against the pycbc-imbh (pycbc-hm) search at a false alarm rate of 1 in 100 years. Compared to the broad pycbc search, this factor is $\sim 100$ for the $q\in (10,18)$. One of the reasons for this leap in volumetric sensitivity is its ability to discriminate between signals with complex waveform morphology and noisy transients, clearly demonstrating the potential of deep learning algorithms in probing complex signal morphology in the field of gravitational-wave astronomy. With the current training set, thames slightly underperforms with respect to pycbc-based searches targeting intermediate-mass black hole binaries with mass ratio $q\in (5,10)$ and detector frame total mass $M_T(1+z)\in (100,200)M_{\odot }$. Because of the independent nature of the search, thames offers a follow-up targeted method for asymmetric IMBH systems with higher inclination. This can help verify and potentially enhance the event’s statistical significance.

This study investigates the antineutrinos production by $\beta$-decay of $r$-process nuclei in two astrophysical sites that are capable of producing gamma-ray bursts (GRBs): binary neutron star mergers (BNSMs) and collapsars, which are promising sites for heavy element nucleosynthesis. We employ a simplified method to compute the $\beta$-decay ${\overline{\nu }}_e$ energy spectrum and consider a number of different representative thermodynamic trajectories for $r$-process simulations, each with four sets of $Y_e$ distribution. The time evolution of the ${\overline{\nu }}_e$ spectrum is derived for both the dynamical ejecta and the disk wind for BNSMs and collapsar outflow, based on approximated mass outflow rates. Our results show that the ${\overline{\nu }}_e$ has an average energy of approximately 3 to 9 MeV, with a high energy tail of up to 20 MeV. The ${\overline{\nu }}_e$ flux evolution is primarily determined by the outflow duration, and can thus remain large for $\mathcal{O}(10)\mathrm{s}$ and $\mathcal{O}(100)\mathrm{s}$ for BNSMs and collapsars, respectively. For a single merger or collapsar at 40 Mpc, the ${\overline{\nu }}_e$ flux is $\mathcal{O}(10-100){\mathrm{cm}}^{-2}{\mathrm{s}}^{-1}$, indicating a possible detection horizon up to 0.1–1 Mpc for Hyper-Kamiokande. We also estimate their contributions to the diffuse ${\overline{\nu }}_e$ background, and find that both sources should only contribute subdominantly to the diffuse background when compared to that expected from core-collapse supernovae.

Narrow Fe $\mathrm{K}\alpha$ fluorescent emission lines arising at $\sim \mathrm{kpc}\text{−}\mathrm{scale}$ separations from the nucleus have only been detected in a few active galactic nuclei (AGN). The detections require that the extended line emission be spatially resolved and sufficiently bright. Compared to narrow Fe $\mathrm{K}\alpha$ lines arising closer to the nucleus, they have much lower fluxes but show substantially larger equivalent widths, ${\mathrm{EW}}_{\mathrm{FeK}\alpha }$. We show that, in the optically thin limit, a purely analytical argument naturally predicts large, ${\mathrm{EW}}_{\mathrm{FeK}\alpha }\sim 1\mathrm{keV}$, values for such lines, regardless of the details of equivalent hydrogen column density, $N_{\mathrm{H}}$, or reprocessor geometry. Monte Carlo simulations corroborate this result and show that the simple analytic ${\mathrm{EW}}_{\mathrm{FeK}\alpha }$ prescription holds up to higher $N_{\mathrm{H}}$ approaching the Compton-thick regime. We compare to Chandra observations from the literature and discuss that our results are consistent with the large ${\mathrm{EW}}_{\mathrm{FeK}\alpha }$ values reported for local AGN, for which the line is detected in extended, up to $\sim \mathrm{kpc}\text{−}\mathrm{scale}$, regions. We argue that large ${\mathrm{EW}}_{\mathrm{FeK}\alpha }$ from kpc-scale regions in AGN should be ubiquitous, because they do not depend on the absolute luminosity of the central x-ray source, and are measured only against the scattered continuum. We predict values to be of the order of $\sim 1\mathrm{keV}$ or larger, even for covering factors $\ll 1$, and for arbitrarily small column densities. We propose that the large-scale molecular material that is now routinely being detected with the Atacama Large Millimeter/Submillimeter Array (ALMA) may act as an extended x-ray scattering reprocessor giving rise to $\sim \mathrm{kpc}\text{−}\mathrm{scale}$ Fe $\mathrm{K}\alpha$ emission.