We study the effect of backreaction on the evaporation of quantum black holes. The method used is based on quantum tunneling formalism as proposed by Banerjee and Majhi [Phys. Lett. B 675, 243 (2009)]. We give a more realistic picture by considering the fact that a black hole looses its energy while modes are tunneled outside the event horizon. It is shown how the tunneling quantum field modes affect the geometry and how this change in geometry is arrested in the quantum field. Exploiting this, we calculate the modified (nonthermal) radiation spectrum and associating energy fluxes and discuss various issues related with these. The results obtained here are often expected on physical grounds, but, importantly, we find them in a quantitative manner.

We present a new class of black hole solutions in third-order Lovelock gravity whose horizons are Einstein space with two supplementary conditions on their Weyl tensors. The existence of these solutions is due to the higher curvature terms in Lovelock gravity. We find that while the solution of third-order Lovelock gravity with constant-curvature horizon in the absence of a mass parameter is the anti–de Sitter (AdS) metric, this kind of solution with nonconstant-curvature horizon is only asymptotically AdS and may have horizon. We also find that one may have an extreme black hole with nonconstant-curvature horizon whose Ricci scalar is zero or a positive constant, while there is no such black hole with constant-curvature horizon. Furthermore, the thermodynamics of the black holes in the two cases of constant- and nonconstant-curvature horizons are different drastically. Specially, we consider the thermodynamics of black holes with vanishing Ricci scalar and find that in contrast to the case of black holes of Lovelock gravity with constant-curvature horizon, the area law of entropy is not satisfied. Finally, we investigate the stability of these black holes both locally and globally and find that while the black holes with constant-curvature horizons are stable both locally and globally, those with nonconstant-curvature horizons have unstable phases.

We show that for any perfect fluid in a static spacetime, if the Einstein constraint equation is satisfied and the temperature of the fluid obeys Tolman’s law, then the other components of Einstein’s equation are implied by the assumption that the total entropy of the fluid achieves an extremum for fixed total particle number and for all variations of metric with certain boundary conditions. Conversely, one can show that the extrema of the total entropy of the fluid are implied by Einstein’s equation. Compared to previous works on this issue, we do not require spherical symmetry for the spacetime. Our results suggest a general and solid connection between thermodynamics and general relativity.

An excess of gamma rays at GeV energies has been pointed out in the Fermi-LAT data. This signal comes from a narrow region centred around the Galactic center and has been interpreted as possible evidence for light dark matter particles annihilating either into a mixture of leptons-antileptons and $b\overline{b}$ or into $b\overline{b}$ only. Focusing on the prompt gamma-ray emission, previous works found that the best fit to the data corresponds to annihilations proceeding predominantly into $b\overline{b}$. However, here we show that omitting the photon emission originating from primary and secondary electrons produced in dark matter annihilations, and undergoing diffusion through the Galactic magnetic field, can actually lead to the wrong conclusion. Accounting for this emission, we find that not only are annihilations of $\sim 10\mathrm{GeV}$ particles into a purely leptonic final state allowed, but the democratic scenario actually provides a better fit to the spectrum of the excess than the pure $b\overline{b}$ channel. We conclude our work with a discussion on constraints on these leptophilic scenarios based on the AMS data and the morphology of the excess.

We present up-to-date cosmological bounds on the sum of active neutrino masses as well as on extended cosmological scenarios with additional thermal relics, as thermal axions or sterile neutrino species. Our analyses consider all the current available cosmological data in the beginning of year 2014, including the very recent and most precise baryon acoustic oscillation measurements from the Baryon Oscillation Spectroscopic Survey. In the minimal three-active-neutrino scenario, we find $\sum m_{\nu }<0.22\mathrm{eV}$ at 95% C.L. from the combination of cosmic microwave background (CMB), baryon acoustic oscillation, and Hubble Space Telescope measurements of the Hubble constant. A nonzero value for the sum of the three active neutrino masses of $\sim 0.3\mathrm{eV}$ is significantly favored at more than three standard deviations when adding the constraints on ${\sigma }_8$ and ${\mathrm{\Omega }}_m$ from the Planck cluster catalog on galaxy number counts. This preference for nonzero thermal relic masses disappears almost completely in both the thermal axion and massive sterile neutrino schemes. Extra light species contribute to the effective number of relativistic degrees of freedom, parametrized via $N_{\text{eff}}$. We found that when the recent detection of B mode polarization from the BICEP2 experiment is considered, an analysis of the combined CMB data in the framework of $\mathrm{LCDM}+\mathrm{r}$ models gives $N_{\text{eff}}=3.90\pm 0.42$, suggesting the presence of an extra relativistic relic at more than 95% C.L. from CMB-only data.

In this paper we present a hierarchical data analysis pipeline for all-sky searches of continuous gravitational wave signals, like those emitted by spinning neutron stars asymmetric with respect to the rotation axis, with unknown position, rotational frequency, and spin-down. The core of the pipeline is an incoherent step based on a particularly efficient implementation of the Hough transform, which we call frequency-Hough, that maps the data time-frequency plane to the source frequency and spin-down plane for each fixed direction in the sky. Theoretical ROCs and sensitivity curves are computed and the dependency on various thresholds is discussed. A comparison of the sensitivity loss with respect to an “optimal” method is also presented. Several other novelties, with respect to other wide-parameter analysis pipelines, are also outlined. They concern, in particular, the construction of the grid in the parameter space, with over-resolution in frequency and parameter refinement, candidate selection, and various data cleaning steps that are introduced to improve search sensitivity and rejection of false candidates.

We consider conformal field theories in $1+1$ dimensions with $\mathcal{W}$-algebra symmetries, deformed by a chemical potential $\mu$ for the spin-three current. We show that the order ${\mu }^2$ correction to the Rényi and entanglement entropies of a single interval in the deformed theory, on the infinite spatial line and at finite temperature, is universal. The correction is completely determined by the operator product expansion of two spin-three currents, and by the expectation values of the stress tensor, its descendants and its composites, evaluated on the $n$-sheeted Riemann surface branched along the interval. This explains the recently found agreement of the order ${\mu }^2$ correction across distinct free field CFTs and higher spin black hole solutions holographically dual to CFTs with $\mathcal{W}$ symmetry.

As repeatedly speculated in the past, the linear polarization of the cosmic microwave background can be rotated via the Faraday effect. An economic explanation of the recent Bicep2 observations, not relying on long-wavelength tensor modes of the geometry, would stipulate that the detected B mode comes exclusively from a Faraday rotated E-mode polarization. We show hereunder that this interpretation is ruled out by the existing upper limits on the B-mode polarization obtained by independent experiments at observational frequencies much lower than the operating frequency of the Bicep2 experiment. We then derive the fraction of the observed B-mode polarization ascribable to the Faraday effect and suggest a dedicated experimental strategy for its detection.

We consider a model of neutrino mass based on $R$-parity-violating supersymmetry, with three ${\mu }_i$, relevant for bilinear $R$-parity-violating terms, and three ${\lambda }_{ijk}^{\prime }$, relevant for the trilinear terms. The present neutrino data, after a precise determination of the mixing angle ${\theta }_{13}$, severely constrain such models. We make a thorough study of one such class of models that may have interesting signatures at the upgraded LHC. In this class of models, the relevant trilinear couplings are of the form ${\lambda }_{i33}^{\prime }$, so if the lighter stop squark ${\tilde{t}}_1$ is the lightest supersymmetric particle, it will decay only through these couplings, giving rise to events with isolated hard leptons and jets. Even when ${\tilde{t}}_1$ is the next-to-lightest supersymmetric particle, it can decay via the tiny ${\lambda }^{\prime }$ couplings allowed by the neutrino data, although it may face stiff competition from some $R$-parity-conserving decay modes. Using a simple Pythia based simulation, we find that in both the cases the signal consisting of a pair of oppositely charged leptons ($ee$, $\mu \mu$ or $e\mu$) plus jets may be observable at the upgraded LHC experiments for a reasonable range of the ${\tilde{t}}_1$ mass.

In a class of Randall-Sundrum(RS) models, matter fermions and gauge bosons live in a five-dimensional bulk, while the Higgs boson lives in a four-dimensional visible brane. The Higgs boson can mix with a radion, by a Higgs-radion mixing term. It is difficult to directly discover the heavy Kaluza-Klein(KK) particles at the Large Hadron Collider(LHC), because the mass of the lightest KK particle is expected to be above 10 TeV to satisfy constraints from flavor changing neutral currents. Instead, the precision measurements of the Higgs sector at the high luminosity LHC(HL-LHC) and the International Linear Collider(ILC) is a promising way to observe the deviation originating from the Higgs-radion mixing and radiative corrections from the KK gauge bosons and matter fermions. For some cases, those effects are separately determined, providing valuable information on the model. We perform an extensive scan of the model parameters to see the expected deviations of the Higgs couplings. We also choose several reference points consistent with the current data to show the precision of the fundamental parameter measurements at the future colliders. We also study the radion-$Z$-$Z$ coupling in the model and discuss the role of the ILC for radion search.

We study the correlation of top asymmetries that are sensitive to the different origin of (a new contribution to) the total asymmetry: loop- or tree-level origins. We find that both the size and the sign of the correlation between total and $t\overline{t}j$ inclusive asymmetries are inherently different depending on the origin. We demonstrate the correlation by using the color-singlet $Z^{\prime }$ and the pure axigluon taken as representative models of loop- and tree-induced total asymmetries. We calculate the next-to-leading order QCD corrections to the $Z^{\prime }$ and perform Monte Carlo event generation. The correlation is understood in the QCD eikonal approximation using its color structure.

We study the dynamics and escape of charged particles initially orbiting a weakly magnetized Kerr black hole after they get kicked in the direction normal to the orbit. The case of neutral particles is analyzed first and the escape conditions are given analytically. A general analysis of charged particles innermost stable circular orbits is performed numerically. We then study the charged particles three-dimensional motion and give an effective condition for their escape. We also discuss how the black hole’s rotation affects the escape of charged particles and the chaoticness in their dynamics.

We show that theories having second-order field equations in the context of higher-dimensional modified gravity are not restricted to the family of Lovelock Lagrangians, but can also be obtained if no a priori assumption on the relation between the metric and affine structures of space-time is made (the Palatini approach). We illustrate this fact by considering the case of Palatini $f(R)$ gravities in five dimensions. Our results provide an alternative avenue to explore new domains of the AdS/CFT correspondence without resorting to ad hoc quasitopological constructions.

MOdified Gravity (MOG) is a covariant modification of Einstein’s general relativity. This theory is one of the current alternatives to dark matter models. We describe the dynamics of collisionless self-gravitating systems in the context of MOG. By studying the weak field approximation of this theory, we derive the equations governing the dynamics of the self-gravitating systems. More specifically, we consider the Jeans instability for self-gravitating fluid and stellar systems and derive new Jeans mass limit ${\tilde{M}}_J$ and wave-number ${\tilde{k}}_J$. Furthermore, considering the gravitational instability in star-forming regions, we show that MOG has not a significant difference with general relativity on this astrophysical scale. However, at larger scales, such as intergalactic space, MOG may lead to different galaxy- and structure-formation processes.

We show that in scalar field inflationary models, the loop corrections in reheating corresponding to the decay of the inflaton can cause nontrivial superhorizon evolution of the curvature perturbation. The effect turns out to be prominent when the decay occurs via parametric resonance, even indicating the breakdown of the perturbation theory, as we demonstrate in a specific model.

The spectral study of the HESS J1745-290 high-energy gamma-ray cutoff from the Galactic center is compatible with a signal of dark matter (DM) annihilation or decay. If this is the case, a neutrino flux from that source is also expected. We analyze the neutrino flux predicted by DM particles able to create the HESS J1745-290 gamma-rays observations. We focus on the electroweak and hadronic channels, which are favored by present measurements. In particular, we study DM annihilating into $W^{+}{W}^{-}$ and $u\overline{u}$ with DM masses of 48.8 and 27.9 TeV, respectively. We estimate the resolution angle and exposition time necessary to test the DM hypothesis as the origin of the gamma-ray signal.

Current gravitational-wave detectors rely on the use of Michelson interferometers. One crucial limitation of their sensitivity is the thermal noise of their optical components. Thus, for example, fluctuational deformations of the mirror surface are probed by a laser beam being reflected from the mirrors at normal incidence. Thermal noise models are well evolved for that case but mainly restricted to single reflections. In this work, we present the effect of two consecutive reflections under a non-normal incidence onto mirror thermal noise. This situation is inherent to detectors using a geometrical folding scheme such as GEO 600. We revise in detail the conventional direct noise analysis scheme to the situation of non-normal incidence allowing for a modified weighting function of mirror fluctuations. An application of these results to the GEO 600 folding mirror for Brownian, thermoelastic, and thermorefractive noise yields an increase of displacement noise amplitude by 20% for most noise processes. The amplitude of thermoelastic substrate noise is increased by a factor of 4 due to the modified weighting function. Thus, the consideration of the correct weighting scheme can drastically alter the noise predictions and demands special care in any thermal noise design process.

We analyze the many-flavor phase diagram of quantum electrodynamics (QED) in $2+1$ (Euclidean) space-time dimensions. We compute the critical flavor number above which the theory is in the quasiconformal massless phase. For this, we study the renormalization group fixed-point structure in the space of gauge interactions and pointlike fermionic self-interactions, the latter of which are induced dynamically by fermion-photon interactions. We find that a reliable estimate of the critical flavor number crucially relies on a careful treatment of the Fierz ambiguity in the fermionic sector. Using a Fierz-complete basis, our results indicate that the phase transition towards a chirally broken phase occurring at small flavor numbers could be separated from the quasiconformal phase at larger flavor numbers, allowing for an intermediate phase which is dominated by fluctuations in a vector channel. If these interactions approach criticality, the intermediate phase could be characterized by a Lorentz-breaking vector condensate.

Candidates for unification of the electroweak and strong interactions include the grand unified groups SU(5), SO(10), and the exceptional group ${\mathrm{E}}_6$. The 27-dimensional fundamental representation of ${\mathrm{E}}_6$ contains exotic fermions, including weak isosinglet quarks of charge $-1/3$, vectorlike weak isodoublet leptons, and neutral leptons which are singlets under both left-handed and right-handed SU(2). These last are candidates for light “sterile” neutrinos, hinted at by some recent short-baseline neutrino experiments.In order to accommodate three families of quarks and charged leptons, an ${\mathrm{E}}_6$ model must contain three 27-plets, each of which contains a sterile neutrino candidate $n$. The mixing pattern within a 27-plet is described, and experimental consequences are discussed.

We present simplified models for the galactic center $\gamma$-ray excess where Dirac dark matter annihilates into pairs or triplets of on-shell bosonic mediators to the standard model. These annihilation modes allow the dark matter mass to be heavier than those of conventional effective theories for the $\gamma$-ray excess. Because the annihilation rate is set by the dark matter–mediator coupling, the standard model coupling can be made parametrically small to “hide” the dark sector by suppressing direct detection and collider signals. We explore the viability of these models as a thermal relic and on the role of the mediators for controlling the $\gamma$-ray spectral shape. We comment on ultraviolet completions for these simplified models and novel options for standard model final states.