We study the stability of AdS black holes rotating in a single two-plane for tensor-type gravitational perturbations in $D>6$ space-time dimensions. First, by an analytic method, we show that there exists no unstable mode when the magnitude $a$ of the angular momentum is smaller than $r_h^2/R$, where $r_h$ is the horizon radius and $R$ is the AdS curvature radius. Then, by numerical calculations of quasinormal modes, using the separability of the relevant perturbation equations, we show that an instability occurs for rapidly rotating black holes with $a>r_h^2/R$, although the growth rate is tiny (of order ${10}^{-12}$ of the inverse horizon radius). We give numerical evidence indicating that this instability is caused by superradiance.

The results of a recent paper [Phys. Rev. D 78, 123521 (2008)] are generalized. A more detailed proof is presented that under essentially all conditions, the nonlinear classical equations governing matter and gravitation in cosmology have “adiabatic” solutions in which, far outside the horizon, in a suitable gauge, the reduced spatial metric $g_{ij}(\mathbf{x},t)/a^2(t)$ becomes a time-independent function ${\mathcal{G}}_{ij}(\mathbf{x})$, and all perturbations to the other metric components and to all matter variables vanish. The corrections are of order $a^{-2}$, and their $\mathbf{x}$ dependence is now explicitly given in terms of ${\mathcal{G}}_{ij}(\mathbf{x})$ and its derivatives. The previous results for the time dependence of the corrections to $g_{ij}(\mathbf{x},t)/a^2(t)$ in the case of multiscalar field theories are now shown to apply for any theory whose anisotropic inertia vanishes to order $a^{-2}$. Further, it is shown that the adiabatic solutions are attractive as $a$ becomes large for the case of single-field inflation and now also for thermal equilibrium with no nonzero conserved quantities, and the $O(a^{-2})$ corrections to the other dynamical variables are explicitly calculated in both cases.

Measurements of baryonic acoustic oscillations (BAOs) in galaxy surveys have been recognized as a powerful tool for constraining dark energy. However, this method relies on the knowledge of the size of the acoustic horizon at recombination derived from cosmic microwave background (CMB) anisotropy measurements. This estimate is typically derived assuming a standard recombination scheme; additional radiation sources can delay recombination altering the cosmic ionization history and the cosmological inferences drawn from CMB and BAO data. In this paper we quantify the effect of delayed recombination on the determination of dark energy parameters from future BAO surveys such as the Baryon Oscillation Spectroscopic Survey and the Wide-Field Multi-Object Spectrograph. We find the impact to be small but still not negligible. In particular, if recombination is nonstandard (to a level still allowed by CMB data), but this is ignored, future surveys may incorrectly suggest the presence of a redshift-dependent dark energy component. On the other hand, in the case of delayed recombination, adding to the analysis one extra parameter describing deviations from standard recombination does not significantly degrade the error bars on dark energy parameters and yields unbiased estimates. This is due to the CMB-BAO complementarity.

We consider corrections to the ratio of the shear viscosity to the entropy density in strongly coupled non-Abelian plasmas using the AdS/CFT correspondence. In particular, higher-derivative terms with the five-form Ramond-Ramond flux, which have been ignored in all previous calculations, are included. This provides the first reliable calculation of the leading order correction in the inverse ’t Hooft coupling to the celebrated result $\eta /s=1/4\pi$. The leading correction in inverse powers of the number of colors is computed. Our results hold very generally for quiver gauge theories with an internal manifold $L_{pqr}$ in the holographic dual. Our analysis implies that any thermal properties, e.g., all hydrodynamic quantities in these theories, will not be affected by the five-form flux terms at this order.

In SO(10) grand unified theories the hierarchy which is present in the Dirac mass term of the neutrinos is generically as strong as the one in the up-type quark mass term. We propose a mechanism to partially or completely cancel this hierarchy in the light neutrino mass matrix in the seesaw context. The two main ingredients of the cancellation mechanism are the existence of three fermionic gauge singlets and of a discrete flavor symmetry $G_f$ which is broken at a higher scale than SO(10). Two realizations of the cancellation mechanism are presented. The realization based on the Frobenius group $T_7\simeq Z_7⋊Z_3$ leads to a partial cancellation of the hierarchy and relates maximal $2-3$ lepton mixing with the geometric hierarchy of the up-quark masses. In the realization with the group $\Sigma (81)$ the cancellation is complete and tribimaximal lepton mixing is reproduced at the lowest order. In both cases, to fully accommodate the leptonic data we take into account additional effects such as effects of higher-dimensional operators involving more than one flavon. The heavy neutral fermion mass spectra are considered. For both realizations we analyze the flavon potential at the renormalizable level as well as ways to generate the Cabibbo angle.

The quark number susceptibility is expressed as an integral in terms of dressed quark propagator and dressed vector vertex. It is then investigated with the latter two- and three-point functions confronted with a Dyson-Schwinger equation model which accommodates both finite temperature and baryon chemical potential. The critical end point in the phase diagram is identified and the behavior of the quark number susceptibility around the critical end point is highlighted. The qualitative features found agree with recent lattice QCD simulation results.

Recently there has been much progress in building models of gauge mediation, often with predictions different than those of minimal gauge mediation. Meade, Seiberg, and Shih have characterized the most general spectrum which can arise in gauge-mediated models. We discuss some of the challenges of building models of general gauge mediation, especially the problem of messenger parity and issues connected with $R$ symmetry breaking and $CP$ violation. We build a variety of viable, weakly coupled models which exhibit some or all of the possible low energy parameters.

In the minimal supersymmetric standard model (the MSSM), the electroweak symmetry is restored as supersymmetry-breaking terms are turned off. We describe a generic extension of the MSSM where the electroweak symmetry is broken in the supersymmetric limit. We call this limit the “sEWSB” phase, short for supersymmetric electroweak symmetry breaking. We define this phase in an effective field theory that only contains the MSSM degrees of freedom. The sEWSB vacua naturally have an inverted scalar spectrum, where the heaviest $CP$-even Higgs state has standard model-like couplings to the massive vector bosons; experimental constraints in the scalar Higgs sector are more easily satisfied than in the MSSM.

We study two-photon exchange (TPE) in the elastic electron-nucleon scattering at high $Q^2$ in the framework of perturbative quantum chromodynamics. The obtained TPE amplitude is of order $\alpha /{\alpha }_s$ with respect to Born approximation. Its shape and value are sensitive to the choice of nucleon wave function, thus study of TPE effects can provide important information about nucleon structure. With the wave functions based on quantum chromodynamics sum rules, TPE correction to the electron-proton cross section has a negative sign, is almost linear in $\epsilon$, and grows logarithmically with $Q^2$ up to 7% at $Q^2=30{\mathrm{GeV}}^2$. The results of existing hadronic calculations, taking into account just the nucleon intermediate state, can be smoothly connected with the perturbative quantum chromodynamics result near $Q^2\sim 3{\mathrm{GeV}}^2$. Above this point two methods disagree, which implies that the hadronic approach becomes inadequate at high $Q^2$. Other relevant observables, such as the electron/positron cross section ratio, are also discussed.

We analyze the phenomenology of a prolonged early epoch of matter domination by an unstable but very long-lived massive particle. This new matter domination era can help to relax some of the requirements on the primordial inflation. Its main effect is the huge entropy production produced by the decays of such a particle that can dilute any possible unwanted relic, as the gravitino in supersymmetric models, and thus relax the constraints on the inflationary reheating temperature. A natural candidate for such a heavy, long-lived particle already present in the standard model of the electroweak interactions would be a heavy right-handed neutrino. In this case, we show that its decays can also generate the observed baryon asymmetry with right-handed neutrino masses well above the bound from gravitino overproduction.

We investigate the influence of the universal extra dimension on the branching ratio in the $B\to \pi (\rho ){\ell }^{+}{\ell }^{-}$ decay. Taking $1/R\sim \{200–1000\}\mathrm{GeV}$ with one universal extra spatial dimension, which is consistent with the experimental data for $\mathcal{B}(B\to X_s\gamma )$, $\mathcal{B}(B\to K^{*}{\mu }^{+}{\mu }^{-})$ and the electroweak precision tests, we obtain that for both $(\mu ,\tau )$ channels the branching ratio strongly depends on the compactification radius $1/R$.

One approach to the calculation of cross sections for infrared-safe observables in high energy collisions at next-to-leading order is to perform all of the integrations, including the virtual loop integration, by Monte Carlo numerical integration. In a previous paper, two of us have shown how one can perform such a virtual loop integration numerically after first introducing a Feynman parameter representation. In this paper, we perform the integration directly, without introducing Feynman parameters, after suitably deforming the integration contour. Our example is the $N$-photon scattering amplitude with a massless electron loop. We report results for $N=6$ and $N=8$.

We systematically analyze the Dirac and the Majorana mass matrices in seesaw models with two heavy right-handed neutrinos. We perform thorough classification of the vanishing matrix elements which are compatible with the results from the current neutrino oscillation experiments. We include the possibility of a nondiagonal Majorana mass matrix which leads to new solutions viable with data. In a basis where the Majorana mass matrix is diagonal, these solutions imply a Dirac matrix with specific relationships amongst its elements. We find that at the level of total four zeros together in $m_D$ and $M_R$ the mass matrices are almost consistent with the data but one mixing angle is predicted to be unsuitable. At the next level, i.e. with total three zeros, only seven patterns of mass matrices describe the experimental data well. The seven solutions have testable predictions for the future neutrino experiments. In particular, each solution has definite predictions about the observation of the 1–3 leptonic mixing angle and the effective mass measured in neutrinoless double beta decay. The solutions of the mass matrices contain novel texture forms and provide new insights into the lepton-generation structure. We also discuss possible connections between these textures and the tri-bimaximal mixing to search for symmetry principles behind the mass matrix structure.

We give a review of the existence of Taub-NUT/bolt solutions in Einstein Gauss-Bonnet gravity with the parameter $\alpha$ in six dimensions. Although the spacetime with base space $S^2\times S^2$ has a curvature singularity at $r=N$, which does not admit NUT solutions, we may proceed with the same computations as in the ${\mathbb{C}\mathbb{P}}^2$ case. The investigation of thermodynamics of NUT/bolt solutions in six dimensions is carried out. We compute the finite action, mass, entropy, and temperature of the black hole. Then the validity of the first law of thermodynamics is demonstrated. It is shown that in NUT solutions all thermodynamic quantities for both base spaces are related to each other by substituting ${\alpha }^{{\mathbb{C}\mathbb{P}}^k}=[(k+1)/k]{\alpha }^{S^2\times S^2\times \dots S_k^2}$. So, no further information is given by investigating NUT solutions in the $S^2\times S^2$ case. This relation is not true for bolt solutions. A generalization of the thermodynamics of black holes to arbitrary even dimensions is made using a new method based on the Gibbs-Duhem relation and Gibbs free energy for NUT solutions. According to this method, the finite action in Einstein Gauss-Bonnet is obtained by considering the generalized finite action in Einstein gravity with an additional term as a function of $\alpha$. Stability analysis is done by investigating the heat capacity and entropy in the allowed range of $\alpha$, $\Lambda$, and $N$. For NUT solutions in $d$ dimensions, there exists a stable phase at a narrow range of $\alpha$. In six-dimensional bolt solutions, the metric is completely stable for $\mathcal{B}=S^2\times S^2$ and is completely unstable for the $\mathcal{B}={\mathbb{C}\mathbb{P}}^2$ case.

We show that a Brans-Dicke model admits some anisotropically inflating solutions which are identical to the solutions found in a higher derivative pure gravity theory. These inflating solutions were shown to break the cosmic no-hair theorem such that they do not approach the de Sitter universe at large times. The stability conditions of these solutions in this scalar-tensor theory are shown explicitly in this paper. It is shown that there exist unstable modes of the anisotropic perturbations. Therefore the inflating solutions are unstable in the scalar-tensor theory.

We present the first light-hadron spectroscopy on a set of $N_f=2+1$ dynamical, anisotropic lattices. A convenient set of coordinates that parameterize the two-dimensional plane of light and strange-quark masses is introduced. These coordinates are used to extrapolate data obtained at the simulated values of the quark masses to the physical light and strange-quark point. A measurement of the Sommer scale on these ensembles is made, and the performance of the hybrid Monte Carlo algorithm used for generating the ensembles is estimated.

A new parametrization of the generalized parton distributions $t$ dependence is proposed. It allows one to reproduce sufficiently well electromagnetic form factors of the proton and neutron at small and large momentum transfer. The description of the data obtained by the Rosenbluth method and the polarization method are compared. The results obtained by the latter method are shown to be compatible with correspondent neutron data. The impact parameter dependence of the neutron charge density is examined. The quark contributions to gravitational form factors of the nucleons are obtained.

We study the effect of interference between the standard model Higgs boson resonance and the continuum background in the process $\gamma \gamma \to H\to b\overline{b}$ at a photon collider. Taking into account virtual gluon exchange between the final-state quarks, we calculate the leading corrections to the height of the resonance for the case of a light ($m_H<160\mathrm{GeV}$) Higgs boson. We find that the interference is destructive and around 0.1%–0.2% of the peak height, depending on the mass of the Higgs and the scattering angle. This suppression is smaller by an order of magnitude than the anticipated experimental accuracy at a photon collider. However, the fractional suppression can be significantly larger if the Higgs coupling to $b$ quarks is increased by physics beyond the standard model.

We discuss the role of $F$-term uplifting in stabilizing moduli within the framework of heterotic string theory. It turns out that the uplifting sector plays an important role in fixing the volume modulus at one of the self-dual points of a modular invariant potential. For the volume modulus stabilized at a self-dual point, the $F$-term uplifting leads to the dilation stabilization which can naturally yield the mirage mediation pattern of soft supersymmetry breaking terms. Generalizing to the case with anomalous $U(1)$ gauge symmetry, we also find that the $U(1)$ sector generically gives a contribution to sfermion masses comparable to the dilaton-mediated one while maintaining the mirage mediation pattern.