We consider the most general parity symmetric effective scalar tensor theory in four dimensions containing terms up to fourth derivative order in the Lagrangian. It has been shown [H. S. Reall, [Phys. Rev. D 103, 084027 (2021)]] that this theory has three polarizations generically governed by different (nested) propagation cones, neither of which, in general, coincides with the light cone as defined by the metric. Consequently, the notion of a black hole horizon must be defined relative to the widest propagation cone and not with respect to the metric. We provide two theorems stating that, nevertheless, the horizon of a stationary black hole is null with respect to the metric and that, in fact, all three propagation cones touch on the horizon. The conditions in these theorems allow for rotating black holes. Our theorems thereby suggest that the notion of a Killing horizon, central in most discussions of black hole thermodynamics, retains its fundamental status and that certain thermodynamic paradoxes associated with multiple propagation cones are evaded.

We provide a set of general tools to study the problem of stellar equilibrium in any gravitational theory in which spherically symmetric spacetimes satisfy master field equations taking the form of an equality between an identically conserved tensor, with derivatives of up to second order in the metric, and an identically conserved matter tensor. We derive the most general expression for the Tolman-Oppenheimer-Volkoff equation of stellar equilibrium that is compatible with these minimal requirements. A general discussion of the conditions that guarantee geodesic completeness at the center of symmetry is also presented. The equations of stellar equilibrium are integrated in a subset of the space of allowed deformations of general relativity proposed by Ziprick and Kunstatter, allowing us to illustrate universal aspects associated with the weakening of the strength of gravity, such as the mitigation of the Buchdahl limit obtained in general relativity or the existence of static solutions describing regular black holes with perfect fluid cores.

We study whether an open FLRW universe with a negative cosmological constant can evade the eventual recollapse characteristic of an anti–de Sitter (AdS)-type universe. Within a power-law realization of fab-four theory, we solve the background equations numerically and analyze the asymptotic dynamics. For the representative branch and parameter choice studied here, we find that the scalar sector provides a self-tuninglike compensation for the negative $\mathrm{\Lambda }$, while the curvature term remains unscreened. As a result, the universe can continue expanding instead of recollapsing. Instead, the universe evolves toward a curvature-dominated linear-expansion regime, $a\propto t$. To probe the underlying compensation mechanism, we further analyze an auxiliary zero-curvature subsystem using Poincaré compactification. In the $\mathrm{\Lambda }<0$ domain, there exist background trajectories that approach a critical point at infinity. Near this point, the compensating scalar-$\mathrm{\Lambda }$ sector becomes stifflike, $w_{\varphi +\mathrm{\Lambda }}\to 1$, so that the system effective energy density redshifts faster than curvature ($w_k=-1/3$). Although this auxiliary analysis does not cover the full curved cosmology, it is consistent with and qualitatively supports the numerical finding that the net $\varphi +\mathrm{\Lambda }$ contribution becomes subdominant to curvature, thereby preventing recollapse despite $\mathrm{\Lambda }<0$. This extends the application of the self-tuning mechanism to the AdS region and offers a possibility for the AdS Universe predicted by string theory to become a reality.

The interaction of charged particles with an intense laser pulse gives rise to a number of characteristic spectral features of emitted radiation, including the generation of harmonics, spectral broadening due to the phase-dependent ponderomotive red shift, and the emergence of intricate subharmonic structures. These effects are accumulated over the course of the interaction with the electromagnetic field and are therefore inherently nonlocal in nature. For a deeper understanding of strong-field quantum electrodynamics (SFQED) processes and their practical applications, it is desirable to employ tools that enable simultaneous analysis in the time and energy domains. In time-frequency analysis, such tools are provided by joint distributions (JDs). In this work, we demonstrate how a JD can be devised within the SFQED framework. Specifically, we focus on constructing a non-negative JD, which allows for a clear probabilistic interpretation. We study the properties of the proposed distribution and test its utility by applying it to the nonlinear Compton scattering in complex laser pulse configurations with carrier-envelope phase and variable polarization.

Since dark matter is only known to have gravitational interactions, it may plausibly decay to gravitons on cosmological timescales. Although such a scenario can be easily realized, there are currently no known limits on this possibility based on indirect-detection methods. We propose a new search strategy that exploits the Gertsenshtein effect, whereby the gravitons produced in dark matter decays can convert to photons in large-scale magnetic fields along the line of sight to an observer. These conversions primarily occur within cosmological filaments which occupy a large (order unity) volume fraction and contain $\sim 10–100\mathrm{nG}$ fields with $\sim \mathrm{Mpc}$ coherence lengths. Thus, dark matter decays to gravitons predict an irreducible population of extragalactic photons, which we constrain using the extragalactic gamma-ray background measured by the Fermi-LAT telescope. Using this method, we derive the first-ever constraints on the dark matter lifetime in the $0.1\mathrm{GeV}-{10}^8\mathrm{GeV}$ mass range, contingent on the assumed filament magnetic field strength. We also make projections for the Advanced Particle-astrophysics Telescope, which can improve sensitivity to this dark matter decay channel by an order of magnitude beyond those we set using Fermi-LAT data.

Searching for dark matter is a primary goal of modern astronomy and particle physics. Invisible decays of heavy quarkonia are particularly promising for probing light dark matter, attracting broad interest due to their unique sensitivity. Experiments searching for radiative invisible decays of the $J/\psi$ have steadily improved upper limits, and upcoming facilities will push sensitivity further—making the precise determination and subtraction of the neutrino background indispensable. Here, we present the first lattice QCD calculation of the Standard Model decay $J/\psi \to \gamma \nu \overline{\nu }$, an irreducible background to $J/\psi \to \gamma +\text{invisible}$. Our result for the branching fraction is $\mathrm{Br}(J/\psi \to \gamma \nu \overline{\nu })=1.04(7)(8)\times {10}^{-10}$, where the first uncertainty is statistical and the second is our systematic estimate. This work advances lattice-based determinations of neutrino backgrounds to quarkonium invisible decays, delivering an ab initio benchmark for $J/\psi \to \gamma +\text{invisible}$. Our approach generalizes to other quarkonium channels (e.g., $\mathrm{\Upsilon }/\varphi \to \gamma +\text{invisible}$) and provides critical theoretical support for dark matter searches at colliders.

We reanalyze the lattice spectra for $I=1/2$ $D\pi$ scattering in the $A_1^{+}$ irreducible representation from [Phys. Rev. D 111, 014503 (2025)] to investigate the impact of chiral and SU(3) flavor symmetries in $S$-wave $D\pi$ scattering and the $D_0^{*}(2300)$ resonance. By fitting the phase shifts obtained via Lüscher’s formula with both traditional and chirally modified effective-range expansion and $K$-matrix parametrizations, we find that the chiral factor shifts the extracted pole mass closer to the threshold (especially for resonances) and substantially reduces the resonance width. These findings are confirmed by unitarized chiral perturbation theory through a direct fit to the lattice spectra with both the single-channel and the $D\pi \text{−}D\eta \text{−}{D}_s\overline{K}$ coupled-channel schemes. Once the coupled channels are incorporated, the two-pole structure of the $D_0^{*}(2300)$ emerges. The trajectories of the two poles are investigated by varying the pion mass.

We investigate the phase structure of QCD in the vacuum as a function of quark flavor number $N_f$ within the chiral limit. By self-consistently solving the coupled Dyson-Schwinger equations for the quark and gluon propagators in a minimal QCD scheme, we elucidate the nonperturbative dynamics governing dynamical chiral symmetry breaking. Our calculations determine a critical flavor number of $N_f^c=6.81$ which marks the chiral symmetry restoration of quarks. Further analysis reveals the critical exponents of the chiral condensate as $-⟨\overline{\psi }\psi ⟩\sim |N_f-N_f^c{|}^{0.53(9)}$, characterized the second order feature of this phase transition of chiral symmetry. Additionally, we discuss the implications for the walking regime towards the conformal window at larger flavor.

A new thermodynamic state function is introduced to describe the thermodynamics relevant for the mean transverse momentum fluctuations of charged particles in heavy-ion collisions, which allows us to compute the temperature fluctuations of different orders in hot quantum chromodynamics (QCD) matter for the first time. Consequently, it is found that the temperature fluctuations are suppressed remarkably as the system transitions from the hadron resonance gas (HRG) to the quark-gluon plasma (QGP) with increasing temperature or baryon chemical potential, alongside a negative skewness. This is attributed to the general fact that the heat capacity of QCD matter increases significantly in QGP in comparison to that in HRG. These predictions provide a candidate observable to discover the thermodynamic temperature fluctuations in upcoming heavy-ion collision experiments, which also paves a novel way to study QCD thermodynamics and QCD phase diagram through measurements of the mean transverse momentum fluctuations of charged particles.

We present our results for the twist-3 gluon contribution to the single transverse-spin asymmetry (SSA) in $J/\psi$ production in proton-proton collisions. Although the data were reported by the RHIC experiment more than a decade ago, a theoretical calculation based on rigorous collinear factorization has remained unavailable for the dominant gluonic contribution. Our results show that only the $C$-even type twist-3 gluon distribution, which has a direct relationship with the gluon transverse-momentum-dependent distribution function, contributes to the $J/\psi$ SSA. Therefore, this observable serves as a key probe to understand the three-dimensional motion of gluons inside the proton. We also perform numerical simulations of the $J/\psi$ SSA at RHIC and LHC energies. Our simulations indicate that a sizable SSA could be generated through a mechanism different from that responsible for the SSA in light hadron and $D$-meson production.

A search for the radiative decays $D^0\to \gamma {\overline{K}}_1(1270{)}^0$ and $D^{+}\to \gamma K_1(1270{)}^{+}$ is conducted using $20.3{\mathrm{fb}}^{-1}$ of $e^{+}{e}^{-}$ annihilation data collected at the center-of-mass energy $\sqrt{s}=3.773\mathrm{GeV}$ by the BESIII detector operating at the BEPCII collider. No significant signals are observed, and upper limits on the branching fractions of $D^0\to \gamma {\overline{K}}_1(1270{)}^0$ and $D^{+}\to \gamma K_1(1270{)}^{+}$ at 90% confidence level are determined to be $7.8\times {10}^{-4}$ and $3.9\times {10}^{-5}$, respectively. This represents the first test of the vector meson dominance mechanism in the radiative decays of charmed mesons to axial-vector mesons.

Remnant black holes formed in compact binary coalescences provide a clean setting for probing additional fields coupled to gravity. By analyzing the ringdown signals of the loudest LIGO-Virgo-KAGRA binary-black hole mergers, we search for massless curvature-coupled (pseudo)scalar fields arising in extensions to general relativity. We find no evidence for such fields and place 90% credible upper limits on the coupling length scale, $\ell \lesssim (25–45)$ km, corresponding to scales significantly below the horizons of the remnant black holes. These results include the first gravitational-wave constraint on an axidilaton-type coupling. By isolating the ringdown phase and performing extensive robustness checks, our analysis provides a complementary observational probe to existing full-waveform constraints. As the gravitational-wave catalog expands, black hole ringdown spectroscopy will enable increasingly sensitive probes of gravity and additional fields using astrophysical black holes.

The conservation of superhorizon curvature perturbations in strongly interacting inflationary models, particularly in the presence of quantum-loop corrections, remains a topic of active debate. We found that this conservation is essentially a direct consequence of the background-fluctuation splitting symmetry. We demonstrate that the associated Ward identity imposes strict nonperturbative constraints on the infrared power spectrum. This finding provides a rigorous, symmetry-based framework for understanding nonlinear quantum fluctuations in the primordial universe.

Holographic black holes exhibit a striking relation between thermal boundary one-point functions and bulk geodesic lengths. In the large conformal-dimension limit, the one-point function of a primary operator is given by the exponential of the geodesic length from its boundary insertion point to the horizon. We test the robustness of this relation under perturbations by considering a class of deformations of an Euclidean Bañados-Teitelboim-Zanelli (BTZ) black hole, working to first order in the perturbation. We find that, at leading order in the large conformal-dimension limit and to first order in the radial horizon-preserving perturbation, the logarithmic variation of the one-point function is governed by the variation of the renormalized boundary-to-horizon geodesic length. The result is established using Wentzel-Kramers-Brillouin (WKB) and saddle-point methods, and WKB expressions at large conformal dimensions are checked against the exact Green function and bulk-boundary propagator.

We investigate the holographic realization of topological operators for continuous non-Abelian symmetries in quantum field theories. As a concrete case study, we focus on type IIB string theory on ${\mathrm{AdS}}_5\times S^5$ which admits an $SO(6)$ isometry, dual to the R-symmetry in 4D $\mathcal{N}=4$ super-Yang-Mills theory. We argue that symmetry operators for continuous symmetries are generally realized by bound states of D5-branes and Kaluza-Klein (KK) monopoles hanging from the conformal boundary. Together they account for the contributions to Gauss’s law constraints from the $G_5$ flux and the Einstein-Hilbert term respectively. We also demonstrate how the D5-KK bound state measures the representation of the end point of Wilson lines constructed by D3-branes.

The superconformal field theory (SCFT)/vertex-operator algebra (VOA) correspondence provides a powerful framework for studying 4d $\mathcal{N}=2$ SCFTs through the mathematical machinery of 2d VOAs. It captures the Schur operators of the underlying SCFT, whose spectrum is encoded by the Schur index and its refinement, the Macdonald index. While the Schur index is identified with the vacuum character of the associated VOA, a general VOA-based derivation of the Macdonald index has remained elusive. In this letter, we propose a novel and intrinsic method for recovering a special non-Schur limit of the Macdonald index directly from the VOA. The construction requires no additional assumptions and applies whenever the underlying 4d theory is unitary. We test the proposal in a variety of examples, and further extend it to the case with surface defects, suggesting a notion of graded unitarity in the presence of defects. Our method also introduces a new class of series for general VOAs, analogous to but distinct from the conventional character, and potentially useful in broader contexts.

Fast and reliable inference of gravitational-wave source parameters is crucial for analyzing large catalogs that are reaching the size of hundreds of detections and for identifying short-lived electromagnetic counterparts. Neural posterior estimation has emerged as a powerful inference method, where the model is trained on simulated gravitational-wave data at considerable computational cost but thereafter enables extremely fast and inexpensive inference at test time. Here, we extend this approach by incorporating domain-specific physical insights and methods in the model architecture. These include compressing the data by heterodyning against a reference waveform chosen via approximate likelihood maximization, removing parameter degeneracies through tailored coordinate systems, and eliminating known multimodalities by folding the parameter space. As a result, the network is approximately equivariant to changes in the source parameters and achieves a reduced training cost and improved model interpretability. Our implementation, called labrador, can be trained end-to-end on a 1-day timescale on $\sim {10}^2$ CPU cores and a V100 GPU, achieving a median importance-sampling efficiency of 1% on quadrupolar, aligned-spin signals in a broad mass range (chirp mass $\mathcal{M}\in 1-50M_{\odot }$, mass ratio $q>0.1$). labrador is the first neural inference code to achieve extensive coverage of long-duration signals with secondary masses $m_2<10M_{\odot }$, rendered possible by its equivariance property. Among our novel contributions is a numerically stable procedure that enables neural posterior estimation when the simulation and inference priors differ.

The standard Komar mass provides an elegant, quasilocal measure of total gravitating energy for stationary spacetimes, but it conventionally fails in dynamical scenarios that lack an exact global timelike Killing vector field. In this paper, we explore a generalized Komar energy integral bounded by a spacelike two-surface, obtained by replacing the Killing vector with the purely kinematic normal evolution vector field ${\xi }^{\mu }=N{\widehat{T}}^{\mu }$ associated with a $3+1$ spacelike foliation. Through a step-by-step mathematical derivation, we show that this generalized integral reduces to the spatial boundary flux of the Eulerian four-acceleration. Furthermore, by evaluating the asymptotic vacuum constraints in generic dynamical spacetimes without restricting the metric to an isotropic or transverse-traceless spatial gauge, we establish, at leading asymptotic order, a relationship mapping this flux to the global Arnowitt-Deser-Misner (ADM) mass. By constructing a superpotential for the linearized spatial Einstein tensor, we prove that the dynamically generalized Komar energy and the ADM mass are equivalent up to a boundary flux of the temporal evolution of the conjugate momentum. We verify this relationship through nontrivial analytical test cases involving dynamical gauge foliations and physical gravitational wave radiation, revealing that the geometric momentum flux isolates longitudinal time-slicing artifacts while naturally decoupling from transverse radiative degrees of freedom.

We present a loop quantization of the marginally bound Lemaître-Tolman-Bondi (LTB) model, describing the gravitational collapse of pressureless dust in spherical symmetry. The full quantum LTB model is constructed as a collection of noninteracting shells, each governed by an individual single-shell loop quantum dynamics. We show that the single-shell evolution is nonsingular and that wave packets initially peaked on a collapsing trajectory undergo a bounce at Planckian energy densities and subsequently follow an expanding classical trajectory, resolving the classical central curvature singularity. We also compare the loop quantum theory with the Wheeler-DeWitt quantization of the same model. Finally, we briefly comment on the accuracy of the loop quantum gravity effective theory in reproducing this full quantum dynamics. Specifically, we find that initially collapsing wave packets generically develop an interference pattern at the bounce, which suppresses the accuracy of the effective theory near the center of the dust cloud.

Next-generation gravitational-wave detectors will make black-hole ringdown an increasingly sensitive probe of small departures from General Relativity in the strong-field regime. This motivates obtaining high-precision predictions of gravitational effective field theory, as spectral shifts can be quite small. Here we perform a focused stress test of a modified black-hole perturbation framework by designing two null diagnostics. First, we consider an action with redundant operators that must produce zero first-order vacuum QNM shifts. Second, we exploit a Ricci-flat identity relating two physical cubic Riemann theories to test such a relation is satisfied by the ringdown spectra obtained. We compute the shifts using two independent numerical approaches; the eigenvalue-perturbation and generalized continued-fraction (Leaver-type) methods. Both null tests are passed across multiple multipoles and overtones, and the control-operator results agree in magnitude with the benchmark values reported in Ref. [1]. These validations support using this modified black-hole perturbation framework for obtaining accurate predictions for robust strong-field tests, with straightforward extensions to rotating backgrounds and coupling with matter fields.