We systematically study the mass spectra of $S$-wave singly heavy tetraquark states $Qq\overline{q}\overline{q}$ ($Q=c$, $b$; $q=u$, $d$, $s$) in a mass splitting model. We adopt the assumption that the $X(4140)$ is the lowest $J^{PC}=1^{++}cs\overline{c}\overline{s}$ tetraquark and use this state as a reference to determine the mass splittings. According to the obtained results, we also estimate the rearrangement decay widths of the tetraquarks within a simple scheme. We find that the recently observed states $T_{c\overline{s}0}^a(2900{)}^{++/0}$ and $T_{cs0}^{*}(2900{)}^0$ by the LHCb Collaboration can be consistently interpreted as the second highest $I(J^P)=1(0^{+})$ $cn\overline{s}\overline{n}$ ($n=u$, $d$) and the higher $I(J^P)=0(0^{+})$ $cs\overline{n}\overline{n}$ tetraquark states, respectively. We predict several narrow tetraquark candidates: the lowest $cn\overline{s}\overline{n}$ and $cs\overline{n}\overline{n}$ with $I(J^P)=0(0^{+})$ and $0(1^{+})$, and their bottom counterparts. The obtained information from mass spectrum and rearrangement decay properties will help search for the new singly heavy tetraquark states.

We initiate the precision study of boosted jet substructure using energy correlators, applying this framework to hadronic Higgs decays. We demonstrate that the two-body decay of the Higgs manifests as a distinct angular peak at $\theta \sim \arccos (1-2/{\gamma }^2)$ for Lorentz boost factor $\gamma$. We show that infrared scales, such as the dead-cone effect and confinement transition, are also resolved within the boosted distribution. Precision analytic studies of boosted jet substructure may enable precision electroweak studies and open new avenues for searches for new physics searches.

We investigate the behavior of the nonradial gravity-pulsation discontinuity $g$-mode in neutron stars with a strong first-order phase transition which give rise to hybrid star configurations. These modes are of utmost relevance, since they can be potentially excited in isolated as well as binary neutron star systems in the inspiral phase, thus allowing us to indirectly detect the presence of a deconfinement transition. In order to do this, we consider four categories of hybrid stars that present distinctive features in their equations of state. We employ the constant speed of sound parametrization, which accounts for a sharp phase transition between confined hadronic matter and deconfined quark matter. Then, working within the relativistic Cowling approximation to obtain the frequencies of nonradial oscillations, we find that, depending on the hybrid star category, the relations between discontinuity $g$-mode frequencies and masses as well as tidal deformabilities display a highly distinct behavior across the diverse hybrid star categories that appear in the slow hadron-quark conversion regime. This distinct phenomenology provides smoking-gun evidence to clearly distinguish and further classify hybrid stars with a strong transition from purely hadronic stars using upcoming gravitational-wave data. In addition, we present for each of the categories studied the relation between the $g$-mode frequency and the normalized energy density jump. Finally, we present a novel universal relation for the discontinuity $g$-mode able to encompass the four categories, including long branches of slow stable hybrid stars and address its asteroseismological capability.

The SUPerconduction AXion search experiment (supax) is a future haloscope-type detector designed to probe axionlike particles as candidates for dark matter and solutions to the strong-$CP$ problem in the mass range between $8\mathrm{\mu }\mathrm{eV}$ and $30\mathrm{\mu }\mathrm{eV}$. In the course of the preparation of supax, a prototype experiment was built and operated. Using a copper cavity, cooled down to a temperature of 2 K and operated in a magnetic field of 12 T, we probe axion masses around $34\mathrm{\mu }\mathrm{eV}$ and exclude axion-photon couplings down to $|g_{a\gamma \gamma }|>1.6\times {10}^{-13}{\mathrm{GeV}}^{-1}$. The data were also used to exclude dark photons in the same mass range with a kinetic mixing parameter of $\chi >1.4\times {10}^{-12}$. Details of the experimental setup and the analysis strategy are summarized in this paper.

Neutrino nonstandard interactions (NSI) constitute an active research field, as they are closely related to potential new physics associated with dark matter searches and exotic interactions arising from fundamental symmetry violations. The Borexino’s unprecedented sensitivity to solar neutrinos, derived from its low background and precision spectral measurements, enables stringent constraints on potential deviations from the standard three-flavor neutrino oscillation paradigm. This work presents an update on the analysis of flavor-diagonal NSI using the full Borexino Phase-III dataset, extending the study previously reported in Constraints on flavor-diagonal nonstandard neutrino interactions from Borexino Phase-II (JHEP 2020, 38). The updated analysis incorporates the extended temporal and statistical coverage of Phase-III. The results indicate improved sensitivity to the diagonal NSI parameters, with constraints exceeding those obtained in Phase-II. Furthermore, a more general analysis that includes all possible off-diagonal NSI terms is presented for the first time, providing a comprehensive exploration of the NSI parameter space associated with the flavors of the incoming and outgoing neutrinos. This work once again underlines the Borexino’s critical role in probing new physics scenarios and reinforces its legacy in neutrino research. Detailed comparisons with Phase-II results are discussed, along with implications for theoretical models of NSI.

We demonstrate that the unitarity of quantum field theory, through the positivity of spectral densities, underlies thermodynamic irreversibility for a subsystem separated by a horizon, in direct analogy with the irreversibility of renormalization-group flows. To this end, we explicitly find the shear and bulk viscosities—the entanglement viscosities—for thermal radiation in Rindler space using the universal spectral representation. A direct consequence of the obtained general formulas is the relationship between the acceleration-induced shear viscosity in flat space and the conformal quantum anomaly in curved space, pointing to a possible novel probe of the conformal anomaly in systems with extreme acceleration. Moreover, for conformal field theories, we explicitly show that globally entanglement viscosity saturates the Kovtun-Son-Starinets bound.

We show that using a Taylor expansion for the dark energy equation-of-state parameter and limiting it to the zeroth and first-order terms, i.e., the so-called Chevallier-Polarski-Linder (CPL) parametrization in regimes where it has been shown to fail as a physics-based two-parameter model, instead of allowing for higher-order terms and then marginalizing over them, adds extra information not present in the data and leads to markedly different and potentially misleading conclusions. Fixing the higher-order terms to zero, one concludes that vacuum energy that is currently nondynamical (e.g., the cosmological constant) is excluded at several $\sigma$ significance as the explanation of cosmic acceleration, even in Dark Energy Spectroscopic Survey (DESI) DR1 data. Meanwhile, instead marginalizing over the higher-order terms shows that we know neither the current dark energy equation of state nor its current rate of change well enough to make such a claim. The CPL parametrization also implies that dark energy exhibits phantom behavior at high redshifts, while we show that by allowing the higher-order terms—which is required in order to capture the behavior of the dark energy equation of state in regimes beyond the validity of the CPL parametrization—the evidence for this phantomlike dark energy significantly weakens. This is not an argument for the higher-order phenomenological parametrizations, but rather a caution regarding such parametrizations in general. This issue has become more prominent now with the recent release of high-quality Stage IV galaxy survey data. The results of analyses using simple parametrizations should be interpreted with great care.

We observe that the transition probability in a static two-level quantum detector interacting with a coherent Rindler field mode differs from that of the Rindler detector interacting with a coherent Minkowski field mode. The situation does not change in the quantum detector’s response in the semiclassical limit of the field state. This we investigate in ($1+1$) and ($3+1$) spacetime dimensions. Interestingly, in ($1+1$) dimensions, the transition probabilities of the “classical” detector in the semiclassical limit of the field state for these two scenarios appear to be identical when the field mode and detector frequencies are taken to be the same. However, in ($3+1$) dimensions, the detector transition probabilities calculated under the large-acceleration condition do not exhibit such a signature. The implications of these observations are also discussed.

We perform a quantum probing of colliding plane-wave spacetimes. In particular, we consider the Khan-Penrose and the Ferrari-Ibáñez solutions, which admit a strong and a weak singularity after the two waves collide. While we find that, like Schwarzschild, for the Khan-Penrose solution the singularity cannot be probed by quantum-field theory, the Ferrari-Ibáñez singularity can be traversed. Our results culminate in a quantum Weyl conjecture: The significant geometric property to classify spacetimes with respect to quantum probes is given by the Coulomb part of the Weyl tensor. We then use this conjecture to sketch a possible backreaction scenario for plane waves.

The analytic integration of single-scale Feynman integrals emerging in perturbative calculations in quantum field theories can be performed within special classes of functions, which appear as consecutive generalizations of the polylogarithm in form of Kummer-Poincaré iterative integrals over special alphabets and extensions thereof. These are the polylogarithms, Nielsen integrals, iterated integrals over linear denominator terms, cyclotomic letters, letters induced by quadratic forms, and square-root valued letters. These integrals are solutions of first-order factorizing differential equations. They are related to specific nested sums via the Mellin transform and their expansions around $x=0$. We construct the $\mu$-extensions of these iterated integrals and the associated nested sums. We present closed form solutions or provide algorithms in the case of more involved cases to derive the respective $\mu$-extensions and study the algebras of the $\mu$-extended function spaces. Except for the case of square-root valued alphabets, the $\mu$-extension maps into the same function space polynomially in $\mu$. This is also the case for the associated nested sums. For square-root valued alphabets or sums containing central binomials, the $\mu$-extension leads to higher transcendental functions. In all other cases the $\mu$- extension preserves the Hopf algebra structure implied by the (quasi)shuffle product, by supplementing $\mu$ to the ground field.

Quantum energy teleportation (QET) has been studied in continuum field theory and in lattice many-body systems, but the relation between the two within a single interacting model is still not well understood. To address this question, we consider the massive Thirring model, equivalently the sine-Gordon theory. In the continuum, the trigonometric measurement is a weak binary positive operator-valued measure (POVM), and its leading signal is set by a conserved-current correlator in the bosonized theory, with both gapless behavior and gapped large-distance asymptotics. On the lattice, the conventional protocol does not access this neutral current sector. For Alice’s local measurement, a lattice $U(1)$ selection rule removes the neutral current contribution from Bob’s subsystem, and the separated signal lies in charged sectors. On the same lattice Hamiltonian we construct a neutral current protocol whose weak signal is exactly a coarse-grained current correlator and whose extracted energy scales quadratically with the measurement strength. This identifies the neutral sector shared by the lattice and continuum descriptions, while separating it from the charged sector that governs the conventional qubit protocol.

In the past few decades, the waveform community has made advances in producing waveforms that span the inspiral-merger-ringdown of comparable-mass-ratio black hole binaries using advances in post-Newtonian and numerical relativity (NR) theory along with state-of-the-art gravitational wave models. Current methods in NR have shown progress toward producing stable simulations reaching mass ratios of $1:100$; however, the computational cost becomes prohibitively expensive as the mass ratio and the length of the simulation increases. Meanwhile, the gravitational self-force (GSF) community has developed waveform models that not only generate extreme mass ratio inspiral waveforms, but also generate near-equal-mass-ratio waveforms with high fidelity. To assess the limits of both the GSF and NR waveforms and alleviate the computational costs of NR, we present hybridized GSF-NR waveforms for nonspinning binary black hole systems in which GSF provides the inspiral, and NR the merger and ringdown. The hybrid waveforms are generated from a set of 68 nonspinning NR waveforms from the SXS catalog with mass ratios spanning $1:1$ to $1:20$ and include the (2, 2), (2, 1), (3, 3), (3, 2), (4, 4), (4, 3), and (5, 5) spin-weighted spherical harmonic modes. In this paper, we will highlight a selection of these hybrid waveforms and examine the error in the hybridization procedure. We will investigate the impact of subdominant modes on the accuracy of the hybrid waveforms by performing mismatch comparisons with surrogate models. To address the feasibility of hybridizing GSF inspirals with short-duration, high-mass ratio NR waveforms, thereby alleviating computational costs, we will discuss the relationship between mass ratio and the placement of the matching window, which can be used to predict the necessary and optimal number of NR cycles that contribute to the hybrid waveform.

Swimming in curved spacetimes is a phenomenon whereby free bodies in curved spacetimes are able to propel themselves by performing cyclic internal motions. When originally proposed, it was further suggested that, in the limit of fast internal cycles, the net motion would display a simple geometric-phase character, in which the displacement per cycle would not depend on the time progression of the internal motions but only on the sequence of shapes assumed by the body, like a swimmer in a nonturbulent viscous fluid (low Reynolds number). In this paper, we develop a general, covariant theory of swimming in curved spacetimes, describing a technique to study the motion of free, small, light, articulated bodies in general relativity by mapping the problem to an analog in special relativity. We give considerable attention to the limit of fast cycles and investigate the conditions in which the overall motion could display such geometric-phase behavior. The conclusion, however, is that this simple behavior is only realized in very specific circumstances, depending on the structure of the body, characteristics of internal motions, initial conditions, and symmetries of the spacetime; whereas, in general, our formulas predict a more complicated dynamics.

In the Newtonian limit of $f(R)$ gravity, for an isolated self-gravitating system consisting of $N$ extended fluid bodies, the interbody dynamics are studied by applying the symmetric and trace-free formalism in terms of irreducible Cartesian tensors. The multipole expansion of each body’s center-of-mass acceleration is derived, and the expansion comprises the Coulomb-type part and the Yukawa-type part, where the former, identical to that in general relativity, is encoded by the products of the mass multipole moments of the body with those of other bodies, and the latter, as the modification introduced by $f(R)$ gravity, is encoded by the products of the scalar multipole moments of the body with those of other bodies. Due to the finite range of the massive scalar mode, the scalar multipole terms in the Yukawa part do not decay systematically with increasing order. As an essential component of the system’s orbital dynamics, the multipole expansion for the total gravitational potential energy is provided, and the expression for the total conserved energy in terms of the mass and scalar multipole moments of the bodies is offered. To investigate the system’s spin dynamics, the equation of motion for each body’s spin angular momentum is further deduced and presented in the form of multipole expansion. These findings constitute the main content of the coarse-grained description of interbody dynamics for the system within the framework of the Newtonian limit of $f(R)$ gravity. As a by-product, for a two-body system, the effective one-body equation governing the relative motion between the two bodies and the total energy of this system are achieved.

We present a systematic derivation of regular black hole solutions—and their horizonless counterparts—that achieve regularization via an anti–de Sitter core. These geometries emerge as polymerized vacuum solutions inspired by loop quantum gravity, constituting effective quantum gravity configurations that admit a Birkhoff-type theorem and are uniquely determined by their mass. Using an auxiliary relational dust clock, together with the absence of gravitational waves in spherical symmetry, we exploit the structural ultralocality of the system to decompose the dynamics into independent shell degrees of freedom. The dust field acts as a reference clock for deparametrization and does not source the vacuum geometries considered here. These assumptions tightly constrain the Lemaître-Tolman-Bondi shell Hamiltonian to a factorized form and the static vacuum metric function to a universal expression. We examine the possibility of a bounce and analyze how its presence is encoded, or missed, in finite-order effective truncations of the full model. The procedure for deriving the explicit physical Hamiltonian is described for a generic case before specializing to a specific model of interest. Finally, we construct a four-dimensional covariant completion of the spatially covariant Lagrangian, showing that it belongs to the class of generalized extended mimetic gravity models.

We present a geometric framework linking classical spacetime geometry to black hole thermodynamics beyond the stationary regime. By evaluating the Komar conserved current on an arbitrary timelike worldtube, with the off-boundary extension fixed by a Gaussian normal foliation, we obtain a local surface density ${\kappa }_{\text{Noether}}$ that requires no Killing vector, no spatial symmetry, and no slow-evolution assumption. It reduces to the Killing surface gravity for stationary non-degenerate horizons, and, applied to a uniformly accelerating worldtube, recovers the Unruh temperature. Adapting the Parikh-Wilczek tunneling method to horizons lacking radial and temporal symmetry, we show the local tunneling temperature is $T={\kappa }_{\text{Noether}}/2\pi$ at leading semiclassical order. For a black hole that is genuinely evolving, the single stationary notion of surface gravity separates, at first order in the evaporation rate, into a family of inequivalent quantities; at the event horizon, two of these carry distinct roles: ${\kappa }_{\text{Noether}}$ governs the local tracking kinematics and the proper temperature at the horizon, while the optical peeling rate ${\kappa }_{\text{peeling}}$ governs the asymptotic Bogoliubov spectrum. Evaluated on the exact Vaidya solution, this yields a closed-form surface gravity for the event horizon and an exact gap equation valid for arbitrary evaporation profiles. The separation has a definite causal character: the tracking rate is fixed by the instantaneous geometry, whereas the peeling rate is a functional of the horizon’s entire future, so local dynamics couples only to the former. Supplying the heat flux independently of the surface gravity, which the Vaidya geometry permits, shows further that the quasilocal first law on the apparent horizon is balanced not by the tracking rate but by the Kodama-Hayward value, with which it coincides only when the horizon’s acceleration vanishes. Four surface gravities on three surfaces therefore answer four distinct questions. These results give a local interpretation of the dynamical Komar charge, identifying the thermal emission of an evolving horizon with a flux of gravitational Noether charge.

We report on numerical simulations of critical phenomena in the collapse of axisymmetric vacuum gravitational waves, adopting families of initial data that, to the best of our knowledge, have not been used in this context before. Like Teukolsky waves, the data are based on linear wave solutions to the Einstein equations. We follow Nakamura’s construction and encode the wave content in the extrinsic curvature rather than the spatial curvature, which leads to several simplifications when the data are “dressed up” so that they satisfy the nonlinear constraint equations. We are able to fine-tune these data to the onset of black hole formation slightly better than in our previous simulations, allowing us to observe and examine one more echo in the approximately self-similar threshold solution. Our findings are consistent with earlier studies: while we find threshold solutions that are approximately discretely self-similar, the self-similarity is not exact, and we find no evidence for a unique critical solution. We discuss common features between the different threshold solutions, including the appearance of alternating maxima in the direction of the poles and the equator.

Weak-gravitational lensing tends to wash out scale- and time-dependent features of the clustering of matter, such as the baryonic acoustic oscillations which appear in the form of wiggles in the matter power spectrum but that disappear in the analogous lensing $C_{\ell }$. This is a direct consequence of lensing being a projected effect. In this paper, we demonstrate how the noise complexity—often deemed “erasing the signal”—induced by a particular deprojection technique, the Bernardeau-Nishimichi-Taruya transform [Mon. Not. R. Astron. Soc. 445, 1526 (2014)], can be used to extract the baryonic acoustic oscillation signal and non-Gaussian aperture-mass-like properties at chosen physical scales. We take into account parts of the data vectors that should effectively be without cosmological signature and also introduce an additional reweighting designed to specifically highlight clustering features—at both the probe (summary statistics) or map (amplitude of the field) level. We thus demonstrate why weak-gravitational lensing by the large-scale structure of the Universe, though only in a tomographic setting, does not erase scale- and time-dependent features of the dynamics of matter while providing a tool to effectively extract them from actual galaxy-shape measurements.

We calculate the $f$-mode frequency of quark stars using the full general relativity method, and evaluate the tidal overlap with an analogy method incorporating effective general relativistic corrections. We verify the universal relations obtained from conventional neutron stars in the case of quark stars, including the $f{M}_{1.4}–\mathrm{\Lambda }$ and $Q_{f}R/M–\mathrm{\Lambda }$ relations, and explore the cases with different values of parameters of the quark star equation of state. Since quark stars have significantly smaller radii compared to neutron stars in the low-mass range, the ${\omega }_{f}R–\mathrm{\Lambda }$ relation differs between neutron stars and quark stars. This difference has an impact on the dynamical tide, which is the lowest-order effect we know of that can distinguish quark stars and neutron stars from the gravitational wave during the inspiral phase. We calculate the tidal dephasing caused by this effect using the post-Newtonian method and estimate that ${34}_{-16}^{+12}$ events for the Einstein Telescope and ${10}_{-6}^{+5}$ events for Cosmic Explorer are required to distinguish between quark stars and neutron stars at the population level.

As the LIGO-Virgo-KAGRA Collaboration’s (LVK’s) gravitational-wave transient catalog grows, we are learning a wealth of information from the population properties of binary black hole mergers. Events in the catalog are represented with posterior samples describing the astrophysical parameters for each event. Population studies combine these samples to measure the distribution of astrophysical parameters such as black hole masses and spins. However, the posterior-sample representation of each event is only approximate. We construct a mock population with masses drawn from an astrophysically motivated distribution with sharp features. Using this, we demonstrate that when $\gtrsim 300$ events are combined, even with each event’s posterior represented by $1\times {10}^4-2\times {10}^4$ samples, the numerical error can become large enough that the resulting population inference is unreliable. We consider two solutions. In the short term, we show that nested samples (already produced by LVK analyses) can be used to more accurately describe each event in population studies. But this will only grant a temporary reprieve until the nested-sample representation becomes inadequate. In the longer term, we propose to represent each event with a normalizing flow. In order to represent each event with sufficient accuracy, each normalizing flow can be used to generate an arbitrarily large number of new posterior samples with a significantly reduced computational cost relative to traditional sampling methods. When compared to nested sampling, our normalizing flows produce posterior draws with a median of $\approx 80\%$ fewer likelihood evaluations per sample, while also providing greater opportunity for parallelization. We believe refinement of normalizing flow architectures and training techniques in future works could further reduce this per-sample cost significantly.