This study investigates the consistency of heterotic supergravity, where the $B$-field gauge transformation becomes anomalous due to the Green-Schwarz mechanism, under $T$-duality transformations. We establish that preserving $T$ duality necessitates an infinite tower of higher-derivative couplings proportional to $e^{-2\mathrm{\Phi }}$. For spacetimes featuring a Killing self-dual circle, these couplings remain immune to quantum corrections. Leveraging $S$ duality in heterotic or type I string theory, we then identify the corresponding couplings in type I theory. Notably, our analysis reveals that standard $S$-duality transformations do not involve higher-derivative corrections. Building on this insight, we derive the explicit form of the effective action for type I theory at the ${\alpha }^{\prime }$ order, adhering to a scheme that omits derivatives of the dilaton.

In this study, we present a detailed investigation of gravastars within the framework of scalar-tensor theories, emphasizing both the background and perturbed levels for trivial and nontrivial scalar field. We derive the background equations that govern the equilibrium configurations of gravastars by examining the interaction between matter and the scalar field through a conformal transformation. By selecting two forms of the coupling function, we identify distinct physical characteristics that lead to deviations from the predictions made by general relativity. Our findings indicate that the scalar field significantly influences the compactness parameter. By extending our study to the perturbed level, we demonstrate that quasinormal modes are considerably affected by the presence of the scalar field. We discover new and intriguing quasinormal modes that are absent in general relativity.

In this paper, we introduce a new interacting mechanism within the dark sector, encompassing both dark energy and dark matter, while grounding our analysis in the familiar framework of the $\mathrm{\Lambda }$ cold dark matter model augmented by baryons and radiation components, including photons and neutrinos. The interaction between dark energy and dark matter is confined to the perturbative level. One significant advantage of this proposal is that all geometric probes yield constraints consistent with the so-called vanilla model or the extended vanilla model, where dark energy has a constant equation of state, $w_x$. However, the introduction of this new interacting mechanism affects several theoretical signatures, involving contrast dark-matter and dark-energy densities. We perform an exploratory analysis of those effects in the cosmic microwave background power spectra, matter-power spectra, and redshift space distortions. For instance, it allows for a decrease/increment in the integrated Sachs-Wolfe (ISW) effect depending on the value taken by the interaction coupling. This effect could be observationally detected by looking for a cross-correlation between the ISW temperature fluctuations and the distribution of galaxies or quasars. At late times, the interaction in the dark sector becomes very effective, affecting the nonlinear scale of structure formation. We discuss how the estimators $f{\sigma }_8(z)$ and $S_8(z)$ are affected by different interacting couplings, indicating that $f{\sigma }_8(z)$ can show a relative change of up to 15% compared to the concordance model at low redshifts. Finally, we show how the various terms in the dark-energy pressure perturbation (both adiabatic and nonadiabatic) are relevant for different scales, demonstrating the absence of large-scale instabilities.

In the fuzzy dark matter (FDM) scenario, dark matter is composed of an ultralight scalar field with coherence length and wave interference on astrophysical scales. Scalar fields generically have quartic self-interactions that modify their dispersion relation and the associated evolution of density perturbations. We perform the first dedicated analysis of the role of wave interference on this evolution due to self-interactions in FDM and vice versa, developing a perturbative treatment applicable at early times and then comparing against a suite of fully nonlinear benchmark simulations, varying the dark matter density, interaction strength, and fiducial momentum scale. We explicitly simulate the limit where this momentum scale is relatively high compared with the scale of the simulation volume, applicable to cases where the dark matter is initially “warm” due to causal constraints on a postinflationary production or in virialized halos and other “thermalized” cases with initially cold production. We find that in such scenarios, density perturbations are unable to grow on the expected self-interaction time scale because of interference effects, instead saturating on the much shorter de Broglie crossing time, with a dependence on the sign of the interaction. Finally, we comment on the implications of our results for astrophysical systems such as high-density ultrafaint dwarf galaxies where wave interference plays an important role.

We consider an appealing scenario for the production of purely gravitational dark matter in the background of warm inflation, a mechanism that maintains stable thermal bath during inflation. Through systematic investigation of various gravitational production channels, we reveal distinctive features compared to the standard inflation scenario. Notably, the inflaton annihilation channel in warm inflation exhibits markedly different thermodynamics from the standard inflation paradigm, leading to a suppression on the production of subinflaton-mass dark matter. For the production channel of inflationary vacuum fluctuations, we find an abundance-mass correlation of ${\rho }_{\chi }\propto m_{\chi }^{1/2}(m_{\chi }^{5/2})$ for the sub-Hubble-mass dark matter with minimal(conformal) coupling. Our results also indicate that a minimum temperature threshold of ${10}^{-6}{M}_P$ is necessary for warm inflation, which allows adequate dark matter production. With observational constraints, our results provide stringent limits on the mass range of purely gravitational dark matter with sufficient density: ${10}^{-8}–{10}^{-2}{M}_P$ for minimal coupling and ${10}^{-14}–{10}^{-2}{M}_P$ for conformal coupling.

We conduct a search for stellar-mass binary black hole mergers in gravitational-wave data collected by the LIGO detectors during the LIGO-Virgo-KAGRA (LVK) third observing run (O3). Our search uses a machine learning (ML)-based method, Aframe, an alternative to traditional matched filtering search techniques. The O3 observing run has been analyzed by the LVK Collaboration, producing GWTC-3, the most recent catalog installment which has been made publicly available in 2021. Various groups outside the LVK have reanalyzed O3 data using both traditional and ML-based approaches. Here, we identify 38 candidates with a probability of astrophysical origin ($p_{\mathrm{astro}}$) greater than 0.5, which were previously reported in GWTC-3. This is comparable to the number of candidates reported by individual matched-filter searches. In addition, we compare Aframe candidates with catalogs from research groups outside of the LVK, identifying three candidates with $p_{\mathrm{astro}}>0.5$. No previously unreported candidates are identified by Aframe. This work demonstrates that Aframe, and ML-based searches more generally, are useful companions to matched filtering pipelines.

Using the Kadanoff-Baym formalism, we perform a detailed study of neutrino-antineutrino synchrotron emission from strongly magnetized, dense quark matter under conditions relevant to compact stars. Starting from an exact expression for the emission rate that fully accounts for Landau-level quantization of quarks, we derive an approximate formula applicable in the regime where quark chemical potentials are much larger than all other relevant energy scales. We demonstrate that the emission rate is largely controlled by a single dimensionless ratio between two low-energy scales: the Landau-level spacing at the Fermi surface, $|e_{f}B|/{\mu }_f$, and the temperature of the quark matter, $T$. When the ratio $|e_{f}B|/({\mu }_{f}T)$ approaches zero, many closely spaced Landau levels contribute to the emission, but the total rate vanishes as $B\to 0$. In the opposite limit, where the ratio is large, the rate is dominated by transitions between adjacent levels and is exponentially suppressed due to Landau-level quantization, which limits the thermal activation of quarks near the Fermi surface. Our results show that, even in the presence of the strongest magnetic fields expected in compact stars, the synchrotron emission remains suppressed by more than 3 orders of magnitude compared to the direct Urca process. This implies that such emission is unlikely to play any substantial role in the cooling of magnetized quark stars, at least those made of unpaired quark matter phases.

In the framework of exploiting very high energy (VHE) gamma-ray observations of extragalactic sources to infer constraints on the intensity of cosmological background radiations, as well as on deviations from the standard model of particles and physical interactions (like violations of Lorentz invariance and axionlike particles—LIV and ALPs), we discuss here possible contaminant effects due to the presence of radiations fields from local sources. We specifically model and analyze the foreground radiations produced inside the host galaxy of the VHE source and the cosmic environment itself hosting the source, as well as radiations produced in the Milky Way, along the VHE source’s observational line-of-sights. Our analysis shows that such contaminant foregrounds may indeed impact on observations of only the very local Active Galactic Nuclei (e.g., Centaurus A), but not significantly those in the Virgo cluster (M87) and beyond.

We perform simulations of magnetohydrodynamic accretion onto equal-mass, nonspinning binary black holes in $3+1$ full general relativity addressing the effects of orbital eccentricity. We find that binary black holes with non-negligible eccentricity accrete matter with periodicity that matches the binary orbital period, whereas quasicircular binaries exhibit accretion rate modulation at approximately $\sim 0.7\times$ their binary orbital period. Additionally, we find that the total jet luminosity is modulated at the orbital period for eccentric binaries, while quasicircular binaries only exhibit long-term modulations. We perform a radiative transfer calculation of the dual jet synchrotron emission and demonstrate that the optically thin synchrotron emission varies on the binary orbital period for eccentric binaries. Moreover, eccentric binaries spend more time in a low state, where the synchrotron emission is minimum, than in a high state, where the synchrotron emission peaks. The quasicircular binary also exhibits variability in its optically thin synchrotron emission but the exact frequency of variability does not appear robust against different parameters. Our suite of simulations is an essential step toward providing a comprehensive catalog of multimessenger theoretical models that will enable studies of supermassive binary black holes detectable across the electromagnetic and gravitational wave spectra.

We extend previous holographic studies of the chiral magnetic effect (CME) by incorporating a time-dependent magnetic field. Various magnetic field profiles proposed in the literature are implemented, and their impact on the CME signal is analyzed in both static and expanding backgrounds. Interestingly, the integrated chiral magnetic current can exhibit a nonmonotonic dependence on the collision energy. Our results suggest that the CME signal is enhanced at collision energies below $\sqrt{s}=200\mathrm{GeV}$. In addition, we derive a quasiequilibrium formula for the chiral magnetic effect in the expanding background that is valid at late times.

Using a general (nonlinear) effective field theory description of the Standard Model electroweak symmetry breaking, we analyze the impact on the electroweak oblique parameters of hypothetical heavy resonance states strongly coupled to the SM particles. We present a next-to-leading order calculation of $S$ and $T$ that updates and generalizes our previous results, including P-odd operators in the Lagrangian, fermionic cuts and the current experimental bounds. We demonstrate that in any strongly coupled underlying theory where the two Weinberg sum rules are satisfied, as happens in asymptotically free gauge theories, the masses of the heavy vector and axial-vector states must be heavier than 10 TeV. Lighter resonances with masses around 2–3 TeV are only possible in theoretical scenarios where the second Weinberg sum rule is not fulfilled.

The isospin-selective reaction $K_{L}p\to {\pi }^{+}{\mathrm{\Sigma }}^0$ provides a clean probe for investigating $I=1{\mathrm{\Sigma }}^{*}$ resonances. In this work, we perform an analysis of this reaction using an effective Lagrangian approach for the first time, incorporating the well-established $\mathrm{\Sigma }(1189)1/2^{+}$, $\mathrm{\Sigma }(1385)3/2^{+}$, $\mathrm{\Sigma }(1670)3/2^{-}$, and $\mathrm{\Sigma }(1775)5/2^{-}$ states, while also exploring contributions from other unestablished states. By fitting the available differential cross-section and recoil polarization data, adhering to partial-wave phase conventions same as the Particle Data Group, we find that besides the established resonances, contributions from $\mathrm{\Sigma }(1660)1/2^{+}$, $\mathrm{\Sigma }(1580)3/2^{-}$, and a ${\mathrm{\Sigma }}^{*}(1/2^{-})$ improve the description. Notably, a ${\mathrm{\Sigma }}^{*}(1/2^{-})$ resonance with mass around 1.54 GeV, consistent with $\mathrm{\Sigma }(1620)1/2^{-}$, is found to be essential for describing the data in this channel, a stronger indication than found in previous analyses focusing on $\pi \mathrm{\Lambda }$ final states. While providing complementary support for $\mathrm{\Sigma }(1660)1/2^{+}$ and $\mathrm{\Sigma }(1580)3/2^{-}$, our results highlight the importance of the $\mathrm{\Sigma }(1620)1/2^{-}$ region in $K_{L}p\to {\pi }^{+}{\mathrm{\Sigma }}^0$. Future high-precision measurements are needed to solidify these findings and further constrain the ${\mathrm{\Sigma }}^{*}$ spectrum.

We present the first calculation of quantum electrodynamics (QED) nuclear medium effects under the experimental conditions of future Electron-Ion Collider (EIC) experiments. Our work offers numerical estimates, particularly in the context of inclusive deep inelastic scattering on a ${}_{82}{}^{208}\mathrm{Pb}$ nucleus. While prior studies have predominantly focused on elastic scattering, our investigation extends to the more complex scenarios of inelastic processes within a nuclear medium. Our findings suggest that the cross section corrections due to QED nuclear medium effects could be substantial, reaching or exceeding the level of experimental precision. This work further compares the effects of single rescattering events with those of multiple rescatterings, as particles travel the nuclear volume. We estimate the dominant source of the uncertainties associated with our formalism by varying the scale of the atomic physics where the screening of the electric field of the nucleus happens. This calculation not only contributes to the understanding of QED nuclear medium effects, but also offers a path to a more precise extraction of the process-independent nonperturbative structure of nuclei.

Quantum kinetic theory is an important tool for studying nonequilibrium, nonperturbative and nonlinear interactions within an open quantum system, and as such is able to provide an unprecedented view on particle production in the relativistic, ultrahigh intensity regime of quantum electrodynamics. By reorganizing the relativistic quantum transport equations for Abelian plasmas and integrating them with a perturbative expansion, we significantly expand the scope for kinetic theories to further elucidate the peculiarities of particle production at a spectral level.

The axion thermalization rate is a crucial input to determine the hot dark matter bound of axions, resulting from the scattering processes in the thermal bath of early Universe. We demonstrate that the commonly employed axion thermalization rate by including the $a\pi \leftrightarrow \pi \pi$ channel alone is significantly underestimated for the temperature $T$ above 100 MeV. This is obtained through the systematical calculation of the axion-light flavor meson scattering amplitudes within the framework of the chiral unitarization approach, paying special attention to the $aK\leftrightarrow \pi K$ reaction. Hadron resonances appearing in $aK\leftrightarrow \pi K$ amplitudes significantly enlarge the cross sections, which turn out to be much bigger than that of $a\pi \leftrightarrow \pi \pi$. The axion thermalization rate is then substantially enhanced by the $aK\leftrightarrow \pi K$ channel for $T\gtrsim 100\mathrm{MeV}$. Especially at $T\simeq 130\mathrm{MeV}$, the contribution from the $aK\leftrightarrow \pi K$ reaction to the axion thermalization rate exceeds the $a\pi \leftrightarrow \pi \pi$ one. Obviously more stringent constraints on the axion parameters are obtained, when confronting the number of extra relativistic degrees of freedom $\mathrm{\Delta }{N}_{\mathrm{eff}}$ from ${\mathrm{Planck}}^{\prime }18$.

We demonstrate that a broad class of modular inflation models predicts the emergence of new physics within an energy range of approximately ${10}^{15}$ to ${10}^{17}\mathrm{GeV}$. This prediction arises by comparing the moduli-dependent species scale with observational constraints on inflation. Specifically, we illustrate this within the context of $SL(2,\mathbb{Z})$-modular inflation models by reexpressing inflationary observables in terms of the species scale. We further discuss the implications of this approach for generic Calabi-Yau threefolds.

The Unruh effect establishes a fundamental equivalence between acceleration and thermality by demonstrating that a uniformly accelerated ground-state detector undergoes excitation as if immersed in a thermal bath. In this paper, we investigate how acceleration influences the interaction between two ground-state atoms that are synchronously and uniformly accelerated in vacuum with proper acceleration $a$ and coupled to a fluctuating electromagnetic field. We find that the resulting interaction potential comprises both diagonal components $(\delta E{)}^{jk}$ with $j=k$, which are present in both inertial and acceleration cases, and off-diagonal components $(\delta E{)}^{jk}$ with $j\ne k$, which arise exclusively due to acceleration and vanish in the inertial case. The dependence of each component on acceleration and interatomic separation $L$ generally differs. For small accelerations, the leading-order diagonal components of the van der Waals (vdW) and Casimir-Polder ($CP$) interaction potentials remain unchanged from their inertial counterparts, exhibiting the standard scaling behaviors $\sim L^{-6}$ and $\sim L^{-7}$, respectively. In contrast, the off-diagonal components scale as $\sim a^2{L}^{-4}$ in the vdW subregions and $\sim a^2{L}^{-5}$ in the $CP$ subregion. However, when the acceleration becomes sufficiently large, both diagonal and off-diagonal components of the vdW and $CP$ interaction potentials are significantly modified, giving rise to entirely new interaction behaviors that deviate from those observed in the inertial case, whether in vacuum or thermal environments, indicating a breakdown of the acceleration-thermality equivalence established by the Unruh effect for single detectors.

We investigate the dynamics of the ground state entanglement entropy for a discretized scalar field propagating within the Oppenheimer-Snyder collapse metric. Starting from a well-controlled initial configuration, we follow the system as it evolves toward the formation of a horizon and, eventually, a singularity. Our approach employs an Ermakov-like equation to determine the time-dependent ground state of the field and calculates the resulting entanglement entropy by tracing out the degrees of freedom inside a spherical region within the matter sphere. We find that the entanglement entropy exhibits nontrivial scaling and time dependence during collapse. Close to the horizon, the entropy can deviate from the simple area law, reflecting the rapid changes in geometry and field configuration. Although the model is idealized, these results provide insights into the generation and scaling of entanglement in the presence of realistic, dynamically evolving gravitational fields.