The Electron-Ion Collider (EIC) is an upcoming accelerator facility aimed at exploring the properties of quarks and gluons in nucleons and nuclei, shedding light on their structure and dynamics. The inaugural experimental apparatus, ePIC (electron-Proton and Ion Collider), is designed as a general-purpose detector to address the National Academy of Sciences and the Nuclear Science Advisory Committee physics program at the EIC. The wider EIC community is strongly supporting a second interaction region and an associated second detector to enhance the full science program. In this study, we evaluate how this second interaction region and detector can be complementary to ePIC. The layout of an interaction region for the second detector offers a secondary focus that provides better forward detector acceptance at scattering angles near $\theta \sim 0\mathrm{mrad}$, which can specifically enhance the exclusive, tagging, and diffractive physics program. This article presents an analysis of a tagging program using the second interaction region layout with incoherent diffractive vector meson production. The current design of the second EIC interaction region is evaluated for its vetoing capabilities of incoherent events required for the study of coherent diffractive measurements. We find an increased vetoing performance compared to the ePIC interaction region, thus improving measurements which are important for the spatial imaging of nucleons and nuclei.

We explore the consequence of generalized symmetries in four-dimensional $\mathcal{N}=1$ superconformal field theories. First, we classify all possible supersymmetric gauge theories with a simple gauge group that have a nontrivial one-form symmetry and flows to a superconformal field theory. Upon identifying unbroken discrete zero-form symmetries from the Adler-Bell-Jackiw (ABJ) anomaly, we find that many of these theories have mixed zero-form or one-form ’t Hooft anomalies. Then we classify the relevant deformations of these SCFTs that preserve the anomaly. From this mixed anomaly together with the anomalies of the discrete zero-form symmetries, we find obstructions for the relevant deformations of these SCFTs to flow to a trivially gapped phase. We also study non-Lagrangian SCFTs formed by gauging copies of Argyres-Douglas theories and constrain their deformations. In particular, we explore a new duality between the diagonal gauging of two ${\mathcal{D}}_3(SU(N))$ theories and $SU(N)$ gauge theory with two adjoints. We also repeat our analysis for a host of nonsupersymmetric gauge theories having nontrivial one-form symmetry including examples that appear to flow to Bank-Zaks type CFTs.

Gravitational lensing of gravitational waves (GWs) provides a unique opportunity to study cosmology and astrophysics at multiple scales. Detecting microlensing signatures, in particular, requires efficient parameter estimation methods due to the high computational cost of traditional Bayesian inference. In this paper we explore the use of deep learning, namely conditional variational autoencoders (CVAE), to estimate parameters of microlensed binary black hole (simulated) waveforms. We find that our CVAE model yields accurate parameter estimation and significant computational savings compared to Bayesian methods such as bilby (up to five orders of magnitude faster inferences). Moreover, the incorporation of CVAE-generated priors into bilby, based on the 95% confidence intervals of the CVAE posterior for the lensing parameters, reduces bilby’s average runtime by around 48% without any penalty on accuracy. Our results suggest that a CVAE model is a promising tool for future low-latency searches of lensed signals. Further applications to actual signals and integration with advanced pipelines could help extend the capabilities of GW observatories in detecting microlensing events.

In this study, we investigate the inspiral dynamics of a stellar-mass object around a central black hole (BH) incorporating loop quantum gravity (LQG) effects. The BH spacetime is characterized by an LQG correction parameter $r_0$, which quantifies deviations from the classical Schwarzschild geometry. Our analysis reveals that LQG effects accelerate the orbital decay compared to the Schwarzschild scenario. Furthermore, we employ the fastemriwaveforms (few) package to generate gravitational waveforms and assess the Laser Interferometer Space Antenna’s capability to detect the LQG effect with faithfulness and the Fisher information matrix method. These results highlight the potential of space-based gravitational wave detectors to probe quantum gravity effects in astrophysical environments.

Stochastic gravitational-wave background (SGWB) is one of the major targets for contemporary gravitational wave (GW) observations, including pulsar timing array (PTA), ground-based laser interferometer (GbLI), and space-based laser interferometer (SbLI). The data analysis of SGWB involves cross-correlating the outputs of a pair of detectors to find the functional form of the correlations, which is referred to as the overlap reduction function (ORF). While conventional approaches employ detector-specific approximations for ORF calculations, in this paper, we present a universal formula to calculate the precise ORF for isotropic SGWB detection with PTA and laser interferometer detectors. Since no approximations are employed, the exact value of the ORF can be obtained for all three types of detectors.

The standard model extension (SME) is an effective field theory framework that can be used to study the possible violations of Lorentz symmetry and diffeomorphism invariance in the gravitational interaction. In this paper, we explore both the Lorentz- and diffeomorphism-violating effects on the propagations of gravitational waves in the SME’s linearized gravity. It is shown that the violations of Lorentz symmetry and diffeomorphism invariance modify the conventional linear dispersion relation of gravitational waves, leading to anisotropy, birefringence, and dispersion effects in the propagation of gravitational waves. With these modified dispersion relations, we then calculate the dephasing effects due to the Lorentz and diffeomorphism violations in the waveforms of gravitational waves produced by the coalescence of compact binaries. With the distorted waveforms, we perform full Bayesian inference with the help of the open source software bilby on the gravitational wave events of the compact binary mergers in the LIGO-Virgo-KAGRA catalogs GWTC-3. We consider the effects from the operators with the lowest mass dimension $d=2$ and $d=3$ due to the Lorentz and diffeomorphism violations in the linearized gravity. No signature of Lorentz and diffeomorphism violations arsing from the SME’s linearized gravity are found for most GW events, which allows us to give a 90% confidence interval for each Lorentz- and diffeomorphism-violating coefficient.

In this work, we present a study on cosmological constraints of dark energy (DE) parametrizations after the observations of Dark Energy Spectroscopic Instruments (DESI) for baryon acoustic oscillations (BAO) in 2024, suggesting potential deviations from the standard flat-$\mathrm{\Lambda }\mathrm{CDM}$ cosmology. This study aims to put observational constraints on equation of state (EoS) parametrizations beyond the standard $\mathrm{\Lambda }\mathrm{CDM}$ model using DESI BAO 2024 data, cosmic microwave background (CMB) anisotropy observations 2018, and various supernovae type Ia (SNIa) compilations: PantheonPlus, Union3, and Dark Energy Survey 5-year photometrically classified SNIa (DES-SN5YR). Our main goal is to validate the result of DESI Collaborations [, J. Cosmol. Astropart. Phys. 02 (2025) 021] in the context of some parametrizations beyond the Chevallier-Polarski-Linder (CPL) approximation known as Barboza-Alcaniz (BA) and Padé parametrizations. These investigations allow us to examine the potential biases in the results presented by DESI Collaborations with respect to CPL parametrization. By comparing our findings using BA and Padé parametrizations to the CPL case, we indicate that the deviation from $w_{\mathrm{\Lambda }}=-1.0$, observed in the CPL parametrization, is also evident in the BA and Padé parametrizations.

We explore the impact of dark matter annihilation on the 21-cm signal during the cosmic dawn and epoch of reionization (EoR). Using modified 21 cmfast simulations and convolutional neural networks (CNNs), we investigate how energy injected into the intergalactic medium (IGM) through dark matter annihilation affects the evolution of the 21-cm differential brightness temperature. Focusing on two annihilation channels, photon-photon ($\gamma \gamma$) and electron-positron ($e^{+}{e}^{-}$), we examine a broad range of dark matter masses and annihilation cross sections. Our results demonstrate that CNNs outperform traditional power spectrum analysis, partly because the input images retain more information than the power spectrum, but primarily because the ${\chi }^2$ minimization approach is suboptimal for distinguishing between dark matter models. We also demonstrate that the structure formation boost, driven by dark matter clumping into halos and subhalos, significantly enhances the annihilation signal and alters the thermal and ionization history of the IGM. This enhancement leads to a noticeable effect on the 21-cm signal, including a shift from absorption to emission as dark matter annihilation heats the IGM at lower redshifts. By incorporating observational noise from upcoming radio interferometers, particularly the Square Kilometer Array (SKA), we show that these effects remain detectable despite observational challenges. We find that the dark matter annihilation models can leave measurable imprints on the 21-cm signal distinguishable from the nonannihilation scenarios for the dark matter masses $m_{\mathrm{DM}}=100\mathrm{MeV}$ and the annihilation cross sections of $⟨\sigma v⟩\simeq {10}^{-31}{\mathrm{cm}}^3/\mathrm{s}(⟨\sigma v⟩\simeq {10}^{-32}{\mathrm{cm}}^3/\mathrm{s}$ for $m_{\mathrm{DM}}=1\mathrm{MeV}$ and $⟨\sigma v⟩\simeq {10}^{-24}{\mathrm{cm}}^3/\mathrm{s}$ for $m_{\mathrm{DM}}=1\mathrm{TeV}$).

We test the standardizability of a homogeneous sample of 41 lower-redshift ($0.00415\le z\le 0.474$) active galactic nuclei (AGNs) reverberation-mapped (RM) using the broad $\mathrm{H}\alpha$ and $\mathrm{H}\beta$ emission lines. We find that these sources can be standardized using four radius-luminosity ($R-L$) relations incorporating $\mathrm{H}\alpha$ and $\mathrm{H}\beta$ time delays and monochromatic and broad $\mathrm{H}\alpha$ luminosities. Although the $R-L$ relation parameters are well-constrained and independent of the six cosmological models considered, the resulting cosmological constraints are weak. The measured $R-L$ relations exhibit slightly steeper slopes than predicted by a simple photoionization model and steeper than those from previous higher-redshift $\mathrm{H}\beta$ analyses based on larger datasets. These differences likely reflect the absence of high-accreting sources in our smaller, lower-redshift sample, which primarily comprises lower-accreting AGNs. The inferred cosmological parameters are consistent within $2\sigma$ (or better) with those from better-established cosmological probes. This contrasts with our earlier findings using a larger, heterogeneous sample of 118 $\mathrm{H}\beta$ AGNs, which yielded cosmological constraints differing by $\gtrsim 2\sigma$ from better-established cosmological probes. Our analysis demonstrates that sample homogeneity—specifically, the use of a consistent time-lag determination method—is crucial for developing RM AGNs as a cosmological probe.

Light feebly-coupled bosonic particles can efficiently extract the rotational energy of rapidly spinning black holes on subastrophysical timescales via a phenomenon known as black hole superradiance. In the case of light axions, the feeble self-interactions of these particles can lead to a nonlinear coupled evolution of many superradiant quasibound states, dramatically altering the rate at which the black hole is spun down. In this work, we extend the study of axion superradiance to higher order states, solving for the first time the coupled evolution of all states with $n\le 5$ in the fully relativistic limit (with $n$ being the principal quantum number). Using a Bayesian framework, we rederive constraints on axions using the inferred spins of solar mass black holes, demonstrating that previously adopted limit-setting procedures have underestimated current sensitivity to the axion decay constant $f_a$ by around 1 order of magnitude and that the inclusion to higher order states allows one to reasonably capture the evolution of typical high-spin black holes across a much wider range of parameter space, thereby allowing constraints to be extended to more massive axions. We conclude with an extensive discussion on the systematics associated with spin inference from x-ray observations.

One of the scientific objectives of the Laser Interferometer Space Antenna (LISA) is to probe the expansion of the Universe using gravitational wave observations. Indeed, as gravitational waves from the coalescence of a massive black hole binary (MBHB) carry direct information of its luminosity distance, an accompanying electromagnetic (EM) counterpart can be used to determine its redshift. This method of “bright sirens,” when applied to LISA, enables one to build a gravitational Hubble diagram to high redshift. In this work, we forecast the ability of LISA-detected MBHB bright sirens to constrain cosmological models. The expected EM emission from MBHBs can be detected up to redshift $z\sim 7$ with future astronomical facilities and the distribution of MBHBs with detectable counterpart peaks at $z\sim 2–3$. Therefore, we propose several methods to leverage the ability of LISA to constrain the expansion of the Universe at $z\sim 2–3$, a poorly charted epoch in cosmography. We find that the most promising method consists in using a model-independent approach based on a spline interpolation of the luminosity distance-redshift relation: in this case, LISA can constrain the Hubble parameter at $z\sim 2–3$ with a relative precision of at least 10%.

We systematically perform long-term (millions of Schwarzschild time) axisymmetric viscous hydrodynamics simulations for tori around black holes in general relativity supposing the super-Eddington accretion flow. The initial condition for the tori is modeled simply by the Fishbone-Moncrief torus with a constant specific angular momentum $j$ but with a wide variety of $j$. Such a torus may be a remnant after tidal disruption of ordinary stars near a relatively low-mass supermassive black hole or an outcome of an inflow of the matter with a low specific angular momentum. We find that, for a given density profile, the fraction of the mass infall onto the black hole is approximately proportional to $j^{-1}$, indicating that only a minor fraction of the matter in the torus formed far from the black hole falls into the black hole, while the majority is ejected with the typical average velocity of a few percent of the speed of light. We also find that the mass ejection is driven only outside $\approx 2r_{\mathrm{ISCO}}$, where $r_{\mathrm{ISCO}}$ is the areal radius of the innermost stable circular orbit around black holes, which depends strongly on the black hole spin. We derive an approximate fitting formula for the spin dependence on the mass infall fraction as $\propto r_{\mathrm{ISCO}}^{0.7}$, which suggests that the rapid growth of supermassive black holes proceeded primarily by the accretion of the matter with the angular momentum counterrotating with the black hole spin.

Based on our recent analysis of the hadronic matrix element of the stress-energy tensor in covariant light-front dynamics, we extract the charmonium gravitational form factor $D(Q^2)$ from shear stress $T^{12}$. This is in contrast to our recent work using the (light-front) energy density $T^{+-}$. Indeed, by comparing these two currents, we identify terms that are responsible for the violation of the current conservation. Numerical results based on basis light-front quantization show that the violation effects are small, and the $D$ term extracted from the two currents are close to each other, hence validating our previous work using $T^{+-}$.

Radiation is a universal friction increasing agent. When two fluid layers are in relative motion, the inevitable exchange of radiation between such layers gives rise to an effective force, which tries to prevent the layers from sliding. This friction is often modeled as a Navier-Stokes shear viscosity. However, non-Newtonian corrections are expected to appear at distances of about one optical depth from the layers’ interface. Such corrections prevent the viscous stress from becoming too large. Here, we set the foundations of a rigorous theory for these corrections, valid along incompressible flows. We show that, in the linear regime, the infinite Chapman-Enskog series can be computed analytically, leading to universal formulas for all transport coefficients, which apply to any fluid, with any composition, with radiation of any type (also neutrinos), and with nearly any type of radiative process. We then show that, with an appropriate shear-heat coupling coefficient, Israel-Stewart theory can correctly describe most non-Newtonian features of radiative shear stresses.

We present measurements of $B^{+}\to {\rho }^{+}\gamma$ and $B^0\to {\rho }^0\gamma$ decays using a combined data sample of $772\times {10}^{6}B\overline{B}$ pairs collected by the Belle experiment and $387\times {10}^{6}B\overline{B}$ pairs collected by the Belle II experiment in $e^{+}{e}^{-}$ collisions at the $\mathrm{\Upsilon }(4S)$ resonance. After an optimized selection, a simultaneous fit to the Belle and Belle II datasets yields $114\pm 12$ $B^{+}\to {\rho }^{+}\gamma$ and $99\pm 12$ $B^0\to {\rho }^0\gamma$ decays. The measured branching fractions are $({13.1}_{-1.9-1.2}^{+2.0+1.3})\times {10}^{-7}$ and $(7.6\pm {1.3}_{-0.8}^{+1.0})\times {10}^{-7}$ for $B^{+}\to {\rho }^{+}\gamma$ and $B^0\to {\rho }^0\gamma$ decays, respectively, where the first uncertainty is statistical and the second is systematic. We also measure the isospin asymmetry $A_{\mathrm{I}}(B\to \rho \gamma )=({10.9}_{-11.7-7.3}^{+11.2+7.8})\%$ and the direct $CP$ asymmetry $A_{CP}(B^{+}\to {\rho }^{+}\gamma )=(-8.2\pm {15.2}_{-1.3}^{+2.0})\%$.

Most of the potential physical effects of loop quantum gravity have been derived in effective models that modify the constraints of canonical general relativity in specific forms. Emergent modified gravity evaluates important conditions that ensure the existence of a compatible geometrical space-time interpretation of canonical solutions, as well as phase-space covariance under different choices of canonical variables. This setting, specialized to modifications suggested by loop quantum gravity, is therefore an important contribution to physical evaluations of this approach to quantum gravity. Here, it is shown that emergent modified gravity restricts several ambiguities that existed in previous formulations, rules out several specific candidates, and provides a unified treatment of different types of (holonomy) modifications that had been thought to be physically distinct.

The Hellings-Downs (HD) correlation, which characterizes the signature of a stochastic gravitational wave background measured via pulsar timing arrays (PTA), is derived using a harmonic formalism. This approach closely follows the theoretical framework traditionally employed to compute correlations of temperature fluctuations in the cosmic microwave background (CMB). This parallel enables a direct comparison between the correlations observed in PTA and those in CMB experiments. After providing analytic estimates of the transmission functions due to the model-fitting procedure, we show that the covariance matrix in frequency space becomes very nondiagonal. We then build formally the quadratic estimator for the HD correlation in multipolar space, for both a perfect experiment, and for a realistic pulsar noise model. For a perfect experiment, we show that the signal to noise ratio grows with the observation time and the number of frequency bins, in turn determined by the cadence of observation. For an imperfect experiment, the behavior is similar, with an effective multipole-dependent number of frequency, obtained after weighting with noise. We predict that with $\sim 200$ pulsars monitored for 25 years, multipoles of the HD correlation up to $\ell =4$ can be measured. Our findings clarify that what has been referred to as cosmic variance in some of the previous literature is not an intrinsic limitation for PTA measurements. Instead, when an optimal estimator is used, this variance can be mitigated by accumulating more observation time or improving the cadence of pulsar monitoring. Therefore, unlike CMB angular correlations, where cosmic variance represents an irreducible constraint, it can be reduced in PTA measurements and will continue to diminish in future experiments. Finally, we show that if the primordial power spectrum of tensor fluctuations was very blue with $n_T>4$, the CMB angular correlation due to these tensor modes would also exhibit a HD correlation. While our results are derived for the case of an isotropic bath of gravitons, we also discuss the case in which the graviton distribution function is anisotropic.

We use galaxy cluster abundance measurements from the South Pole Telescope enhanced by multicomponent matched filter confirmation and complemented with mass information obtained using weak-lensing data from Dark Energy Survey Year 3 (DES Y3) and targeted Hubble Space Telescope observations for probing deviations from the cold dark matter paradigm. Concretely, we consider a class of dark sector models featuring interactions between dark matter (DM) and a dark radiation (DR) component within the framework of the effective theory of structure formation (ETHOS). We focus on scenarios that lead to power suppression over a wide range of scales, and thus can be tested with data sensitive to large scales, as realized, for example, for DM–DR interactions following from an unbroken non-Abelian $SU(N)$ gauge theory (interaction rate with power-law index $n=0$ within the ETHOS parametrization). Cluster abundance measurements are mostly sensitive to the amount of DR interacting with DM, parametrized by the ratio of DR temperature to the cosmic microwave background (CMB) temperature, ${\xi }_{\mathrm{DR}}=T_{\mathrm{DR}}/T_{\mathrm{CMB}}$. We find an upper limit ${\xi }_{\mathrm{DR}}<17\%$ at 95% credibility. When the cluster data are combined with Planck 2018 CMB data along with baryon acoustic oscillation (BAO) measurements we find ${\xi }_{\mathrm{DR}}<10\%$, corresponding to a limit on the abundance of interacting DR that is around 3 times tighter than that from CMB + BAO data alone. We also discuss the complementarity of weak lensing informed cluster abundance studies with probes sensitive to smaller scales, explore the impact on our analysis of massive neutrinos, and comment on a slight preference for the presence of a nonzero interacting DR abundance, which enables a physical solution to the $S_8$ tension.

Diffusion models have been used in cosmological applications as a generative model for fast simulations and to reconstruct underlying cosmological fields or astrophysical images from noisy data. These two tasks are often treated as separate: diffusion models trained for one purpose do not generalize to perform the other task. In this paper, we develop a single diffusion model that can be used for both tasks. By using the diffusion posterior sampling (DPS) approach, we use a diffusion model trained to simulate weak lensing maps for the inverse problem of reconstructing mass maps from noisy weak lensing data. We find that the standard DPS method leads to biased inference but we correct this bias by down weighting the likelihood term at early sampling time steps of the diffusion. Our method gives us a way to reconstruct accurate high-resolution (subarcminute) mass maps that have the correct power spectrum and a range of non-Gaussian summary statistics. We discuss several applications enabled by the computational efficiency and accuracy of our model. These include generation of simulation quality mass maps at a fraction of the computational cost, which in turn enables applications such as covariance estimation for higher order statistics. The higher resolution of the reconstructed maps will enable finding filaments, voids, and clusters from noisy lensing shear data and cross-correlation studies with optical and Sunyaev-Zeldovich maps.

In this paper, we evaluate the potential of multiband gravitational wave observations from a dHz space-based detector and third-generation ground-based gravitational wave detectors to constrain the properties of dark matter spikes around intermediate-mass ratio inspirals. The presence of dark matter influences the orbital evolution of the secondary compact object through dynamic friction, which leads to a phase shift in the gravitational waveform compared to the vacuum case. Our analysis shows that the proposed Indian space-based detector GWSat, operating in the dHz frequency band, provides the most stringent constraints on the dark matter spike parameters, as IMRIs spend a significant portion of their inspiral phase within its sensitivity range. While third-generation ground-based detectors such as the Einstein Telescope and Cosmic Explorer offer additional constraints, their contribution is somewhat limited, particularly for higher mass systems where the signal duration in their frequency bands is shorter. However, for systems with detector-frame total masses $M_z<400M_{\odot }$, Cosmic Explorer and Einstein Telescope could improve the estimation of the chirp mass, symmetric mass ratio, luminosity distance, and dark matter spike power-law index by more than 15%. Nonetheless, their impact on the constraint of spike density is minimal. These results highlight the crucial role of dHz space-based detectors in probing dark matter interactions with gravitational wave sources.