We study the effects of off-shellness in the generalized parton distributions of the pion. On general grounds, these distributions exhibit a richer structure than in the on-shell case due to absence of the crossing symmetry. In particular, their moments involve additional terms odd in the skewness parameter, associated with new form factors. We bring up relations between the off-shell charge and gravitational form factors, as well as the pion form factor, and discuss their derivations based on the Ward-Takahashi identities. We illustrate the features at the (leading-$N_c$) one-quark-loop level with the help of the spectral quark model of the pion, constructed to embed the vector meson dominance. Simple analytic expressions for the form factors and the distributions follow. Thus obtained off-shell generalized parton distributions are evolved from the quark model scale to higher scales with the leading-order Dokshitzer-Gribov-Lipatov-Altarelli-Parisi equations. We evaluate the corresponding Compton amplitudes which enter the cross section for the electroproduction of the pion off the proton (the Sullivan process). It is found in our model that the effects of off-shellness in the generalized parton distribution are substantial, however, they can be largely canceled by the corresponding off-shell corrections to the pion propagator. In particular, this is the case of the Compton form factors entering the deeply virtual Compton scattering amplitude. As a result, we expect small off-shellness effects in electroproduction reactions, such as the Sullivan process.

We use the Kovchegov-Levin equation to resum contributions of large invariant mass diffractive final states to diffractive structure functions in the dipole picture of deep inelastic scattering. For protons we use a (modified) McLerran-Venugopalan model as the initial condition for the evolution, with free parameters obtained from fits to the HERA inclusive data. We obtain an adequate agreement to the HERA diffractive data in the moderately high-mass regimes when the proton density profile is fitted to the diffractive structure function data in the low-mass region. The HERA data is found to prefer a proton shape that is steeper than a Gaussian. The initial conditions are generalized to the nuclear case using the optical Glauber model. Strong nuclear modification effects are predicted in diffractive scattering off a nuclear target in kinematics accessible at the future Electron-Ion Collider. In particular, the Kovchegov-Levin evolution has a strong effect on the $Q^2$-dependence of the diffractive cross section.

In this work, the SuSAv2 and dynamical coupled-channels (DCC) models have been combined and tested in the inelastic regime for electron and neutrino reactions on nuclei. The DCC model, an approach to study baryon resonances through electron and neutrino induced meson production reactions, has been implemented for the first time in the SuSAv2-inelastic model to analyze the resonance region. Within this framework, we also present a novel description about other inelasticities in the resonance region (SoftDIS). The outcomes of these approaches are firstly benchmarked against ($e$, $e^{\prime }$) data on ${}^{12}\mathrm{C}$. The description is thus extended to the study of neutrino-nucleus inclusive cross sections on ${}^{12}\mathrm{C}$ and ${}^{40}\mathrm{Ar}$ and compared with data from the T2K, MicroBooNE, ArgoNEUT, and MINERvA experiments, thus covering a wide kinematical range.

Using data samples collected at center-of-mass energies between 2.000 and 3.080 GeV with the BESIII detector operating at the BEPCII collider, a partial-wave analysis is performed on the process $e^{+}{e}^{-}\to \eta {\pi }^{+}{\pi }^{-}$. In addition to the dominant $e^{+}{e}^{-}\to \rho \eta$ component, the $e^{+}{e}^{-}\to a_2(1320)\pi$ process is also sizable, contributing up to 24% of the total reaction. The measured cross sections of the process $e^{+}{e}^{-}\to \eta {\pi }^{+}{\pi }^{-}$ are systematically higher than those of BABAR by more than $3\sigma$ at center-of-mass energies between 2.000 and 2.300 GeV. In the cross section line shape for $e^{+}{e}^{-}\to a_2(1320)\pi$, a resonant structure is observed with a significance of $5.5\sigma$, with $M=(2044\pm 31\pm 4)\mathrm{MeV}/c^2$, $\mathrm{\Gamma }=(163\pm 69\pm 24)\mathrm{MeV}$, and ${\mathcal{B}}_{\mathcal{R}}·{\mathrm{\Gamma }}_{e^{+}{e}^{-}}^R=(34.6\pm 17.1\pm 6.0)\mathrm{eV}$ or $(137.1\pm 73.3\pm 2.1)\mathrm{eV}$. In the cross section line shape for $e^{+}{e}^{-}\to \rho \eta$, an evidence of a dip structure around $2180\mathrm{MeV}/c^2$ is observed with statistical significance of $3.0\sigma$.

We investigate the entanglement between the eternal black hole and Hawking radiation. For this purpose, we utilize the doubly holographic theories and study the entanglement entropy of the radiation to find the Page curve consistent with the unitarity principle. Doubly holographic theories introduce two types of boundaries in the AdS bulk, namely the usual anti–de Sitter boundary and the Planck brane. In such a setup, we calculate the entanglement entropy by examining two extremal surfaces: the Hartman-Maldacena (HM) surface and the island surface. The latter surface emerges when the island appears on the Planck brane. In this paper, we provide a detailed analysis of dyonic black holes with regard to the Page curve in the context of the doubly holographic setup. To begin with, we ascertain that the pertinent topological terms must be included in the Planck brane to describe the systems at finite density and magnetic field. Furthermore, we also develop a general numerical method to compute the time-dependent HM surface and achieve excellent agreement between the numerical results and analytical expressions. Utilizing numerical methodology, we find that the entanglement entropy of dyonic black holes exhibits unitary evolution over time, wherein it grows in early time and reaches saturation after the Page time. The initial growth can be explained by the HM surface, while the saturation is attributed to the island surface. In addition, using the holographic entanglement density, we also show that, for the first time, the saturated value of the entanglement entropy is twice the Bekenstein-Hawking entropy with the tensionless brane in double holography.

We analyze the entanglement of a Schwinger pair created by a time-dependent pulse. In the semiclassical approximation, the pair creation by a pulse of external electric field is captured by a periodic world line instanton. At strong gauge coupling, the gauge-gravity dual world sheet instanton exhibits a falling wormhole in AdS. We identify the tunneling time at the boundary with the inverse Unruh temperature, and derive the pertinent entanglement entropy between the created pair using thermodynamics. The entanglement entropy is enhanced by the subbarrier tunneling process, and partly depleted by the radiation in the postbarrier process.

The classical black hole spacetime is modified semiclassically, depending strongly on the choice of the quantum states. In particular, for the Boulware state the spacetime often takes a wormhole structure mimicking closely a spacetime with a horizon. In this paper, in the context of the two-dimensional dilaton Russo-Susskind-Thorlacius model, we consider all possible important interplays between the Hartle-Hawking, Unruh and Boulware quantum states. Special attention is given to the hybrid states made up of quantum fields either in the Hartle-Hawking or Unruh states, and some nonphysical fields (with the wrong sign in the kinetic term in the action) in the Boulware state. We present a detailed analysis of the semiclassical geometry in all these cases paying attention to the presence or absence of horizons, curvature singularities and to the geodesic completeness of the spacetime. In the space of parameters specifying the generic quantum state, we find a wide domain (with dominating nonphysical fields) where the semiclassical geometry represents a geodesically complete, asymptotically flat causal diamond, free of horizon or curvature singularity. However, a distant observer still finds Hawking radiation at asymptotic infinity. In the Unruh-Boulware hybrid state solution, we find that the energy flux at asymptotic infinity receives important corrections from its thermal behavior, leading to information recovery as we go from early to late retarded times. As a result, the corresponding entropy shows a typical Page curve behavior.

In this paper, the massless Nambu–Jona-Lasinio model extended by the diquark interaction channel is considered. We study its phase structure at zero temperature and in the presence of baryon ${\mu }_B$, isospin ${\mu }_I$, chiral ${\mu }_5$, and chiral isospin ${\mu }_{I5}$ chemical potentials in the mean-field approximation. It is shown that the model thermodynamic potential, which depends on three order parameters, $M$, ${\pi }_1$, and $\mathrm{\Delta }$ (where $M$, ${\pi }_1$, and $\mathrm{\Delta }$ are, respectively, the chiral, charged pion, and diquark condensates of the model), is symmetric with respect to the (dual) transformation when $M\leftrightarrow {\pi }_1$ and simultaneously ${\mu }_I\leftrightarrow {\mu }_{I5}$. As a result, on the mean-field phase portrait of the model, the chiral symmetry breaking (CSB) and charged pion condensation (PC) phases turn out to be dually conjugate with each other, which greatly simplifies the study of the phase portrait of the model. In particular, the duality between CSB and charged PC phases means that in the $({\mu }_I,{\mu }_{I5})$-phase portrait these phases are mirror symmetrical with respect to the line ${\mu }_I={\mu }_{I5}$, which at the same time is the symmetry axis of the color superconducting (CSC) phase. Moreover, it follows from our analysis that chiral ${\mu }_5$ chemical potential promotes the formation of CSC phase in dense quark matter. And together with ${\mu }_{I5}$, it can generate the charged PC phase even at ${\mu }_I=0$.

We explore the reflected entropy and the Markov gap between two modes of a free fermionic field as observed by accelerating observers. This is done for both a bipartite system, which is described by the Bell state, and tripartite systems, which are represented by the Werner and Greenberger-Horne-Zeilinger states. The reflected entropy of the fermionic modes degrades monotonically as a result of the Unruh effect, eventually reaching a nonzero minimum value in the limit of infinite acceleration. Furthermore, we show that the Markov gap exhibits monotonic behavior with regard to acceleration in all three cases. In addition, we suggest a function for reflected entropy which decreases monotonically with decreasing Unruh temperature for all states. Finally, we confirm that the reflected entropy for our system does reduce under the partial tracing of the degrees of freedom for our states.

We consider the optical appearance under a thin accretion disk of a regular black hole with a central de Sitter core implementing $\mathcal{O}(l^2/r^2)$ far corrections to the Schwarzschild black hole. We use the choice $l=0.25M$, which satisfies recently found constraints from the motion of the S2 star around Sgr ${\mathrm{A}}^{*}$ in this model, and which leads to thermodynamically stable black holes. As the emission model, we suitably adapt ten samples of the standard unbound emission profile for a monochromatic intensity in the disk’s frame, which have been previously employed in the literature within the context of reproducing general relativistic magnetohydrodynamic simulations of the accretion flow. We find the usual central brightness depression surrounded by the bright ring cast by the disk’s direct emission as well as two non-negligible photon ring contributions. As compared to the usual Schwarzschild solution, the relative luminosities of the latter are significantly boosted, while the size of the former is strongly decreased. We discuss the entanglement of the background geometry and the choice of emission model in generating these black hole images, as well as the capability of these modifications of Schwarzschild solution to pass present and future tests based on their optical appearance when illuminated by an accretion disk.

Analog gravity models of black holes and exotic compact objects provide a unique opportunity to study key properties of such systems in controlled laboratory environments. In contrast to astrophysical systems, analog gravity systems can be prepared carefully and their dynamical aspects thus investigated in unprecedented ways. While gravitational wave scattering properties of astrophysical compact objects are more connected to quasinormal modes, laboratory experiments can also access the transmission and reflection coefficients, which are otherwise mostly relevant for Hawking radiation related phenomena. In this work, we report two distinct results. First, we outline a semiclassical, nonparametric method that allows for the reconstruction of the effective perturbation potential from the knowledge of transmission and reflection coefficients for certain types of potentials in the Schrödinger wave equation admitting resonant tunneling. Second, we show how to use our method by applying it to an imperfect draining vortex, which has been suggested as an analog of extreme compact objects. Although the inverse problem is, in general, not unique, choosing physically motivated assumptions and requiring the validity of semiclassical theory, we demonstrate that the method provides efficient and accurate results.

We compare recent one-loop-level, scattering-amplitude-based, computations of the classical part of the gravitational bremsstrahlung waveform to the frequency-domain version of the corresponding multipolar-post-Minkowskian waveform result. When referring the one-loop result to the classical averaged momenta ${\overline{p}}_a=\frac{1}{2}(p_a+p_a^{\prime })$, the two waveforms are found to agree at the Newtonian and first post-Newtonian levels, as well as at the first-and-a-half post-Newtonian level, i.e., for the leading-order quadrupolar tail. However, we find that there are significant differences at the second-and-a-half post-Newtonian level, $O(\frac{G^2}{c^5})$, i.e., when reaching he following: (i) the first post-Newtonian correction to the linear quadrupole tail; (ii) Newtonian-level linear tails of higher multipolarity (odd octupole and even hexadecapole); (iii) radiation-reaction effects on the worldlines; and (iv) various contributions of cubically nonlinear origin (notably linked to the quadrupole $\times$ quadrupole $\times$ quadrupole coupling in the wave zone). These differences are reflected at the sub-sub-sub-leading level in the soft expansion, $\sim \omega \ln \omega$, i.e., $O(\frac{1}{t^2})$ in the time domain. Finally, we computed the first four terms of the low-frequency expansion of the multipolar-post-Minkowskian waveform and checked that they agree with the corresponding existing classical soft graviton results.

We study the Carrollian limit of the (general) quadratic gravity in four dimensions. We find that in order for the Carrollian theory to be a modification of the Carrollian limit of general relativity, the parameters in the action must depend on the speed of light in a specific way. By focusing on the leading and the next-to-leading orders in the Carrollian expansion, we show that there are four such nonequivalent Carrollian theories. Imposing conditions to remove tachyons (from the linearized theory), we end up with a classification of Carrollian theories according to the leading-order and next-to-leading-order actions. All modify the Carrollian limit of general relativity with quartic terms of the extrinsic curvature. To the leading order, we show that two theories are equivalent to general relativity, one to $R+R^2$ theory and one to the general quadratic gravity. To the next-to-leading order, two are equivalent to $R+R^2$ while the other two are equivalent to the general quadratic gravity. We study the two theories that are equivalent to $R+R^2$ to the leading order and write their magnetic limit actions.

We investigate the interplay between numerical relativity (NR) and adiabatic point-particle black hole perturbation theory (ppBHPT) in the comparable mass regime for quasicircular nonspinning binary black holes. Specifically, we reassess the $\alpha \text{−}\beta$ scaling technique, previously introduced by Islam et al. [Surrogate model for gravitational wave signals from nonspinning, comparable-to large-mass-ratio black hole binaries built on black hole perturbation theory waveforms calibrated to numerical relativity, Phys. Rev. D 106, 104025 (2022)], as a means to effectively match ppBHPT waveforms to NR waveforms within this regime. In particular, $\alpha$ rescales the amplitude and $\beta$ rescales the time (and hence the phase). Utilizing publicly available long NR data (SXS:BBH:2265 [SXS Collaboration, Binary black-hole simulation SXS:BBH:2265 (2019)]) for a mass ratio of $1:3$, encompassing the final $\sim 65$ orbital cycles of the binary evolution, we examine the range of applicability of such scalings. We observe that the scaling technique remains effective even during the earlier stages of the inspiral. Additionally, we provide commentary on the temporal evolution of the $\alpha$ and $\beta$ parameters and discuss whether they can be approximated as constant values. Consequently, we derive the $\alpha \text{−}\beta$ scaling as a function of orbital frequencies and demonstrate that it is equivalent to a frequency-dependent correction. We further provide a brief comparison between post-Newtonian (PN) waveforms and the rescaled ppBHPT waveform at a mass ratio of $1:3$ and comment on their regime of validity. Finally, we explore the possibility of using PN theory to obtain the $\alpha \text{−}\beta$ calibration parameters and still provide a rescaled ppBHPT waveform that matches NR.

Radio frequency, indirect dark matter searches have recently been gaining prevalence due to the high sensitivity and resolution capabilities of the new generation of radio interferometers. MeerKAT is currently one of the most sensitive instruments of its kind, making it ideal for indirect dark matter searches. By making use of publicly available data from the MeerKAT galaxy cluster legacy survey we are able to use both the observed diffuse synchrotron emission and nondetections to constrain the weakly interacting massive particle (WIMP) dark matter parameter space. In addition to a subset of generic WIMP annihilation channels, we probe the dark matter candidate within the $2\mathrm{HDM}+\mathrm{S}$ particle physics model, which was developed as an explanation for anomalies observed in the Large Hadron Collider data from runs 1 and 2. By undertaking a statistical analysis of the radio flux densities within galaxy clusters we are able to exclude the thermal relic value for WIMP masses $<\sim 1000\mathrm{GeV}$ for annihilation into bottom quarks with our median case. This is competitive with the best constraints in the current literature.

It was conjectured that the basic units of the ground state of bulk strong matter may be strange-clusters called strangeons, and they can form self-bound strangeon stars that are highly compact. Strangeon stars can develop a strange quark matter (SQM) core at high densities, particularly in the color-flavor-locking phase, yielding a branch of hybrid strangeon stars. We explore the stellar structure and astrophysical implications of hybrid strangeon stars. We find that hybrid strangeon stars can meet various astrophysical constraints on pulsar masses, radii, and tidal deformabilities. Finally, we show that the strangeon-SQM mixed phase is not preferred if the charge-neutrality condition is imposed at the strangeon-SQM transition region.

Within the self-gravitating Bose-Einstein condensate (BEC) model of dark matter (DM), we argue that the axionlike self-interaction of ultralight bosons ensures the existence of both rarefied and dense phases in the DM halo core of (dwarf) galaxies. In fact, this stems from two independent solutions of the Gross-Pitaevskii equation corresponding to the same model parameters. The existence of the two-phase structure did also appear in previously studied models with polynomial self-interactions, which actually involve the truncated expansion series of the axionlike self-interaction. For a small number of particles, this structure disappears along with the gravitational interaction, and the Gross-Pitaevskii equation reduces to the stationary sine-Gordon equation, the one-dimensional antikink solution of which mimics a single-phase DM radial distribution in the halo core. Quantum mechanically, this solution corresponds to a zero-energy bound state of two particles in a closed scattering channel formed by the domain-wall potential with a finite asymptotics. To produce a two-particle composite with low positive energy and a finite lifetime, we appeal to the resonant transition of one asymptotically free particle of a pair from an open channel (with a model scattering potential) to the closed channel. Using the Feshbach resonance concept, the problem of two-channel quantum mechanics is solved in the presence of a small external influence which couples the two channels, and an analytical solution is obtained in the first approximation. Analyzing the dependence of scattering data on interaction parameters, we reveal a long-lived two-particle composite (dimer) possessing a lifetime of millions of years. This result is rather surprising and supposes important implications of dimers being involved in forming large DM structures. It is shown that the dimers’ appearance is related with the regime of infinite scattering length due to resonance. The revealed dependence of the DM scattering length $a$ on the parameters of interactions can theoretically justify variation of $a$ in the DM dominated galaxies and its role for large DM structures.

The Laser Interferometer Space Antenna (LISA), space-based gravitational wave observatory involves a complex multidimensional closed-loop dynamical system. Its instrument performance is expected to be less efficiently isolated from platform motion than was its simpler technological demonstrator, LISA Pathfinder. It is of crucial importance to understand and model LISA dynamical behavior accurately to understand the propagation of dynamical excitations through the response of the instrument down to the interferometer data streams. More generally, simulation of the system allows for the preparation of the processing and interpretation of in-flight metrology data. In this work, we present a comprehensive mathematical modeling of the closed-loop system dynamics and its numerical implementation within the LISA Consortium simulation suite. We provide, for the first time, a full time-domain numerical demonstration of postprocessing time delay interferometer techniques combining multiple position measurements with realistic control loops to create a synthetic Michelson interferometer. We show that in the absence of physical coupling to spacecraft and telescope motion (through tilt-to-length, stiffness, and actuation cross-talk) the effect of noisy spacecraft motion is efficiently suppressed to a level below the noise originating in the rest of the instrument.

We compute the density of a spin-$\frac{3}{2}$ particle, the raritron, produced at the end of inflation due to gravitational interactions. We consider a background inflaton condensate as the source of this production, mediated by the exchange of a graviton. This production greatly exceeds the gravitational production from the emergent thermal bath during reheating. The relic abundance limit sets an absolute minimum mass for a stable raritron, though there are also model-dependent constraints imposed by unitarity. We also examine the case of gravitational production of a gravitino, taking into account the goldstino evolution during reheating. We compare these results with conventional gravitino production mechanisms.

Simplified models of light new physics provide a convenient benchmark for experimental searches for new physics signatures, including dark matter (DM). However, additional detection modes can arise in less simplified and more realistic scenarios where new degrees of freedom are invoked. In this study, we introduce a nonminimal model based on a popular dark photon portal to DM where the mediator mass is obtained by interactions with the dark Higgs boson which acts as a long-lived particle. We further add to this scenario a new heavy DM species secluded from the Standard Model. In this model, which involves light and heavy particles in the dark sector, we find some new interesting phenomenological features that lead to complementary probes in intensity frontier searches for light long-lived particles, indirect detection searches for dark matter, and cosmic microwave background surveys. We also find possible nonlocal effects in the DM indirect detection searches that could significantly affect the usual detection strategies.