We investigate the quantum correlation effects between electrons and positrons produced via Schwinger tunneling in localized supercritical electric fields. Using the framework of computational quantum field theory, we calculate the two-particle correlation functions in both momentum and real space. Our results demonstrate that the generated electron-positron pairs exhibit strong mutual correlations that evolve dynamically. In momentum space, the correlation function increases in magnitude over time while maintaining its characteristic profile. In real space, the correlation function undergoes spatial spreading without a reduction in peak amplitude. This persistence indicates that the correlation strength remains robust even as the pairs propagate beyond the localized interaction region. These findings suggest that quantum correlations in the Schwinger process are experimentally accessible, offering new opportunities to probe many-body effects under extreme field conditions.

We analyze the infrared structure and memory effects of a massless vector-tensor theory with nonminimal curvature coupling in asymptotically flat spacetimes. Using Bondi-Sachs expansions, we identify the independent radiative data and derive the effective Bondi mass aspect, whose balance law receives an additional positive definite flux from the vector sector. This leads to modified displacement, spin, and center-of-mass memory (CM) expressions, where the gravitational contributions retain their general relativity (GR) form and the vector field enters only through well-defined flux terms. We also describe persistent vector memory effects associated with the leading angular vector mode, which are gauge-invariant but do not affect the leading tidal observables. The Bondi-Metzner-Sachs transformations act kinematically as in GR; tensor vacua remain supertranslation degenerate, whereas the vector vacuum, defined by the vanishing vector field, is nondegenerate. All results reduce continuously to GR when the coupling is removed, isolating the precise channels through which vector-curvature interactions modify the infrared dynamics.

Using the worldline effective field theory formalism, we derive the nonlocal-in-time conservative contributions arising from tail effects in gravitational scattering to the fifth post-Minkowskian (5PM) and tenth self-force (10SF) orders. The result features multiple polylogarithms of up to weight 3. This challenging computation relies on state-of-the-art integration techniques, including a novel integration-by-parts algorithm: the “Sparse Integral Reducer” (). We find perfect agreement in the overlap with all existing literature through the sixth post-Newtonian order. The results presented here provide a key ingredient for isolating the local-in-time component of the conservative two-body dynamics of binary inspirals at the 5PM order.

Nonradial oscillation modes of neutron stars serve as diagnostics of their internal composition and relativistic structure. In this work, we investigate the perturbations of static and spherically symmetric neutron stars characterized by an anisotropic pressure. Given the background symmetry, perturbations decouple into polar and axial modes. To date, axial modes have remained less explored, primarily because matter and metric perturbations decouple in the isotropic limit. In this work, we provide a consistent treatment of axial modes and demonstrate that pressure anisotropy induces a direct coupling between matter and metric perturbations. We employ parametrized anisotropy models that ensure consistency with the treatment of matter perturbations. We numerically integrate the linearized Einstein field equations for the axial modes, employing a diverse set of realistic equations of state. Our results indicate that as the stellar mass grows, the frequency of the base $w$ mode generally decreases, while its damping time increases. Softer equations of state typically yield slightly higher oscillation frequencies. Furthermore, larger anisotropy (i.e., when the tangential pressure exceeds the radial pressure) allows for more massive equilibrium configurations, which correspondingly leads to lower oscillation frequencies and prolonged damping times. Finally, we demonstrate that the frequency and damping time, both scaled by the stellar mass, exhibit a nearly universal quadratic dependence on the stellar compactness, remaining largely insensitive to the underlying equation of state, but slightly dependent to the specific anisotropy model.

We derive new exact gravitational wave solutions with dynamical torsion and nonmetricity tensors in the framework of cubic metric-affine gravity (MAG). For this purpose, we consider the full algebraic classification of the gravitational field in general metric-affine geometries and impose a set of type N conditions on the field strength tensors that implement the kinetics of torsion and nonmetricity in a particular cubic MAG model, recently considered to eliminate ghostly instabilities from the vector and axial sectors of the theory. The new solutions represent pp waves characterized by a metric function that includes the dynamical contributions of the torsion and nonmetricity tensors provided by the field equations of the model. In particular, these quantities induce a scalar polarization mode in the gravitational-wave spectrum, thus offering a distinctive phenomenological signature beyond the ordinary tensor polarization modes of general relativity.

Rotating black holes can form dense boson clouds through superradiant instability, making Kerr black holes a powerful probe of ultralight massive bosons. Previous studies of black hole superradiance have often treated bosonic fields classically, leaving open questions about how particles are produced and how the clouds grow over time. In this work, we canonically quantize a massive scalar field around a Kerr black hole, providing a fully quantum description of black hole superradiance. We show that the evolution of the particle number in the cloud, as well as the energy and angular momentum of the scalar field, can be consistently explained within the standard framework of quantum field theory in curved spacetime. Furthermore, we prove that the growth of the cloud occurs independently of the choice of initial state. We also explore several phenomena related to a massive scalar field in a rotating black hole spacetime, including Hawking radiation, adiabatic backreaction on the black hole spin, and the direction of level transitions in the presence of self-interactions of the field. Our analysis provides a consistent quantum-mechanical perspective that includes all these phenomena.

We study primordial gravitational waves (GWs) generated from first-order phase transitions (PTs) during cosmic reheating. Using a minimal particle physics model, and a general parametrization of the inflaton energy density and the evolution of the Standard Model temperature, we explore the conditions under which PTs occur and determine the corresponding PT parameters (the PT temperature, duration, and strength), which depend on the evolution of the background during reheating. We find that, in certain cosmological scenarios, PTs can be delayed and prolonged compared to the standard postinflationary evolution. Incorporating these PT parameters, we compute the resulting GW spectrum generated from the various processes occurring during a first-order PT. We find that, in comparison to the standard cosmological history, the GW amplitude and peak frequency can be modified by several orders of magnitude due to the cosmological evolution during reheating. In particular, the GW spectra could be within the reach of next-generation GW observatories.

There is tentative evidence for a mismatch between the rest frames of matter and the cosmic microwave background, the “quasar dipole anomaly.” We consider such a dipole in tilted anisotropic models, for a range of scenarios and sources: spatial curvature, cosmic heat flux, large scale electromagnetic fields, and a Khronon field. Crucially, we determine the ancillary effects on other cosmological observables in each of these models, and we show that, apart from the case of the Khronon field, it is unlikely that one can obtain a dipole with the amplitude that is being observed unless one considers additional exotica.

Ultralight dark matter is an interesting dark matter candidate describing the lightest end of the mass parameter space. This model produces an oscillating granular pattern in halo densities. These fluctuations have the potential to produce a time-varying density along the line of sight creating a small lensing signal for any stars observed through a dark matter halo which oscillates on the de Broglie timescale. In this work, we study this stochastic lensing signal taking into account the impact of density granules as well as the central soliton. We calculate the amplitude and temporal properties of this signal and estimate how stellar observations may be used to constrain the ultralight dark matter mass and abundance. We find that the expected signal from fluctuation ultralight dark matter is a few orders of magnitude smaller than current observational limits.

The Blandford-Znajek (BZ) mechanism is widely recognized as the most compelling process to extract rotational energy from an accreting black hole and power the emission of relativistic jets. We explore the universality of this process for generic black-hole spacetimes within the Konoplya-Rezzolla-Zhidenko formalism and find that the lowest-order contribution to the BZ power is invariant across different black-hole spacetimes. We also show that, at the next-leading order, different black-hole spacetimes will lead to different BZ luminosities. As a result, while slowly rotating black holes cannot be distinguished via measurements of their jet power, rapidly rotating ones have the potential of providing information on the strong-field properties of the spacetime when independent measurements of the BZ luminosity and of the black-hole angular velocity are available.

The nonlinear Breit-Wheeler process is a fundamental phenomenon of strong-field quantum electrodynamics and is usually studied for classically prescribed laser backgrounds. Here we examine how the statistical properties of a squeezed coherent driving field modify nonlinear Breit-Wheeler pair production. Using a polarization-resolved Monte Carlo framework with stochastic averaging over the field-amplitude distribution derived from the Husimi $Q$-function, we simulate collisions of $\gamma$ photons with squeezed light and identify clear source-state-dependent modifications of the pair production signal. These effects include the smoothing of harmonic structure, the enhancement of higher-order multiphoton channels, and the suppression of the single-laser-photon absorption channel when stronger-field realizations raise the dressed-mass threshold. Within the selected spectral window, the degree of positron polarization increases monotonically with the squeezing parameter, while the angular distributions broaden as the statistical weight of larger field amplitudes increases. Our results show that, even at fixed mean electric-field amplitude, the statistical fluctuations inherent to the squeezed coherent state can substantially reshape spectral, angular, and spin-resolved observables in strong-field pair production. These findings illustrate a direct link between source-state-dependent field statistics and strong-field pair production observables, and provide a theoretical framework for studying how squeezed-state preparation of the driving field can influence high-energy quantum electrodynamics processes.

We introduce optimal transport (OT) as a physics-based intermediate event representation for weakly supervised anomaly detection. With only 0.5% injection of resonant signals in the LHC Olympics benchmark datasets, the OT-augmented feature set achieves nearly twice the significance improvement of the standard high-level observables using an idealized setup, while end-to-end deep learning on low-level four-momenta is less effective in this low-signal regime. The observed gains persist across signal types and classifiers considered in this study, suggesting that structured, physics-informed representations can provide a useful complement to existing approaches for anomaly detection.

In this work, we investigate the valence quark parton distribution functions (PDFs) of the pion within the light-cone quark model. The initial quark PDFs are calculated by solving the quark-quark correlation function for the pseudoscalar mesons. The initial quark PDFs have been evolved to higher energy scales through the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) evolution equations. We also find that our calculated evolved PDFs match experimental and available theoretical extraction data. For the first time, we have also predicted the $F_2$ structure function at next-to-leading (NLO) order accuracy. The calculated $F_2$ structure function has been compared with the available ZEUS and H1 experimental data at DESY-HERA over a wide range of energy scales. Additionally, we display the forward pion production cross-section for the Drell-Yan process caused by pions using the pion PDFs that were calculated and the target nucleon PDFs from the LHAPDF nucleus datasets. The evolved $F_2$ structure function of the pion has been studied at the upcoming electron-ion collider energy kinematics. Overall, it was observed that the quark PDFs of pions computed using the light-cone quark model are consistent with the experimental results.

We explore a standard model extension based on a local $U(1{)}_B$ symmetry, where a baryon-charged scalar mediates interactions between a fermionic dark matter candidate and standard model quarks. In this setup, the dark matter relic abundance is shaped not only by standard annihilation channels but also by additional coannihilation processes induced by a new scalar. The presence of this mediator provides a unified link between dark sector and flavor physics, yielding distinctive phenomenological consequences. We conduct a detailed study of dark matter phenomenology, emphasizing the role of the mass splitting between the dark matter particles and the scalar mediator in determining the efficiency of coannihilation. The parameter space is examined in light of existing constraints from cosmological observations, direct and indirect detection experiments, as well as the collider searches at the LHC. Our analysis shows that the extended scalar sector opens up viable regions of parameter space beyond those accessible in minimal $U(1{)}_B$ realizations, many of which are expected to be tested by forthcoming searches at XENONnT and the Cherenkov Telescope Array. Moreover, the model induces correlated signatures from flavor observables associated with the $b\to s$ transitions as well, serving as complementary tests of the underlying framework.

Previously, we proposed an infrared vacuum wave functional for $SU(N)$ Yang-Mills theory peaked at thin center vortices and showed that it yields an area law for the Wilson loop. In this work, we use this wave functional to calculate the spatial ’t Hooft loop, for which we find a perimeter law, in accordance with ’t Hooft’s criterion for confinement.

We propose a nonlocal realization of the Stueckelberg portal between the Standard Model and dark sector, which decouple in the local limit. This implies that the mediator, $U(1{)}_D$ dark photon $A^{\prime }$ with a Stueckelberg mass, interacts nonlocally with the Standard Model quarks and leptons. We study phenomenological implications of this scenario for the meson decays into semi-invisible and invisible channels. We discuss the experimental limitations on the model parameters, including the nonlocality scale.

An effective chiral model is introduced to illustrate finite-size effects, incorporating the standard zero-mode treatment, momentum-space discretization, and gradient effects modeled via a prescribed finite-volume profile. The fluctuations of the chiral order parameter and the net-baryon number, as well as their scaling properties, are investigated near a critical point and a first-order transition in finite-size systems. The finite-volume effects on the Binder cumulant and the kurtosis are shown along the phase boundary and the approximate freeze-out line, respectively. Phenomenological implications on fluctuation observables are pointed out and explained.

The SHIFT@LHC proposal introduced a novel shifted gaseous fixed-target concept at the LHC to search for exotic particles. In this article, we explore an entirely different physics opportunity enabled by this setup: the observation of neutrinos in general-purpose LHC detectors. Using simulations of proton-gas collisions, hadron propagation, and neutrino interactions, we estimate that $\mathcal{O}({10}^4)$ muon-neutrino and $\mathcal{O}({10}^3)$ electron-neutrino interactions, with energies from 20 GeV to 1 TeV, would occur in the CMS and ATLAS detectors with 1% of the LHC Run-4 integrated luminosity ($\approx 4\times {10}^{25}$ protons on target). This unique configuration provides access to hadron production in the pseudorapidity range $5<\eta <8$, complementary to existing LHC detectors. If realized, this would mark the first detection of neutrinos in a hadron collider detector, demonstrating the feasibility of such measurements in this experimental environment.

We investigate the dissipative dynamics of a two-level atom in a weak gravitational field. Using the Feynman-Vernon influence functional formalism, we derive a quantum master equation describing the two-level atom interacting with a scalar field in a Newtonian gravitational field and compute the energy dissipation rate of the atom. We find that the spontaneous emission rate (the dissipation rate in vacuum) is modified by the gravitational field. Specifically, this modification depends on the atom’s dipole, the position of the atom relative to the source of the gravitational field, and the frequency of the scalar radiation emitted by the atom. Furthermore, we identify the parameter regimes in which the spontaneous emission rate is enhanced or suppressed by gravity. We also discuss how the modification arises from time dilation and dipole radiation in a weak gravitational field. These findings provide a theoretical basis for exploring gravitational effects in open quantum systems.