The existence of dark matter (DM) is supported by various macroscopic observations, but its microscopic nature remains elusive. The Galactic Center GeV gamma-ray excess (GCE) has been a leading candidate signal for particle DM annihilation. However, an unresolved population of millisecond pulsars (MSPs) in the bulge provides the alternative explanation for the excess. Identifying these MSPs in electromagnetic bands is difficult due to source confusion, pulse broadening, and extinction. Gravitational waves (GWs) provide a complementary probe: a steadily rotating, nonaxisymmetric MSP emits a nearly monochromatic GW signal in the sensitive band of ground-based detectors, with amplitude set by its ellipticity. In this work, we systematically investigate the GW emission from the MSP population proposed to explain the GCE and its detectability with current and future detectors. We consider three major scenarios for the origin of ellipticity and model the population properties of these MSPs. We also consider both isolated MSPs and MSPs in binary systems, as well as Doppler effects in the detection. We find that while the signal is generally below the reach of current interferometers, next-generation detectors such as the Einstein Telescope and Cosmic Explorer may detect a fraction of those MSPs, offering a novel test of the MSP interpretation of the GCE. Future directed searches toward the Galactic Center may either uncover this long-sought MSP population or place stringent constraints on bulge MSP properties. Continued improvements in detector sensitivity will provide increasingly stringent tests of the MSP interpretation, with growing power to distinguish between the astrophysical and DM interpretations of the GCE.

Binary systems surrounded by a circumbinary accretion flow can be subject to strong magnetic fields, potentially altering the character of the accretion flow itself, the evolution of the orbital dynamics, and outflow properties from the system. Here, we focus on a regime where magnetic fields become so strong that the outer circumbinary flow becomes magnetically arrested, establishing a (circum)binary magnetically arrested disk (BMAD) state. Such flows feature quasiperiodic magnetic flux eruptions, power jet-like magnetic tower outflows, and consequently alter the predominant contribution to angular momentum transfer inside the circumbinary disk. In this work, we provide a comprehensive analysis of the properties of these flows around equal-mass binary systems on circular orbits utilizing massively parallel three-dimensional Newtonian magnetohydrodynamics simulations. We investigate the impact of the equation of state and of dynamical cooling, as well as that of the (large-scale) magnetic field topology. Our findings are as follows: (1) A magnetically arrested accretion flow through the cavity can generally be achieved, so long as the initial seed field is strong enough. (2) The cavity, and magnetic flux tube properties and their subsequent propagation are subject to the choice of equation of state/cooling physics. (3) We find tentative evidence that in some regimes the BMAD state, particularly during a flux eruption cycle, can aid in shrinking of the binary’s orbit. The regimes we explore have implications for multimessenger transients to stars, supermassive and stellar black hole binaries and their orbital evolution in gaseous environments.

We compute the charm-quark current–current correlation function within the Langevin framework and extract the heavy-quark diffusion coefficient using the Green–Kubo formula. The formalism is further extended to evaluate the correlation function using a generalized Langevin equation that incorporates memory effects via an exponentially decaying memory kernel. We find that while memory effects qualitatively modify the transient structure of the current correlations, the value of the transport coefficient remains unchanged. In addition, we investigate heavy-quark thermalization in the presence of memory and compare the nonequilibrium solution of a generalized Fokker–Planck equation with the one obtained from the generalized Langevin equation in the nonrelativistic limit. We also consider the relativistic case with correlated noise and observe that memory effects can give rise to a damped, oscillatory equilibration of the heavy-quark momentum distribution in a non-Markovian bath.

Motivated by the long-standing “$\pi \pi$ puzzle” in nonleptonic $B$ decays, we revisit the $B\to \pi \pi$ decays within the QCD factorization (QCDF) framework, now incorporating the soft color-octet matrix element (COME) contributions, an ingredient that has been largely overlooked in earlier QCDF studies. A comprehensive phenomenological analysis is performed under three distinct scenarios, with the free parameters determined via fits to the available experimental data using the ${\chi }^2$ method. The goodness-of-fit is very poor for Scenario S1, which corresponds to the traditional QCDF case without the soft COME contributions, and for Scenario S2, which includes the soft COME contributions but omits the weak annihilation (WA) contributions. Scenario S3, in which both the COME and WA contributions are included simultaneously, achieves an excellent overall fit. In Scenario S3, the QCDF approach can accommodate almost all $B\to \pi \pi$ observables in a consistent and satisfactory manner, and the fitted parameters ${\rho }_A<1$ (WA) and ${\rho }_c\sim 0.3$ (soft COME) are in good agreement with the QCDF power counting scheme and the factorization hypothesis.

We study a minimal framework where a Majorana fermion dark matter particle interacts with a light scalar mediator coupled mainly to electrons. We examine both freeze-out and freeze-in production to determine the regions of parameter space that yield the correct relic abundance with particular emphasis on a detailed comparison with results in the recent literature. The analysis includes cosmological and astrophysical constraints as well as laboratory bounds from electron-recoil experiments, fixed target searches, and precision measurements. The combined results identify a narrow but viable parameter region, favoring sub-GeV dark matter, and define clear targets for future experimental tests. This highlights the strong complementarity between direct-detection experiments and collider searches. We additionally investigate the mediator-mass region around 17 MeV, motivated by the hints reported by the ATOMKI experiment and the PADME collaboration, including couplings between the mediator and light quarks. Direct searches already constrain a large region of the parameter space, even when dark matter is produced via freeze-in, pointing again to sub-GeV dark matter.

Tensor-polarized parton distribution functions (PDFs) are calculated for the deuteron by using a convolution formalism, where the tensor-polarized PDFs are given by the corresponding nucleon’s unpolarized PDFs convoluted with the tensor-polarized nucleon momentum distribution in the deuteron. These distributions are obtained at $Q^2=2.5{\mathrm{GeV}}^2$ in order to compare with the tensor-polarized PDFs which were determined by HERMES $b_1$ data. The obtained distributions are very different from the ones determined from the HERMES data, which indicates further studies are needed to clarify the difference, possibly by considering a new mechanism beyond the simple bound system of a proton and a neutron. The obtained PDFs ${\delta }_{T}q$ and ${\delta }_T\overline{q}$ are converted to the PDFs of the Trento convention $f_{1LL}^q$ and $f_{1LL}^{\overline{q}}$, and they are used for estimating the twist-3 PDFs $f_{LT}^q$ and $f_{LT}^{\overline{q}}$ by using a Wandzura-Wilczek-like relation. Because deep-inelastic-scattering experiments are under preparation for structure functions with a tensor-polarized deuteron target at the Thomas Jefferson National Accelerator Facility, and a Drell-Yan experiment will be possible at hadron accelerator facilities, such as the Fermi National Accelerator Laboratory, the obtained tensor-polarized PDFs will be tested experimentally.

We revisit the calculation of the strong couplings $D^{*}{D}^{*}\pi$ and $B^{*}{B}^{*}\pi$ from the light-cone sum rules (LCSR) using the pion light-cone distribution amplitudes. The accuracy of the underlying correlation function is upgraded by establishing the hard-collinear factorization formula at the leading power up to the next-to-leading order in ${\alpha }_s$. Furthermore, the next-to-leading power contributions are incorporated at the leading order by including the two-particle and three-particle higher-twist pion distribution amplitudes up to twist-4 accuracy. We perform a comprehensive numerical analysis with a systematic evaluation of theoretical uncertainties, predicting $g_{D^{*}{D}^{*}\pi }=5.71_{-0.89}^{+0.70}{\mathrm{GeV}}^{-1}$ and $g_{B^{*}{B}^{*}\pi }=4.90_{-0.67}^{+0.59}{\mathrm{GeV}}^{-1}$. Finally, by parametrizing the $1/m_H$ (with $H=D$, $B$) power corrections to extract the universal static coupling $\widehat{g}=0.30\pm 0.04$, we compare our results with previous theoretical determinations and experimental data, and discuss the current limitations in disentangling the heavy quark spin symmetry breaking effects.

We determine a normalized two-variable longitudinal distribution of the ${\mathrm{\Lambda }}_b=(ud)b$ baryon from a covariant three-quark light-front wave function. The scalar $ud$ channel is selected with the good-component structure $C{\gamma }_5{\gamma }^{+}$, and the two independent transverse momenta are integrated without introducing an elementary diquark. The resulting model-scale valence distribution ${\mathrm{\Psi }}_2^{\mathrm{LF}}(x_u,x_d)$ retains both the heavy-light and internal-light momentum scales of the parent wave function. It is symmetric under $x_u\leftrightarrow x_d$, is concentrated where both light-quark fractions are small and separates the total light-pair momentum from its internal sharing. For the central parameter set we find $⟨x_u⟩=⟨x_d⟩=0.130$, $⟨x_b⟩=0.739$, $⟨{\zeta }^2⟩=0.153$, and $⟨{\zeta }^4⟩=0.055$, where $\zeta =(x_u-x_d)/(x_u+x_d)$. Parameter variations give $⟨x_u⟩=0.130_{-0.007}^{+0.007}$, $⟨x_b⟩=0.739_{-0.014}^{+0.014}$, $⟨{\zeta }^2⟩=0.153_{-0.016}^{+0.014}$, and $⟨{\zeta }^4⟩=0.055_{-0.009}^{+0.009}$. The heavy-light momentum partition is controlled mainly by ${\beta }_{b,ud}$ and $m_b$, whereas the internal $u\text{−}d$ sharing is most sensitive to ${\beta }_{ud}$. The result provides a compact finite-mass benchmark for three-quark longitudinal structure, with distinct observables for heavy-light momentum sharing and correlations inside the light pair.

Liquid scintillator detectors are widely used in neutrino experiments due to their low energy threshold and high energy resolution. Despite the tiny abundance of ${}^{14}\mathrm{C}$ in LS, the photons induced by the $\beta$ decay of the ${}^{14}\mathrm{C}$ isotope inevitably contaminate the signal, degrading the energy resolution. In this work, we propose three models to tag ${}^{14}\mathrm{C}$ photon hits in $e^{+}$ events with ${}^{14}\mathrm{C}$ pileup, thereby suppressing its impact on the energy resolution at the hit level: a gated spatiotemporal graph neural network and two transformer-based models with scalar and vector charge encoding. For a simulated test dataset in which each event contains one ${}^{14}\mathrm{C}$ and one ${\mathrm{e}}^{+}$ with kinetic energy below 5 MeV, the models achieve ${}^{14}\mathrm{C}$ recall rates of 25%–48% while maintaining ${\mathrm{e}}^{+}$ to ${}^{14}\mathrm{C}$ misidentification below 1%, leading to a large improvement in the resolution of total charge for events where ${\mathrm{e}}^{+}$ and ${}^{14}\mathrm{C}$ photon hits strongly overlap in space and time.

In this paper, we study the renormalization of a three-dimensional quartic model on a compact connected Riemannian manifold with a boundary. We show that, in addition to the standard shift of the mass parameter, it is necessary to take into account boundary contributions involving singular coefficients. This indicates the need to extend the classical action within the framework of standard renormalization theory. The requirements of consistency regarding the gluing of manifolds lead to renormalization of an operator on the boundary.

We present an exact solution describing multirotating black holes in 4D Einstein-Maxwell-dilaton theory, which can be obtained from 5D Kaluza-Klein theory via dimensional reduction. The solution represents a multicentered configuration of rotating black holes carrying both electric and magnetic charges, with each black hole possessing a non-aligned angular momentum. This work generalizes our previous solution for black holes with aligned angular momenta to the more general case of nonaligned angular momenta. It includes, as special cases, the Majumdar-Papapetrou solution, the recent multicentered rotating black hole solutions of Teo and Wan, and our previous solution with unequal electric and magnetic charges. The resulting spacetimes are free of curvature singularities and closed timelike curves, both on and outside the horizons, provided that the magnitude of the spin angular momentum of each black hole remains below a certain upper bound. The absence of conical singularities has not been established for the general case with nonaligned angular momenta.

We develop a thermodynamic framework for dynamical thin-shell wormholes consistent with the exact junction conservation law. In a general static spherical bulk, energy transfer to the dynamic shell is determined by the redshift gradients and vanishes in the transparent, one-function geometry. Reversible transparent evolution conserves the shell entropy, whereas nontransparent evolution obeys a geometric energy balance whose division into heat and work depends on the thermodynamic state space. We distinguish the shell temperature from its acceleration scale, formulate intrinsic stability conditions, and establish the compatibility requirements for scalar-field and radiative flux models. The results identify the thermodynamic conclusions supported by junction dynamics and the additional assumptions needed for heat exchange and entropy production.

We analyze the vacuum dynamics of gravity from entropy, including its algebraically constrained $G$-field formulation. Evaluating the curvature traces over 0-, 1-, and 2-form sectors, we show that the complete Minkowski Hessian is exactly that of the quadratic-gravity action $AR+B{R}_{\mu \nu }{R}^{\mu \nu }$, with $A=3\beta /{\ell }_{\mathrm{P}}^4$ and $B=5{\beta }^2/(2{\ell }_{\mathrm{P}}^4)$. For diagonalizable-curvature blocks, the same action reduces to a sum over eigenvalue logarithms and reproduces these coefficients exactly. A strict diagonal-curvature restriction on the perturbations is instead only a reduced subsector and excludes nondiagonalizable type-N wave curvatures. Linearizing the $G$-field equations and subsequently imposing the algebraic vacuum constraint reproduces the same reduced metric equation and covariant Minkowski Hessian. The spectrum contains the massless graviton, a scalar with $m_0^2=3/(5\beta )$, and an opposite-residue spin-2 branch with $m_2^2=-6/(5\beta )=-2m_0^2$. For the foundational choice $\beta >0$, conventional Einstein normalization yields an opposite-residue tachyonic spin-2 pole at a characteristic scale of order ${\beta }^{-1/2}$, whose physical interpretation may depend on the ultraviolet completion of the theory. We also show that every four-dimensional Ricci-flat metric solves the local bulk equations through quadratic-curvature order, while square-zero Ricci-flat $pp$-waves are exact local vacuum solutions of the analytic metric-only logarithmic branch. On the isolated massless transverse-traceless eigenspace, the quadratic translation current has the standard general-relativistic normalization.

The Laser Interferometer Space Antenna (LISA) will detect gravitational waves (GWs) from dozens of extreme- and intermediate-mass-ratio inspirals. These sources will stay in band for months to years, offering extraordinary scientific potential. However, their fully phase-coherent analysis standard in current pipelines imposes stringent waveform accuracy requirements; failing to model the signal over such long durations can result in significant systematic biases. To address this, we formulate a robust Bayesian inference framework that segments the data into blocks, infers each block coherently, and recombines the results using loosely-coherent phase information. By restricting full phase tracking to much shorter block durations, this approach prevents significant accumulation of phase errors. We implement this methodology in (Segmented Posteriors for Long-Inspiral Templates (split), a graphics-processing-unit-accelerated Python package. Applying split to an environment-rich injection, we demonstrate that, while a fully-coherent vacuum-GR analysis incurs a maximum one-dimensional (1D) systematic bias of $\approx 4.8\sigma$ from the truth, the shorter integration window of our loosely-coherent approach restricts such biases to $\lesssim 0.5\sigma$. Overall, despite a fractional loss of optimal signal-to-noise ratio, the substantial improvement in parameter accuracy offered by our method presents a highly advantageous tradeoff for LISA and other future GW detectors.

Higher-dimensional theories of gravity predict that gravitational waves (GWs) can propagate into extra spatial dimensions, leading to modified amplitude damping over cosmological distances. Measurements of GW luminosity distances therefore provide a unique probe of the dimensionality of spacetime. In this work, we constrain higher-dimensional GW propagation using the dark-siren method with the Gravitational-Wave Transient Catalog 4.0 (GWTC-4). We adopt a phenomenological parametrization motivated by braneworld scenarios, in which deviations from general relativity are characterized by the spacetime dimension number $D$ and a crossover scale $R_c$ governing the transition between four- and higher-dimensional gravity. We perform a hierarchical Bayesian analysis combining 141 compact binary coalescences from GWTC-4 with line-of-sight Galaxy information from the GLADE+ catalog. For a prior $H_0\in [65,77]\mathrm{km}{\mathrm{s}}^{-1}{\mathrm{Mpc}}^{-1}$ and $\log (R_c/\mathrm{Mpc})\in [2.7,4.0]$, we obtain $D=4.38_{-1.01}^{+1.91}$ (68% credible interval). We also find that the inferred posterior distribution of $R_c$ accumulates near the upper prior boundary, indicating that the crossover scale remains poorly constrained by current observations. We further show that the inferred constraint on $D$ depends sensitively on the assumed prior range of $R_c$, which determines the characteristic distance scale at which deviations from general relativity become significant. Our results provide the first GWTC-4 dark-siren constraints on higher-dimensional GW propagation and demonstrate that current observations remain consistent with four-dimensional general relativity.

We present an astrophysical science-case study of IndIGO-D, a decihertz gravitational-wave mission concept, focusing on compact binary sources across the 0.1–10 Hz band bridging LISA and next-generation ground-based interferometers. For these science projections, we consider a specific configuration in which three spacecraft fly in formation to form an L-shaped interferometer in a heliocentric orbit. The two orthogonal arms share a common vertex, providing a space-based analog of terrestrial Michelson detectors. A central element of our study is a detailed calculation of the time-dependent antenna response of this L-shaped geometry, including the modulation produced by the orbital motion of the constellation. Assuming 1000 km arm lengths, we treat the strain-sensitivity curve supplied by the IndIGO-D collaboration as an input and investigate the astrophysical science enabled by this configuration. For the assumed sensitivity, we estimate a binary neutron star (BNS) detection rate of $\sim 76–767{\mathrm{yr}}^{-1}$. We compute horizon distances for different source classes and find that intermediate-mass black-hole binaries with masses ${10}^2–{10}^3{M}_{\odot }$ are detectable throughout their formation history, complementing the reach of LISA and terrestrial detectors. BNS systems are observable to a horizon redshift of $z\lesssim 0.3$, allowing continuous multiband coverage with Voyager-class interferometers from the decihertz regime to merger. A Bayesian parameter-estimation study of a GW170817-like binary shows that the sky localization area improves from $\sim 21{\mathrm{deg}}^2$ at one month, $\sim 1{\mathrm{deg}}^2$ at one week, down to $0.3{\mathrm{deg}}^2$ at six hours premerger. These sky areas are readily tiled by wide-field time-domain telescopes such as the Rubin Observatory, whose $9.6{\mathrm{deg}}^2$ field of view and r-band depth enable high-cadence, repeated coverage of GW170817-like kilonovae at this distance and beyond. IndIGO-D exploits the rapid evolution of binaries in the decihertz band to bridge the gap between millihertz and terrestrial observations, enabling early warnings on timescales from months to hours and enhancing the prospects for multiband and multimessenger discoveries.

In this paper, we illustrate how a Schrödinger cat state created via a matter-wave interferometer can be viewed as the simplest quantum-gravity setup where we can treat both matter and gravity on an equal footing at a perturbative level. Here, we treat Einstein’s theory of general relativity using an effective field theory approach, quantizing the massless spin-2 graviton in the presence of a quantum spatial superposition of matter that creates a matter-wave interferometer in the nonrelativistic limit. We show that, due to the matter-graviton coupling, the graviton vacuum is displaced analogous to the coherent state. We study the contrast/overlap between the coherent states of the left and right superpositions in the matter-wave interferometer. We also study the entanglement between matter and the graviton in this setup and relate it to a gravitational contrast, or the overlap of the quantum geometries led by the coherent states. In Appendix B, we provide an example of a time-dependent harmonic oscillator and study the contrast/overlap of such coherent states of the graviton.

Electromagnetic duality is a symmetry of the source-free Einstein-Maxwell equations that rotates electric and magnetic fields while leaving the stress-energy tensor invariant. We present the first fully nonlinear realization of this symmetry in dynamical strong-gravity regimes by performing numerical relativity simulations of charged black hole mergers across a continuous duality family. Starting from electrically charged binaries, we generate dyonic and magnetically charged configurations via duality rotations and evolve them within a common numerical framework. We find that all dual configurations exhibit identical spacetime dynamics, while the emitted electromagnetic radiation is related by a rotation of its polarization equal to the duality angle. Our results demonstrate a degeneracy of gravitational observables under electromagnetic duality and provide a concrete mapping between dual configurations at the level of radiation, establishing electromagnetic duality as an organizing principle for dynamical Einstein-Maxwell solutions.

We investigate vacuum generalized Brans-Dicke theory with scalar-dependent coupling $\omega (\varphi )$ in an Einstein-Rosen-type metric. Let $W$ be the area density of the two-dimensional Killing orbits, $\varphi$ the Brans-Dicke scalar, and $\mathrm{\Omega }=W\varphi$ their composite area density. On regions where the gradient of $\mathrm{\Omega }$ is non-null, we impose $W=W(\varphi )$ and local invertibility of $\mathrm{\Omega }(\varphi )$. The scalar equation admits the exact first integral $(3+2\omega )[(\mathrm{\Omega }/\varphi )(d\varphi /d\mathrm{\Omega }){]}^2=\kappa$, where $\kappa$ is a signed integration constant, giving direct and inverse reconstruction of the coupling. For $\varphi =b(\mathrm{\Omega }/{\mathrm{\Omega }}_{*}{)}^a{e}^{q\mathrm{\Omega }}$ one obtains $3+2\omega =\kappa /(a+q\mathrm{\Omega }{)}^2$. The choices $\mathrm{\Omega }=\rho$ and $\mathrm{\Omega }=t$ define the spacelike- and timelike-gradient branches, each yielding a closed exact solution family. Their mode functions obey the cylindrical Einstein-Rosen and Euler-Poisson-Darboux equations, respectively. In the Einstein frame the normalized scalar is $\sigma ={\sigma }_0+\sqrt{|\kappa |}\ln (\mathrm{\Omega }/{\mathrm{\Omega }}_0)$, while $q$ cancels from the metric. In the spacelike branch the scalar contributes to the radial C-energy profile separately from the tensor flux, and the reconstructed smooth-mode class has no curvature-regular axis. In the static subclass, $q=0$ reproduces the circular-speed law of a singular isothermal dark-matter halo, while $q<0$ gives a local correspondence with the rising inner NFW rotation curve. The homogeneous timelike subclass is locally Bianchi I, reduces in the Einstein frame to an exact scalar-Kasner geometry, and has a Jordan-frame effective Planck mass that evolves monotonically with Jordan-frame comoving proper time on each connected time interval on which the reconstructed scalar profile is locally invertible.

Modified theories of gravity often introduce geometric structure beyond general relativity to address unresolved problems in the gravitational sector without invoking ad hoc matter fields. Mimetic gravity, for example, generates an effective cosmological dark sector by isolating the conformal mode of the metric, while Hořava-Lifshitz gravity attains power-counting renormalizability by endowing spacetime with a preferred dynamical foliation. Although chronology protection was not the original motivation for either theory, both can realize it classically through stable causality. This suggests that chronology protection itself may be elevated from a derived property to a guiding principle for constructing modified gravitational theories, especially if its implementation at the quantum-gravitational level leaves infrared imprints in the effective action. Motivated by this possibility, we introduce a toy metric-affine gravity model whose chronology-protecting sector is purely geometric. The model breaks projective invariance and selects a timelike, closed nonmetricity one-form. In the globally exact sector, this one-form defines a time function, realizing stable causality through affine geometry. On the matter-free, spatially flat FLRW branch with noncompact slices, $\mathrm{\Lambda }=0$, and positive chronology-sector density, the local quadratic gravitational spectrum contains the two tensor modes of GR and a single scalar mode. The scalar has positive kinetic energy but a gradient instability, $c_s^2=-2$, requiring stabilization before a viable cosmological application can be established. We investigate the classical cosmological effects and scalar-mode dynamics of this purely geometric chronology-protecting extension of general relativity.