Quantum chromodynamics (QCD) admits a topological $\overline{\theta }$ term that violates charge-parity ($CP$) symmetry, yet experiments indicate that $\overline{\theta }$ is extremely small. To investigate this problem in a controlled setting, we derive a Hamiltonian formulation of QCD through a ($1+1$)-dimensional Schwinger-model analog. Fermionic and gauge degrees of freedom are encoded into qubits using Jordan-Wigner and quantum-link mappings, yielding a compact Pauli Hamiltonian that preserves the essential topological vacuum structure. Ground states are prepared using a feedback-based quantum optimization protocol, providing access to the vacuum energy on few-qubit simulators. We observe vacuum minima at $\overline{\theta }=0$ and $2\pi$, consistent with the continuum QCD expectations within the accessible regime. Upon coupling to a dynamical axion field, the system relaxes to ${\theta }_{\mathrm{eff}}=0$, realizing the Peccei-Quinn mechanism within a minimal quantum simulation. These results demonstrate how quantum simulation can probe $CP$ violation and its dynamical resolution in gauge theories.

We evaluate the Collins-Soper kernel and the reduced soft function in lattice QCD, incorporating $\mathcal{O}({\alpha }_s)$ matching corrections. The calculation relies on the evaluation of the quasitransverse momentum–dependent wave function with asymmetric staple-shaped quark bilinear operators and four-point meson form factors. These quantities are computed nonperturbatively using two $N_f=2+1+1$ twisted-mass fermion ensembles with the same lattice spacing of $a=0.093\mathrm{fm}$: the first ensemble has a lattice size of ${24}^3\times 48$ and a pion mass of 346 MeV, and the second one has a lattice size of ${32}^3\times 64$ and a pion mass of 261 MeV. The Collins-Soper kernel and the soft function are needed for the determination of the transverse momentum–dependent parton distribution functions.

Jet quenching—the modification of high-energy jets in the quark-gluon plasma—has been extensively studied through weakly coupled scattering amplitudes embedded in parton-shower frameworks. These models, often combined with bulk hydrodynamic evolution, successfully describe a wide range of observables, though they typically rely on assumptions of rapid thermalization and simplified treatments of medium response. Parallel to these developments, jet thermalization has been investigated within the finite-temperature QCD effective kinetic theory, which provides our best microscopic understanding of equilibration in heavy-ion collisions. Early studies of linearized perturbations have highlighted both the promise and the limitations of current approaches, as existing MC implementations face challenges—particularly in the treatment of recoils and particle merging. Building on this foundation, we introduce a new parton-shower algorithm that exactly reproduces the dynamics of the linearized effective kinetic theory, enabling a first-principles description of jet thermalization with proper inclusion of recoils, holes, quantum statistics, and merging processes.

Utilizing the 2012 transversely polarized proton data from the Relativistic Heavy Ion Collider at Brookhaven National Laboratory, the forward $\eta$-meson transverse single-spin asymmetry ($A_N$) was measured for $p^{\uparrow }+p$ collisions at $\sqrt{s}=200\mathrm{GeV}$ as a function of Feynman-x ($x_F$) for $0.2<|x_F|<0.8$ and transverse momentum ($p_T$) for $1.0<p_T<5.0\mathrm{GeV}/c$. Large asymmetries at positive $x_F$ are observed ($⟨A_N⟩=0.086\pm 0.019$), agreeing well with previous measurements of ${\pi }^0$ and $\eta A_N$, but with reach to higher $x_F$ and $p_T$. The contribution of initial-state spin-momentum correlations to the asymmetry, as calculated in the collinear twist-3 framework, appears insufficient to describe the data.

We study the nonrelativistic (NR) limit of Hohm-Siegel-Zwiebach (HSZ) theory, a higher-derivative theory of gravity with exact and manifest T-duality invariance. Since the theory can be formulated using the generalized metric formalism, the HSZ Lagrangian remains convergent to all orders in derivatives when taking the NR limit. In this work, we analyze the three-derivative corrections to the symmetry transformations of the fields in the NR case, as well as the terms in the four-derivative action depending on the b field. Interestingly, the corrections to the metric degrees of freedom cannot be fully trivialized, as in the relativistic case, in order to preserve the convergence of the theory. As HSZ theory interpolates order by order between heterotic and bosonic string theories, the results of this work can be interpreted as a truncation of the four-derivative structure of heterotic supergravity in the NR limit.

In the presence of a strong electric field, the vacuum is unstable to the production of pairs of charged particles—the Schwinger effect. The created pairs extract energy from the electric field, resulting in nontrivial backreaction. In this paper, we study $1+1\mathrm{D}$ massive QED subject to strong external electric fields in a self-consistent and fully quantum manner. We use the bosonized version of the theory, which attains a cosine interaction term in the presence of nonzero fermion mass $m$. However, the assumption of a strong electric field justifies a perturbative treatment of the cosine interaction, i.e., an expansion in $m$. We calculate the vacuum expectation value of the electric field to first order in $m$ and show that—surprisingly—it satisfies a classical nonlinear partial differential equation (related to the sine-Gordon equation). We show that the electric field exhibits dissipation-free oscillations (analogous to ordinary plasma oscillations) and calculate the plasma frequency analytically. We also compare to the semiclassical approximation commonly used to study backreaction, showing that it fails to capture the $O(m)$ shift in the plasma frequency.

Nonlinear effects play a fundamental role in the late-time ringdown of black holes, with direct implications for gravitational-wave observations. For massive fields, these dynamics become richer, yet their nonlinear signatures remain poorly understood. Here, we systematically study nonlinear tails of massive scalar perturbations, from a toy model with ingoing and outgoing sources to a self-interacting scalar model, revealing nonlinear tails and contrasting the results with their linear counterparts. We find that the nonlinear tails of massive scalar fields, opposite to massless ones, decay as the same rate as linear tails at intermediate late times, independent of source parameters or initial conditions. Nevertheless, quadratic quasinormal modes could serve as a probe to the nonlinear effects of massive fields.

Greybody factors for Proca fields in Schwarzschild black hole spacetime are investigated. The radial equations are derived by separating the field equations using vector spherical harmonics and decoupling the even-parity sector through a set of transformations related to the Frolov-Krtouš-Kubizňák-Santos separation in the static limit. Semianalytical methods, including a rigorous bound and the Wentzel-Kramers-Brillouin approximation, are used to compute the transmission probabilities. In addition to reproducing known results, two distinctive features are identified. In the even-parity vector mode, a low-mass regime is found where the transmission probability exceeds that of the massless case for a set of common energy and angular momentum parameters. In the even-parity scalar mode, the massless limit reproduces the result of massless scalar perturbations and corresponds to a pure gauge mode in Maxwell theory. In the same mode, the transmission probability in the massive case is systematically lower than that of a massive scalar field with the same parameters.

Astrophysical luminous objects such as the first stars have not yet formed in the dark ages. However, primordial black holes (PBHs) have always existed throughout cosmic history since the inflation epoch. During the dark ages, PBHs may accrete the ambient gas and release radiation like astrophysical luminous objects, and change the cosmic radiation field, the thermal status of the intergalactic medium (IGM), and the hydrogen spin temperature. The accretion rate is modulated by the relic supersonic relative streaming velocities between dark matter (DM) and baryons, imprinting velocity acoustic oscillation (VAO) features in the 21-cm power spectrum. Such VAO features could be a promising probe for detecting the PBHs in the dark ages. We find that even if PBHs comprise only a small fraction of DM, they can generate VAO wiggles with a relative amplitude up to $\sim 30\%$ in dark ages. For example, for PBHs with mass $M_{\mathrm{PBH},\mathrm{rec}}=200M_{\odot }$ and mass fraction in the total DM $f_{\mathrm{PBH},\mathrm{rec}}\sim {10}^{-13}$ at the recombination era, VAO features appear at $z\sim 20$; if $f_{\mathrm{PBH},\mathrm{rec}}\sim 3\times {10}^{-10}$, then VAO features could appear as early as $z\sim 40$. Moreover, the redshift evolution of the VAO features exhibits clearly separated stages dominated by inhomogeneous $\mathrm{Ly}\alpha$ scattering, and inhomogeneous x-ray heating, respectively. It reflects the characteristics of PBHs (mass and fraction in total DM) and their interactions with the IGM. We also estimate that, the VAO wiggles at $z\sim 20$ are detectable for the upcoming SKA-low AA*, while wiggles at $z\sim 40$ are detectable for an hypothetic lunar surface-based interferometer array in the future.

The nature of the compact objects within the supposed “lower mass gap” remains uncertain. Observations of GW190814 and GW230529 highlight the challenges gravitational waves face in distinguishing neutron stars from black holes. Interpreting these systems is especially difficult because classifications depend simultaneously on measurement noise, compact binary population models, and equation of state (EOS) constraints on the maximum neutron star mass. We analyze 66 confident events from the third Gravitational-Wave Transient Catalog to quantify how the probability of a component being a neutron star, $P(\mathrm{NS})$, varies across the population. The effects are substantial; the dominant drivers of classification are the pairing preferences of neutron stars with other compact objects and the neutron star spin distributions. The data reveals that $P(\mathrm{NS})$ varies between 1%–67% for GW230529’s primary and between 51%–100% for GW190425’s primary. By contrast, $P(\mathrm{NS})$ for GW190814’s secondary varies by $\le 10\%$, demonstrating robustness from its high signal-to-noise ratio and small mass ratio. Analysis using EOS information tends to affect $P(\mathrm{NS})$ through the inferred maximum neutron star mass rather than the maximum spin. As it stands, $P(\mathrm{NS})$ remains sensitive to numerous population parameters, limiting its reliability and potentially leading to ambiguous classifications of future gravitational wave events.

We provide an extended lattice study of the SU(2) gauge theory coupled to one Dirac fermion flavor ($N_{\mathrm{f}}=1$) transforming in the adjoint representation as the continuum limit is approached. This investigation is supplemented by results obtained for the SU(2) gauge theory with two Dirac fermion flavors ($N_{\mathrm{f}}=2$) transforming in the adjoint representation, for which we perform numerical investigations at three values of the lattice spacing. The purpose of our study is to advance the characterization of the infrared properties of both theories, which previous investigations have concluded to be in the conformal window. For both, we determine the mass spectrum and the anomalous dimension of the fermion condensate using finite-size hyperscaling of the spectrum, mode number analysis of the Dirac operator (for which we improve on our previous proposal) and the ratio of masses of the lightest spin-2 particle over the lightest scalar. All methods provide a consistent picture, with the anomalous dimension of the condensate ${\gamma }_{*}$ decreasing significantly as one approaches the continuum limit for the $N_{\mathrm{f}}=1$ theory towards a value consistent with ${\gamma }_{*}=0.170(6)$, while for $N_{\mathrm{f}}=2$ the anomalous dimension converges more rapidly with $\beta$ to a value of ${\gamma }_{*}=0.291(9)$. A chiral perturbation theory analysis shows that the infrared behavior of both theories is incompatible with the breaking of chiral symmetry.

The efficient classification of electromagnetic activity from ${\pi }^0$ and electrons remains an open problem in the reconstruction of neutrino interactions in liquid argon time projection chamber (LArTPC) detectors. We address this problem using the mathematical framework of optimal transport (OT), which has been successfully employed for event classification in other high energy physics contexts and is ideally suited to the high-resolution calorimetry of LArTPCs. Using a publicly available simulated dataset from the MicroBooNE Collaboration, we show that OT methods achieve state-of-the-art reconstruction performance in $e/{\pi }^0$ classification. The success of this first application indicates the broader promise of OT methods for LArTPC-based neutrino experiments.

In the experiment to study the $e^{+}{e}^{-}\to n\overline{n}$ process at the VEPP-2000 $e^{+}{e}^{-}$ collider, the ratio $|G_E|/|G_M|$ of the neutron timelike electric and magnetic form factors has been measured. The experiment was carried out with the SND detector in the center-of-mass energy range 1890–2000 MeV in eight energy points with an integrated luminosity of $83{\mathrm{pb}}^{-1}$. The $|G_E|/|G_M|$ ratio is determined by the analyzing the distribution of the polar angle of the produced antineutron. The measured $|G_E|/|G_M|$ value in the energy range under study is between 1.0 and 1.5 with an average value of $1.21\pm 0.13$.

We present a semiclassical framework in which stress-tensor deformations of a quantum field theory (QFT) reorganize into a gravitational action evaluated at a metric saddle. The deformed partition function can be written as a gravitational path integral evaluated at the saddle, establishing a direct link between stress-tensor flows and gravitational dynamics. Two complementary routes arise: (i) from gravitational actions such as Einstein and Palatini, which map to stress-tensor deformations of a seed QFT; and (ii) from deformed QFTs such as generalized Nambu-Goto and $T\overline{T}$-like deformed models, which reconstruct the corresponding gravitational actions. Finally, in a free, massive scalar theory, we show that the one-loop effective action of the nonlocal deformation contains a local curvature term; its coefficient defines an induced Newton constant at a chosen renormalization scale, thereby demonstrating a bidirectional link between stress-tensor flows and classical gravity.

Relativistic continuous matrix product states (RCMPSs) are a powerful variational ansatz for quantum field theories of a single field. However, they inherit a property of their nonrelativistic counterpart that makes them divergent for models with multiple fields, unless a regularity condition is satisfied. This has so far restricted the use of RCMPSs to toy models with a single self-interacting field. We address this long-standing problem by introducing a Riemannian optimization framework, that allows us to minimize the energy density over the regular submanifold of multifield RCMPSs, and thus to retain purely variational results. We demonstrate its power on a model of two interacting scalar fields in $1+1$ dimensions. The method captures distinct symmetry-breaking phases, and the signature of a Berezinskii-Kosterlitz-Thouless transition along an $O(2)$-symmetric parameter line. This makes RCMPSs usable for a far larger class of problems than before.

The first four-dimensional amplitude analysis of the $B^{+}\to \psi (2S)K_{\mathrm{S}}^0{\pi }^{+}$ decay is performed with proton-proton collision data collected by the LHCb experiment at $\sqrt{s}=13\mathrm{TeV}$, corresponding to an integrated luminosity of $5.4\mathrm{f}{\mathrm{b}}^{-1}$. The data cannot be fully explained by $B^{+}\to \psi (2S)K^{*+}$ contributions alone. A significantly better description of the data is obtained by adding a $T_{c\overline{c}}^{+}$ contribution decaying to $\psi (2S){\pi }^{+}$. The properties of the $T_{c\overline{c}}^{+}$ structure are consistent with the exotic state $T_{c\overline{c}1}(4430{)}^{+}$ reported in the isospin-related ${\overline{B}}^0\to \psi (2S)K^{-}{\pi }^{+}$ decay. Effects of a possible $T_{c\overline{c}1}(4430{)}^{+}\to {\overline{D}}_1^{*}(2600{)}^0{D}^{+}$ decay mode on the $T_{c\overline{c}1}(4430{)}^{+}\to \psi (2S){\pi }^{+}$ mass distribution are investigated through a Flatté parametrization, providing constraints on the relative decay strength. A description of the $T_{c\overline{c}1}(4430{)}^{+}$ structure using the triangle singularity mechanism is studied and also found to be consistent with the data.

We study ultra-Planckian $2\to 2$ scattering in an Abelian gauge theory coupled to agravity, the scale-free and renormalizable realization of quadratic quantum gravity. Focusing on charged fermions and scalars interacting with the photon and the higher-derivative graviton, we present compact analytic expressions for the unpolarized squared matrix elements for a broad set of tree-level processes, including photon–photon, fermion–fermion, fermion–photon, scalar–fermion, scalar–photon, scalar–scalar, and annihilation channels. In contrast to purely graviton-mediated analyses, we retain systematically the photon–graviton interference contributions and verify explicitly the independence of the results on the gravitational gauge-fixing parameter. The amplitudes display characteristic forward/backward enhancements associated with small momentum transfer, amplified by the $1/p^4$ graviton propagator, while their high-energy scaling reflects the underlying dimensionless gravitational couplings. Moreover, for all channels analyzed, the corresponding differential cross sections exhibit the universal ultra-Planckian scaling $d\sigma /d\mathrm{\Omega }\propto 1/s$, where $s$ is the Mandelstam invariant (the squared center-of-momentum energy). Our results furnish a unified amplitude-level description of how higher-derivative gravity reshapes familiar QED scattering at ultra-Planckian energies and provide analytic building blocks for further studies of IR definitions and UV consistency in agravity with matter.

We present a fully analytic treatment of Schwarzschild–de Sitter (SdS) black-hole evaporation in two-dimensional dilaton gravity with anomaly-induced backreaction. Starting from the spherical reduction of four-dimensional Einstein gravity with a cosmological constant, we construct an exactly solvable 2D model that captures the full causal and thermodynamic structure of the SdS static patch, including both black-hole and cosmological horizons. Incorporating the trace anomaly of $N$ conformal matter fields via the Polyakov action, we determine the evolution of the black-hole mass and geometry in the Unruh–de Sitter state, track the steady nonequilibrium Hawking flux, and compute local thermodynamic observables for static observers. The conserved Killing energy flux drives an irreversible heat current from the black hole to the cosmological horizon whenever their surface gravities differ, ensuring monotonic entropy growth and satisfaction of the generalized second law. We prove that ${\kappa }_b>{\kappa }_c$ throughout the physical static patch, so the only zero-flux configuration is the Nariai limit where the horizons coincide. Extending the framework to the quantum-information regime, we construct a thermo-controlled estimate of the Page curve and show how quantum extremal surfaces and entanglement islands emerge naturally within the anomaly-induced steady state. These results constitute a fully analytic, backreacted solution for SdS evaporation that unifies semiclassical thermodynamics and information flow in a cosmological setting, thereby elucidating the ultimate fate of evaporating black holes in de Sitter space.

Binary neutron stars (BNSs) are one of the most important gravitational wave (GW) sources, which provide key insights into the evolution of massive binary stars and nuclear physics. The Beyond Laser Interferometer Space Antenna (LISA), Taiji, and Tianqin missions’ proposed concepts for next-generation space-based GW observatories, including LISAmax, Folkner, and eASTROD, aim to explore the submillihertz (mHz) to microhertz frequency band. Because the proposed designs substantially suppress low-frequency noise, these detectors are expected to outperform LISA, Taiji, and Tianqin in detecting eccentric Galactic BNS systems. In this paper, we estimate the detectability of nearby inspiraling BNSs using future sub-mHz GW detectors. By utilizing compact binary population synthesis simulations to generate mock BNS samples and estimate their signal-to-noise ratios (SNRs) correspondingly for each GW detector over an observation period of five to ten years, we find that LISAmax may detect $\sim 520–900$ Galactic BNSs, whereas Folkner and eASTROD may detect $\sim 780–1370$ Galactic BNSs. Notably, LISAmax excels in detecting highly eccentric systems ($e>0.90$) owing to its higher sensitivity at relatively higher sub-mHz frequencies. We further identify seven observed radio BNSs as viable candidates for validation, in particular, J0737-3039, which reaches an SNR of $\sim 100$. The expected detection number of Large Magellanic Cloud inspiraling BNSs is $\sim 4–18$ for these sub-mHz detectors over an observation period of five to ten years, while detecting inspiraling BNSs in the Small Magellanic Cloud is challenging. This study highlights the significant potential of future sub-mHz GW missions in unraveling BNS formation and evolution physics.