Paleo detectors are emerging dark matter detection technology that exploits ancient minerals as passive, time-integrated detectors. Unlike conventional real-time experiments, they search for permanent damage tracks—typically tens of nanometers to micrometers long—left in crystal lattices by rare particle interactions, most notably dark matter induced nuclear recoils accumulated over millions to billions of years. In this paper I propose a direct detection strategy for cosmic walls—either bubble walls produced by a late-time first-order phase transition or domain walls in a scaling regime—using paleo detectors as the target medium. Because the cosmic wall is expected to traverse Earth at most $\mathcal{O}(1)$ time(s) in cosmic history, an ancient, continuously exposed detector is the only feasible way to observe it directly. By calculating the target recoils, I find that the smoking-gun signature would be parallel damage tracks found worldwide in minerals older than the wall-crossing epoch. I derive the limit on the wall-target coupling by assuming that a wall passed through the Earth within the last 0.5 Gyr. I also mention a novel indirect detection of ultrarelativistic cosmic walls by noting the induced cosmic rays.

We discuss the measurement of the charged-current elastic scattering process $e^{-}p\to {\nu }_{e}n$ at the Electron-Ion Collider (EIC). This process provides sensitivity to the poorly constrained axial radius of the nucleon. Collisions of electrons with polarized protons enable measuring the $e^{-}\overrightarrow{p}\to {\nu }_{e}n$ target-spin asymmetry for the first time. We conclude that a measurement of charged-current elastic scattering at the EIC will, perhaps unsurprisingly, prove very challenging. However, with dedicated instrumentation at a second EIC detector, the measurement may be possible.

We report on several previously overlooked families of static spherically symmetric solutions in quadratic gravity. Our main result concerns the existence of solutions whose leading exponents depend on the ratio $\omega =\alpha /(3\beta )$ of the four-derivative couplings. We demonstrate that the space of models with $\omega >1$ contains a dense set that admits non-Frobenius solutions $(s_{*},2-3s_{*}{)}_0$ (in standard Schwarzschild coordinates), with certain rational numbers $s_{*}(\omega )$. These solutions correspond to a singular core at $\overline{r}=0$. Another related non-Frobenius family, $(s_{*},2-3s_{*}{)}_{\infty }$, exists for a dense set of models with $1/4<\omega <1$, describing a singular boundary at $\overline{r}\to \infty$. Both families are uncovered by recasting the metric into special coordinates in which the solutions become Frobenius. Additionally, for models with real ratios $\omega \ne 1$ we identify six novel families of non-Frobenius solutions around points $\overline{r}={\overline{r}}_0\ne 0$, describing horizons and wormhole throats. Finally, we rederive and summarize all known families of solutions in modified as well as in the standard Schwarzschild coordinates.

We study the quasinormal modes (QNMs) of dilaton black holes in Einstein-Maxwell-dilaton gravity through a correspondence with the quantum Seiberg-Witten (SW) curve of $\mathcal{N}=2$ SU(2) gauge theory with $N_f=3$ hypermultiplets. By mapping both the black hole perturbation equation and the quantum SW curve to the confluent Heun form, the QNM problem is reformulated in a gauge-theoretic framework, and the spectrum is obtained via the SW quantization condition. The resulting frequencies show excellent agreement with those computed using the WKB and continued fraction methods, with typical deviations below ${10}^{-3}$. The QNM spectrum exhibits consistent trends: increasing the black hole charge or scalar field mass raises the oscillation frequency, while higher angular momentum reduces the damping rate. These results demonstrate the precision of the quantum SW framework in describing black hole perturbations and reveal new links between supersymmetric gauge theories and gravitational dynamics.

According to the flat/CCFT correspondence, Carrollian conformal field theories (CCFT) in $d$ dimensions are dual to asymptotically flat spacetimes in $d+1$ dimensions. In this paper, starting from the holographic interpretation of pseudoentropy in the (A)${\text{dS}}_3/{\mathrm{CFT}}_2$, we show that both extremal spacelike and timelike curves possess a well-defined flat-space limit. The length of these curves can be regarded as the real and imaginary parts of the pseudoentropy for the underlying field theory, where only the real part has been considered thus far. Our calculations can confirm that the entanglement entropy in the CCFTs is fundamentally pseudoentropy.

A representative quantity that characterizes the dynamics of conformal interfaces is the transmission coefficient, which is defined through correlation functions of the stress tensor. Typically, this coefficient is complicated and highly dependent on its details. In this work, we introduce a new perspective based on the notion of a “phantom current”. We have shown that a spin-2 phantom current arising from the folding trick determines the transmission coefficient. As a result, our framework provides a unified explanation of known results in minimal models and the free boson, while also yielding concrete predictions for previously unexplored interfaces.

The Schur index is a powerful tool to probe the spectrum and dualities of four-dimensional $\mathcal{N}=2$ superconformal field theories, deeply related to two-dimensional vertex operator algebras (VOAs). In this paper, we compute the Schur index in closed form for two series of non-Lagrangian theories. We explore and classify the Argyres-Douglas (AD) theories $D_p^b({\mathfrak{sl}}_N,[Y])$ realized as the $SU(2)$ gauging of two AD matter theories, where we identify several infinite families with interesting central charge relations analogous to the $a_{4\mathrm{d}}=c_{4\mathrm{d}}$ of $\mathcal{N}=4$ theories. We focus on $D_{N-4}(\mathfrak{sl}(N),[N-4,4])$ and $D_{N-2}(\mathfrak{sl}(N),[N-3,3])$ and compute their flavored and unflavored Schur and Wilson line indices in compact form. We also explore their large-$N$ behavior and show that they arise as special limits of the $SU(2)$ SQCD flavored index, also analogous to the relation among the $a_{4\mathrm{d}}=c_{4\mathrm{d}}$ theories. We also generalize the elliptic function integration formula in the presence of higher-order poles to compute in closed form the partially flavored indices of the Minahan-Nemeschansky $E_6$ and $E_7$ theories. Our results point to a universal structure underlying the residues of elliptic integrands, Wilson loop indices, and nonvacuum modules of the corresponding VOAs.

We investigate quantum field excitations in a rigid cavity that undergoes a transition from inertial motion to uniform acceleration while maintaining constant proper length. By constructing exact Bogoliubov transformations between inertial and accelerated mode bases, we analyze the induced excitations and identify a universal power-law decay in the excitation power spectrum and an alternating pattern in particle production. The spectrum’s dependence solely on the acceleration, and not on the size of the box or the observer’s position, highlights a kinematic universality akin to that seen in horizon thermodynamics. Generalization to time-dependent accelerations reveals a convolution structure for the Bogoliubov coefficients, with resonant oscillations selectively enhancing mode excitations. These results provide new analytical insights into the interplay between acceleration, confinement, and quantum excitations.

We construct new black holes using the curvature-induced scalarization mechanism in Einstein gravity coupled to a massless phantom scalar. We find that the general wormhole solutions with independent scalar charge can turn into a black hole with secondary scalar hair that is a function of the mass only. The long-range force between the two identical black holes can be attractive, zero, or repulsive, depending on the mass/scalar charge relation. Furthermore, the black hole mass can be negative. Our finding suggests that exotic matter responsible for wormholes can also lead to exotic black holes.

We derive the master equations governing axial and polar gravitational perturbations of a generic static and spherically symmetric black hole spacetime within the framework of the revised Deser-Woodard nonlocal gravity theory. We then apply our general formalism to a one-parameter family of black hole solutions recently obtained by the present authors, representing small first-order deviations from the Schwarzschild geometry. We provide well-motivated arguments that allow us to render the analysis analytically tractable. Our results provide the first complete perturbative characterization of nonlocal black holes and lay the groundwork for future investigations.

We investigate several geometrical and physical properties of the recently found $W$-soliton solution (neutral case). We discuss both the genuine five-dimensional solution and its reduction to four dimensions and highlight similarities and differences. In both cases, we study scattering processes of massless and massive particles in the background, reconstructing the gauge-invariant scattering angle, either with exact expressions or with large-angular momentum expansion expressions, which we show how to resum in a useful form. Finally, we analyze the propagation of a test scalar field in the $W$-soliton background and compute the spectrum of quasinormal modes in the case of (non)minimal coupling and the radiated energy in the case of minimal coupling. Our result for the energy loss is fully analytic and presented in a post-Newtonian expansion, following the approach termed gravitational self-force.

We explore the possibility that part of what we call dark matter may be the mark of a preferred frame, revealing a breakdown of diffeomorphism invariance. In the nonrelativistic limit, this appears as a deviant matter source capable of attracting normal matter, but not feeling the attraction from other forms of matter or from itself. While this implies a violation of momentum conservation, no logical inconsistencies arise in this deviant “Newtonian” limit. In contrast, due to Bianchi identities, the relativistic theory must undergo core change, and we discuss a modification of Einstein’s gravity capable of coupling a nonconserved source to gravity. It results from fixing some of the spatial components of the metric, thereby constraining the possible diffeomorphisms and clipping some of the equations. Bianchi identities can always be used to refill the equations, but the effective Stückelberg stresses are so outlandish that this defines symmetry breakdown and violations of local energy-momentum conservation. We work out spherically symmetric solutions with static halos and flat rotation curves, with and without a central black hole. The model has the drawback that it can evade experimental constraints simply by setting to zero the local density of deviant matter (which is a nondynamic input). Its presence, in contrast, would leave inimitable signatures. We briefly discuss the Hamiltonian formulation of these models, where such dark matter appears as a central charge in the Poisson bracket of the Hamiltonian and the momentum.

The stochastic gravitational wave background from compact binary coalescences is expected to be the first detectable stochastic signal via cross-correlation searches with terrestrial detectors. It encodes the cumulative merger history of stellar-mass binaries across cosmic time, offering a unique probe of the high-redshift Universe. However, predicting the background spectrum is challenging due to numerous modeling choices, each with distinct uncertainties. In this work, we present a comprehensive forecast of the astrophysical gravitational wave background from binary black holes, binary neutron stars, and neutron star–black hole systems. We systematically assess the impact of uncertainties in population properties, waveform features, and the modeling of the merger rate evolution. By combining all uncertainties, we derive credible bands for the background spectrum, spanning approximately an order of magnitude in the fractional energy density. These results provide thorough predictions to facilitate the interpretation of current upper limits and future detections.

Recent nonmodal analyses have uncovered spectral instabilities in the quasinormal-mode spectrum of black holes, a phenomenon that intriguingly extends to spherically symmetric exotic compact objects. These results point to a sensitivity of the spectrum with potentially far-reaching implications for black-hole spectroscopy. At the same time, growing attention has turned to astrophysical environments around compact objects and their role in shaping gravitational-wave astrophysics. In this work, we establish a direct link between spectral instabilities and environmental effects by modeling matter as a localized bump outside the light ring of a spectrally unstable exotic compact object with a purely reflective surface. We find that while such environments can destabilize the fundamental quasinormal modes of loosely compact exotic objects, the fundamental modes of ultracompact horizonless objects remain remarkably robust. In contrast, overtones are shown to develop spectral instabilities in the presence of the bump. By tracking both interior modes, trapped between the light ring and the surface of the exotic compact object, and exterior modes, confined between the bump and the light ring, we uncover an overtaking instability in which “unperturbed” exterior overtones metamorphose into “perturbed” fundamental modes as the bump moves outward. Finally, we demonstrate that environmental effects, while capable of further amplifying spectral instabilities, cannot induce next-to-leading-order perturbations strong enough to trigger a modal instability.

We reinvestigate the stability properties of ultracompact spinning boson stars with a stable light ring using fully nonlinear $3+1$ and $2+1$ numerical relativity simulations and two different formulations of the Einstein equations. We find no evidence of an instability on timescales of $t\mu \sim {10}^4$ (in units of the scalar mass), when allowing the star to be perturbed either solely by discretization error or by imposing various types of perturbations to our initial data. We find that the initially imposed perturbations exhibit slow decay, even for magnitudes just below the order where immediate collapse is induced.

The cosmological principle is a cornerstone of the standard cosmological model. However, recent observations suggest potential deviations from this assumption, hinting at a small anisotropic expansion. Such an expansion can arise from sources that break rotational invariance. A minimal realization of this scenario is described by a Bianchi I geometry, where the degree of anisotropy is quantified by the shear parameter $\mathrm{\Sigma }$. In this work, we constrain the present-day value of the shear ${\mathrm{\Sigma }}_0$ by confronting theoretical predictions with recent cosmological data. We implement various anisotropic models within the Boltzmann code class and explore their parameter space using the sampler montepython. Although our results show that ${\mathrm{\Sigma }}_0$ is model dependent, notably, in one specific scenario considering a homogeneous scalar field coupled to a 2-form field, ${\mathrm{\Sigma }}_0=0$ is excluded at the $2\sigma$ confidence level, with mean value around $|{\mathrm{\Sigma }}_0|\sim {10}^{-4}$ while remaining consistent with observations. These findings challenge the conventional assumption that cosmic shear is negligible in the present Universe. Moreover, the anisotropic expansion in this model is driven by a steep scalar field potential, a feature often found in supergravity-inspired scenarios. While anisotropic models offer interesting alternatives and could help explain some cosmological anomalies, they generally introduce additional parameters, making the standard $\mathrm{\Lambda }\mathrm{CDM}$ model statistically favored in most cases. Still, they remain compatible with current observations and provide new perspectives on features not fully explained within the standard framework. These results highlight the importance of further exploring anisotropic cosmologies to better understand their implications.

Recent papers have reported an unexplained cooling of cosmic microwave background (CMB) photons passing through galaxies in nearby cosmic filaments $z<0.02$ at the $>5\sigma$ level. Here we show for the first time that this effect is also present at higher redshifts $0.02<z<0.04$. Instead of calculating the CMB temperature around individual galaxies as in previous works, we analyze mean CMB temperature profiles associated to cosmic filaments in three dimensions. We have considered different thresholds in the linear K-band luminosity density of the filaments as a proxy to mass density. Furthermore, we have analyzed the dependence of the results on the average orientation of filaments with respect to the line of sight. These studies were implemented to test the expected dependence on mass density as well as on photon trajectory length within the cosmic filaments. We find a $3-4\sigma$ detection of a CMB temperature decrement trend toward the spine of the filaments, the larger the mass and the more radially oriented the filament, the stronger the CMB temperature decrement. This trend is seen independently in both redshift ranges $0.004<z<0.02$ and $0.02<z<0.04$. We therefore conclude that our results provide strong evidence for a lower CMB temperature along massive cosmic filaments in the nearby Universe $z<0.04$.

We demonstrate Bayesian analyses of the complete gravitational-wave spectrum of binary neutron star mergers events with the next-generation detector Einstein Telescope. Our mock analyses are performed for 20 different signals using the TEOBResumSPA_NRPMw waveform that models gravitational waves from the inspiral to the postmerger phase. They are employed to validate a pipeline for neutron star’s extreme matter constraints with prospective detections and under minimal hypotheses on the equation of state. The proposed analysis stack delivers inferences for the mass-radius curve, the mass dependence of the quadrupolar tidal polarizability parameter, the neutron star’s maximum density, the maximum mass and the relative radius, and the pressure-density relation itself. We show that a single event at a signal-to-noise ratio close to the minimum threshold for postmerger detection is sufficient to tightly constrain all the above relations as well as quantities like the maximum mass (maximum density) to precision of $\sim 6\%$ ($\sim 10\%$) at 90% credibility level. We also revisit inferences of prompt black hole formation with full spectrum signals and find that the latter can be robustly identified, even when the postmerger is not detectable due to a low signal-to-noise ratio. New results on the impact of the initial signal frequency and of the detector configuration (triangular vs two-L) on the source’s parameters estimation are also reported. An improvement of approximately one order of magnitude in the precision of the chirp mass and mass ratio can be achieved by lowering the initial frequency from 20 Hz to 2 Hz. The two-L configuration shows instead significant improvements on the inference of the source declination, due to geographical separation of the two detectors.