We present the analysis techniques developed to explore the keV-scale energy region of the Cryogenic Underground Observatory for Rare Events (CUORE) experiment, based on more than 2 metric ton yr of data collected over five years. By prioritizing a stricter selection over a larger exposure, we are able to optimize data selection for thresholds at 10 keV and 3 keV with 691 kg yr and 11 kg yr of data, respectively. We study how the performance varies among the 988-detector array with different detector characteristics and data-taking conditions. We achieve an average baseline resolution of $2.54\pm 0.14\mathrm{keV}$ FWHM and $1.18\pm 0.02\mathrm{keV}$ FWHM for the data selection at 10 keV and 3 keV, respectively. The analysis methods employed reduce the overall background by about an order of magnitude, reaching $2.06\pm 0.05\mathrm{counts}/(\mathrm{keV}\mathrm{kg}\mathrm{days})$ and $16\pm 2\mathrm{counts}/(\mathrm{keV}\mathrm{kg}\mathrm{days})$ at the thresholds of 10 keV and 3 keV. We evaluate for the first time the near-threshold reconstruction efficiencies of the CUORE experiment, and find these to be $50\pm 2\%$ and $26\pm 4\%$ at 10 keV and 3 keV, respectively. This analysis provides crucial insights into rare decay studies, new physics searches, and keV-scale background modeling with CUORE. We demonstrate that ton-scale cryogenic calorimeters can operate across a wide energy range, from keV to MeV, establishing their scalability as versatile detectors for rare event and dark matter physics. These findings also inform the optimization of future large mass cryogenic calorimeters to enhance the sensitivity to low-energy phenomena.

This paper systematically develops the concept of entanglement threads that characterize the entanglement structure of holographic duality. Behind this framework lies a simple philosophy: holographic quantum entanglement can be visualized using threadlike objects. Inspired by the fact that tensor network models can be deformed into a quantum circuit form with flow-conserving features, we abstract the concept of entanglement threads. These entanglement threads can be understood as a preset ensemble of wires in a holographic quantum circuit, and we propose that they characterize the underlying partially ordered structure of holographic quantum entanglement. Combining the concepts of entanglement threads and kinematic space, a elegant circuit interpretation for the holographic complexity is provided. We also clarify the connection and distinction between entanglement threads and the previously proposed concept of bit threads.

We present an asymptotically flat spherically symmetric nonsingular metric that describes gravitational collapse and matter bounce with transient black hole and white hole regions. The metric provides a dynamical counterpart to proposed static nonsingular black holes, and a phenomenological model for possible black hole to white hole transitions in quantum gravity.

In four-dimensional vacuum general relativity the only known static, exact and analytical black hole solution is given by the Schwarzschild spacetime. In this paper this renowned metric is generalized by adding another integrating constant, a hair that switches the metric from the Petrov type $D$ to the type $I$. This new parameter represents the intensity of an external gravitational field, which can be considered the hyperbolic generalization of the Witten’s bubble of nothing. No curvature or conical singularities are present outside the event horizon. The no hair arguments are circumvented because the metric is not asymptotically flat, and neither is the black hole spherical. The gravitational hair continuously deforms the Schwarzschild geometry: the horizon becomes oblate, while its area is reduced. Conserved charges and thermodynamic properties of the black hole are studied.

Causal set theory is an intrinsically nonlocal approach to quantum gravity, inheriting its nonlocality from Lorentzian nonlocality. This nonlocality causes problems in defining differential operators—such as the d’Alembert operator, a cornerstone of any relativistic field theory—within the causal set framework. It has been proposed that d’Alembertians in causal sets must themselves be nonlocal to respect causal set nonlocality. However, we show that such nonlocal d’Alembertians do not converge to the standard continuum d’Alembertian for some basic fields. To address this problem, we introduce a local d’Alembert operator for causal sets and demonstrate its convergence to its continuum counterpart for arbitrary fields in Minkowski spacetimes. Our construction leverages recent developments in measuring both timelike and spacelike distances in causal sets using only their intrinsic structure. This approach thus reconciles locality with Lorentz invariance, and paves a way toward defining converging discrete approximations to locality-based differential operators even in theories that are inherently nonlocal.

The standard $\mathrm{\Lambda }$CDM model, based on a highly symmetric Friedmann-Lemaître-Robertson-Walker (FLRW) geometry, successfully explains many observations but faces unresolved issues, motivating the exploration of alternative cosmological frameworks. We investigate the influence of spacetime geometry on the matter-antimatter asymmetry of the Universe within the Bianchi IX cosmological model. Motivated by early-Universe dynamics, potential contributions to cosmological angular momentum, and the axisymmetric Bianchi IX model’s relevance to certain cosmic microwave background anomalies, we formulate the Dirac field in this background. Starting with a Lagrangian formalism, we derive the Dirac equation and develop the harmonic analysis of spinor fields, extending previous treatments in the mixmaster universe. We solve the Dirac equations for nonrotating and rotating axisymmetric Bianchi IX spacetimes using a fixed-background approximation. We find that spatial anisotropy induces spin-dependent energy splittings, while global rotation produces particle-antiparticle asymmetries in the energy spectra, effects absent in FLRW models. These results demonstrate that spacetime geometry alone can imprint nontrivial structure on particle spectra, suggesting that geometric effects may contribute to the matter-antimatter asymmetry.

Compact objects evolving in an astrophysical environment experience a gravitational drag force known as dynamical friction. We present a multipole-frequency decomposition to evaluate the orbit-averaged energy and angular momentum dissipation experienced by point masses on periodic orbits within a homogeneous, fluidlike background. Our focus is on eccentric Keplerian trajectories. Although our approach is currently restricted to linear response theory, it is fully consistent within that framework. We validate our theoretical expressions for the specific case of an ideal fluid, using semi-numerical simulations of the linear response acoustic wake. We demonstrate that, for a finite-time perturbation switched on at $t=0$, a steady dissipation state is reached after a time bounded by twice the sound crossing time of the apocenter distance. We apply our results to model the secular evolution of compact eccentric binaries in a gaseous medium, assuming low-density conditions where the orbital elements evolve adiabatically. For unequal-mass systems with moderate initial eccentricity, the late-time eccentricity growth is significantly delayed compared to the equal-mass case, due to the binary components becoming transonic at different times along their orbital trajectory. Our approach offers a computationally efficient alternative to full simulations of the linear response wake.

Broad all-sky searches for continuous gravitational waves have high computational costs and require hierarchical pipelines. The sensitivity of these approaches is set by the initial search and by the number of candidates from that stage that can be followed up. The current follow-up schemes for the deepest surveys require careful tuning and setup, and have a significant human-labor cost and this impacts the number of follow-ups that can be afforded. Here we present and demonstrate a new follow-up framework based on Bayesian parameter estimation for the rapid, highly automated follow-up of candidates produced by the early stages of deep, wide-parameter space searches for continuous waves.

In this paper, we investigate the small-$x$ behavior of the flavor-singlet, leading-twist quark transverse-momentum-dependent parton distribution functions (TMDs) using the light-cone operator treatment. This formalism allows us to express TMD operators at small $x$ in terms of polarized dipole amplitudes, enabling a systematic approach to their small-$x$ evolution. We derive the evolution equations for these TMDs and solve them within the large-$N_c$ approximation under the linearized, double-logarithmic approximation, where $N_c$ represents the number of quark colors. Expanding on previous work on unpolarized and helicity TMDs, we present the small-$x$ asymptotics for a comprehensive set of TMDs, including the Sivers function, helicity worm-gear, transversity, pretzelosity, Boer-Mulders, and transversity worm-gear distributions. Our results provide a complete picture of the small-$x$ asymptotic behavior for all leading-twist flavor-singlet quark TMDs. We also discuss the implications of our findings for phenomenological applications and outline potential avenues for further research, particularly in understanding nonlinear effects and extending beyond the double-logarithmic approximation and large-$N_c$ approximations.

The interstellar magnetic field is essential in various astrophysical phenomena and processes. Pulsar halos are a recently discovered class of TeV $\gamma$-ray sources formed by escaping electrons/positrons from pulsars. The morphology of the halo is regulated by the diffusion of those escaping particles and hence carries information of the interstellar magnetic field. We suggest that the morphology of TeV pulsar halos can be used as a novel probe of the properties of the interstellar magnetic field around the pulsar, such as the Alfvénic Mach number and the mean direction. We establish a theoretical relation between these quantities and the observational features of the halo’s morphology based on the anisotropic diffusion model and show how x-ray observations of the pulsar halos can further improve the diagnosis of the magnetic field.

The quantum nature of the Schwarzschild black hole interior is investigated through the Wheeler-DeWitt (WDW) equation. The interior of a static, spherically symmetric black hole is described by the Kantowski-Sachs metric, which represents a homogeneous but anisotropic cosmology. We derive the Hamiltonian for the gravitational system corresponding to the black hole interior and obtain the associated WDW equation. By varying the gravitational constant as a parameter controlling quantum effects, we examine how the solutions of the WDW equation change with respect to this parameter. In the parameter regime where quantum effects are negligible, we find that the wave packet solutions closely follow the classical trajectory of the black hole interior. On the other hand, as quantum effects are enhanced, the wave packet deviates from the classical trajectory and exhibits behavior suggestive of singularity avoidance. To quantify this behavior, we introduce an appropriate “clock” inside the black hole and compute the time to singularity formation with respect to this clock. The results show that stronger quantum effects lead to a longer formation time, suggesting a tendency toward the avoidance of singularity formation due to quantum gravity effects.

We study the symmetry-resolved genuine multientropy, a measure that captures genuine multipartite entanglement, in Haar random states and random graph states in the presence of a conserved quantity. For Haar random states, we derive explicit formulas for the genuine multientropy under a global $U(1)$ symmetry in the thermodynamic limit, and find that its dependence on subsystem sizes closely resembles that of fully Haar random states without a conserved charge. We also perform numerical analyses, focusing on spin systems for both Haar random and graph states. For random graph states, our numerical analyses reveal distinctive features of their multipartite entanglement structure and we contrast them with the Haar random case.

We investigate pinched geometries in a two-dimensional Lorentzian model of quantum Regge calculus using the tensor renormalization group method. A pinched geometry refers to a configuration with an infinitely long temporal extent, even when the total spacetime area is fixed. We examine several choices of integration measures and triangulations to study whether such geometries can dominate in the limit of infinitely many triangles. Our results indicate that pinched geometries are strongly suppressed, and this suppression is observed across different integral measures and triangulations. These results suggest the possible emergence of smooth geometries as well as a sort of universality for infinitely many triangles.

We solve the Dirac equation for a massive charged fermion in the near-extremal charged Nariai black hole with the near-horizon geometry ${\mathrm{dS}}_2\times {\mathrm{S}}^2$. At the one-loop level, contrary to the catastrophic emission of charged spinless bosons in C.-M. Chen et al., [Phys. Rev. D 110, 085020 (2024)], we show that the emission of fermions in a narrow timelike inner region between the cosmological horizon and black hole horizon saturates the bound from the Pauli blocking and does not give an amplification (quantum superradiance). Using the reciprocal relation, we find the Schwinger emission of fermions from ${\mathrm{AdS}}_2\times {\mathrm{S}}^2$, and compare the Schwinger emission of fermions and bosons from near-extremal Nariai black holes.

We investigate the formulation of work distributions for quantum scalar fields in static curved spacetimes by extending the Ramsey interferometric protocol originally developed in previous works for flat spacetimes. The use of Unruh-DeWitt particle detectors provides a causally consistent framework to define and measure work statistics, avoiding the limitations of the two-time projective measurement scheme in relativistic quantum field theory. We derive a nonperturbative expression for the characteristic function of the quantum field and apply it to thermal Kubo-Martin-Schwinger states, showing that the resulting work distributions satisfy both the Crooks fluctuation theorem and the Jarzynski equality. Furthermore, we analyze the case of a pointlike detector, obtaining compact expressions for the first two moments of the work distribution, allowing us to recover the standard fluctuation-dissipation relation in the high-temperature limit. Our results demonstrate that fluctuation theorems hold for quantum fields interacting with Unruh-DeWitt particle detectors in static curved spacetimes.

We investigate boson stars in an $O(3)$ scalar field theory with a symmetry-breaking potential. By constructing numerically spherically symmetric solutions, we demonstrate that the model gives rise to a rich set of field configurations. The negative coupling constant of the scalar self-interactions allows for two types of boson stars: type I solutions represent the usual boson stars, which emerge from the vacuum as the boson frequency is decreased below the boson mass, whereas type II boson stars emerge from a set of static soliton solutions. Depending on the strength of the gravitational coupling constant, both types, or only one type, are present. At a critical set of coupling constants, both types undergo a bifurcation. There the spirals of both types disconnect from their branches and reconnect with each other, while the remaining branches of both types also reconnect with each other. Analogous features are seen for U(1)-gauged boson stars.

The Small-Correlated-Against-Large Estimator (SCALE) for small-scale lensing of the cosmic microwave background (CMB) provides a novel method for measuring the amplitude of CMB lensing power without the need for reconstruction of the lensing field. In our previous study, we showed that the SCALE method can outperform existing reconstruction methods to detect the presence of lensing at small scales ($\ell \gg 3000$). Here we develop a procedure to include information from SCALE in cosmological parameter inference. We construct a precise neural network emulator to quickly map cosmological parameters to desired CMB observables such as temperature and lensing power spectra and SCALE cross spectra. We also outline a method to apply SCALE to full-sky maps of the CMB temperature field, and construct a likelihood for the application of SCALE in parameter estimation. SCALE supplements conventional observables such as the CMB power spectra and baryon acoustic oscillations in constraining parameters that are sensitive to the small-scale lensing amplitude such as the neutrino mass $m_{\nu }$. We show that including estimates of the small-scale lensing amplitude from SCALE in such an analysis provides enough constraining information to measure the minimum neutrino mass at $4\sigma$ significance in the scenario of minimal mass, and higher significance for higher mass. Finally, we show that SCALE will play a powerful role in constraining models of clustering that generate scale-dependent modulation to the distribution of matter and the lensing power spectrum, as predicted by models of warm or fuzzy dark matter.

We present a complete method for the initialization and extraction of first-order inflationary tensor perturbations for fully relativistic simulations which incorporate gravitational backreaction. We outline a correspondence between the cosmological perturbation theory framework and the numerical relativity variables in the appropriate limit. We describe a generation method for stochastic tensoral initial conditions, inspired by the standard scalar initial condition used from inflation and implemented in lattice cosmology. We discuss the implementation of this procedure in the grchombo/grteclyn code, and demonstrate the detailed quantitative correspondence between the linearized and fully nonlinear solutions in the perturbative limit, through the evolution of the background and the tensor power spectrum. We also validate the methodology by showing that energy and momentum constraints are introduced and preserved to second-order or better. We provide some preliminary indicative results probing tensoral non-Gaussianity using the skewness and kurtosis. The computational pipeline presented here will be used to study the emergence of a primordial tensor bispectra and cross spectra that incorporate the effect of nonlinear gravitational couplings with the metric, which has potential applications for the analysis of next-generation cosmic microwave background observations.

We investigate the impact of statistical inhomogeneity and anisotropy in primordial scalar perturbations on the scalar-induced gravitational waves (SIGWs). Assuming inflationary quantum fluctuations originate from a coherent state, the resulting primordial scalar perturbations acquire a nonzero space-dependent mean, violating statistical homogeneity, statistical isotropy, and parity. As a consequence of statistical inhomogeneities, the SIGW acquires distinct scale-dependent features in its correlation function. Statistical anisotropies further lead to possible parity violation and correlation between different polarization modes in the tensor perturbations. Therefore, detection of these signatures in the stochastic gravitational wave background would offer probes to the statistical nature of primordial scalar perturbations beyond the scales accessible to cosmic microwave background observations.