Explicitly computed Penrose diagrams are plotted for a classical model of black hole formation and evaporation, in which black holes form by the accretion of infalling spherical shells of matter and subsequently evaporate by emitting spherical shells of Hawking radiation. This model is based on known semiclassical effects, but is not a full solution of semiclassical gravity. The method allows arbitrary interior metrics of the form $d{s}^2=-f(r)d{t}^2+f(r{)}^{-1}d{r}^2+r^{2}d{\mathrm{\Omega }}^2$, including singular and nonsingular models. Matter dynamics are visualized by explicitly plotting proper density in the diagrams, as well as by tracking the location of trapped surfaces and energy condition violations. The most illustrative model accurately approximates the standard time evolution for black hole thermal evaporation; its time dependence and causal structure are analyzed by inspection of the diagram. The resulting insights contradict some common intuitions and assumptions, and we point out some examples in the literature with assumptions that do not hold up in this more detailed model. Based on the new diagrams, we argue for an improved understanding of the Hawking radiation process, propose an alternate definition of “black hole” in the presence of evaporation, and suggest some implications regarding information preservation and unitarity.

The superradiant scattering of Alfvén waves (Alfvénic superradiance) in a forcefree magnetosphere is discussed to reveal the relationship between the Blandford-Znajek (BZ) process and superradiance. For simplicity, we consider a four-dimensional rotating black string spacetime of which each $z=\text{const}$ slice is a Bañados-Teitelboim-Zanelli solution as an analogy of the equatorial plane of the Kerr spacetime. Then, it is confirmed that the condition for Alfvénic superradiance coincides with that for the BZ process, and the wave amplification can be very large due to a resonant scattering for some parameter sets of the wave frequency and the angular velocity of the magnetic field line. Moreover, by analysis of the Poynting flux, we first show that the BZ process can be interpreted as the long wavelength limit of Alfvénic superradiance.

We perform a multivariate analysis of Higgs-pair production in $HH\to b\overline{b}\gamma \gamma$ channel at the HL-LHC to probe the trilinear Higgs self-coupling (THSC) ${\lambda }_{3H}$, which takes the value of 1 in the standard model (SM). We consider all known background processes. For the signal we are the first to adopt the most recent event generator of POWHEG-BOX-V2 to exploit the next-to-leading order (NLO) distributions for the toolkit for multivariate data analysis (TMVA), taking account of the full top-quark mass dependence. Through boosted decision tree (BDT) analysis trained for ${\lambda }_{3H}=1$, we find that the significance can reach up to 1.95 with about 9 signal and 18 background events. In addition, the THSC can be constrained to $1.00<{\lambda }_{3H}<6.22$ at 95% confidence level (CL). We also perform a likelihood fitting of $M_{\gamma \gamma bb}$ distribution and find the $1\sigma$ confidence interval (CI) of $0.1<{\lambda }_{3H}<2.2\cup 5.4<{\lambda }_{3H}<6.6$ for the ${\lambda }_{3H}=1$ nominal set. On the other hand, using BDTs trained for each value of ${\lambda }_{3H}$, we find a bulk region of $0.5\lesssim {\lambda }_{3H}\lesssim 4.5$, for which it is hard to pin down the THSC.

Past and current direct neutrino mass experiments set limits on the so-called effective neutrino mass, which is an incoherent sum of neutrino masses and lepton mixing matrix elements. The electron energy spectrum which neglects the relativistic and nuclear recoil effects is often assumed. Alternative definitions of effective masses exist, and an exact relativistic spectrum is calculable. We quantitatively compare the validity of those different approximations as function of energy resolution and exposure in view of tritium beta decays in the KATRIN, Project 8, and PTOLEMY experiments. Furthermore, adopting the Bayesian approach, we present the posterior distributions of the effective neutrino mass by including current experimental information from neutrino oscillations, beta decay, neutrinoless double-beta decay, and cosmological observations. Both linear and logarithmic priors for the smallest neutrino mass are assumed.

We present the results of a direct detection search for mirror dark matter interactions, using data collected from the Large Underground Xenon experiment during 2013, with an exposure of $95\mathrm{live}\text{−}\mathrm{days}\times 118\mathrm{kg}$. Here, the calculations of the mirror electron scattering rate in liquid xenon take into account the shielding effects from mirror dark matter captured within the Earth. Annual and diurnal modulation of the dark matter flux and atomic shell effects in xenon are also accounted for. Having found no evidence for an electron recoil signal induced by mirror dark matter interactions we place an upper limit on the kinetic mixing parameter over a range of local mirror electron temperatures between 0.1 and 0.9 keV. This limit shows significant improvement over the previous experimental constraint from orthopositronium decays and significantly reduces the allowed parameter space for the model. We exclude mirror electron temperatures above 0.3 keV at a 90% confidence level, for this model, and constrain the kinetic mixing below this temperature.

Combined measurements of Higgs boson production cross sections and branching fractions are presented. The combination is based on the analyses of the Higgs boson decay modes $H\to \gamma \gamma$, $Z{Z}^{*}$, $W{W}^{*}$, $\tau \tau$, $b\overline{b}$, $\mu \mu$, searches for decays into invisible final states, and on measurements of off-shell Higgs boson production. Up to $79.8{\mathrm{fb}}^{-1}$ of proton–proton collision data collected at $\sqrt{s}=13\mathrm{TeV}$ with the ATLAS detector are used. Results are presented for the gluon–gluon fusion and vector-boson fusion processes, and for associated production with vector bosons or top-quarks. The global signal strength is determined to be $\mu =1.11_{-0.08}^{+0.09}$. The combined measurement yields an observed (expected) significance for the vector-boson fusion production process of $6.5\sigma$ ($5.3\sigma$). Measurements in kinematic regions defined within the simplified template cross section framework are also shown. The results are interpreted in terms of modifiers applied to the Standard Model couplings of the Higgs boson to other particles, and are used to set exclusion limits on parameters in two-Higgs-doublet models and in the simplified minimal supersymmetric Standard Model. No significant deviations from Standard Model predictions are observed.

In this paper, we consider the evaluation of the effective action for photons coupled to charged scalar fields in the framework of a ($2+1$)-dimensional noncommutative spacetime. In order to determine the noncommutative Maxwell Lagrangian density, we follow a perturbative approach, by integrating out the charged scalar fields, to compute the respective graphs for the vev’s $⟨AA⟩$, $⟨AAA⟩$, and $⟨AAAA⟩$. Surprisingly, it is shown that these contributions are planar and that, in the highly noncommutative limit, correspond to the Maxwell effective action and its higher-derivative corrections. It is explicitly verified that the one-loop effective action is gauge invariant, as well as under discrete symmetries: parity, time reversal, and charge conjugation. Moreover, a comparison of the main results with the noncommutative ${\mathrm{QED}}_3$ is established. In particular, the main difference is the absence of parity violating terms in the photon’s effective action coming from integrating out the charged scalar fields.

In the present paper we consider a special classes of massive tensor-multiscalar theories of gravity whose target space metric admits Killing field(s) with a periodic flow. For such tensor-multiscalar theories we show that there exist mixed configurations of tensor-multiscalar solitons and neutron stars. The influence of the curvature of the target space on the structure of the mixed configurations is studied for two explicit tensor-multiscalar theories. The stability of the obtained compact objects is examined and it turns out that the stability region spans to larger central energy densities and central values of the scalar field compared to the pure neutron stars or the pure tensor-multiscalar solitons.

We propose a simple and efficient way to compute quasinormal frequencies of spherically symmetric black holes. We revisit an old idea that relates them to bound state energies of anharmonic oscillators by an analytic continuation. This connection enables us to achieve remarkable high-order computations of WKB series by Rayleigh–Schrödinger perturbation theory. The known WKB results are easily reproduced. Our analysis shows that the perturbative WKB series of the quasinormal frequencies turns out to be a Borel summable divergent series both for the Schwarzschild and for the Reissner–Nordström black holes. Their Borel sums reproduce the correct numerical values.

We present results supporting the Horowitz-Myers conjecture, that the Horowitz-Myers metrics minimize energy amongst metrics on the same spacetime manifold and with the same asymptotic behavior.

We study the behavior of geodesics in the plane-fronted wave background of the three-dimensional gravity with propagating torsion, which possesses only massive degrees of freedom. We discover the velocity memory effect, in contrast to the current belief that its existence is due to the presence of soft particles.

In this article we derive the post-Newtonian limit of a class of teleparallel theories of gravity, where the action is a free function $L(T,X,Y,\varphi )$ of the torsion scalar $T$ and scalar quantities $X$ and $Y$ built from the dynamical scalar field $\varphi$. We restrict the analysis to a massless scalar field in order to use the parametrized post-Newtonian formalism without modifications, such as introducing an effective gravitational constant which depends on the distance between the interacting masses. In particular the results show a class of fully conservative theories of gravity, where the only nonvanishing parameters are $\gamma$ and $\beta$. For a particular choice of the function $L(T,X,Y,\varphi )$ the theory cannot be distinguished from general relativity in its post-Newtonian approximation.

We consider higher-dimensional massive Brans-Dicke theory with Ricci-flat internal space. The background model is perturbed by a massive gravitating source which is pressureless in the external (our space) but has an arbitrary equation-of-state parameter $\mathrm{\Omega }$ in the internal space. We obtain the exact solution of the system of linearized equations for the perturbations of the metric coefficients and scalar field. For a massless scalar field, relying on the fine-tuning between the Brans-Dicke parameter $\omega$ and $\mathrm{\Omega }$, we demonstrate that (i) the model does not contradict gravitational tests relevant to the parameterized post-Newtonian parameter $\gamma$, and (ii) the scalar field is not ghost in the case of nonzero $|\mathrm{\Omega }|\sim O(1)$ along with the natural value $|\omega |\sim O(1)$. In the general case of a massive scalar field, the metric coefficients acquire the Yukawa correction terms, where the Yukawa mass scale $m$ is defined by the mass of the scalar field. For the natural value $\omega \sim O(1)$, the inverse-square-law experiments impose the following restriction on the lower bound of the mass: $m\gtrsim 10^{-11}\mathrm{GeV}$. The experimental constraints on $\gamma$ require that $\mathrm{\Omega }$ be extremely close to $-1/2$.

In the information loss problem in black hole evaporation, the investigation of the purification partner of a Hawking particle is crucial. It is a well-known fact that the $3+1$ dimensional spherically symmetric gravitational collapse can be mimicked by $1+1$ dimensional moving mirror models. Since a detected particle in field theory is defined by what a particle detector observes, the diversity of detector designs yields a variety of particles and their partners. We provide a formula of generalized partners of detected particles emitted out of mirrors in an arbitrary motion for any Gaussian state in a free massless scalar field theory. Using our formula, we directly demonstrate information storage about initial phase information in a pure state of a detected particle and its partner. The form of the partner drastically changes depending on the detailed designs of particle detectors for Hawking radiation. In the case of a detected particle and its partner sensitive to information about initial phase, spatial configurations of the partner has long tails in a stage where only zero-point fluctuation is emitted out of the mirror.

As an extension of our previous work [J. Qiao , arXiv:1909.03815.], in this article, we calculate the effects of parity violation on gravitational-wave (GW) waveforms during their propagation in the most general parity-violating gravities, including Chern-Simons modified gravity, ghost-free scalar-tensor gravity, the symmetric teleparallel equivalence of General Relativity theory, Hořava-Lifshitz gravity, and so on. For this purpose, we consider the GWs generated by the coalescence of compact binaries and concentrate on the imprints of the parity violation in the propagation of GWs. With a unified description of GW in the theories of parity-violating gravity, we study the effects of velocity and amplitude birefringence on the GW waveforms. Decomposing the GWs into the circular polarization modes, the two birefringence effects exactly correspond to the modifications in phase and amplitude of GW waveforms, respectively. We find that, for each circular polarization mode, the amplitude, phase, and velocity of GW can be modified by both the parity-violating terms and parity-conserving terms in gravity. Therefore, in order to test the parity symmetry in gravity, we should compare the difference between two circular polarization modes, rather than measure an individual mode. Combining two circular modes, we obtain the GW waveforms in the Fourier domain and obtain the deviations from those in General Relativity. The GW waveforms derived in this paper are also applicable to the theories of parity-conserving gravity, which have the modified dispersion relations (e.g., massive gravity, double special relativity theory, extra-dimensional theories, etc.) or/and have the modified friction terms (e.g., nonlocal gravity, gravitational theory with time-dependent Planck mass, etc.).

This paper, in addition to our recent works, intends to improve and give in detail the behavior of the Wetterich flow equations in the physical theory space. We focus on the local potential approximation and present a new framework of investigation, namely the effective vertex expansion coupled with Ward’s identities for quartic melonic interactions, allowing us to consider infinite sectors rather than finite dimensional subspaces of the full theory space. The flow behavior in the vicinity of the Gaussian fixed point and the correction given by the effective vertex expansion is also analyzed. The dynamical constrained flow allows us to identify the influence of the number of melonic interactions related to the existence of divergence at which the possible first order phase transition may be identified is studied. Comparing our results using the formalism of Callan Symanzik equation is also scrutinized.

We present a novel source of dark energy, which is motivated by the prevalence of hidden sectors in string theory models and is consistent with all of the proposed swampland conjectures. Thermal effects hold a light hidden sector scalar at a point in field space that is not a minimum of its zero temperature potential. This leads to an effective “cosmological constant,” with an equation of state $w=-1$, despite the scalar’s zero temperature potential having only a four-dimensional Minkowski or anti–de Sitter vacuum. For scalar masses $\lesssim \mu \mathrm{eV}$, which could be technically natural via sequestering, there are large regions of phenomenologically viable parameter space such that the induced vacuum energy matches the measured dark energy density. Additionally, in many models a standard cosmological history automatically leads to the scalar having the required initial conditions. We study the possible observational signals of such a model, including at fifth force experiments and through $\mathrm{\Delta }{N}_{\mathrm{eff}}$ measurements. Similar dynamics that are active at earlier times could resolve the tension between different measurements of $H_0$ and can lead to a detectable stochastic gravitational wave background.

In this work we study the growth of cold dark matter density perturbations in the nonlinear regime on a conformally coupled quintessence model in which the background is designed to mimic a $\mathrm{\Lambda }\mathrm{CDM}$ cosmology. The spherical collapse of overdense regions is analyzed. We highlight the role of the coupling on the overall dynamics, trace the evolution of the density contrast throughout the cosmic history and compute perturbative parameters such as the critical density contrast. We find that the coupling has the influence of delaying the collapse due to the slower growth of matter perturbations. We follow to compute the cluster number counts using the Press-Schechter and Sheth-Tormen mass functions. In both cases, the transfer of energy between the dark energy field and dark matter suppresses the number of objects at low redshifts and enhances the number at high redshifts. Finally, we compute the expected cluster number counts for the future eROSITA mission and the current South Pole Telescope survey.

Ultralight axions (ULAs) are a promising dark-matter candidate. ULAs may have implications for small-scale challenges to the $\mathrm{\Lambda }\mathrm{CDM}$ model and arise in string scenarios. ULAs are already constrained by cosmic microwave background (CMB) experiments and large-scale structure surveys, and will be probed with much greater sensitivity by future efforts. It is challenging to compute observables in ULA scenarios with sufficient speed and accuracy for cosmological data analysis because the ULA field oscillates rapidly. In past work, an effective fluid approximation has been used to make these computations feasible. Here this approximation is tested against an exact solution of the ULA equations, comparing the induced error of CMB observables with the sensitivity of current and future experiments. In the most constrained mass range for a ULA dark-matter component (${10}^{-27}\mathrm{eV}\le m_{\mathrm{ax}}\le {10}^{-25}\mathrm{eV}$), the induced bias on the allowed ULA fraction of dark matter from Planck data is less than $1\sigma$. In the cosmic-variance limit (including temperature and polarization data), the bias is $\lesssim 2\sigma$ for primary CMB anisotropies, with more severe biases (as high as $\sim 4\sigma$) resulting for less reliable versions of the effective fluid approximation. If all of the standard cosmological parameters are fixed by other measurements, the expected bias rises to $4-20\sigma$ (well beyond the validity of the Fisher approximation), though the required level of degeneracy breaking will not be achieved by any planned surveys.

We construct the relativistic standard steady, optically thick, cold, and geometrically thin accretion disk around a distorted Schwarzschild black hole. The distortion of this static and axially symmetric black hole solution is connected to an external distribution of matter. If the effects due to the rotation are negligible, this distribution can describe the exterior of any axially symmetric astrophysical model. Also, the distortion could be related to the outer parts of the accretion disk. We study the effects due to a distortion up to the quadrupole and compare the physical characteristics of this disk to the usual Schwarzschild case.