Coherent elastic neutrino-nucleus scattering ($\mathrm{CE}\nu \mathrm{NS}$) is a key process for probing Standard Model and beyond the Standard Model (BSM) properties. Following its first detection by the COHERENT Collaboration, recent reactor-based experiments provide a unique opportunity to refine our current understanding. In particular, the high-precision data from $\mathrm{CONUS}+$, combined with the strong bounds from TEXONO, not only validate the $\mathrm{CE}\nu \mathrm{NS}$ process at low energies but also provide improved constraints on the weak mixing angle, neutrino electromagnetic properties (including the charge radius, millicharge, and magnetic moment), and nonstandard interactions and light mediators. We also examine the role of elastic neutrino-electron scattering, which gains significance in certain BSM scenarios and allows us to obtain the best limit for the millicharge of the electron neutrinos. By combining reactor and higher-energy spallation neutron source measurements, this work strengthens $\mathrm{CE}\nu \mathrm{NS}$ as a precision tool for testing the Standard Model and beyond.

We introduce a new approach to modeling transition distribution amplitudes (TDAs) for the processes $ep\to en{\pi }^{+}$ and $ep\to ep{\pi }^0$. The modeling is flexible, constrained by sparsely available experimental data, and satisfies theoretical requirements, including reduction to nucleon distribution amplitudes in the appropriate limit. We study the sensitivity of observable predictions to various modeling assumptions. We discuss unpolarized cross sections, as well as the three nonvanishing polarization observables at leading twist, namely, the single transverse target spin asymmetry and the two double spin asymmetries that occur with a polarized lepton beam on either a longitudinally or transversely polarized target. The analysis is complemented by a simple Monte Carlo study to provide guidance for exploring exclusive processes in the so-called backward kinematics. Our work aims to highlight the importance of future measurements to better constrain TDAs and to support upcoming experimental proposals.

Using a symmetry-preserving treatment of a vector $\times$ vector contact interaction at nonzero temperature, we compute the screening masses of flavor-SU(3) ground-state $J^P=0^{\pm }$, $1^{\pm }$ mesons, and $J^P=1/2^{\pm }$, $3/2^{\pm }$ baryons. We find that all correlation channels allowed at $T=0$ persist when the temperature increases, even above the QCD phase transition temperature. The results for mesons qualitatively agree with those obtained from the contemporary lattice-regularized quantum chromodynamics simulations. One of the most remarkable features is that each parity-partner-pair degenerates when $T>T_c$, with $T_c$ being the critical temperature. For each pair, the screening mass of the negative parity meson increases monotonously with temperature. In contrast, the screening mass of the meson with positive parity is almost invariant on the domain $T\lesssim T_c/2$; when $T$ gets close to $T_c$, it decreases but soon increases again and finally degenerates with its parity partner, which signals the restoration of chiral symmetry. We also find that the $T$-dependent behaviors of baryon screening masses are quite similar to those of the mesons. For baryons, the dynamical, nonpointlike diquark correlations play a crucial role in the screening mass evolution. We further calculate the evolution of the fraction of each kind of diquark within baryons respective to temperature. We observe that, at high temperatures, only $J=0$ scalar and pseudoscalar diquark correlations can survive within $J^P=1/2^{\pm }$ baryons.

In this manuscript we study the exclusive photoproduction of ${\chi }_c\gamma$ pairs in the collinear factorization framework. We found the coefficient functions for all possible spins and helicity projections of ${\chi }_c$ mesons and final-state photons in the leading order in the strong coupling ${\alpha }_s$. In our analysis we focused on the contribution of the leading twist chiral-even generalized parton distributions (GPDs) and found that for all spin states of ${\chi }_c$ the suggested process is largely determined by the behavior of the gluon GPDs $H_g$. Using the phenomenological parametrizations of the GPDs from the literature, we estimated numerically the photoproduction cross sections and the expected counting rates in the kinematics of medium-energy photoproduction experiments that could be realized at the Electron-Ion Collider. We observed that the ${\chi }_{c1}$, ${\chi }_{c2}$ mesons are produced predominantly with the same polarization as the incoming photon, and the expected counting rates of ${\chi }_{c1}\gamma$ and ${\chi }_{c2}\gamma$ pairs are sufficiently large for their experimental study. We also analyzed the angular distribution of ${\chi }_c$ mesons in electroproduction experiments and noticed that for some helicity components there are sizable angular asymmetries, which can be used as complementary observables for experimental study. Finally, we estimated the role of this process as a potential background to ${\chi }_c$ photoproduction, which has been recently suggested as a tool for studies of odderons. We found that the contribution of ${\chi }_c\gamma$ (with undetected photon) is on par with expected contributions of odderons and Primakoff mechanisms in the kinematics of small momentum transfer $|t|\lesssim 1{\mathrm{GeV}}^2$, but becomes negligible at larger $|t|$.

Spin correlation observables of particles produced at colliders generally depend on the coordinate basis. While spin correlations and their associated basis dependence have been studied in top-quark pair production, the basis dependence of spin correlations of $W^{\pm }$ pairs has not been studied. In this work, we focus on the azimuthal-angle correlation in the decay of $W^{\pm }$ pairs, which encodes spin information in the direction transverse to the rotational axis. We quantitatively describe the basis dependence of the relative azimuthal angle. We further present the optimal coordinate direction to define the azimuthal angle between the decay products of $W^{\pm }$ bosons to achieve the maximal spin correlation based on symmetry considerations. The results can be used to optimize the measurement of the $CP$-even and $CP$-odd interactions, and have applications to quantum information observables in the vector boson pair system.

The choice of unfolding method for a cross-section measurement is tightly coupled to the model dependence of the efficiency correction and the overall impact of cross-section modeling uncertainties in the analysis. A key issue is the dimensionality used in unfolding, as the kinematics of all outgoing particles in an event typically affect the reconstruction performance in a neutrino detector. OmniFold is an unfolding method that iteratively reweights a simulated dataset, using machine learning to utilize arbitrarily high-dimensional information, that has previously been applied to proton-proton and proton-electron datasets. This paper demonstrates OmniFold’s application to a neutrino cross-section measurement for the first time using a public T2K near detector simulated dataset, comparing its performance with traditional approaches using a mock data study.

Circular polarization in the cosmic microwave background (CMB) offers a promising probe of the parity-violating physics of the early Universe. In this paper, we propose a novel method to constrain the primordial circular polarization of high-frequency gravitational waves (GW) in the GHz range. An efficient conversion of gravitons to photons in a transverse cosmological magnetic field at the epoch of last scattering can generate excess chiral photons if the GW background is chiral in nature. This excess radiation distorts the CMB thermal black-body spectrum, which can be estimated by measuring the V-Stokes parameter in the CMB polarization. Using current upper limits on the angular power spectrum of circular polarization $C_l^{VV}$ from the CLASS, MIPOL, and SPIDER experiments, we obtain the most stringent constraints on the characteristic strain and circular polarization of the isotropic background of stochastic GWs at 40 GHz and 150 GHz, respectively. Our work, therefore, provides an interesting possibility to constrain the circular polarization of high-frequency GWs using the V-mode polarization measurements of CMB.

This work employs the quantum extremal surface framework to compute the Page curve for black holes corrected by nonextensive entropy. The entropy of Hawking radiation increases linearly with time, leading to the persistence of the information paradox for nonextensive entropy-corrected black holes. At late time, we extremize the generalized entropy functional; incorporating contributions from both matter and the quantum extremal island, we establish that the entanglement entropy of Hawking radiation saturates to the nonextensive extension of the Bekenstein-Hawking entropy. Finally, we study the dependence of nonextensive parameters on the Page time.

In recent years, the holographic duality between $T\overline{T}$-deformed conformal field theory (CFT) and Anti-de Sitter (AdS) spacetime with finite radial cutoff has received significant attention. The study of $T\overline{T}$ deformation within the framework of de Sitter (dS)/CFT duality has also progressed. This paper shows that the trace flow equation in dS spacetime can be analytically extended from its AdS counterpart through double Wick rotations. Meanwhile, we generalize the replica method in both AdS and dS holography to derive a general expression for the entanglement entropy of arbitrary single spatial intervals within the $T\overline{T}$-deformed framework. For both finite size and finite temperature systems, we obtain the analytical expression for the entanglement entropy after $T\overline{T}$ deformation. Finally, in dS/dS holography and half-dS holography, we find that the dual field theory exhibits nonlocality by analyzing the strong subadditivity and boosted strong subadditivity of entanglement entropy.

In a flat background, the canonical energy momentum tensor of Lorentz and conformally invariant matter field theories can be improved to a symmetric and traceless tensor that gives the same conserved charges. We argue that the geometric origin of this improvement process is unveiled when the matter theory is coupled to metric-affine gravity. In particular, we show that the Belinfante-Rosenfeld improvement terms correspond to the matter theory’s hypermomentum. The improvement terms in conformally invariant matter theories are also related to the hypermomentum; however, a general proof would require an extended investigation. We demonstrate our results through various examples, such as the free massless scalar, the Maxwell field, Abelian $p$-forms, the Dirac field, and a nonunitary massless scalar field. Possible applications of our method for theories that break Lorentz or special conformal invariance are briefly discussed.

In the absence of a unique, gauge-independent definition of eccentricity in general relativity, there have been efforts to standardize the definition for gravitational-wave astronomy. Recently, Shaikh et al. proposed a model-independent measurement of eccentricity $e_{\mathrm{gw}}$ from the phase evolution of the dominant mode. Many works use loss functions (LFs) to assign eccentricity to a reference waveform, for instance by fitting a post-Newtonian expression to assign eccentricity to numerical relativity (NR) simulations. Therefore, we ask whether minimizing common LFs on gauge-dependent model parameters, such as the mismatch $\mathcal{M}$ or the $L_2$-norm of the dominant mode ${\mathcal{h}}_{22}$ residuals, for nonprecessing binaries, ensures a sufficient $e_{\mathrm{gw}}$ agreement. We use 10 eccentric NR simulations and the eccentric waveform teobresums-dalí as the parametric model to fit on eccentricity $e_0$ and reference frequency $f_0$. We first show that a minimized mismatch, the $\mathcal{M}\sim {10}^{-3}–{10}^{-2}$ results in better $e_{\mathrm{gw}}$ fractional differences ($\sim 1\%$) than with the minimized ${\mathcal{h}}_{22}$ residuals. Nonetheless, for small eccentricity NR simulations $(e_{\mathrm{gw}}\lesssim {10}^{-2})$, the mismatch can favor quasicircular ($e_0=0$) best-fit models. Thus, with sufficiently long NR simulations, we can include $e_{\mathrm{gw}}$ in the LF. We explain why solely fitting with $e_{\mathrm{gw}}$ constitutes a degenerate problem. To circumvent these limitations, we propose to minimize a convex sum of $\mathcal{M}$ and the $e_{\mathrm{gw}}$ difference to both assign nonzero eccentric values to NR strains and to control the mismatch threshold.

In this work we investigate some non-Newtonian effects in exact solutions of the Einstein equations, which describe stationary and axisymmetric configurations of self-gravitating dust. A distinctive feature of these solutions is the potential presence of conical singularities along the rotation axis, manifesting as angular deficits. While such singularities can be removed by imposing suitable boundary conditions along the axis, asymptotically far away from it the geometry becomes locally flat, in the sense that the Riemann tensor vanishes, but globally, instead of reducing to Minkowski space, it takes the form of a cone. We refer to these spacetimes as asymptotically conically Minkowskian (ACM). We show that such conical structure can originate some interesting effects as seen by asymptotic local observers. These include modifications to the gravitational lensing and the misinterpretation of the vacuum state of a scalar field as a distribution of scalar particles.

Compact binary sources that emit gravitational waves (GW) are expected to be both spinning and on eccentric orbits. No closed-form expression for the phasing of GWs are available to date that contain information from both spin and eccentricity. The introduction of eccentricity can slow waveform generation, often requiring slower numerical methods governing its evolution. However, closed-form expressions for the waveform phase can be obtained when eccentricity is treated as a small parameter, enabling quick waveform generation. In this paper, closed-form expressions for the GW phasing in the form of Taylor approximants up to the eighth power in initial eccentricity ($e_0$) are obtained while also including aligned spins up to the third post-Newtonian order. The phasing is obtained in both time and frequency domains. The fully analytical approximant (taylort2) is also resummed for usage in scenarios where initial eccentricities are as high as 0.5. The frequency domain approximant (taylorf2) based on stationary phase approximation is compared with an existing model (taylorf2ecc) to assess the importance of the newly computed eccentric/spinning terms. The findings indicate that for eccentricities $\gtrsim 0.15$ (defined at 10 Hz) and small spins ($\sim 0.2$), the mismatches can be higher than 1%. This leads to an overall loss in signal-to-noise ratio and lower detection efficiency of GWs coming from eccentric spinning compact binary inspirals if the combined effects of eccentricity and aligned spins are neglected in the waveforms.

In linear perturbation theory, the ringdown of a gravitational wave (GW) signal is described by a linear combination of quasinormal modes (QNMs). Detecting QNMs from GW signals is a promising way to test GR, central to the developing field of black-hole spectroscopy. More robust black hole spectroscopy tests could also consider the ringdown amplitude-phase consistency. That requires an accurate understanding of the excitation and stability of the QNM expansion coefficients. In this paper, we investigate the robustness of the extracted $m=2$ QNM coefficients obtained from a high-accuracy numerical relativity waveform. We explore a framework to assess the robustness of QNM coefficients. Within this framework, we not only consider the traditional criterion related to the constancy of a QNM’s expansion coefficients over a window in time, but also emphasize the importance of consistency among fitting models. In addition, we implement an iterative greedy approach within which we fix certain QNM coefficients. We apply this approach to linear fitting, and to nonlinear fitting where the properties of the remnant black hole are treated as unknown variables. We find that the robustness of overtone coefficients is enhanced by our greedy approach, particularly for the $(2,2,2,+)$ overtone. Based on our robustness criteria applied to the $m=2$ signal modes, we find the $(2\sim 4,2,0,+)$ and $(2,2,1\sim 2,+)$ modes are robust, while the $(3,2,1,+)$ subdominant mode is only marginally robust. After we subtract the contributions of the $(2\sim 4,2,0,+)$ and $(2\sim 3,2,1,+)$ QNMs from signal mode (4, 2), we also find evidence for the quadratic QNM $(2,1,0,+)\times (2,1,0,+)$.

Regular and spherically symmetric black holes that solve the singularity problems of the Schwarzschild solution are phenomenologically viable at large distances but usually suffer from the Cauchy horizon instability. To overcome this drawback, we extended the analysis to include hyperbolic and toroidal horizon topologies within the framework of static, topologically maximally symmetric spacetimes. We show that both hyperbolic and toroidal black holes can be constructed without Cauchy horizons and without curvature singularities, thereby avoiding the mass inflation instability. These solutions exhibit asymptotic flatness in a generalized quasi-Minkowskian sense. The phenomenological aspects of these solutions are also studied by examining their thermodynamic properties, the photon sphere, and the effective potentials, ensuring consistency with observable properties such as black hole shadows. Lastly, we investigate a reconstruction technique within a scalar-tensor gravity framework, illustrating how the discussed metrics can arise from well-defined scalar field dynamics. Our investigation presents a viable pathway for constructing physically realistic, regular black holes in both general relativity and modified gravity, broadening the landscape of singularity-free spacetimes and offering models that may better reflect the nature of strong gravitational fields in astrophysical and cosmological settings.

Schwarzschild black holes evolve toward their static configuration by emitting gravitational waves, which decay over time following a power law at fixed spatial positions. We derive this power law analytically for the second-order even gravitational perturbations, demonstrating that it is determined by the fact that the second-order source decays as the inverse square of the distance. Quadratic gravitational modes with multipole $\ell$ decay according to a law $\sim t^{-2\ell -1}$, in contrast to the linear Price law scaling $\sim t^{-2\ell -3}$. Consequently, nonlinear tails may persist longer than their linear counterparts.

In this article, the quantum representation of the algebra among reduced twisted geometries (with respect to the Gauss constraint) is constructed in the gauge-invariant Hilbert space of loop quantum gravity. It is shown that the reduced twisted geometric variables not only describe the spatial discrete geometry more clearly, but also form a simple Poisson algebra which is analogous to that in quantum mechanics. By regularizing the reduced twisted geometric variables properly, the fundamental algebra of reduced twisted geometry is established, with the gauge-invariant Hilbert space in loop quantum gravity as the corresponding quantum representation space. This quantum representation also leads to fundamental operators associated with reduced twisted geometry. Based on these fundamental operators, a new type of extrinsic curvature operator is constructed in loop quantum gravity.

We study deviations from geodesic motions in a topological star spacetime for either massive, charged and spinning particles, elucidating different behaviors with the Schwarzschild spacetime. We also consider the deviations for the motion of electrically charged stringy probes in $D=5$, framing all cases within a unified picture.

In the presence of nonminimal gravitational couplings, matter field perturbations on a static black hole spacetime may develop unphysical poles in their linearized equations. Physical solutions confined in the domain between the event horizon and a pole satisfy a boundary value problem, although with boundary conditions which are different from standard quasinormal modes. We refer to them as “trapped quasinormal modes.” Focusing on a Schwarzschild black hole in Einstein-Proca theory, we find that trapped quasinormal modes accurately capture the behavior of perturbations under time evolution. In particular, axial-vector modes are unstable, with a growth rate that increases with multipole number. More interestingly, we uncover a new instability that affects monopole perturbations. These results confirm the existence of a novel destabilization mechanism of black holes by nonminimally coupled vector fields, with potential implications to well-studied models of modified gravity and cosmology based on vector particles.