We investigate light-cone smearing induced by quantum fluctuations of gravitons and its implications for the ultraviolet structure of quantum field theory. By treating the first-order correction to Synge’s world function as an operator, we show that the retarded Green’s function is smeared by the variance of graviton fluctuations. The smearing width depends on the quantum state of gravitons: vacuum fluctuations generate a Gaussian smearing of the light cone, coherent states shift the light-cone position, and squeezed states modify the smearing width itself. We then apply the smeared Feynman propagator to one-loop self-energies in interacting scalar field theories. Within a phenomenological finite-resolution prescription that keeps the effective width nonzero, the ultraviolet-sensitive short-distance terms in the ${\varphi }^3$ bubble and ${\varphi }^4$ tadpole diagram expressions are finite. For the illustrative choice that the coarse-graining scale is the Planck length, primordial gravitons induce a relative correction of order ${10}^{-10}$ to the one-loop self-energy. Our results suggest that the quantum state of gravitons can leave a finite imprint on the causal and short-distance structure of quantum field theory.

The standard $\mathrm{\Lambda }$ cold dark matter ($\mathrm{\Lambda }\mathrm{CDM}$) cosmological model faces increasing tensions between key observations, motivating tests that probe its underlying assumptions. In a companion Letter [S. M. Koksbang and A. Heinesen, Diagnostic consistency tests of the concordance cosmology, Phys. Rev. Lett. 137, 091001 (2026)], we present a model-independent framework that combines derivatives of the angular diameter distance, $d_A(z)$, and the line-of-sight expansion rate, $\mathcal{H}(z)$, to clarify the physical content of Friedmann-LeMaître-Robertson-Walker (FLRW) consistency relations and to construct a general-spacetime estimator of the cosmic density field. Here, we apply these tests to data, introducing a nonparametric reconstruction method based on symbolic regression combined with bootstrapping to provide data-driven uncertainty estimates. Using supernova and baryon acoustic oscillations data, we reconstruct $d_A$, $\mathcal{H}$, and their derivatives, enabling model-independent evaluation of FLRW relations and recovery of the sky-averaged density field over $z\in [0.38,\sim 2]$. Current data are too sparse to tightly constrain $\mathcal{H}(z)$, and the reconstructed density is consistent with both Planck and Supernova, $H_0$, for the Equation of State (SH0ES) data $\mathrm{\Lambda }\mathrm{CDM}$. Reconstructed FLRW consistency tests show mild to moderate deviations from FLRW expectations at the $\sim 2–4\sigma$ level, although their significance depends on data selection and reconstruction stability. If these indicated deviations from an FLRW geometry are real, it would signify that most of the cosmological solutions considered for solving the cosmological tensions (evolving/interacting dark energy, new types of matter/energy, modified gravity, etc., within the FLRW framework) are ruled out. These preliminary indications highlight the importance of future, denser distance and expansion rate measurements, as well as further work toward standardizing uncertainty estimation for symbolic-regression reconstructions.

In a gravitational lensing system, the relative transverse velocities of the lens, source, and observer induce a frequency shift in the observed radiation. While this shift is typically negligible in most astrophysical contexts, strategies for its detection have been proposed for both electromagnetic and gravitational waves. This paper provides a rigorous theoretical treatment of the effect, deriving general expressions for the frequency shift within a lensing system embedded in a cosmological spacetime. Our formulation remains valid for arbitrary distances and velocities—including highly relativistic regimes—under any Friedmann-Lemaître-Robertson-Walker metric. Expanding upon previous papers on moving lenses, we provide a detailed analysis of frequency effects induced by lenses moving at relativistic speeds. Furthermore, we extend standard lensing theory by deriving an exact formula for the variation in the source’s viewing direction. This result is of interest for strongly anisotropic emitters, such as compact binary systems emitting gravitational waves. Finally, we quantify the apparent misalignment between the lens and the source’s two images produced by time-delay effects in lens systems moving with high velocity.

In anticipation of the new wave of ALICE experiments on particle-resonance correlation functions, we study the interaction of a kaon with the $D_{s0}^{*}(2317)$ resonance. Assuming the $D_{s0}^{*}(2317)$ to be a $DK$ molecular state in isospin $I=0$, we employ the fixed center approximation to describe the kaon scattering off the $DK$ cluster, and implement elastic unitarity in the $K{D}_{s0}^{*}(2317)$ amplitude via an optical potential and the Lippmann-Schwinger equation. We evaluate the scattering length, effective range, and correlation function, which exhibits a shape characteristic of a strongly attractive interaction. Notably, the amplitude develops a narrow resonant peak about 40 MeV below the $K{D}_{s0}^{*}(2317)$ threshold, signaling a three-body bound state. We discuss the experimental feasibility of observing this state through the invariant mass distribution of $K{D}_s^{+}{\pi }^0$, and argue that such three-body states, predicted by various theoretical approaches, offer promising targets for future experimental searches, providing valuable insights into the nature of exotic hadronic resonances.

We study the dimension-six SMEFT four-lepton operators in the $\mu –\tau$ sector. These operators control both charged-lepton scattering and neutrino self-interactions, the latter being weakly constrained by direct laboratory probes despite their importance for cosmological tensions. We compare three classes of constraints on the Warsaw-basis coefficients $[C_{\ell \ell }{]}_{2222}$, $[C_{\ell \ell }{]}_{2233}$, and $[C_{\ell \ell }{]}_{2332}$. We use perturbative unitarity from $2\to 2$ partial-wave analysis, spin-summing positivity sum rules, and the experimental bounds from $\mathrm{NA}64\mu$ and the global fit [Adam Falkowski et al., Compilation of low-energy constraints on 4-fermion operators in the SMEFT, J. High Energy Phys. 08 (2017) 123.]. We find that the global fit dominates for $[C_{\ell \ell }{]}_{2222}$ and $[C_{\ell \ell }{]}_{2332}$, while $\mathrm{NA}64\mu$ provides the leading bound on $[C_{\ell \ell }{]}_{2233}$, with the unitarity line for this direction entering the range of collider energies near 200 GeV. Renormalization-group running between 1 GeV and 30 TeV modifies these coefficients by up to 10%. Translating these bounds onto the effective four-neutrino coupling $G_{\mathrm{eff}}$, we find values many orders of magnitude smaller than the strongly interacting regime motivated by the Hubble tension; this excludes heavy-mediator UV completions of strong ${\nu }_{\mu }–{\nu }_{\mu }$ and ${\nu }_{\mu }–{\nu }_{\tau }$ self-interactions within the validity of the dimension-six SMEFT and in the absence of tuned cancellations between operators, while leaving the cosmologically motivated light-mediator scenarios unconstrained by this analysis. Finally, we comment on the bounds these coefficients place on a leptophilic $L_{\mu }-L_{\tau }$ $Z^{\prime }$ UV completion. Our SMEFT-based current and projected $\mathrm{NA}64\mu$ bounds reproduce the dedicated $Z^{\prime }$ analyses already available in the literature. We also present a complementary analysis for the $e–\mu$ sector using projected JUNO sensitivities.

The singlet axial form factor of the nucleon provides essential input for a complete understanding of the nucleon axial structure. Together with the isovector and isoscalar octet channels, in the forward limit it forms the basis for a full flavor decomposition of the proton spin. In this work we present a lattice QCD determination of the singlet axial form factor $G_A^{u+d+s}(Q^2)$ and related strange contribution $G_A^s(Q^2)$ using a set of $N_f=2+1$ gauge ensembles generated by the Coordinated Lattice Simulations effort with $O(a)$-improved Wilson fermions, with a full error budget for the extrapolation to the chiral, continuum and infinite-volume limits. Particular focus is placed on the treatment of the disconnected contributions, which constitute the crucial element for the extraction of the strange component. Together with determinations of the isovector and isoscalar octet axial form factors, this work provides a comprehensive lattice QCD determination of the nucleon axial structure across different flavor channels.

We apply for the first time, to the best of our knowledge, the flow matching method to the problem of phase-space sampling for event generation in high-energy collider physics. By training the model to remap the random numbers used to generate the momenta and helicities of the scattering matrix elements as implemented in the portable partonic event generator pepper, we find substantial efficiency improvements in the studied processes. We focus our study on the highest final-state multiplicities in Drell-Yan and top-antitop pair production used in simulated samples for the Large Hadron Collider, which computationally are the most relevant ones. We find that the unweighting efficiencies improve by factors of 184 and 25, respectively, when compared to the standard approach of using a vegas-based optimization. We also compare continuous normalizing flows trained with flow matching against the previously studied normalizing flows based on coupling layers and find that the former leads to better results, faster training and a better scaling behavior across the studied multiplicity range, while the latter evaluate faster. When combining the advantages of both methods using the regflow approach, we find parton-level unweighted event generation walltime gains of about a factor of 10 at the highest final-state multiplicities.

The $B$-factory experiments operate at electron-positron colliders with beam energies precisely tuned for optimal $B^0\text{−}{\overline{B}}^0$ meson pair production. These $B^0\text{−}{\overline{B}}^0$ meson pairs are entangled and offer a unique opportunity to explore quantum correlations and examine the foundational aspects of quantum mechanics. In this work, we present a comprehensive analysis of entanglement metrics in the $B$-meson system within the framework of open quantum systems, which introduces decoherence due to interactions with the environment. We examine several distinct entanglement measures, each highlighting different facets of quantum entanglement and its sensitivity to decoherence effects. We further analyze the impact of decoherence by systematically varying the decoherence parameter across different scales.

Using $e^{+}{e}^{-}$ collision data corresponding to an integrated luminosity of $20.3{\mathrm{fb}}^{-1}$, collected at the center-of-mass energy of 3.773 GeV with the BESIII detector, we present precise measurements of $D^0\to K^{-}{\ell }^{+}{\nu }_{\ell }$ and $D^{+}\to {\overline{K}}^0{\ell }^{+}{\nu }_{\ell }$ ($\ell =e$, $\mu$) decays. The branching fractions of $D^0\to K^{-}{e}^{+}{\nu }_e$, $D^0\to K^{-}{\mu }^{+}{\nu }_{\mu }$, $D^{+}\to {\overline{K}}^0{e}^{+}{\nu }_e$, and $D^{+}\to {\overline{K}}^0{\mu }^{+}{\nu }_{\mu }$ are measured to be $(3.548\pm 0.006_{\mathrm{stat}}\pm 0.017_{\mathrm{syst}})\%$, $(3.445\pm 0.007_{\mathrm{stat}}\pm 0.017_{\mathrm{syst}})\%$, $(8.928\pm 0.025_{\mathrm{stat}}\pm 0.050_{\mathrm{syst}})\%$, and $(8.770\pm 0.029_{\mathrm{stat}}\pm 0.053_{\mathrm{syst}})\%$, respectively. The partial decay rates of these four decays are measured with improved precision, and their forward-backward asymmetries are determined for the first time. By performing a simultaneous fit to the measured partial decay rates and the forward-backward asymmetries of $D\to \overline{K}{\ell }^{+}{\nu }_{\ell }$, a search for a possible scalar current contribution in the $c\to s{\ell }^{+}{\nu }_{\ell }$ transition is performed. The results are $\mathrm{Re}(c_S^{\mu })=0.017\pm 0.008_{\mathrm{stat}}\pm 0.006_{\mathrm{syst}}$ and $\mathrm{Im}(c_S^{\mu })=\pm (0.077\pm 0.011_{\mathrm{stat}}\pm 0.009_{\mathrm{syst}})$, corresponding to a difference from the Standard Model (SM) with a significance of $2.3\sigma$. The product of the form factor $f_{+}(0)$ and the modulus of the $c\to s$ Cabibbo-Kobayashi-Maskawa matrix element $|V_{\mathrm{cs}}|$ is determined to be $f_{+}(0)|V_{\mathrm{cs}}|=0.7183\pm 0.0007_{\mathrm{stat}}\pm 0.0014_{\mathrm{syst}}$. With the inputs $|V_{\mathrm{cs}}|=0.97349\pm 0.00016$ from the SM global fit or $f_{+}(0)=0.7452\pm 0.0031$ from the lattice quantum chromodynamics calculation, we derive $f_{+}(0)=0.7383\pm 0.0007_{\mathrm{stat}}\pm 0.0014_{\mathrm{syst}}$ and $|V_{\mathrm{cs}}|=0.9639\pm 0.0009_{\mathrm{stat}}\pm 0.0018_{\mathrm{syst}}\pm 0.0040_{\mathrm{LQCD}}$. Combining with the results of the semimuonic and semielectronic decays, lepton flavor universality is tested via the ratios of the decay rates between semimuonic and semielectronic decays in the full and different momentum transfer ranges.

We develop bootstrap methods for mixed heavy-light four-point correlators $⟨GGOO⟩$ in $\mathcal{N}=4$ super-Yang-Mills theory at large $N$, where $O\equiv {\mathcal{O}}_2$ is the chiral primary operator in the stress-tensor multiplet and $G$ are (dual) giant graviton operators with dimension of order $N$, including the maximal determinant case. The loop integrand is expanded in a basis of labeled $f$-graphs—necessarily including nonplanar topologies due to the dimension-$N$ nature of the giant gravitons—and the coefficients are fixed by various bootstrap conditions, including double-triangle and triangle rules in the cusp and operator product expansion limits, integrated correlators from supersymmetric localization, and a ten-dimensional hidden symmetry, the latter also allowing extension to correlators involving generic chiral primaries ${\mathcal{O}}_k$. Together, these inputs uniquely determine the correlator through three loops, passing further nontrivial consistency checks. For the maximal determinant operator, we reproduce the known results through two loops and obtain the full three-loop correction.

This paper is a continuation of our earlier work, which aimed to develop methods for understanding the renormalization group of tensorial group field theories within the stochastic quantization framework. In that first study, we showed that the equations governing melonic structures, together with Ward identities, make it possible to close the hierarchy of flow equations, thereby reproducing the results of equilibrium theory. In the present work, we go further by extending the formalism to the out-of-equilibrium regime, while also examining the stability of dynamical equilibrium, specifically, potential violations of the fluctuation-dissipation theorem. Our objective here is purely methodological, and we focus on a simplified “toy” Abelian model that retains only the characteristic nonlocalities of group field theories.

Fliss et al. [Phys. Rev. D 95, 126001 (2017).] extended the exact renormalization group (ERG) to arbitrary wave functionals in quantum field theory. Applying this formalism, we show that a Lindblad master equation gives the ERG flow of density matrices. The Lindbladian consists of a “Hamiltonian” term, which is the sum of a scaling and a coarse-graining (disentangling) operator, and a dissipative term with absorption and emission rates for each momentum mode. We consider as examples the flow of Gaussian states and the perturbative ground state of $\lambda {\varphi }^4$ theory and highlight the role of the dissipative terms in generating accurate contributions to the flow of couplings at nontrivial order in $\lambda$. Integrating the Lindblad master equation, we find that a finite ERG flow of density matrices is described by a quantum channel. It follows from the data processing inequality that any distinguishability measure of states is an ERG monotone.

GW250114 is the loudest gravitational wave event to date observed by LIGO-Virgo-KAGRA Collaboration. Owing to its high signal-to-noise ratio (SNR), previous analyses based on quasinormal mode (QNM) superpositions have suggested evidence of the fundamental and the first overtone of the $\ell =m=2$ mode in this event. However, QNMs are not orthogonal and the inclusion of multiple QNMs induces correlations among them, which can hinder the robust identification of subdominant QNMs. To address this challenge, we apply an analysis based on orthonormalized QNMs [S. Morisaki et al., Phys. Rev. D 112, 124083 (2025)] to GW250114. We find that, in the model including three $\ell =m=2$ QNMs up to the second overtone, the first overtone of the $\ell =m=2$ mode is more strongly supported than in previous nonorthogonal analyses, with the inferred significance increasing from 86.2% to 99.9%. Furthermore, we estimate deviations from the Kerr prediction using the orthonormal QNM framework and find no significant deviation, consistent with previous analyses. These results demonstrate that the orthonormal QNM framework provides a more robust way to identify subdominant modes in high-SNR ringdown signals, highlighting its potential for future gravitational wave observations.

We study how dark matter environments influence nonlinear gravitational memory from intermediate-mass-ratio binaries. Incorporating environmental effects from the dark matter gravitational potential, dynamical friction, and accretion, we compute the leading-order nonlinear memory for both bound and unbound orbits under dark matter minispike profile. For quasicircular inspirals in a minispike, we additionally include an empirical prescription for the time-dependent evolution of the dark matter profile, which gradually evolves along the inspiral and captures the cumulative environmental response. We find that dark matter can modify the orbital evolution and mode content of the memory relative to the vacuum case, with the cumulative effect depending sensitively on the density profile and on how the environment accelerates the inspiral. We use these waveforms to calculate mismatches in the Laser Interferometer Space Antenna space-based detector, highlighting where memory-driven differences may be large enough to warrant targeted parameter-estimation studies. Our results emphasize that astrophysical environments can leave a hereditary imprint on gravitational memory and provide a framework for connecting memory observables with dark matter dynamics.

The threshold of black hole formation in axisymmetric vacuum gravity is proving to be more complicated than had been anticipated, but, following recent advances, a consensus between independent codes and methods is emerging. Building on earlier work, we provide further details of a comparison between three independent numerical codes (the bamps, prague, and sphgr codes), paying special attention to the relative strengths and weaknesses of each and examining various features of near-threshold collapse of vacuum gravitational waves for the first time. In particular, we observe quasiuniversal strong-field features appearing in curvature scalars. Focusing on geometric features on the symmetry axis, we construct reference coordinates to aid the comparison of strong-field data. We evolve, for the first time, time-asymmetric wave initial data within the bamps code. To the extent possible with current methods, we compare apparent horizons and attempt to determine what causes difficulties in the classification of these strong-field and highly dynamical spacetimes. In all cases the results from the three codes agree very well.

Gravitational-wave memory is a low-frequency, nonoscillatory component of the radiation field that provides a potentially powerful but as yet undetected probe of strong-field gravity. We present the first calculation of gravitational memory from full inspiral-merger-ringdown waveforms in a theory beyond general relativity, focusing on scalar-Gauss-Bonnet gravity as a theoretically well-motivated and numerically accessible extension of GR. Starting from the general memory formulas in Horndeski gravity, we derive explicit spin-weighted spherical-harmonic expressions for the tensor null memory in scalar-Gauss-Bonnet theory and evaluate them on existing numerical-relativity waveforms for both shift-symmetric and dynamically scalarizing binary black hole mergers. We find that the dominant effect is an indirect modification of the tensor memory through changes in the nonlinear merger dynamics, while the direct scalar contribution to the tensor memory remains suppressed by orders of magnitude for the systems considered in this work. For the largest deviations in our dataset, the final memory amplitude differs from the corresponding GR prediction by a few percent and by up to $\sim 4\%$ when compared to the GR template that minimizes the waveform mismatch in a detector-oriented analysis. We further show that including memory increases the mismatch between GR and scalar-Gauss-Bonnet waveforms by more than an order of magnitude, indicating that memory can provide complementary information for testing gravity with third-generation detectors, especially for low-mass binaries.

We study the spinning two-body system in the aligned spin case for hyperboliclike motions computing all radiative losses [at the 2 post-Newtonian (PN) absolute accuracy and including spin-squared corrections] using the MPM formalism and generalizing previous results valid at linear order in spin [D. Bini et al., Spin-orbit contribution to radiative losses for spinning binaries with aligned spins, Phys. Rev. D 108, 064049 (2023)]. Leading PM order results are checked against existing literature, whereas higher-order PM results (within the 2PN accuracy) are new with this work. As a byproduct of our general results we analyze the spinning situation which supports radial fall (at 2PN and including spin-squared accuracy level contributions), showing that as soon as the PN accuracy increases deviations from radial fall appear necessarily.

Dark matter and dark energy could be ultralight pseudoscalar fields that couple to electromagnetism through a Chern-Simons term. This would cause a parity-breaking rotation of the plane of linearly polarized light from the cosmic microwave background, known as cosmic birefringence, which is not predicted by $\mathrm{\Lambda }$ cold dark matter. Recent hints of a nonzero cosmic birefringence angle have been found in both the Planck Data Release 4 and Atacama Cosmology Telescope Data Release 6 datasets independently. This work jointly analyzes the polarized maps of both, leveraging the cross-power spectra between the two telescopes. Taking the reported instrumental priors at face value, the joint analysis yields $\beta =0.277°\pm 0.057°$, which is nonzero with a statistical significance of $4.8\sigma$. A robustness test mitigating contamination from dust emission excludes $\beta =0°$ at $3.5\sigma$, and retrieving $\beta =0°$ would require both the dust $EB$ modeling and instrumental priors to fail simultaneously. However, unresolved systematics in the data must be understood before we can draw strong cosmological conclusions.

We study the optical depth to reionization in a cosmological setting that includes backreaction from matter inhomogeneities, using the Buchert averaging formalism. We construct a spacetime model consisting of multiple inhomogeneous domains, hereafter referred to as the backreaction model, characterized by a set of parameters. We first examine how these parameters influence the computation of the optical depth to reionization, ${\tau }_{\mathrm{reion}}$. Next, we carry out a Markov chain Monte Carlo (MCMC) analysis based on the Pantheon+sh0es type Ia supernova sample to infer the best-fit values of the model parameters, and then use these to evaluate ${\tau }_{\mathrm{reion}}$. We obtain ${\tau }_{\mathrm{reion}}=0.0581_{-0.0096}^{+0.0105}$ (68% confidence limits). This result indicates that, when Pantheon+sh0es data are used to constrain the model parameters, our backreaction model yields a value of ${\tau }_{\mathrm{reion}}$ that aligns more closely with observational estimates than the value predicted by the standard cosmological model. We further demonstrate that the backreaction model leads to a modest reduction of the Hubble tension, while avoiding the need for exotic or nonstandard physics.