We consider curvature-squared corrections to Einstein-Hilbert gravity action in the form of a Gauss-Bonnet term in $D>4$ dimensions. In this theory, we study the thermodynamics of charged static black holes with anti–de Sitter (AdS) asymptotics, and whose electric field is described by nonlinear electrodynamics. These objects have received considerable attention in recent literature on gravity/gauge dualities. It is well-known that, within the framework of anti–de Sitter/conformal field theory (AdS/CFT) correspondence, there exists a nonvanishing Casimir contribution to the internal energy of the system, manifested as the vacuum energy for global AdS spacetime in odd dimensions. Because of this reason, we derive a quantum statistical relation directly from the Euclidean action and not from the integration of the first law of thermodynamics. To this end, we employ a background-independent regularization scheme which consists, in addition to the bulk action, of counterterms that depend on both extrinsic and intrinsic curvatures of the boundary (Kounterterm series). This procedure results in a consistent inclusion of the vacuum energy and chemical potential in the thermodynamic description for Einstein-Gauss-Bonnet AdS gravity regardless of the explicit form of the nonlinear electrodynamics Lagrangian.

We discuss Hawking radiation from a five-dimensional squashed Kaluza-Klein black hole on the basis of the tunneling mechanism. A simple method, which was recently suggested by Umetsu, may be used to extend the original derivation by Parikh and Wilczek to various black holes. That is, we use the two-dimensional effective metric, which is obtained by the dimensional reduction near the horizon, as the background metric. Using the same method, we derive both the desired result of the Hawking temperature and the effect of the backreaction associated with the radiation in the squashed Kaluza-Klein black hole background.

Cosmological analyses based on currently available observations are unable to rule out a sizeable coupling between dark energy and dark matter. However, the signature of the coupling is not easy to grasp, since the coupling is degenerate with other cosmological parameters, such as the dark energy equation of state and the dark matter abundance. We discuss possible ways to break such degeneracy. Based on the perturbation formalism, we carry out the global fitting by using the latest observational data and get a tight constraint on the interaction between dark sectors. We find that the appropriate interaction can alleviate the coincidence problem.

In the Hamiltonian formulation of general relativity, the energy associated to an asymptotically flat space-time with metric $g_{\mu \nu }$ is related to the Hamiltonian $H_{\mathrm{GR}}$ by $E=H_{\mathrm{GR}}[g_{\mu \nu }]-H_{\mathrm{GR}}[{\eta }_{\mu \nu }]$, where the subtraction of the flat-space contribution is necessary to get rid of an otherwise divergent boundary term. This classic result indicates that the energy associated to flat space does not gravitate. We apply the same principle to study the effect of the zero-point fluctuations of quantum fields in cosmology, proposing that their contribution to cosmic expansion is obtained computing the vacuum energy of quantum fields in a Friedmann-Robertson-Walker space-time with Hubble parameter $H(t)$ and subtracting from it the flat-space contribution. Then the term proportional to ${\Lambda }_c^4$ (where ${\Lambda }_c$ is the UV cutoff) cancels, and the remaining (bare) value of the vacuum energy density is proportional to ${\Lambda }_c^2{H}^2(t)$. After renormalization, this produces a renormalized vacuum energy density $\sim M^2{H}^2(t)$, where $M$ is the scale where quantum gravity sets is, so for $M$ of the order of the Planck mass a vacuum energy density of the order of the critical density can be obtained without any fine-tuning. The counterterms can be chosen so that the renormalized energy density and pressure satisfy $p=w\rho$, with $w$ a parameter that can be fixed by comparison to the observed value, so, in particular, one can choose $w=-1$. An energy density evolving in time as $H^2(t)$ is however observationally excluded as an explanation for the dominant dark energy component that is responsible for the observed acceleration of the Universe. We rather propose that zero-point vacuum fluctuations provide a new subdominant “dark” contribution to the cosmic expansion that, for a UV scale $M$ slightly smaller than the Planck mass, is consistent with existing limits and potentially detectable.

In this brief report, we propose a new definition of charge asymmetry in top pair production at the LHC, namely, the edge charge asymmetry (ECA). ECA utilizes the information of drifting direction only for single top (or antitop) with hadronic decay. Therefore, ECA can be free from the uncertainty arising from the missing neutrino in the $t\overline{t}$ event reconstruction. Moreover, rapidity $Y$ of top (or antitop) is required to be greater than a critical value $Y_{\mathrm{C}}$ in order to suppress the symmetric $t\overline{t}$ events mainly due to the gluon-gluon fusion process. In this paper, ECA is calculated up to next-to-leading order QCD in the standard model and the choice of the optimal $Y_{\mathrm{C}}$ is investigated.

We provide a theoretical update of the calculations of the ${\pi }^0{\gamma }^{*}\gamma$ form factor in the light cone sum rules framework, including up to six polynomials in the conformal expansion of the pion distribution amplitude and taking into account twist-six corrections related to the photon emission at large distances. The results are compared with the calculations of the $B\to \pi \ell \nu$ decay and pion electromagnetic form factors in the same framework. Our conclusion is that the recent BABAR measurements of the ${\pi }^0{\gamma }^{*}\gamma$ form factor at large momentum transfers [B. Aubert et al. (The BABAR Collaboration), Phys. Rev. D 80, 052002 (2009)] are consistent with QCD, although they do suggest that the pion distribution amplitude may have more structure than usually assumed.

We derive a factorization theorem for the differential distributions of electroweak gauge bosons in Drell-Yan processes, valid at low transverse momentum, using the soft-collinear effective theory. We present the next-to-leading logarithmic transverse momentum distribution for the Z-boson and find good agreement with Tevatron data collected by the CDF and D0 collaborations. We also give predictions for the Higgs boson differential distributions at next-to-leading logarithmic accuracy based on a factorization theorem derived in earlier work. We derive formulas for all quantities needed to study low transverse momentum production of color-neutral particles within the effective theory. This effective field theory approach is free of Landau poles and can be formulated entirely in momentum space. Consequently, our results are free of the Landau-pole prescriptions necessary in the standard approach.

We report a study of the decays $B\to D_{s1}(2536{)}^{+}{\overline{D}}^{(*)}$, where ${\overline{D}}^{(*)}$ is ${\overline{D}}^0$, $D^{-}$ or $D^{*-}$, using a sample of $657\times {10}^{6}B\overline{B}$ pairs collected at the ${\rm Y}(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. The branching fractions of the decays $B^{+}\to D_{s1}(2536{)}^{+}{\overline{D}}^0$, $B^0\to D_{s1}(2536{)}^{+}{D}^{-}$ and $B^0\to D_{s1}(2536{)}^{+}{D}^{*-}$ multiplied by that of $D_{s1}(2536{)}^{+}\to (D^{*0}{K}^{+}+D^{*+}{K}^0)$ are found to be $(3.97\pm 0.85\pm 0.56)\times {10}^{-4}$, $(2.75\pm 0.62\pm 0.36)\times {10}^{-4}$ and $(5.01\pm 1.21\pm 0.70)\times {10}^{-4}$, respectively. The ratio $\mathcal{B}(D_{s1}\to D^{*0}{K}^{+})/\mathcal{B}(D_{s1}\to D^{*+}{K}^0)$ is measured to be $0.88\pm 0.24\pm 0.08$.

The effective field theory of massive gravity has long been formulated in a generally covariant way [N. Arkani-Hamed, H. Georgi, and M. D. Schwartz, Ann. Phys. (N.Y.) 305, 96 (2003).]. Using this formalism, it has been found recently that there exists a class of massive nonlinear theories that are free of the Boulware-Deser ghosts, at least in the decoupling limit [C. de Rham and G. Gabadadze, Phys. Rev. D 82, 044020 (2010).]. In this work we study other recently proposed models that go under the name of “gravitational Higgs theories” [A. H. Chamseddine and V. Mukhanov, J. High Energy Phys. 08 (2010) 011.]. We show that these models, although seemingly different from the effective field theories of massive gravity, are in fact equivalent to them. Furthermore, based on the results obtained in the effective field theory approach, we conclude that the gravitational Higgs theories need the same adjustment of the Lagrangian to avoid the ghosts. We also show the equivalence between the noncovariant mode decomposition used in the Higgs theories, and the covariant Stückelberg parametrization adopted in the effective field theories, thus proving that the presence or absence of the ghost is independent of the parametrization used in either theory.

Recently there has been progress on the computation of two- and three-point correlation functions with two heavy states via semiclassical methods. We extend this analysis to the case of ${\mathrm{AdS}}_4\times C{P}^3$, and examine the suggested procedure for the case of several simple string solutions. By making use of AdS/CFT duality, we derive the relevant correlation functions of operators belonging to the dual $\mathcal{N}=6$ Chern-Simons gauge theory.

We investigate the holographic superconductors in Gauss-Bonnet gravity with Born-Infeld electrodynamics. We find that the Gauss-Bonnet constant, the model parameters, and the Born-Infeld coupling parameter will affect the formation of the scalar hair, the transition point of the phase transition from the second order to the first order, and the relation connecting the gap frequency in conductivity with the critical temperature. The combination of Gauss-Bonnet gravity and the Born-Infeld electrodynamics provides richer physics in the phase transition and the condensation of the scalar hair.

We study black hole phase transitions in (deformed) Hořava-Lifshitz (H-L) gravity, including the charged/uncharged topological black holes and KS black hole. Stability analysis and state space geometry are both used. We find interesting phase structures in these black holes, some of the properties are never observed in Einstein gravity. Particularly, the stability properties of black holes in H-L gravity with small radius change dramatically, which can be considered as a leak of information about the small scale behavior of spacetime. A new black hole local phase transition in H-L gravity which cannot be revealed by thermodynamical metrics has been found. There is an infinite discontinuity at the specific heat curve for charged black hole in H-L gravity with hyperbolic event horizon. However, this discontinuity does not have a corresponding curvature singularity of thermodynamical metrics. Our results may provide new insights towards a better understanding of the H-L gravity, as well as black hole thermodynamics.

The accelerated expansion of the Universe together with its present day isotropy has posed an interesting challenge to the numerous model theories presented over the years to describe them. In this paper, we address the above questions in the context of a braneworld model where the Universe is filled with Born-Infeld matter. We show that in such a model, the Universe evolves from a highly anisotropic state to its present isotropic form, which has entered an accelerated expanding phase.

We present a family of dynamic rotating cylindrically symmetric Ricci-flat gravitational fields whose geodesic motions have the structure of gravitomagnetic jets. These correspond to helical motions of free test particles up and down parallel to the axis of cylindrical symmetry and are reminiscent of the motion of test charges in a magnetic field. The speed of a test particle in a gravitomagnetic jet asymptotically approaches the speed of light. Moreover, numerical evidence suggests that jets are attractors. The possible implications of our results for the role of gravitomagnetism in the formation of astrophysical jets are briefly discussed.

In this paper the possibility of generating large scale curvature perturbations induced from the entropic perturbations during the waterfall phase transition of the standard hybrid inflation model is studied. We show that whether or not appreciable amounts of large scale curvature perturbations are produced during the waterfall phase transition depends crucially on the competition between the classical and the quantum mechanical backreactions to terminate inflation. If one considers only the classical evolution of the system, we show that the highly blue-tilted entropy perturbations induce highly blue-tilted large scale curvature perturbations during the waterfall phase transition which dominate over the original adiabatic curvature perturbations. However, we show that the quantum backreactions of the waterfall field inhomogeneities produced during the phase transition dominate completely over the classical backreactions. The cumulative quantum backreactions of very small scale tachyonic modes terminate inflation very efficiently and shut off the curvature perturbation evolution during the waterfall phase transition. This indicates that the standard hybrid inflation model is safe under large scale curvature perturbations during the waterfall phase transition.

We find the natural embedding of the ($R+R^2$) inflationary model into the recently constructed $F(\mathcal{R})$ supergravity. It gives a simple and viable realization of chaotic inflation in supergravity. The only requirement for a slow-roll inflation is the existence of the ${\mathcal{R}}^3$ term with an anomalously large coefficient in Taylor expansion of the $F(\mathcal{R})$ function.

It is shown that Schwarzschild black hole and de Sitter solutions exist as exact solutions of a recently proposed relativistic covariant formulation of (power-counting) renormalizable gravity with a fluid. The formulation without a fluid is presented here too. The stability of the solutions is studied and their corresponding entropies are computed by using the covariant Wald method. The area law is shown to hold both for the Schwarzschild and for the de Sitter solutions found, confirming that, for the $\beta =1$ case, one is dealing with a minimal modification of general relativity.