Using $e^{+}{e}^{-}$ collision data corresponding to an integrated luminosity of $44{\mathrm{fb}}^{-1}$ collected with the BESIII detector at the BEPCII Collider, we report the first measurement of Born cross sections and effective form factors for $e^{+}{e}^{-}\to {\mathrm{\Sigma }}^{-}{\overline{\mathrm{\Sigma }}}^{+}$ at center-of-mass energies between 3.51 and 4.95 GeV. With a fit to the $\sqrt{s}$-dependent dressed cross sections, the decay $\psi (3770)\to {\mathrm{\Sigma }}^{-}{\overline{\mathrm{\Sigma }}}^{+}$ is observed for the first time with a significance of $5.5\sigma$, including systematic uncertainties. The corresponding branching fraction is determined to have two solutions, $(2.9\pm 0.3)\times {10}^{-4}$ and $(1.1\pm 0.1)\times {10}^{-4}$, where the quoted uncertainties also include systematic uncertainties. Upper limits at the 90% confidence level on the product of the branching fraction and the electronic partial width are provided for other possible charmonium(like) states. The ratios of Born cross sections for the $\mathrm{\Sigma }$ isospin-triplet states are determined and can be used to test the vector-meson-dominance model.

Motivated by the temporal dynamics identified in the $1+1$ Carroll-Schrödinger theory, we derive a post-Carrollian Schrödinger dynamics in flat Klein space with signature (2, 2). Starting from the tachyonic Klein-Gordon equation in double-polar coordinates and removing a spacelike carrier, the spatial radius behaves as an effective evolution parameter, whereas the temporal two-plane $(t_1,t_2)$ serves as the equal-radius configuration space. The additional time direction supplies an $SO(2)$ temporal angular momentum $J$, produces temporal vortex sectors, and gives the centrifugal contribution to the post-Carrollian momentum $P_{\mathrm{PC}}=E_{\tau }^2/(2M_{\mathrm{eff}})+J^2/(2M_{\mathrm{eff}}{\tau }^2)$ in the Hamilton-Jacobi limit. We determine the regular Bessel modes, Gaussian packets, oscillator spectrum, radial $SU(1,1)$ tower, equal-$r$ continuity equation, $\mathfrak{sch}(2)$ symmetry algebra, radial-ordered propagator, and the metaplectic organization of the quadratic sectors. Starting from a minimally coupled complex scalar-$U(1)$ parent action, we derive the Maxwell-matter equations and their Bianchi constraints, identify a regular finite-interaction branch with $q_{\epsilon }=q/\epsilon$, and obtain the corresponding gauge-covariant Carroll-Schrödinger equation together with its sourced Maxwell responses and optional temporal gauge backgrounds. As a curved extension, we derive a branch-dependent carrier reduction and apply it to an illustrative $SO(2,1)$-symmetric Kleinian Schwarzschild exterior.

Compact binary systems consisting of a black hole (BH) and a neutron star (NS) are expected to provide detectable signals both in the gravitational-wave and in the electromagnetic channels, thus representing excellent sources for multimessenger astronomy. In this third paper in a series, we report on the geometric and thermodynamic properties of the purely dynamical ejecta component modeled in our general-relativistic magnetohydrodynamical simulations of BHNS systems over a comprehensive binary parameter space consisting of large mass ratio and high BH spin. The tidal disruption and dynamical mass ejection is studied by monitoring the transfer of energy and angular momentum to matter for the particular case of a highly unequal-mass binary with large BH spin, extending known results for low-mass-ratio, irrotational BHNS binaries. By varying the binary parameters, we investigate their influence on the geometric, thermodynamic, and kinematic properties of the ejected matter. Furthermore, we employ the nuclear-reaction network skynet to obtain the elemental abundances resulting from the $r$ process active in the ejecta and study how they depend on the properties of the progenitor objects. Finally, using the radiative-transfer code possis, we compute the kilonova light curves from the results of our simulations, discuss their bolometric and optical/near-infrared evolution, and compare them with the AT2017gfo data and upper limits for S190814bv, finding overall consistency.

We present a scheme and implementation code for time-domain integration of the Teukolsky equation in $1+1$ dimensions with a point-particle source, based on comoving, spatially compactified hyperboloidal coordinates. We demonstrate that the scheme evades the problem of nonphysical growing modes that plague some numerical evolution schemes without compactification. Our use of comoving coordinates greatly simplifies the application of jump conditions on the particle’s worldline. We develop our method and test its performance for a scalar field on a Schwarzschild background, first for a circular geodesic orbit source and then for a scattering geodesic orbit. We then present a test implementation of the method for the $s=-2$ Teukolsky equation, illustrating its long-term stability and absence of growing-mode behavior through comparison with similar results using noncompactified characteristic coordinates. Our method paves the way to calculations of the full gravitational self-force in extreme-mass-ratio scattering.

We perform the first $k$-cut cosmic shear analysis of the KiDS-Legacy survey. This method uses the Bernardeau-Nishimichi-Taruya (BNT) transform to construct weak-lensing kernels that are more localized than conventional ones, and remove information from selected physical scales while retaining the constraining power of the targeted range. Removing the scale of $k\ge 0.33{\mathrm{Mpc}}^{-1}$ from the KiDS-Legacy pseudo-$C_{\ell }$ data vector, and using a covariance matrix whose Gaussian component is computed from the theoretical data vector, we find $S_8=0.798_{-0.045}^{+0.045}$. This agrees with both the fiducial KiDS-Legacy bandpower result and our no-$k$-cut pseudo-$C_{\ell }$ posterior to within $0.1\sigma$, indicating no significant bias from nonlinear astrophysical feedback at the precision of KiDS-Legacy. We also study the case in which the Gaussian covariance is computed from the observed data vector. In this setup, the same scale cut of $k<0.33{\mathrm{Mpc}}^{-1}$ gives a much lower $S_8=0.717_{-0.046}^{+0.047}$. Further $k$-cut tests reveal a mild scale-dependent trend, with larger physical scales preferring lower $S_8$ values and a maximum low- versus high-$k$ deviation of $1.80\sigma$. Mock tests show that this behavior is not produced by the covariance prescription or data vector alone, but may arise from their interplay. These results show that BNT $k$-cuts provide both a mitigation strategy for nonlinear systematics and a diagnostic of weak-lensing inference pipelines.

The convective turbulent motion of the fluid below the shock in a core-collapse supernova stretches and amplifies the magnetic field of the progenitor star. The energy contained in the field is sourced from the work done by the fluid on the field which comes at the expense of the fluid’s kinetic and internal energy. In addition to the energy exchange with the fluid, the magnetic field also has a backreaction upon the fluid via a contribution to the baroclinic vector and thus affects the fluid vorticity. In this paper we explore the interaction of the magnetic field with the fluid in core-collapse supernovae using the elephant code with solar-metallicity stars of 15 and $20{\mathrm{M}}_{\odot }$ zero-age main sequence mass and purely toroidal initial magnetic fields of $B_0=0,{10}^{10}$, and ${10}^{12}\mathrm{G}$. We find that the magnetic field in the gain region does not become so large that it alters the global dynamics above the 10% level in the early postbounce evolution. The turbulent kinetic energy of the fluid in the gain region is smaller in simulations with a strong initial magnetic field, but the exact amount of reduction is uncertain due to limitations of the methods for measuring turbulent kinetic energy. The structure of the field in the simulations quickly becomes a tangled mass of flux ropes as soon as convection begins, which leads to a large magnetic field contribution to the baroclinic vector that dominates over the hydrodynamic contribution. Although governed by very similar transport equations to the magnetic field, the fluid vorticity and magnetic field are always close to being randomly aligned at every stage of the evolution. The enstrophy, which is seen to be closely associated with the turbulent kinetic energy, is found to be reduced in simulations with a strong initial magnetic field supporting the inference that the magnetic field reduces the amount of turbulence in the fluid.

Generating dense grids of detailed stellar evolution simulations is computationally prohibitive, as resolving progressively complex nucleosynthesis chains and dynamical timescales incurs a rapidly increasing computational cost that scales with dimensionality and resolution. Existing simulation grids are sparse, heterogeneous, and often cover disparate regions of parameter space, limiting (direct) systematic comparison and broader generalization to downstream science analyses. We present active simulation tuning and regression for astrophysical libraries (ASTRAL), a publicly available framework for optimal placement and emulation of stellar evolution models. The ASTRAL framework builds surrogate models that provide a continuous representation of the parameter space which is populated by sparse simulation grids. Furthermore, ASTRAL interpolates across the simulation parameter space (e.g. zero-age-main-sequence mass) to predict stellar properties of stars with associated uncertainty estimates for systems not explicitly simulated. We show that ASTRAL significantly outperforms uniform placement in constructing emulation-ready model libraries that capture both global and local variability in the output features. We showcase the performance of our framework in the context of a simple, one-dimensional MESA model. Finally, we examine how our methodology can inform downstream applications by analyzing our emulator’s predictive confidence when applied to supernova simulations. We emphasize that, while developed for stellar evolution, the ASTRAL framework is directly extensible to other simulation-driven domains where model evaluations are expensive and parameter spaces are high dimensional.

Nonlinear Compton scattering is the process of emission of a single photon by a charge driven by an intense laser field. Here, we study the infrared behavior of the photon yield emitted via nonlinear Compton scattering. We first consider the idealized case of an electron in the presence of a plane wave and derive an analytical expression of the total yield in the form of a double integral over the laser phase. As it is known, the total yield is finite in the experimentally common case of a plane wave laser field without a dc component whereas it diverges logarithmically in the complementary case of so-called unipolar fields. The divergence is found here to correspond to the longer-and-longer formation lengths of emitted photons with lower-and-lower frequency. Interestingly, we also find that the corrections to the Volkov states stemming from the fact that the field is unipolar cancel out in the computation of the probability of nonlinear Compton scattering, which is in agreement with the fact that in the classical limit the expression of the photon yield is independent of whether the plane wave is unipolar or not. Then, we pass to the more realistic case of an electron in a tightly focused laser beam by assuming that the electron is ultrarelativistic. In this case we determine analytically the classical angular distribution of the yield of photons with an energy larger than a fixed value $\hslash {\omega }_m$ as a double integral over the electron’s trajectory. Indeed, in the case of a focused laser beam the electron does typically undergo a net acceleration and it is therefore appropriate to fix a lower bound to avoid the infrared divergence. After obtaining also the corresponding quantum expression of the angular distribution of the photon yield within the quasiclassical approximation, we determine analytically the leading-order quantum correction, which scales as $\hslash {\omega }_m/ϵ$, where $ϵ$ is the initial electron energy. Considerations on the experimental feasibility of the found results in the latter situations are also presented.

The muon trident process, which involves coherent scattering to produce tau pairs, is a powerful tool for constraining dark sectors. We propose to explore this channel using future high-energy muon beams with the dedicated active-target detector, High-Energy Muon Electronic Research Apparatus (HEMERA). The detector would complement muon beam-dump searches by resolving prompt signatures and could operate from preparatory facilities involving an individual muon beam of the full muon collider. We illustrate its capabilities for a leptophilic scalar with Yukawa-like couplings that can mediate thermal dark matter production. With ${10}^{18}$ incident TeV-scale muons, even a compact 10 kg silicon-based HEMERA will extend current $B$-factory and $(g-2{)}_{\mu }$ bounds by over an order of magnitude in coupling strength. In the leptophilic thermal dark matter paradigm, this search offers a way to probe dark sector targets beyond the neutrino floor of dark matter direct detection. This provides an additional compelling motivation for the development of high-energy muon beam infrastructure.

We investigate the phase transition of quantum chromodynamics (QCD) with three degenerate quark flavors at zero baryon chemical potential. Using Möbius domain-wall fermions as the lattice fermion formulation, we ensure excellent chiral symmetry preservation. Our simulations are performed at three different temporal lattice extents, $N_t=6$, 8, 12, with a fixed lattice spacing $a=0.1361(20)\mathrm{fm}$, corresponding to temperatures of 242(4), 181(3), and 121(2) MeV, respectively. We explore a range of quark masses and spatial volumes with aspect ratios $N_s/N_t$ spanning from 2 to 4. By analyzing the mass and volume dependencies of the plaquette, plaquette susceptibility, chiral condensate, chiral susceptibilities, and Binder cumulant, we identify the pseudocritical transition quark masses from our largest lattice volumes. For $N_t=6$, this is 184(10) MeV (determined from the plaquette susceptibility), corresponding to $m_{\pi }\simeq 0.96\mathrm{GeV}$. For $N_t=8$ and 12, the transition points vary slightly depending on whether the total or disconnected chiral susceptibility is used, yielding ranges of 36(1)–39.1(9) MeV and 3.5(3)–3.7(2) MeV, respectively, in the $\overline{\mathrm{MS}}$ scheme at a scale of $\mu =2\mathrm{GeV}$. In terms of the pseudoscalar mass, these correspond to $m_{\pi }\simeq 427–445\mathrm{MeV}$ and 133–137 MeV. The negligible volume dependence at $N_t=6$ and 8, combined with finite-size scaling analysis at $N_t=12$ revealing volume growth significantly weaker than expected for a first- or second-order phase transition, points to a continuous crossover at these specific quark mass points. Additionally, we study the effects of residual chiral symmetry breaking on the chiral condensate and chiral susceptibilities using two different values of $L_s$.

We analyze the $B^0\to K_S^0{\mathrm{\Lambda }}_c^{+}\overline{\mathrm{\Lambda }}{}_c^{-}$ decay recently observed by the LHCb Collaboration. The ${\mathrm{\Lambda }}_c^{+}\overline{\mathrm{\Lambda }}{}_c^{-}$ invariant-mass spectrum exhibits an accumulation near 4.63 GeV, which we investigate together with the accompanying ${\mathrm{\Lambda }}_c^{+}{K}_S^0$ spectrum constrained by the known ${\mathrm{\Xi }}_c(2923)$ and ${\mathrm{\Xi }}_c(2939)$ states. Our amplitude model includes a nonresonant term, the two established ${\mathrm{\Xi }}_c$ contributions, and high-lying charmonium states in the ${\mathrm{\Lambda }}_c^{+}\overline{\mathrm{\Lambda }}{}_c^{-}$ channel. Guided by screened Godfrey-Isgur and quark-pair-creation calculations, we test the 4.63 GeV enhancement with a fixed ${\eta }_c(6S)$ amplitude at $(M_1,{\mathrm{\Gamma }}_1)=(4629.00,24.20)\mathrm{MeV}$, which improves the description of the 4.63 GeV region, and examine a fixed ${\eta }_c(7S)$ contribution at $(M_2,{\mathrm{\Gamma }}_2)=(4718.84,22.84)\mathrm{MeV}$, which improves the higher-mass region of the spectrum. We also evaluate the ${\eta }_c(nS)\to {\mathrm{\Lambda }}_c^{+}\overline{\mathrm{\Lambda }}{}_c^{-}$ baryonic decays via a hadron-loop mechanism and estimate the $B^0\to K_S^0{\eta }_c(nS)$ production in naive factorization. Within the narrow width approximation, the fit yields a $\mathcal{B}(B^0\to K_S^0{\eta }_c(6S))\times \mathcal{B}({\eta }_c(6S)\to {\mathrm{\Lambda }}_c^{+}\overline{\mathrm{\Lambda }}{}_c^{-})$ of about $6.2\times {10}^{-6}$, while the factorization and hadron-loop calculations give rates roughly one to three orders of magnitude lower than the above fitted ratio. These results highlight the need for more precise data and a full amplitude analysis to determine the line shapes and clarify the nature of the higher-mass contribution.

Multipartite entanglement is a uniquely quantum form of correlation that captures collective properties of a composite quantum state beyond those encoded in its bipartite subsystems. We investigate this phenomenon in the process $e^{+}{e}^{-}\to t\overline{t}Z$ at a future lepton collider, where the final-state spins span the tripartite Hilbert space $\mathcal{H}={\mathbb{C}}^2\otimes {\mathbb{C}}^2\otimes {\mathbb{C}}^3$. Starting from the standard model helicity amplitudes, we reconstruct the full $12\times 12$ spin density matrix and characterize its entanglement structure through one-to-one negativities, one-to-other negativities, and the genuine multipartite negativity, evaluated at three increasingly inclusive levels of phase-space integration. Pairwise entanglement is generally suppressed relative to the collective (one-to-other) and the genuine multipartite entanglement, and all measures decrease as more kinematic information is integrated out. Assuming quantum tomography in the fully leptonic decay channel at $\sqrt{s}=1\mathrm{TeV}$, we find that collective entanglement should be accessible at a realistic high-luminosity polarized lepton collider. By contrast, certifying genuine multipartite entanglement is more challenging, with only limited sensitivity projected for a specific polarization benchmark within the luminosity expected at the International Linear Collider. The study establishes $e^{+}{e}^{-}\to t\overline{t}Z$ as an attractive laboratory for probing multipartite entanglement in high-energy collisions and provides a general mixed state framework that applies to any tripartite spin system.

The dual-phase xenon time projection chamber (TPC) is a powerful technology to detect rare interactions such as scatters of dark matter particles on nuclei. In particular, the built-in gain of ionization signals in a dual-phase TPC makes it sensitive to events in the few-electron regime, as expected from low-mass dark matter interactions. The pursuit of this low-energy sensitivity through ionization-only signal detection has so far been hindered by excessive electron backgrounds observed across experiments. Much of this background is attributed to the plate-out of ${}^{222}\mathrm{Rn}$ decay chain isotopes on the high-voltage electrode grid surfaces that span the full cross section of the TPC. This work presents a first-principles model constructed for this background, the predictions of which are consistent with data from the LZ and LUX experiments. We then discuss strategies to mitigate this background in future dual-phase TPCs and the possibility of applying this grid background model to ionization-only dark matter searches.

Spontaneous Lorentz-violating models of an antisymmetric tensor field are known to possess a singular Hamiltonian on the vacuum manifold, leading to unresolvable pathologies that render such theories unfit for cosmological studies. In this work, we introduce an auxiliary vector field inspired by the Stückelberg mechanism to investigate whether this resolves the fundamental phase space singularities. The total Hamiltonian is found to be globally ill defined. For completeness, in an effective field theoretic sense where the phase space is restricted to near the vacuum manifold of Lorentz-violating models, we derive the singularity conditions near the vacuum manifold for an explicit model and find that the resulting constraint matrix acquires an explicit dependence on the gradients and conjugate momenta of the Stückelberg field components that can still lead to a singular Hamiltonian.

We investigate the conditions under which black hole fragmentation, the splitting of a black hole into two or multiple smaller ones, may occur via an unspecified dynamics, which would have the topology of a pair-of-pants. We employ kinematical and entropical consideration on time-sliced quasistatic black hole configurations to check under what conditions the pants dynamics is permitted. In classical general relativity, the Bekenstein-Hawking area law forbids such processes for Schwarzschild black holes. For spinning Kerr black holes, purely kinematic analyses impose constraints that prevent fragmentation, even in regimes where entropy considerations might allow it, except possibly in near-extremal cases. We then hunt for scenarios where black holes can wear pants: from the well-known Gregory-Laflamme instability in higher dimensions, to the potential effect of superradiant instabilities in nonaxisymmetric radiation trapping, to finally gravitational models that modify the relations between entropy and/or horizon radius and the black hole mass in four dimensions. In all such cases, emission of small fragments can be entropically favored. However, its occurrence still depends on the kinematic configuration of the initial state. Our analysis clarifies the theoretical landscape where black holes may fragment, which is particularly relevant for primordial black holes and catastrophic events such as black hole mergers.

Black hole thermodynamics in Lorentz-violating gravity is subtle because different excitations propagate at different speeds and hence identify different causal horizons. We revisit Einstein–æther gravity using the covariant phase space formalism with boundaries and derive a consistent first law for stationary black holes. For a mode of propagation speed $s$, we introduce a disformal frame in which the corresponding $s$-horizon is a Killing horizon, so that a standard Wald-type derivation can be carried out. We then map the result back to the original (horizon) frame, showing that the first law retains the same formal structure. The associated horizon charge contains, besides the usual geometric (Komar/Wald) contribution, an irreducible æther term that admits an interpretation as an additional entropy sourced by the æther flux across the horizon; accordingly, the total entropy splits into a gravitational part and an æther part. We further develop an extended-thermodynamics framework in which the couplings (and $\mathrm{\Lambda }$) are allowed to vary, obtaining generalized Smarr relations. Finally, we analyze the probe-mode limit $c_s\to +\infty$, clarifying its connection to universal-horizon thermodynamics and resolving the apparent tension in the literature between approaches that (i) fix the entropy to be proportional to the area and infer a corresponding temperature, and (ii) impose the Hawking temperature associated with modes peeling from the universal horizon and infer a nonarea entropy. Once the independent æther entropy contribution is properly taken into account, the two prescriptions are reconciled.

Astrophysical black holes (BHs) are not isolated, but embedded in matter supplied by their host galaxies. We study how the shape of a surrounding dark matter halo modifies the ringdown and tidal response of an asymptotically flat, static, spherically symmetric BH. The halo is modeled as an anisotropic Einstein cluster with vanishing radial pressure and a generalized $(\alpha ,\beta ,\gamma )$ density profile, supplemented by an inner cutoff near the BH and, where required, an outer tidal truncation. We derive the axial gravitational perturbation equation and compute the quasinormal mode (QNM) spectrum using sixth-order Wentzel-Kramers-Brillouin (WKB) methods and time-domain evolutions. The halo redshifts both the oscillation frequency and the damping rate, by an amount set not only by the halo compactness but also by the profile parameters: the inner logarithmic slope $\gamma$ dominates for centrally concentrated halos, while $\alpha$ and $\beta$ give subleading but profile-dependent corrections. In the eikonal limit, the shift is governed by a single redshift integral encoding the halo mass distribution outside the light ring, explaining the close correspondence between the QNM frequencies, the light ring frequency, and the Lyapunov exponent. We also show that different combinations of compactness and profile shape can yield nearly degenerate ringdown spectra. Time-domain evolutions confirm the WKB frequencies and display the expected late-time Price-law decay, with an intermediate tail controlled by the outer density falloff for slowly decaying profiles. Finally, we compute the static axial tidal Love number and show that it probes the halo with a radial weighting different from the ringdown sector. The combined ringdown and tidal response therefore provides a possible way to distinguish environmental effects from genuine deviations of the vacuum BH geometry.

Merging binary black holes exhibit a ringdown phase in which they primarily emit gravitational waves in the shape of damped sinusoids corresponding to quasinormal modes of the Kerr remnant. In general, each mode carries 4 degrees of freedom encoding amplitude and phase information. When the modes are excited with equatorial reflection symmetry, as is the case for black hole mergers with spins (anti)aligned to the orbital angular momentum, the symmetry constrains 2 degrees of freedom. As a result, the relationship between polarization amplitudes and phases in each mode is fixed by the viewing (inclination) angle to the equatorial plane. We use such a constrained model to fit the ringdown signals of both nonprecessing and precessing systems such as GW150914 and GW190521, respectively. We show that we can measure the degree of circular polarization and handedness of ringdown signals like those of GW150914, even if only the two LIGO detectors are available; such a polarization measurement can be translated into an inferred source inclination assuming the reflection symmetry above, again using the ringdown signal alone. On the other hand, the constrained polarization model is insufficient to capture the polarization structure of signals from precessing systems, leading to biases in the inferred mode frequencies and amplitudes. We explore the magnitude of this effect by fitting GW190521-like injections with the restricted model, finding weaker predictive accuracy relative to the arbitrary-polarization model and potentially significant systematic biases. As our detectors continue to improve, using the correct polarization model is increasingly important to avoid biased ringdown measurements.