We investigate the restoration patterns of chiral and $U(1)$ axial symmetries at finite temperature using a soft-wall holographic QCD model. The study employs two distinct parameter sets (cases I and II), both calibrated to reproduce a pseudocritical temperature $T_{\mathrm{pc}}\sim 155\mathrm{MeV}$ and the physical pion mass. The temperature dependence of the light and strange quark condensates confirms a smooth chiral crossover transition, with pseudocritical temperatures of $T_{\mathrm{pc}}=0.157$ and $T_{\mathrm{pc}}=0.154\mathrm{GeV}$ for cases I and II, respectively. The screening masses of chiral partner mesons ($\pi -\sigma$ and $\eta -a_0$) become degenerate near $T_{\mathrm{pc}}$, providing a clear signature of chiral symmetry restoration. Analysis of the corresponding meson susceptibilities further supports this conclusion. However, the effective restoration of the $U(1{)}_A$ symmetry—probed via the susceptibility difference ${\chi }_{\pi }-{\chi }_{a_0}$—occurs more slowly than that of chiral symmetry. This indicates a separation between the chiral and axial symmetry restoration scales within the present holographic framework. The temperature-dependent topological susceptibility ${\chi }_{\mathrm{top}}^{1/4}$ is also computed, showing a sharp drop near $T_{\mathrm{pc}}$ and a subsequent slight decrease. While the model qualitatively captures established features of the chiral transition, the results highlight a limitation in the quantitative description of the $U(1)$ axial anomaly compared to lattice QCD in our work.

We present a theoretical analysis of the one-loop effective potential of a self-interacting real scalar field in the presence of two parallel conducting plates with geometric roughness. The analysis is restricted to the adiabatic regime of smoothly varying surface deformations, where derivative contributions to the surface profile can be neglected. Using Wentzel-Kramers-Brillouin methods to evaluate the spectral density of the modified Laplace-Beltrami operator, together with contour integration within a $\zeta$-function regularization scheme, we derive analytical expressions for the quantum corrections to the effective potential induced by perturbative boundary roughness and finite temperature. Furthermore, within this regime, we compute explicit contributions to the Casimir energy and to the topological mass generation associated with the geometry.

Noninvertible one-form symmetries are naturally realized in $(2+1)\mathrm{D}$ topological quantum field theories. In this work, we consider the potential realization of such symmetries in $(2+1)\mathrm{D}$ conformal field theories, investigating whether gapless systems can exhibit similar symmetry structures. To that end, we discuss transitions between topological field theories in $(2+1)\mathrm{D}$ which are driven by the Higgs mechanism in Chern-Simons matter theories. Such transitions can be modeled mesoscopically by filling spacetime with a lattice-shaped domain wall network separating the two topological phases. Along the domain walls are coset conformal field theories describing gapless chiral modes trapped by a locally vanishing scalar mass. In this presentation, the one-form symmetries of the transition point can be deduced by using anyon condensation to track lines through the domain wall network. Using this framework, we discuss a variety of concrete examples of noninvertible one-form symmetry in fixed-point theories. For instance, $SU(k{)}_2$ Chern-Simons theory coupled to a scalar in the symmetric tensor representation produces a transition from an $SU(k{)}_2$ phase to an $SO(k{)}_4$ phase and has noninvertible one-form symmetry $\mathrm{PSU}(2{)}_{-k}$ at the fixed point. We also discuss theories with $\mathrm{Spin}(2N)$ and $E_7$ gauge groups manifesting other patterns of noninvertible one-form symmetry. In many of our examples, the noninvertible one-form symmetry is not a modular invariant topological quantum field theory on its own and thus is an intrinsic part of the fixed-point dynamics.

We present a covariant mechanism in which a smooth change of metric signature, from a Euclidean to a Lorentzian regime, drives a finite interval of accelerated expansion. The transition, encoded by a scalar interpolator along a timelike congruence, occurs on a codimension-one hypersurface where the continued metric is degenerate but curvature invariants remain finite, so the surface is curvature-regular. Using this covariant continuation, we rewrite the Einstein tensor of the continued metric as a localized, interpolator-dependent effective source for the post-transition Lorentzian branch, yielding a purely geometric stress tensor supported near the crossing. In the Lorentzian regime we derive a model-independent, local criterion for acceleration: inflation persists while the interpolator’s slope exceeds a critical value fixed by the extrinsic curvature and the spatial Ricci curvature on the initial hypersurface, and ends when this inequality is first saturated. Standard smooth profiles (tanh, generalized logistic, and power-law/arctan) admit closed-form expressions for the proper-time duration of the accelerated epoch, showing that, for fixed geometric data, the profile shape controls this duration. The construction provides a nonsingular, inflaton-free route from a regular Euclidean origin to an early Lorentzian phase of accelerated expansion, in a manner compatible with no-boundary-type boundary conditions.

We establish an exact bidirectional map between the effective homogeneous interior density of a collapsing star and the exterior metric function in generalized Oppenheimer-Snyder collapse. The Darmois-Israel junction conditions reduce this relation to a purely algebraic form, providing a direct way to reconstruct candidate static geometries and their surface dynamics without solving the corresponding differential field equations separately. Correction powers diagnose models; integer exponents signal ultraviolet completions, while fractional powers identify phenomenological ones. Our framework not only simplifies the construction of regular black holes but also provides a universal benchmark for testing singularity resolution and cosmic censorship in quantum gravity phenomenology.

We investigate the orbital structure and observable appearance of rotating Kerr black holes endowed with synchronized scalar hair described by two time-periodic scalar fields with a flat target-space geometry. The presence of scalar hair enriches the geodesic structure of the spacetime relative to the Kerr case and significantly modifies the emission properties of geometrically thin Novikov-Thorne accretion disks. Combining an analysis of timelike circular orbits with backward ray tracing, we show that the normalized Noether charge governs the morphology and luminosity of both prograde and counterrotating disks. In the strongly scalarized regime, additional light rings and modified circular-orbit regions produce multiple inner emitting zones and strongly enhanced redshift patterns that depart markedly from the Kerr prediction. The most pronounced deviations occur in the counterrotating sector, where scalar hair generates inner retrograde radiative rings with substantially enhanced luminosity and distinctive frequency-shift signatures. Even when the spacetime approaches the Kerr geometry at weaker scalarization, the retrograde disk remains highly sensitive to the presence of scalar hair. Our results demonstrate that geometrically thin accretion disks can provide robust observational diagnostics of synchronized scalar hair and may offer a promising avenue for testing tensor-multiscalar gravity with future horizon-scale black-hole imaging observations.

We investigate the scalar emission from binary neutron stars in shift-symmetric scalar-tensor theories with kinetic screening ($K$-essence), using $3+1$ numerical simulations in the decoupling limit. To construct static binary initial data in the regime where the screening radius $r_{*}$ greatly exceeds the orbital separation, we introduce a hyperbolization of the static field equations that bypasses the Keldysh-type breakdown affecting direct time evolutions. For equal-mass binaries, where the scalar emission is dominated by the $\ell =m=2$ mode, kinetic screening acts nonmonotonically on the scalar radiation, suppressing or enhancing the quadrupolar amplitude depending on the relative size of $r_{*}$ and ${\lambda }_{22}$ (with ${\lambda }_{22}$ the wavelength): for ${\lambda }_{22}\ll r_{*}$ it is suppressed relative to the Fierz-Jordan-Brans-Dicke (FJBD) case, while for ${\lambda }_{22}\gtrsim r_{*}$ it is amplified above FJBD. For unequal-mass binaries a scalar dipole reemerges, growing linearly with the mass asymmetry, while the quadrupolar screening remains close to the equal-mass case down to mass ratios $\sim 0.6$. The nonmonotonic behavior of kinetic screening that we uncover has potential implications for gravitational-wave-based tests of gravity. The relativistic double pulsar, in particular, requires $r_{*}\gg {10}^9\mathrm{km}$ to efficiently suppress the scalar quadrupole; for cosmologically-motivated $\mathrm{\Lambda }$, $r_{*}\sim {10}^{11}\mathrm{km}$ (for a solar-mass source), giving only moderate suppression.

Strong theoretical arguments suggest that a breakdown of Lorentz Invariance could arise under some very particular conditions. From an experimental point of view, it is important to test the local Lorentz invariance with ever greater precision and in all contexts, regardless of the theoretical motivation for the possible violation. In this paper we discuss some aspects of the gravitational sector. Tests of Lorentz Invariance in the context of gravity are difficult and rare in the literature. Possible violations could arise from quantum physics applied to gravity or the presence of vector and tensor fields mediating the gravitational interaction together with the metric tensor of general relativity. We present our results in the latter case. We analyzed the orbit of the LAGEOS and LAGEOS II satellites over a period of almost three decades. The effects of the possible preferred frame represented by the cosmic microwave background radiation on the mean argument of latitude of the satellites orbit were considered. These effects would manifest themselves mainly through the post-Newtonian parameter ${\alpha }_1$, a parameter that has a null value in general relativity. We constrain this parametrized post-Newtonian parameter down to the level of $\sim 2\times {10}^{-5}$, improving a previous limit obtained through the lunar laser ranging technique.

We present a Bayesian framework to jointly constrain the Hubble constant ($H_0$) and the post-Newtonian parameter ($\gamma$), a key indicator of deviations from general relativity, using the population characteristics of strongly lensed gravitational wave (GW) events from binary black hole mergers. Our method extracts cosmological and gravitational information directly from the statistical properties of lensed GW populations, without relying on electromagnetic counterparts of the GW events, waveform modeling, and resolved stellar kinematics of the lens galaxy. This establishes lensed GW statistics as a clean and independent probe of cosmic expansion and gravitational physics. Assuming a flat $\mathrm{\Lambda }$ cold dark matter cosmology and simulating a GW population observed by the third-generation detector Einstein Telescope, we demonstrate that this method can achieve precision levels of $0.60\%\sim 0.99\%$ for $H_0$ and $0.53\%\sim 3.3\%$ for $\gamma$ with various priors of matter density, significantly outperforming existing joint constraints, which typically achieve 2% precision on $H_0$ and 20% precision on $\gamma$. These results highlight the potential of lensed GW population statistics as a robust and efficient tool for probing both the expansion history of the Universe and the nature of gravity.

Vacuum quasitopological gravity with infinitely many terms in the action satisfies Markov’s limiting curvature hypothesis: the spherically symmetric solutions are regular and all curvature invariants are bounded by solution-independent scales. We study how this picture changes when the theory is coupled to matter. We find that minimally coupled matter spoils the scaling properties of the vacuum equations that lead to the validity of Markov’s hypothesis but find that the corresponding geometries often remain regular. We make this precise by developing a set of sufficient conditions on general static, spherically symmetric stress tensors such that the corresponding solutions have bounded curvature. These conditions cover regular matter sectors but also singular matter profiles that are sufficiently singular in a sense we quantify. Our conclusions hold independently of the matter field equations and include configurations in which matter exhibits divergent energy density and pressure at finite radius or at Killing horizons, results that may have implications for mass inflation in these models. We then explore nonminimal couplings, focusing on theories with infinite towers of higher-curvature and electromagnetic terms in the action. In this class, Markov’s hypothesis can be restored: we present theories admitting a universal upper bound on curvature, independent of the mass and charge. Overall, our results highlight subtleties in coupling quasitopological gravity to matter and suggest Markov’s hypothesis as a potential selection criterion for resummed gravity-matter effective theories.

Wormholes, spacetimes with a nontrivial topology, can exhibit multiple light rings. The existence of stable light rings can lead to the emergence of trapped modes around the throat of these objects, resulting in echoes in their ringdown profile and spectral lines in the absorption spectra. We investigate the scattering of light rays and massless scalar fields by thin-shell wormholes formed by gluing two (not necessarily identical) Reissner-Nordström spacetimes in the context of the Palatini $f(\mathcal{R})$ theory. These asymmetric wormholes can have different numbers of light rings on each of their sides; for instance, one side can exhibit a pair of light rings (one unstable and the other stable) while the other side exhibits a single unstable light ring. The (asymmetric) light ring structure of these wormholes may lead to stationary points in the deflection function, and consequently to the existence of caustics and rainbow scattering in the spacetime. In order to probe these phenomena in the wave dynamics, we investigate the scattering of massless scalar waves by these objects. Moreover, we discuss the impact of trapped modes on wave scattering, showing that near the trapped modes the partial scattering cross section presents a Fano resonance.

The outskirts of galaxy clusters present a promising avenue for constraining cluster masses in a way that is robust to the impact of baryonic physics. We assess the accuracy to which the cluster infall regions can be used for cluster mass calibration. Building on previous work, we parametrize the velocity distribution $P(v_{\mathrm{r}},v_{\tan }|r,M)$ of dark matter halos on scales $r\ge 5h^{-1}\mathrm{Mpc}$ as the product of the marginalized distribution $P(v_{\mathrm{r}}|r,M)$ and the conditional distribution $P(v_{\tan }|v_{\mathrm{r}},r,M)$, calibrating the radial and mass dependence of these distributions in numerical simulations. We then project our model along the line of sight to obtain accurate predictions for the distributions of line-of-sight velocities at a given projected radius and cluster mass $P(v_{\mathrm{LOS}}|R,M)$, which we can observe with spectroscopic survey data. With our model, we forecast that spectra from the Dark Energy Spectroscopic Instrument can constrain cluster masses with subpercent-level precision, comparable to that of stage-IV weak lensing surveys.

In this work, we explore the production of primordial black holes (PBHs) within the context of $\alpha$-attractor inflationary models, focusing on the preheating phase following inflation. During this phase, self-resonance instabilities arise due to deviations of the inflationary potential from a quadratic form. PBH formation is analyzed using three criteria: (i) the perturbation must lie within the instability band, (ii) its characteristic length must exceed the Jeans length, and (iii) it must have sufficient time to collapse based on the estimations of massive scalar field spherical collapse in an Einstein–de Sitter universe. Based on these criteria, we calculate the PBH mass fraction using the altered Press-Schechter (PS) that is generally implemented in preheating scenarios and Khlopov-Polnarev (KP) formalism that considers nonspherical effects. Our results show that the altered PS formalism tends to overestimate PBH abundance during preheating in contrast to the KP formalism. We provide a detailed comparison between these two frameworks with observational constraints from evaporating PBHs. Notably, the altered PS formalism is excluded by these constraints, which are based on Hawking radiation, while the KP formalism remains viable. These findings underscore the importance of accounting for nonspherical effects and accurate collapse dynamics in studies of PBH formation during preheating.

We investigate a realistic nonsupersymmetric hybrid inflation model incorporating right-handed neutrinos and assess its viability in light of recent cosmological observations. At tree level, the inflaton potential yields a blue-tilted scalar spectrum, which is disfavored by current data from Planck and the Atacama Cosmology Telescope that instead support a red tilt. We show that including one-loop quantum corrections arising from generic couplings required for reheating significantly modifies the potential, flattening it at large field values. This leads to a red-tilted spectral index ($n_s<1$) and a suppressed tensor-to-scalar ratio $r$, both consistent with observational constraints. To ensure theoretical control, we focus on sub-Planckian field values, where the effective field theory description remains valid. The coupling of the inflaton to right-handed neutrinos naturally facilitates efficient reheating and enables the generation of the baryon asymmetry via nonthermal leptogenesis. We further explore the model’s parameter space using a multioutput random forest classifier, achieving prediction accuracies in the range of 87.5% to 98.9%. Our analysis shows that approximately 15% of the parameter space satisfies at least one current experimental constraint, underscoring the essential role of quantum corrections in reconciling particle physics models with precision cosmology and highlighting the effectiveness of machine learning techniques in probing complex theoretical frameworks.

We present the spectrum of $n_s$ constraints from current cosmic microwave background (CMB) data [Planck, Atacama Cosmology Telescope (ACT), and South Pole Telescope (SPT)-3G] combined with Dark Energy Spectroscopic Instrument (DESI) baryon acoustic oscillation (BAO) data, and highlight the interplay of $n_s$ with the optical depth to reionization $\tau$. The spectral index $n_s$ of the primordial power spectrum provides a window into the early Universe, and constraints on $n_s$ play an important role in discriminating early Universe models such as models of cosmic inflation. Historically constrained by CMB experiments, the constraints on $n_s$ shift upward when CMB data are combined with the latest BAO data from the DESI. Recent work explained the origin of this and the relation to the BAO-CMB tension between CMB experiments and DESI BAO, and as a case study presented constraints on $n_s$ from the combination of ACT DR6 data and DESI DR2 data. Here we present constraints from Planck (PR3 and PR4), ACT, the SPT, and the combination of all three CMB experiments, CMB-SPT + Planck + ACT (CMB-SPA), with and without DESI DR2 BAO data, and with and without CMB lensing data. In all cases the constraint on $n_s$ is shifted upwards when DESI is included, with the largest shift exhibited by ACT. This is accompanied by a commensurate shift in the constraint on the optical depth to reionization $\tau$, which is again greatest for ACT. When CMB data are combined into CMB-SPA and combined with DESI the $n_s$ constraint disfavors at more than $2\sigma$ the inflation models preferred by Planck alone, such as Higgs, Starobinsky, and exponential $\alpha$-attractors, in favor of other models, such as polynomial $\alpha$-attractors. This work motivates the further study of the tension between CMB and DESI BAO data, and of the rich interplay between $n_s$ and $\tau$.

Among the most fundamental properties of a dark matter halo is its density profile. Motivated by the recent proposal by García et al. [Mon. Not. R. Astron. Soc. 521, 2464 (2023)] to define a dynamical halo as the collection of orbiting particles in a gravitationally bound structure, we characterize the mean and scatter of the orbiting profile of dynamical halos as a function of their orbiting mass. We demonstrate that the orbiting profile of individual halos at fixed mass depends on a single dynamical variable, the halo radius $r_{\mathrm{h}}$, which characterizes the spatial extent of the profile. The scatter in halo radius at fixed orbiting mass is $\approx 16\%$. Only a small fraction of this scatter arises due to differences in halo formation time, with late-forming halos being more compact (smaller halo radii). Accounting for this additional correlation results in an $\approx 11\%$ scatter in halo radius at fixed mass and halo formation time.

Gravitational-wave observations of extreme mass-ratio inspirals (EMRIs) in vacuum are largely insensitive to the internal structure of the small compact companion. We show that this conclusion can change when the central black hole is surrounded by a dense dark matter environment. We compute, for the first time, the relativistic dynamical-friction force on a neutron star moving through a collisionless medium and its impact on the evolution of EMRIs embedded in dense dark matter spikes. We then perform a Bayesian parameter-estimation analysis of simulated LISA observations to assess the measurability of both spike properties and the companion’s internal structure.We find that, in our fiducial dark matter spike models, EMRIs with signal-to-noise ratio (SNR) $\gtrsim 120$ can already distinguish neutron star from black hole companions. At comparable signal-to-noise ratios, discrimination among neutron star equations of state begins to emerge and becomes significantly stronger toward the high-SNR tail.

Gravitational waves from core-collapse supernovae offer a unique probe of the equation of state (EOS) of dense nuclear matter. For rapidly rotating stars, previous machine-learning studies demonstrated promising EOS classification accuracy. However, these analyses relied on several simplifying assumptions. In this work, we relax three key assumptions. First, we include real detector noise. Second, we expand the analysis from a single progenitor model to four models spanning 12–40 solar masses, and for each mass we consider multiple rotational configurations, from slow to rapid. Third, we introduce uncertainty in the core-bounce time of up to 20 ms, rather than assuming it is known precisely. We find that none of these effects significantly degrades EOS classification performance. Instead, the larger dataset associated with multiple progenitor models and noise realizations improves training and classification accuracy. This study is a step in a broader effort to progressively incorporate more realistic conditions into gravitational-wave inference for core-collapse supernovae.

We demonstrate that Higgsino dark matter (DM) could be discovered within the next few years using the Cherenkov Telescope Array Observatory’s soon-to-be-operational northern site (CTAO-North). A 1.1 TeV thermal Higgsino is a highly motivated yet untested model of DM. Despite its strong theoretical motivation in supersymmetry and beyond, the Higgsino is notoriously difficult to detect; it lies deep within the neutrino fog of direct detection experiments and could pose a challenge even for a future muon collider. We show that, in contrast, Higgsino detection could be possible within this decade with CTAO-North in La Palma, Spain. The Galactic Center is the region where the dominant DM annihilation signature emerges, but it only barely rises above the horizon at the CTAO-North site. However, we project that this challenge can be overcome with large-zenith-angle observations at the northern site, enabling the conclusive detection of a Higgsino signal by 2030 for a range of DM density profiles in the inner Galaxy.

We construct a static, spherically symmetric black hole spacetime sourced by an effective anisotropic matter distribution whose energy density follows the cored Burkert profile. The source should be understood as a Burkert-density effective fluid, rather than as a microscopic model of pressureless collisionless dark matter. Solving the Einstein equations under this closure condition, we obtain an analytic Schwarzschild-like metric that reduces smoothly to the vacuum Schwarzschild solution when the halo contribution vanishes. We then study axial gravitational perturbations of this geometry and determine the associated quasinormal spectrum using complementary frequency-domain and time-domain methods. We find that increasing either the core radius $r_0$ or the central density ${\rho }_0$ shifts the ringdown toward lower frequency and weaker damping, with the effect of $r_0$ being more pronounced. The close agreement among the numerical extractions supports the reliability of the results. Our analysis provides a useful benchmark for assessing how a cored Burkert-type effective environment can modify black hole ringdown.