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In this paper, we propose a novel expansion to compute the large interval limit of the Rényi entropy of 2D conformal field theory (CFT) at high temperature. Via the replica trick, the single interval Rényi entropy of 2D CFT at finite temperature could be read from the partition function on w-sheeted torus connected with each other along a branch cut. We calculate the partition function by inserting a complete basis across the branch cut. Because of the monodromy condition across the branch cut in the large interval limit, the basis of the states should be the ones in the twist sector. We study the twist sector of a general module of CFT and find that there is a one-to-one correspondence between the twist sector states and the normal sector states. As an application, we revisit the noncompact free scalar theory and discuss the large interval limit of the Renyi entropy of this theory by using our proposal. We find complete agreement in the leading and nextleading orders with direct expansion of the exact partition function. Moreover, we prove the relation (10) between thermal entropy and the entanglement entropy for a generic CFT with discrete spectrum. [ABSTRACT FROM AUTHOR]

In this paper, we study the holographic Rényi entropy of a large interval on a circle at high temperature for the two-dimensional conformal field theory (CFT) dual to pure AdS3 gravity. In the field theory, the Rényi entropy is encoded in the CFT partition function on n-sheeted torus connected with each other by a large branch cut. As proposed by Chen and Wu [Large interval limit of Rényi entropy at high temperature, arXiv:1412.0763], the effective way to read the entropy in the large interval limit is to insert a complete set of state bases of the twist sector at the branch cut. Then the calculation transforms into an expansion of four-point functions in the twist sector with respect to .... By using the operator product expansion of the twist operators at the branch points, we read the first few terms of the Rényi entropy, including the leading and next-to-leading contributions in the large central charge limit. Moreover, we show that the leading contribution is actually captured by the twist vacuum module. In this case by the Ward identity the four-point functions can be derived from the correlation function of four twist operators, which is related to double interval entanglement entropy. Holographically, we apply the recipe in [T. Faulkner, The entanglement Rényi entropies of disjoint intervals in AdS/CFT, arXiv:1303.7221] and [T. Barrella et al., Holographic entanglement beyond classical gravity, J. High Energy Phys. 09 (2013) 109] to compute the classical Rényi entropy and its one-loop quantum correction, after imposing a new set of monodromy conditions. The holographic classical result matches exactly with the leading contribution in the field theory up to ... and l6, while the holographical one-loop contribution is in exact agreement with next-to-leading results in field theory up to ... and l4 as well. [ABSTRACT FROM AUTHOR]

In this paper, we reconsider the single-interval Rényi entropy of a free compact scalar on a torus. In this case, the contribution to the entropy could be decomposed into a classical part and a quantum part. The classical part includes the contribution from all the saddle points, while the quantum part is universal. After considering a different monodromy condition from the one in the literature, we reevaluate the classical part of the Rényi entropy. Moreover, we expand the entropy in the low-temperature limit and find the leading thermal correction term, which is consistent with the universal behavior suggested in [J. Cardy and C. P. Herzog, Phys. Rev. Lett. 112, 171603 (2014)]. Furthermore, we investigate the large-interval behavior of the entanglement entropy and show that the universal relation between the entanglement entropy and thermal entropy holds in this case. [ABSTRACT FROM AUTHOR]

Inspired by the holographic computation of large interval entanglement entropy of two dimensional conformal field theory at high temperature, it was proposed that the thermal entropy is related to the entanglement entropy as Sth=liml→0(SEE(R-l)-SEE(l)). In this letter, we prove this relation for 2D CFT with discrete spectrum in two different ways. Moreover we discuss this relation for a 2Dnoncompact free scalar, which is a gapless CFT with continuous spectrum. We show that it could be recovered, after appropriately regularizing the theory. [ABSTRACT FROM AUTHOR]

The discovery of gravitational waves (GWs) from the compact binary components by LIGO/Virgo Collaboration provides an unprecedented opportunity for testing gravity in the strong and highly dynamical field regime of gravity. Currently a lot of model-independent tests have been performed by LIGO/Virgo Collaboration and no any significant derivation from general relativity has been found. In this paper, we study the parity violating effects on the propagation of GWs in the Nieh-Yan modified teleparallel gravity, a theory which modifies general relativity by a parity violating Nieh-Yan term. We calculate the corresponding parity violating waveform of GWs produced by the coalescence of compact binaries. By comparing the two circular polarization modes, we find the effects of the velocity birefringence of GWs in their propagation caused by the parity violation due to the Nieh-Yan term, which are explicitly presented in the GW waveforms by the phase modification. With such phase modifications to the waveform, we perform the full Bayesian inference with the help of the open source software Bilby on the GW events of binary black hole merges (BBH) in the LIGO-Virgo catalogs GWTC-1 and GWTC-2. We do not find any significant evidence of parity violation due to the parity violating Nieh-Yan term and thus place an upper bound on the energy scale MPV<6.5×10-42 GeV at 90% confidence level, which represents the first constraint on the Nieh-Yan modified teleparallel gravity so far. [ABSTRACT FROM AUTHOR]

In this paper, we study the shadow cast by two types of charged and slowly rotating black holes in the Einstein-Æther theory of gravity. These two types of black holes correspond to two specific combinations of the coupling constants of the æther field, i.e., c14=0 but c123≠0 for the first type and c123=0 for the second type. For both types of black holes, in addition to the mass and charge of the black holes, we show that the presence of the æther field can also affect the size of the shadow. For the first type of black hole, it is shown that the shadow size increases with the parameter c13, while for the second type of black hole, the shadow size still increases with c13 but decreases with the parameter c14. With these properties of the æther parameters, we also discuss the observational constraints on these parameters by using the data of the first black hole image by the Event Horizon Telescope. In addition, we also explore the effect of the æther field on the deflection angle of light and the time delay by using the Gauss-Bonnet theorem. It is shown that, for a specific combination c123=0, the deflection angle/time delay is slightly affected by the æther parameter c13 at the leading order. [ABSTRACT FROM AUTHOR]

While loop quantum cosmology predicts a robust quantum bounce of the background evolution of a Friedmann-Robertson-Walker spacetime prior to the standard slow-roll inflation, whereby the big bang singularity is resolved, there are several different quantization procedures to cosmological perturbations, for instance, the deformed algebra, dressed metric, and hybrid quantizations. This paper is devoted to studying the quantum bounce effects of primordial perturbations in the hybrid approach. The main discrepancy of this approach is the effective positive mass at the quantum bounce for the evolution of the background that is dominated by the kinetic energy of the inflaton field at the bounce, while this mass is always nonpositive in the dressed metric approach. It is this positivity of the effective mass that violates the adiabatic evolution of primordial perturbations at the initial moments of the quantum bounce. With the assumption that the evolution of the background is dominated by the kinetic energy of the inflaton at the bounce, we find that the effective potentials for both scalar and tensor perturbations can be well approximately described by a Pöschl-Teller potential, which allows us to find analytical solutions of perturbations, and from these analytical expressions we are able to study the nonadiabatic evolution of primordial perturbations in detail. In particular, we derive their quantum bounce effects and investigate their observational constraints. In addition, the impacts of quantum bounce effects on the non-Gaussianity and their implication on the explanations of the observed power asymmetry in the cosmic microwave background are also explored. [ABSTRACT FROM AUTHOR]

The slow-roll inflation for a single scalar field that couples to the Gauss-Bonnet (GB) term represents an important higher-order curvature correction inspired by string theory. With the arrival of the era of precision cosmology, it is expected that the high-order corrections become more and more important. In this paper we study the observational predictions of the slow-roll inflation with the GB term by using the third-order uniform asymptotic approximation method. We calculate explicitly the primordial power spectra, spectral indices, running of the spectral indices for both scalar and tensor perturbations, and the ratio between tensor and scalar spectra. These expressions are all written in terms of the Hubble and GB coupling flow parameters and expanded up to the next-to-leading order in the slow-roll expansions so they represent the most accurate results obtained so far in the literature. In addition, by studying the theoretical predictions of the scalar spectral index and the tensor-to-scalar ratio with the Planck 2015 constraints in a model with power-law potential and GB coupling, we show that the second-order corrections are important in the future measurements. We expect that the understanding of the GB corrections in the primordial spectra and their constraints by forthcoming observational data will provide clues for the UV complete theory of quantum gravity, such as the string/M-theory. [ABSTRACT FROM AUTHOR]

In this paper, we construct an effective rotating loop quantum black hole (LQBH) solution, starting from the spherical symmetric LQBH by applying the Newman-Janis algorithm modified by Azreg-Aïnou's noncomplexification procedure, and study the effects of loop quantum gravity (LQG) on its shadow. Given the rotating LQBH, we discuss its horizon, ergosurface, and regularity as r→0. Depending on the values of the specific angular momentum a and the polymeric function P arising from LQG, we find that the rotating solution we obtained can represent a regular black hole, a regular extreme black hole, or a regular spacetime without horizon (a non-black-hole solution). We also study the effects of LQG and rotation, and show that, in addition to the specific angular momentum, the polymeric function also causes deformations in the size and shape of the black hole shadow. Interestingly, for a given value of a and inclination angle θ0, the apparent size of the shadow monotonically decreases, and the shadow gets more distorted with increasing P. We also consider the effects of P on the deviations from the circularity of the shadow, and find that the deviation from circularity increases with increasing P for fixed values of a and θ0. Additionally, we explore the observational implications of P in comparing with the latest Event Horizon Telescope observation of the supermassive black hole, M87*. The connection between the shadow radius and quasinormal modes in the eikonal limit as well as the deflection of massive particles are also considered. [ABSTRACT FROM AUTHOR]

In this paper, we study the preinflationary dynamics for the power-law potential [V(ϕ)∝ϕn] with n<2 in the framework of loop quantum cosmology. When the kinetic energy of the inflaton initially dominates, the evolution of the Universe can always be divided into three different phases prior to preheating: bouncing, transition, and slow-roll inflation. During the bouncing phase, the evolution of the expansion factor is independent not only on the initial conditions but also the inflationary potentials and is given explicitly by an analytical solution. In contrast, for the potential energy dominated initial conditions, this universality is lost. We also obtain the total number of e-folds during the slow-roll inflation, whereby physically viable models are identified. In addition, we present phase space analysis for the inflationary potentials under consideration and compare our results with the ones obtained previously for different potentials. [ABSTRACT FROM AUTHOR]

In this paper, we present all [(d + 1) + 1]-dimensional static diagonal vacuum solutions of the nonprojectable Horava-Lifshitz gravity in the IR limit and show that they give rise to very rich Lifshitz-type structures, depending on the choice of the free parameters of the solutions. These include the Lifshitz space-times with or without hyperscaling violation, Lifshitz solitons, and black holes. Remarkably, even the theory breaks explicitly the Lorentz symmetry and allows genetically instantaneous propagations, universal horizons still exist, which serve as one-way membranes for signals moving with any large velocities. In particular, particles even with infinitely large velocities would just move around on these boundaries and would not be able to escape to infinity. Another remarkable feature appearing in the Lifshitz-type space-times is that the dynamical exponent z can take its values only in the ranges 1 ≤ z < 2 for d ≥ 3 and 1 ≤ z < ∞ for d = 2, due to the stability and ghost-free conditions of the theory. [ABSTRACT FROM AUTHOR]

In this paper, we obtain an effective metric describing a regular and rotating magnetic black hole (BH) solution with a Yang-Mills electromagnetic source in Einstein-Yang-Mills (EYM) theory using the Newman-Janis (NJ) algorithm via the noncomplexification radial coordinate procedure. We then study the BH shadow and the quasinormal modes (QNMs) for massless scalar and electromagnetic fields and the quasiperiodic oscillations (QPOs). To this end, we also study the embedding diagram for the rotating EYM BH. The energy conditions, shadow curvature radius, topology, and the dynamical evolution of scalar and electromagnetic perturbations using the time domain integration method are investigated. We show that the shadow radius decreases by increasing the magnetic charge, while the real part of QNMs of scalar and electromagnetic fields increases by increasing the magnetic charge. This result is consistent with the inverse relation between the shadow radius and the real part of QNMs. In addition, we have studied observational constraints on the EYM parameter via frequency analysis of QPOs and the EHT data of shadow cast by the M87 central black hole. We also find that the decaying rate of the EYM BH is slower than that of the neutral and ends up with a tail. We argue that the rotating EYM black hole can be distinguished from the Kerr-Newman black hole with a magnetic charge based on the difference between the angular diameters of their shadows. [ABSTRACT FROM AUTHOR]

In this paper, we study the motion of test particles around two exact charged black hole solutions in Einstein-Æther theory. Specifically, we first consider the quasiperiodic oscillations (QPOs) and their resonances generated by the particle moving in the Einstein-Æther black hole and then turn to study the periodic orbits of the massive particles. For QPOs, we drop the usually adopted assumptions νU=νθ, νL=νr, and νU/νL=3/2 with νU (νL) and νr (νθ) being the upper (lower) frequency of QPOs and radial (vertical) epicyclic frequency of the orbiting particles, respectively. Instead, we put-forward a new working ansatz for which the Keplerian radius is much closer to that of the innermost stable circular orbit and explore in detail the effects of the Æther field on the frequencies of QPOs. We then realize good curves for the frequencies of QPOs, which fit to data of three microquasars very well by ignoring any effects of rotation and magnetic fields. The innermost stable circular orbits (isco) of timelike particles are also analyzed, and we find the isco radius increases with increasing c13 for the first type black hole while decreases with increasing c14 for the second one. We also obtain several periodic orbits and find that they share similar taxonomy schemes as the periodic equatorial orbits in the Schwarzschild/Kerr metrics, in addition to exact solutions for certain choices of the Einstein-Æ ther parameters. The equations for null geodesics are also briefly considered, where we study circular photon orbits and bending angles for gravitational lensing. [ABSTRACT FROM AUTHOR]

In this paper, we use a suitable conformal rescaling to construct static and rotating regular black holes in conformal massive gravity. The new metric is characterized by the mass M, the "scalar charge" Q, the angular momentum parameter a, the "hair parameter" λ, and the conformal scale factor encoded in the parameter L. We explore the shadow images and the deflection angles of relativistic massive particles in the spacetime geometry of a rotating regular black hole. For λ≠0 and Q>0, the shadow is larger than the shadow of a Kerr black hole. In particular, if λ<0, the shadow radius increases considerably. For λ≠0 and Q<0, the shadow is smaller than the shadow of a Kerr black hole. Additionally, we put observational constraints on the parameter Q using the latest Event Horizon Telescope observation of the supermassive black hole M87*. Lastly, using the Gauss-Bonnet theorem, we show that the deflection angle of massive particles is strongly affected by the parameter L. The deflection angle might be used to distinguish rotating regular black holes from rotating singular black holes. [ABSTRACT FROM AUTHOR]