We provide a quantum unifying picture for black holes of all masses and their main properties covering classical, semiclassical, Planckian, and trans-Planckian gravity domains: space-time, size, mass, vacuum (“zero-point”) energy, temperature, partition function, density of states, and entropy. Novel results of this paper are that black hole interiors are always quantum, trans-Planckian, and of constant curvature. This is so for all black holes, including the most macroscopic and astrophysical ones. The black hole interior trans-Planckian vacuum is similar to the earliest cosmological vacuum, where the classical gravity dual is the low energy gravity vacuum—today, dark energy. There is no singularity boundary at $r=0$; the quantum space-time is regular. We display the quantum Penrose diagram of the Schwarzschild-Kruskal black hole. The complete black hole instanton (imaginary time) covers the known classical Gibbons-Hawking instanton plus a new, central, highly dense quantum core of Planck length radius and constant curvature. The complete partition function, entropy, temperature, decay rate, discrete levels, and density of states all include the trans-Planckian domain. The semiclassical black hole entropy (the Bekenstein-Hawking entropy) $(\sqrt{n}{)}^2$ “interpolates” between the quantum point particle entropy ($n$) and the quantum string entropy $\sqrt{n}$, while the quantum trans-Planckian entropy is $1/(\sqrt{n}{)}^2$. Black hole evaporation finishes in a pure (nonmixed) quantum state of particles, gravitons, and radiation.

In a previous article we have introduced an operator representing the three-dimensional scalar curvature in loop quantum gravity. In this article we examine the new curvature operator in the setting of quantum-reduced loop gravity. We derive the explicit form of the curvature operator as an operator on the Hilbert space of the quantum-reduced model. As a simple practical example, we study the expectation values of the operator with respect to basis states of the reduced Hilbert space.

In this paper, the Casimir energy density, loop corrections, and generation of topological mass are investigated for a system consisting of two interacting real and complex scalar fields. The interaction considered is the quartic interaction in the form of a product of the modulus square of the complex field and the square of the real field. In addition, it is also considered the self-interaction associated with each field. In this theory, the scalar field is constrained to always obey periodic condition, while the complex field obeys in one case a quasiperiodic condition and in the other case mixed boundary conditions. The Casimir energy density, loop corrections, and topological mass are evaluated analytically for the massive and massless scalar fields considered. An analysis of possible different stable vacuum states and the corresponding stability condition is also provided. In order to better understand our investigation, some graphs are also presented. The formalism we use here to perform such investigation is the effective potential, which is written as loop expansions via path integral in quantum field theory.

We study the interaction among gravitational and electromagnetic plane waves by means of an analog electromagnetic model of gravity, where the gravitational properties are encoded in the electromagnetic properties of a material in flat space-time. In this setup, the variations in the metric tensor produced by the gravitational waves are codified as space-time-varying electromagnetic properties. We use an in-house code based on the finite-difference time-domain method to conduct numerical experiments, where we find that, when a monochromatic gravitational plane wave interacts with a narrow-band electromagnetic plane wave, an infinite number of sidebands, equally separated between themselves, are induced by the gravitational wave. Finally, we discuss possible future applications of this effect as an alternative method to directly detect gravitational waves.

In massive scalar-tensor gravity, core-collapse supernovae are strong sources of scalar-polarized gravitational waves. These can be detectable out to large distances. The dispersive nature of the propagation of waves in the massive scalar field implies that the gravitational wave signals are long-lived, and many such signals can overlap to form a stochastic background. Using different models for the population of supernova events in the nearby universe, we compute predictions for the energy density in the stochastic scalar-polarized gravitational wave background from core-collapse events in massive scalar-tensor gravity for theory parameters that facilitate strong scalarization. The resulting energy density is below the current constraints on a Gaussian stochastic gravitational wave background but large enough to be detectable with the current generation of detectors when they reach design sensitivity, indicating that it will soon be possible to place new constraints on the parameter space of massive scalar-tensor gravity.

Domain wall networks in the early universe, formed upon spontaneous breaking of a discrete symmetry, have a rich impact on cosmology. Yet, they remain somewhat unexplored. We introduce a new analytic strategy to understand better the domain wall epoch, from formation to annihilation. Our method includes a quantum field theoretical treatment of the initial state at domain wall formation, as well as of the time evolution. We find that the domain wall area density for a network with biased initial condition in $d+1$ dimensional flat spacetime evolves as $t^{-1/2}\exp (-(t/t_{\mathrm{ann}}{)}^{d/2})$. We comment on the relation between this and previous results obtained in condensed matter and in cosmology. The extrapolation of this law to an expanding universe applies to networks that are close to the domain wall “gas” limit.

Using the fact that the comoving angular diameter distance to the last scattering surface is strictly constrained almost model independently, we show that, for any model agreeing with the standard $\mathrm{\Lambda }$CDM model on its background dynamics at $z\sim 0$ and size of the comoving sound horizon at last scattering, the deviations of the Hubble radius from the one of the standard $\mathrm{\Lambda }$CDM model must be a member of the set of admissible wavelets. The family of models characterized by this framework also offers nontrivial oscillatory behaviors in various functions that define the kinematics of the Universe, even when the wavelets themselves are very simple. We also discuss the consequences of attributing these kinematics to, first, dark energy, and second, varying gravitational coupling strength. Utilizing some simplest wavelets, we demonstrate the competence of this framework in describing the baryon acoustic oscillation (BAO) data without any modifications to the agreement with cosmic microwave background measurements. This framework also provides a natural explanation for the bumps found in nonparametric observational reconstructions of the Hubble parameter and dark energy density as compensations of the dips suggested by some BAO data, and questions the physical reality of their existence. We note that utilizing this framework on top of the models that agree with both the cosmic microwave background and local $H_0$ measurements but are held back by BAO data, one may resurrect these models through the wiggly nature of wavelets that can naturally accommodate the BAO data. Finally, we also suggest narrowing the plausible set of admissible wavelets to further improve our framework by imposing conditions from expected kinematics of a viable cosmological model or first principle fundamental physics such as energy conditions.

Black hole evaporation is generally considered inevitable for low-mass black holes, yet there is no confirmation of this remarkable hypothesis. Here, we propose a phenomenological model that appeals to the possible survival of light quasiextremal primordial black holes as a significant dark matter component and show that the related cosmological and astrophysical constraints disappear for reasonable degrees of quasiextremality. The results obtained are general, conservative, and should be taken as a proof of principle for future, model-specific analyses.

We illustrate the effect of boundary conditions on the evolution of structure in fuzzy dark matter. Scenarios explored include the evolution of single, ground-state equilibrium solutions of the Schrödinger-Poisson system, relaxation of a Gaussian density fluctuation, mergers of two equilibrium configurations, and the random merger of many solitons. For comparison, each scenario is evolved twice, with isolation vs periodic boundary conditions, the two commonly used to simulate isolated systems and structure formation, respectively. Replacing isolation boundary conditions (implemented by an absorbing sponge at large radius) by periodic boundary conditions changes the domain topology and dynamics of each scenario by affecting the outcome of gravitational cooling. With periodic boundary conditions, the initial ground-state equilibrium solution and Gaussian fluctuation each evolve toward the single equilibrium solitonic core of the isolated case, but surrounded by an envelope, or tail, in which additional mass is distributed nearly uniformly, unlike the isolated versions. The case of head-on, binary merger introduces additional effects caused by the pull on the system due to the infinite network of periodic images along each axis of the domain. Adding angular momentum to this binary merger results in a tail with polynomial profile when using a periodic domain. Finally, the 3D merger of many, randomly placed solitonic cores of different mass makes a solitonic core surrounded by a tail with power-law-like profile, for periodic boundary conditions, while producing a core with a much sharper falloff in the isolated case. This suggests the conclusion of earlier work, that the ground-state equilibrium solution is an attractor for the asymptotic state, is true even in 3D and for more general circumstances than previously considered, but only if gravitational cooling is able to carry mass and energy off to infinity, which isolation boundary conditions allow, but periodic ones do not.

We consider a dense neutrino gas in the “fast-flavor limit” (vanishing neutrino masses). For the first time, we identify exact solutions of the nonlinear wave equation in the form of solitons. They can propagate with both subluminal or superluminal speed, the latter not violating causality. The soliton with infinite speed is a homogeneous solution and coincides with the usual fast-flavor pendulum except that it swings only once instead of being periodic. The subluminal soliton in the static limit corresponds to a one-swing “spatial pendulum.” A necessary condition for such solutions to exist is a “crossed” neutrino angle distribution. Based on the Nyquist criterion, we derive a new sufficient condition without solving the dispersion relation. The solitons are very fragile; they are as unstable as the homogeneous neutrino gas alone. Moreover, in the presence of matter, only the solution survives that is homogeneous in a frame comoving with the matter current. Generally, the matter effect cannot be eliminated by transformations in flavor space, but has real physical impact.

A stochastic gravitational-wave (GW) background consists of a large number of weak, independent and uncorrelated events of astrophysical or cosmological origin. The GW power on the sky is assumed to contain anisotropies on top of an isotropic component, i.e., the angular monopole. Complementary to the LIGO-Virgo-KAGRA (LVK) searches, we develop an efficient analysis pipeline to compute the maximum-likelihood anisotropic sky maps in stochastic backgrounds directly in the sky pixel domain using data folded over one sidereal day. We invert the full pixel-pixel correlation matrix in map-making of the GW sky, up to an optimal eigenmode cutoff decided systematically using simulations. In addition to modeled mapping, we implement a model-independent method to probe spectral shapes of stochastic backgrounds. Using data from LIGO-Virgo’s first three observing runs, we obtain upper limits on anisotropies as well as the isotropic monopole as a limiting case, consistent with the LVK results. We also set constraints on the spectral shape of the stochastic background using this novel model-independent method.

We revisit the calculation of chiral anomalies for global and gauge symmetries in the framework of the covariant derivative expansion (CDE). Due to the presence of UV divergences, the result is an ambiguous quantity that depends on the regularization procedure and the renormalization scheme. We introduce a class of regulators that facilitate a straightforward evaluation of the anomaly exclusively in $d=4$ spacetime dimensions using the CDE methodology. We derive a master formula for the anomaly that integrates various known results into a unified framework.

In usual (nonstochastic) tensor network calculations, the truncated singular value decomposition is often used for approximating a tensor, and it causes systematic errors. By introducing stochastic noise in the approximation, however, one can avoid such systematic errors at the expense of statistical errors, which can be straightforwardly controlled. Therefore in principle, exact results can be obtained even at finite bond dimension up to the statistical errors. A previous study of the unbiased method implemented in tensor renormalization group algorithm, however, showed that the statistical errors for physical quantity are not negligible, and furthermore the computational cost is linearly proportional to a system volume. In this paper, we introduce a new way of stochastic noise such that the statistical error is suppressed, and moreover, in order to reduce the computational cost we propose common noise method whose cost is proportional to the logarithm of volume. We find that the method provides better accuracy for the free energy compared with the truncated singular value decomposition when applying to tensor renormalization group for Ising model on square lattice. Although the common noise method introduces systematic error originated from a correlation of noises, we show that the error can be described by a simple functional form in terms of the number of noises, thus the error can be straightforwardly controlled in an actual analysis. We also apply the method to the graph independent local truncation algorithm and show that the accuracy is further improved.

We present a lattice-QCD calculation of the light-quark connected contribution to window observables associated with the leading-order hadronic vacuum polarization contribution to the anomalous magnetic moment of the muon, $a_{\mu }^{\mathrm{HVP},\mathrm{LO}}$. We employ the MILC Collaboration’s isospin-symmetric QCD gauge-field ensembles, which contain four flavors of dynamical highly improved staggered quarks with four lattice spacings between $a\approx 0.06–0.15\mathrm{fm}$ and close-to-physical quark masses. We consider several effective-field-theory-based schemes for finite volume and other lattice corrections and combine the results via Bayesian model averaging to obtain robust estimates of the associated systematic uncertainties. After unblinding, our final results for the intermediate and “W2” windows are $a_{\mu }^{ll,\mathrm{W}}(\text{conn})=206.6(1.0)\times {10}^{-10}$ and $a_{\mu }^{ll,\mathrm{W}2}(\text{conn})=100.7(3.2)\times {10}^{-10}$, respectively.

Motivated by quantum simulation, we consider lattice Hamiltonians for Yang-Mills gauge theories with finite gauge group, for example a finite subgroup of a compact Lie group. We show that the electric Hamiltonian admits an interpretation as a certain natural, nonunique Laplacian operator on the finite Abelian or non-Abelian group and derive some consequences from this fact. Independent of the chosen Hamiltonian, we provide a full explicit description of the physical, gauge-invariant Hilbert space for pure gauge theories and derive a simple formula to compute its dimension. We illustrate the use of the gauge-invariant basis to diagonalize a dihedral gauge theory on a small periodic lattice.

We report on the calculation of the next-to-leading order (NLO) QCD corrections to top quark pair production in association with two hard jets at the LHC. We take into account higher-order effects in both the production and decays of the top-quark pair. The latter are treated in the narrow width approximation and $t\overline{t}$ spin correlations are preserved throughout the calculation. This is the first time that such a complete study for this process is conducted at NLO in QCD. We present results for fiducial cross sections at the integrated and differential level. Furthermore, we investigate kinematic properties of the additional light jets and their distribution in the $pp\to t\overline{t}jj$ process. We examine jets in production and top-quark decays as well as the mixed contribution, where the two hardest non-$b$ jets are present simultaneously in the production and decay processes.

We consider the heavy-quark expansion for the nonleptonic decay rates of heavy hadrons, and compute the next-to-leading-order QCD corrections to power terms up to order $1/m_Q^2$. We neglect the masses of the final-state quarks, so the application of our result is mainly for charmed hadrons. Our result can be applied also to bottomed hadrons as they constitute the main effect to this order up to corrections of $\mathcal{O}(m_c/m_b)$ and contributions due to penguin operators. We discuss the impact of our result for the lifetimes of heavy hadrons.

Dark matter lighter than $10\mathrm{GeV}/c^2$ encompasses a promising range of candidates. A conceptual design for a new detector, DarkSide-LowMass, is presented, based on the DarkSide-50 detector and progress toward DarkSide-20k, optimized for a low-threshold electron-counting measurement. Sensitivity to light dark matter is explored for various potential energy thresholds and background rates. These studies show that DarkSide-LowMass can achieve sensitivity to light dark matter down to the solar neutrino fog for GeV-scale masses and significant sensitivity down to $10\mathrm{MeV}/c^2$ considering the Migdal effect or interactions with electrons. Requirements for optimizing the detector’s sensitivity are explored, as are potential sensitivity gains from modeling and mitigating spurious electron backgrounds that may dominate the signal at the lowest energies.

We numerically obtain gravastar solutions as nontopological solitons in a system that consists of a U(1) gauge Higgs model with a complex scalar field and Einstein gravity. The solitonic gravastar solutions are compact enough to have a photon sphere.

The failure to calculate the vacuum energy is a central problem in theoretical physics. Presumably the problem arises from the insistent use of effective field theory reasoning in a context that is well beyond its intended scope. If one follows this path, then one is led inevitably to statistical or anthropic reasoning for observations. It appears that a more palatable resolution of the vacuum energy problem requires some form of UV/IR feedback. In this paper we take the point of view that such feedback can be thought of as arising by defining a notion of quantum space-time. We reformulate the regularized computation of vacuum energy in such a way that it can be interpreted in terms of a sum over elementary phase space volumes, that we identify with a ground state degeneracy. This observation yields a precise notion of UV/IR feedback, while leaving a scale unfixed. Here we argue that holography can be thought to provide a key piece of information: we show that equating this microscopic ground state degeneracy with macroscopic gravitational entropy yields a prediction for the vacuum energy that can easily be consistent with observations. Essentially, the smallness of the vacuum energy is tied to the large size of the Universe. We discuss how within this scenario notions of effective field theory can go so wrong.