The Teleparallel Equivalent to General Relativity (TEGR) is often presented as a gauge theory of translations, i.e., that uses only the translation group $T_4=({\mathbb{R}}^4,+)$ as its gauge group. In a previous work we argued against this translation-only formalism on the basis of its mathematical shortcomings. We then provided an alternative proposal using a Cartan connection. Recently, a reply by some of the authors defending TEGR as a translation-only gauge theory discussed our objections. Here, we first clarify our arguments, and give new proofs of some statements, to answer to these discussions, maintaining our first claim. We then amend one of the arguments that originally led us to propose the Cartan connection in this context. This broadens the a priori possible choices for a TEGR connection.

It has very recently been realized that coupling branes to higher dimensional quantum gravity theories and considering the consistency of what lives on the branes, one is able to understand whether such theories can belong either to the swampland or to the landscape. In this regard, in the present work, we study a warm inflation model embedded in the Randall-Sundrum brane-world scenario. It is explicitly shown that this model belongs to the landscape by supporting a strong dissipative regime with an inflaton steep exponential potential. The presence of extra dimension effects from the braneworld allow achieving this strong dissipative regime, which is shown to be both theoretically and observationally consistent. In fact, such strong dissipation effects, which decrease towards the end of inflation, together with the extra dimension effect, allow the present realization to simultaneously satisfy all previous restrictions imposed on such a model and to evade the recently proposed swampland conjectures. The present implementation of this model, in terms of an exponential potential for the scalar field, makes it also a possible candidate for describing the late-time Universe in the context of a dissipative quintessential inflation model, and we discuss this possibility in the Conclusions.

We calculate the quantum gravitational corrections to the Mukhanov-Sasaki equation obtained by the canonical quantization of the inflaton-gravity system. Our approach, which is based on the Born-Oppenheimer decomposition of the resulting Wheeler-DeWitt equation, was previously applied to a minimally coupled inflaton. In this article we examine the case of a nonminimally coupled inflaton and, in particular, the induced gravity case is also discussed. Finally, the equation governing the quantum evolution of the inflationary perturbations is derived on a de Sitter background. Moreover the problem of the introduction of time is addressed and a generalized method, with respect to that used for the minimal coupling case, is illustrated. Such a generalized method can be applied to the universe wave function when, through the Born-Oppenheimer factorization, we decompose it into a part that contains the minisuperspace degrees of freedom and another that describes the perturbations.

Neutrinos are believed to have a key role in the explosion mechanism of core-collapse supernovae as they carry most of the energy released by the gravitational collapse of a massive star. If their flavor is converted fast inside the neutrino sphere, the supernova explosion may be influenced. This paper is reporting the results of the extended work of our previous paper. We perform a thorough survey of the electron lepton number (ELN) crossing in one of our self-consistent, realistic Boltzmann simulations in two spatial dimensions under axisymmetry for the existence of the crossings between ${\nu }_e$ and ${\overline{\nu }}_e$ angular distributions, or the ELN crossing. We report for the first time the positive detections deep inside the core of the massive star in the vicinity of neutrino sphere at $r\approx 16–21\mathrm{km}$. We find that low values of the electron fraction $Y_e$ produced by convective motions together with the appearance of light elements are critically important to give rise to the ELN crossing by enhancing the chemical potential difference between proton and neutron, and hence by mitigating the Fermi-degeneracy of ${\nu }_e$. Since the region of positive detection are sustained and, in fact, expanding with time, it may have an impact on the explosion of core-collapse supernovae, observational neutrino astronomy, and nucleosynthesis of heavy nuclei.

We examine the quantum loop effects on the single-field inflationary models in a spatially flat Friedmann-Robertson-Walker cosmological space-time with a general self-interacting scalar field potential, which is modeled in terms of the Hubble flow parameters in the effective field theory approach. In particular, we focus on the scenarios in both slow-roll (SR) to ultra-slow-roll (USR) and SR-USR-SR inflation, in which it is shown that density perturbations originating from quantum vacuum fluctuations can be enhanced at small scales and then potentially collapse into primordial black holes. Here, our estimates indicate significant one-loop corrections around the peak of the density power spectrum in both scenarios. The induced large quantum loop effects should be confirmed by a more formal quantum field theory and, if so, should be treated in a self-consistent manner that will be discussed.

We analyze the flow of energy and entropy emitted by a class of moving mirror trajectories which provide models for important aspects of the radiation fields produced by black hole evaporation. The mirror radiation fields provide natural, concrete examples of processes that follow thermal distributions for long periods, accompanied by transients which are brief and carry little net energy, yet ultimately represent pure quantum states. A burst of negative energy flux is a generic feature of these fields, but it need not be prominent.

A central aspect of the cosmological constant problem is to understand why vacuum energy does not gravitate. In order to account for this observation, while allowing for nontrivial dynamics of the quantum vacuum, we motivate a novel background independent theory of gravity. The theory is an extension of unimodular gravity that is described in geometric terms by means of a conformal (light-cone) structure and differential forms of degrees one and two. We show that the subset of the classical field equations describing the dynamics of matter degrees of freedom and the conformal structure of spacetime are equivalent to that of unimodular gravity. The sector with vanishing matter fields and a flat conformal structure is governed by the field equations of BF theory and contains topological invariants that are influenced by quantum vacuum fluctuations. Perturbative deviations from this sector lead to classical solutions that necessarily display relatively small values of the cosmological constant with respect to the would-be contribution of quantum vacuum fluctuations. This feature that goes beyond general relativity (and unimodular gravity) offers an interpretation of the smallness of the currently observed cosmological constant.

The superentropic black hole, which possesses a noncompact horizon topology and violates the reverse isoperimetric inequality, has been found to satisfy both the thermodynamic first law and the Bekenstein-Smarr mass formula. In this paper, we first derive a new Christodoulou-Ruffini-like squared-mass formula for the four-dimensional Kerr-Newman-AdS superentropic black hole and then establish a set of very simple relations between thermodynamic quantities of the superentropic Kerr-Newman-${\mathrm{AdS}}_4$ black hole and its usual counterparts. Using these relations, the thermodynamic quantities of the Kerr-Newman-${\mathrm{AdS}}_4$ superentropic black hole can be obtained from those of the usual protype by taking the ultraspinning limit properly. Then these relations are extended to the singly rotating Kerr-AdS black holes in arbitrary dimensions and the double-rotating charged black hole in the five-dimensional minimal gauged supergravity. It can be inferred that the thermodynamic quantities of all superentropic black holes obey similar limiting relations to those of their corresponding conventional rotating AdS black holes and thus can be obtained by taking the ultraspinning limit appropriately.

Estimates of the source parameters of gravitational-wave (GW) events produced by compact binary mergers rely on theoretical models for the GW signal. We present the first frequency-domain model for the inspiral, merger, and ringdown of the GW signal from precessing binary black hole systems that also includes multipoles beyond the leading-order quadrupole. Our model, PhenomPv3HM, is a combination of the higher-multipole nonprecessing model PhenomHM and the spin-precessing model PhenomPv3 that includes two-spin precession via a dynamical rotation of the GW multipoles. We validate the new model by comparing to a large set of precessing numerical-relativity simulations and find excellent agreement across the majority of the parameter space they cover. For mass ratios $<5$ the mismatch improves, on average, from $\sim 6\%$ to $\sim 2\%$ compared to PhenomPv3 when we include higher multipoles in the model. However, we find mismatches $\sim 8\%$ for a mass-ratio-6 and highly spinning simulation. We quantify the statistical uncertainty in the recovery of binary parameters by applying standard Bayesian parameter estimation methods to simulated signals. We find that, while the primary black hole spin parameters should be measurable even at moderate signal-to-noise ratios (SNRs) $\sim 30$, the secondary spin requires much larger SNRs $\sim 200$. We also quantify the systematic uncertainty expected by recovering our simulated signals with different waveform models in which various physical effects—such as the inclusion of higher modes and/or precession—are omitted and find that even in the low-SNR case ($\sim 17$) the recovered parameters can be biased. Finally, as a first application of the new model we analyze the binary black hole event GW170729. We find larger values for the primary black hole mass of ${58.25}_{-12.53}^{+11.73}{M}_{\odot }$ (90% credible interval). The lower limit ($\sim 46M_{\odot }$) is comparable to the proposed maximum black hole mass predicted by different stellar evolution models due to the pulsation pair-instability supernova (PPISN) mechanism. If we assume that the primary black hole in GW170729 formed through a PPISN, then out of the four PPISN models we consider only the model of Woosley [1] is consistent with our mass measurements at the 90% confidence level.

We analytically study the optical appearance of an isotropically emitter orbiting near the horizon of a near-extremely rotating Kerr-Sen (KS) black hole which is an electrically charged black hole arising in heterotic string theory. We study the influence of the Sen charge on the observational quantities, including the image position, flux and redshift factor. Moreover, we compare the results with those for a near-extremal Kerr-Newman (KN) black hole, which is the charged rotating black hole in general relativity. We find quantitative corrections of the signatures of these charged black holes (both KS and KN) compare to that of a neutral Kerr black hole. This may serve as distinctive features of different black holes for future tests by the Event Horizon Telescope.

We study the null geodesics extending from the near-horizon region out to the far region in the background of the Schwarzschild and the singly spinning Myers-Perry black holes in the large dimension limit. We find that in this limit the radial integrals of these geodesics can be obtained by using the method of matched asymptotic expansions. If the motion of the photon is confined to the equator plane, then all geodesic equations are solvable analytically. The study in this paper may provide a toy model to analyze the observables relevant to the electromagnetic phenomena occurring near the black holes.

A connection-independent formulation of general relativity is presented, in which the dynamics does not depend on the choice of connection. The gravity action in this formulation includes one additional scalar term in addition to the Einstein-Hilbert action. No conditions on the connection are imposed. Nevertheless, this formulation yields the Einstein equations, without adding the Gibbons-Hawking-York term even when a manifold has a boundary. Furthermore, this formulation yields a unified description of general relativity, teleparallel gravity, and symmetric teleparallel gravity.

Starting with the light-cone Hamiltonian for gravity, we perform a field redefinition that reveals a hidden symmetry in four dimensions, namely the Ehlers $SL(2,\mathbb{R})$ symmetry. The field redefinition, which is nonlocal in space but local in time, acts as a canonical transformation in the Hamiltonian formulation keeping the Poisson bracket relations unaltered. We discuss the electromagnetic duality symmetry of gravity in the light-cone formalism, which forms the $SO(2)$ subgroup of this Ehlers symmetry. The helicity states in the original Hamiltonian are not in a representation of the enhanced symmetry group. In order to make the symmetry manifest, we make a change of variables in the path integral from the helicity states to new fields that transform linearly under the $SO(2)$ duality symmetry.

The formation of primordial black holes (PBHs) is studied using superconformal inflationary $\alpha$ attractors. An inflaton potential is constructed with a plateaulike region, which brings about the onset of an ultra slow-roll region where the required enhancement in the curvature power spectrum takes place. This is accomplished by carefully fine-tuning the parameters in the potential. For the parameter sets, the amount of observable inflation is such that the curvature perturbation ${\mathcal{P}}_{\mathcal{R}}$ peaks at $\sim {10}^{14}{\mathrm{Mpc}}^{-1}$, producing PBHs in the mass window $10^{16}\mathrm{g}\le M\le {10}^{18}\mathrm{g}$. The reheating period after inflation is taken into account to determine whether or not PBH formation takes place in such a phase. Finally, the spectrum of second order gravitational waves that can arise due to the curvature perturbation enhancement is calculated.

The Debye mass sets a scale for the screening of static charges and the scattering of fast charges within a gauge plasma. Inspired by its potential cosmological applications, we determine a QCD Debye mass at two-loop order in a broad temperature range (1 GeV–10 TeV), demonstrating how quark mass thresholds get smoothly crossed. Along the way, integration-by-parts identities pertinent to massive loops at finite temperature are illuminated.

In the present work, we have studied the spectrum of the primordial gravitational waves due to magnetic instability in the presence of neutrino asymmetry. The magnetic instability generates a helical magnetic field on a large scale. The anisotropic stress generated by the magnetic field is shown to be a source of primordial gravitational waves at the time of matter-neutrino decoupling. We expect that the theoretically predicted gravitational waves by this mechanism may be detected by the Square Kilometer Array or pulsar time array observations. We also compare our findings with the results obtained by the earlier work where the effect of magnetic instability was not considered.

We present a new public python package, darkhistory, for computing the effects of dark matter annihilation and decay on the temperature and ionization history of the early universe. darkhistory simultaneously solves for the evolution of the free electron fraction and gas temperature, and for the cooling of annihilation/decay products and the secondary particles produced in the process. Consequently, we can self-consistently include the effects of both astrophysical and exotic sources of heating and ionization, and automatically take into account backreaction, where modifications to the ionization/temperature history in turn modify the energy-loss processes for injected particles. We present a number of worked examples, demonstrating how to use the code in a range of different configurations, in particular for arbitrary dark matter masses and annihilation/decay final states. Possible applications of darkhistory include mapping out the effects of dark matter annihilation/decay on the global 21 cm signal and the epoch of reionization, as well as the effects of exotic energy injections other than dark matter annihilation/decay. The code is available at https://github.com/hongwanliu/DarkHistory with documentation at https://darkhistory.readthedocs.io. Data files required to run the code can be downloaded at https://doi.org/10.7910/DVN/DUOUWA.

We study the scalar induced gravitational wave (GW) background in inflation with gravitationally enhanced friction (GEF). The GEF mechanism, which is realized by assuming a nonminimal derivative coupling between the inflaton field and gravity, is used to amplify the small-scale curvature perturbations to generate a sizable amount of primordial black holes. We find that the GW energy spectra can reach the detectable scopes of the future GW projects, and the power spectrum of curvature perturbations has a power-law form in the vicinity of the peak. The scaling of the GW spectrum in the ultraviolet regions is two times that of the power spectrum slope, and has a lower bound. In the infrared regions, the slope of the GW spectrum can be described roughly by a log-dependent form. These features of the GW spectrum may be used to check the GEF mechanism if the scalar induced GWs are detected in the future.

We investigate the impact of the gravity portal on the properties of white dwarfs, such the as equation of state and the cooling time. We find that the interaction between dark matter spin-zero bosons and electrons in the mean-field approximation softens the equation of state, and the objects cool down more slowly compared to the usual case.