Recent analyses of the WMAP 5-year data constrain possible nonadiabatic contributions to the initial conditions of cosmic microwave background anisotropies. Depending upon the early dynamics of the plasma, the amplitude of the entropic modes can experience a different suppression by the time of photon decoupling. Explicit examples of the latter observation are presented both analytically and numerically when the post-inflationary dynamics is dominated by a stiff contribution.

In a type II seesaw utilized to explain the observed neutrino masses and mixings, one extends the standard model (SM) by introducing scalar fields which transform as a triplet under the electroweak gauge symmetry. New scalar couplings involving the Higgs doublet then appear and, as we show, these have important implications for the Higgs boson mass bounds obtained using vacuum stability and perturbativity arguments. We identify, in particular, regions of the parameter space which permit the SM Higgs boson to be as light as 114.4 GeV, the LEP2 bound. The triplet scalars include doubly charged particles whose masses could, in principle, be in the few hundred GeV range, and so they may be accessible at the LHC.

We study whether broken dual gauge symmetry, as detected by a monopole order parameter introduced by the Pisa group, is necessarily associated with the confinement phase of a lattice gauge theory. We find a number of examples, including SU(2) gauge-Higgs theory, mixed fundamental-adjoint SU(2) gauge theory, and pure SU(5) gauge theory, which appear to indicate a dual gauge symmetry transition in the absence of a transition to or from a confined phase. While these results are not necessarily fatal to the dual superconductor hypothesis, they may pose some problems of interpretation for the present formulation of the Pisa monopole criterion.

We study evolution of gravitational perturbations of black strings. It is well known that for all wave numbers less than some threshold value, the black string is unstable against the scalar type of gravitational perturbations, which is named the Gregory-Laflamme instability. Using numerical methods, we find the quasinormal modes and time-domain profiles of the black string perturbations in the stable sector and also show the appearance of the Gregory-Laflamme instability in the time domain. The dependence of the black string quasinormal spectrum and late-time tails on such parameters as the wave vector and the number of extra dimensions is discussed. There is numerical evidence that at the threshold point of instability, the static solution of the wave equation is dominant. For wave numbers slightly larger than the threshold value, in the region of stability, we see tiny oscillations with very small damping rate. While, for wave numbers slightly smaller than the threshold value, in the region of the Gregory-Laflamme instability, we observe tiny oscillations with very small growth rate. We also find the level crossing of imaginary part of quasinormal modes between the fundamental mode and the first overtone mode, which accounts for the peculiar time domain profiles.

The ergoregion instability is known to affect very compact objects that rotate very rapidly and do not possess a horizon. We present here a detailed analysis on the relevance of the ergoregion instability for the viability of gravastars. Expanding on some recent results, we show that not all rotating gravastars are unstable. Rather, stable models can be constructed also with $J/M^2\sim 1$, where $J$ and $M$ are the angular momentum and mass of the gravastar, respectively. The genesis of gravastars is still highly speculative and fundamentally unclear if not dubious. Yet, their existence cannot be ruled out by invoking the ergoregion instability. For the same reason, not all ultracompact astrophysical objects rotating with $J/M^2\lesssim 1$ are to be considered necessarily black holes.

Recently, there have been suggestions that the Type Ia supernova data can be explained using only general relativity and cold dark matter with no dark energy. In “Swiss cheese” models of the Universe, the standard Friedmann-Robertson-Walker picture is modified by the introduction of mass-compensating spherical inhomogeneities, typically described by the Lemaître-Tolman-Bondi metric. If these inhomogeneities correspond to underdense cores surrounded by mass-compensating overdense shells, then they can modify the luminosity distance-redshift relation in a way that can mimic accelerated expansion. It has been argued that this effect could be large enough to explain the supernova data without introducing dark energy or modified gravity. We show that the large apparent acceleration seen in some models can be explained in terms of standard weak field gravitational lensing together with insufficient randomization of void locations. The underdense regions focus the light less than the homogeneous background, thus dimming supernovae in a way that can mimic the effects of acceleration. With insufficient randomization of the spatial location of the voids and of the lines of sight, coherent defocusing can lead to anomalously large demagnification effects. We show that a proper randomization of the voids and lines of sight reduces the effect to the point that it can no longer explain the supernova data.

It is known that a relative translational motion between the deflector and the observer affects gravitational lensing. In this paper, a lens equation is obtained to describe such effects on actual lensing observables. Results can be easily interpreted in terms of aberration of light rays. Both radial and transverse motions with relativistic velocities are considered. The lens equation is derived by first considering geodesic motion of photons in the rest-frame Schwarzschild space-time of the lens, and, then, light-ray detection in the moving observer’s frame. Because of the transverse motion images are displaced and distorted in the observer’s celestial sphere, whereas the radial velocity along the line of sight causes an effective rescaling of the lens mass. The Einstein ring is distorted to an ellipse whereas the caustics in the source plane are still pointlike. Either for null transverse motion or up to linear order in velocities, the critical curve is still a circle with its radius corrected by a factor ($1+z_{\mathrm{d}}$) with respect to the static case, $z_{\mathrm{d}}$ being the relativistic Doppler shift of the deflector. From the observational point of view, the orbital motion of the Earth can cause potentially observable corrections of the order of the $\mu \mathrm{arcsec}$ in lensing towards the supermassive black hole at the Galactic center. On a cosmological scale, tangential peculiar velocities of a cluster of galaxies bring about a typical flexion in images of background galaxies in the weak lensing regime but future measurements seem to be too challenging.

Chern-Simons modified gravity comprises the Einstein-Hilbert action and a higher-derivative interaction containing the Chern-Pontryagin density. We derive the analog of the Gibbons-Hawking-York boundary term required to render the Dirichlet boundary-value problem well defined. It turns out to be a boundary Chern-Simons action for the extrinsic curvature. We address applications to black hole thermodynamics.

We study the final-state interaction (FSI) effects in charmless ${\overline{B}}_{u,d,s}\to PP$ decays. We consider a FSI approach with both short- and long-distance contributions, where the former are from inelastic channels and are contained in factorization amplitudes, while the latter are from the residual rescattering among $PP$ states. Flavor SU(3) symmetry is used to constrain the residual rescattering $S$ matrix. We fit to all available data on the $CP$-averaged decay rates and $CP$ asymmetries, and make predictions on unmeasured ones. We investigate the $K\pi$ direct $CP$ violations that lead to the so-called $K\pi$ puzzle in $CP$ violation. Our main results are as follows: (i) Results are in agreement with data in the presence of FSI. (ii) For $\overline{B}$ decays, the ${\pi }^{+}{\pi }^{-}$ and ${\pi }^0{\pi }^0$ rates are suppressed and enhanced, respectively, by FSI. (iii) The FSI has a large impact on direct $CP$ asymmetries ($\mathcal{A}$) of many modes. (iv) The deviation ($\Delta \mathcal{A}$) between $\mathcal{A}({\overline{B}}^0\to K^{-}{\pi }^{+})$ and $\mathcal{A}(B^{-}\to K^{-}{\pi }^0)$ can be understood in the FSI approach. Since $\mathcal{A}(K^{-}{\pi }^0)$ is more sensitive to the residual rescattering, the degeneracy of these two direct $CP$ violations can be successfully lifted. (v) Sizable and complex color-suppressed tree amplitudes, which are crucial for the large ${\pi }^0{\pi }^0$ rate and $\Delta \mathcal{A}$, are generated through exchange rescattering. The correlation of the ratio $\mathcal{B}({\pi }^0{\pi }^0)/\mathcal{B}({\pi }^{+}{\pi }^{-})$ and $\Delta \mathcal{A}$ is studied. (vi) The $B^{-}\to {\pi }^{-}{\pi }^0$ direct $CP$ violation is very small and is not affected by FSI. (vii) Several ${\overline{B}}_s$ decay rates are enhanced. In particular, the ${\eta }^{\prime }{\eta }^{\prime }$ branching ratio is enhanced to the level of $1.0\times {10}^{-4}$, which can be checked experimentally. (viii) Time-dependent $CP$ asymmetries $S$ in ${\overline{B}}_{d,s}$ decays are studied. The $\Delta S({\overline{B}}^0\to K_S{\eta }^{\prime })$ is very small ($\le 1\%$). This asymmetry remains to be one of the cleanest measurements to search for new physics phases. The asymmetry $S$ from ${\overline{B}}_s$ to $PP$ states with strangeness $S=+1$ are expected to be small. We found that the $|S|$ for ${\overline{B}}_s^0\to \eta \eta$, $\eta {\eta }^{\prime }$, and ${\eta }^{\prime }{\eta }^{\prime }$ decays are all below 0.06. $CP$ asymmetries in these modes will be useful to test the SM.

The so-called supersymmetric flavor and $CP$ problems are deeply related to the origin of flavor and hence to the origin of the standard model Yukawa couplings themselves. We show that realistic $SU(3)$ flavor symmetries with spontaneous $CP$ violation reproducing correctly the standard model Yukawa matrices can simultaneously solve both problems without ad hoc modifications of the supersymmetric model. We analyze the leptonic electric dipole moments and lepton flavor violation processes in these models. We show that the electron electric dipole moment and the decay $\mu \to e\gamma$ are naturally within reach of the proposed experiments if the sfermion masses are measurable at the LHC.

The spectrum of low-lying eigenvalues of the overlap Dirac operator in quenched $SU(2)$ lattice gauge theory with tadpole-improved Symanzik action is studied at finite temperatures in the vicinity of the confinement-deconfinement phase transition defined by the expectation value of the Polyakov line. The value of the chiral condensate obtained from the Banks-Casher relation is found to drop down rapidly at $T=T_c$, though not going to zero. At $T_c^{\prime }\approx 1.5T_c\approx 480\mathrm{MeV}$ the chiral condensate decreases rapidly once again and becomes either very small or zero. At $T<T_c$ the distributions of small eigenvalues are universal and are well described by the chiral orthogonal ensemble of random matrices. In the temperature range above $T_c$ where both the chiral condensate and the expectation value of the Polyakov line are nonzero the distributions of small eigenvalues are not universal. Here the eigenvalue spectrum is better described by a phenomenological model of dilute instanton-anti-instanton gas.

We present a new method to test the standard model expectations at the LHC using photon-induced $WW$ production. Both $W$ decay in the main ATLAS or CMS detectors while scattered protons are measured in forward detectors. The sensitivity to anomalous $WW\gamma$ triple gauge coupling can be improved by more than a factor of 5 or 30 compared to the present LEP or Tevatron sensitivity, respectively.

When GLAST is in the South Atlantic Anomaly (SAA), the rate of charged particles is too high to be efficiently filtered out. Moreover the high rate can cause saturation effects in the readout electronics and the sensors must be turned off. The SAA area relative to the total area of GLAST’s orbit is approximately 12.5% and GLAST spends 18% of the time in it. In spite of these cares, we show in this work that, due to drift processes, particle precipitation can still trigger GLAST when it is close to the SAA region. Here, we report two GLAST gamma ray burst monitor (GBM) triggers, trigger 239895229 and trigger 239913100, on August, 08, 2008 whose characteristics are similar to the ones observed in the Swift-BAT noise triggers (due to particle precipitation in the SAA region). Both GLAST triggers happened during a plentiful particle precipitation in the SAA region, observed by Tupi telescopes at the ground with their trigger coordinates close to the field of view of the telescopes. Details of these results are reported.

String theory compactification involves manifolds with multiple warp factors. For cosmological applications, we often introduce a short, high-energy inflationary throat, and a long, low-energy standard model (SM) throat. It is assumed that at the end of inflation, the excited Kaluza-Klein modes from the inflationary throat tunnel to the SM throat and reheat standard model degrees of freedom, which are attached to probe brane(s). However, the huge hierarchy of energy scales can result in a highly dynamic transition of the throat geometry. We point out that in such a cosmological scenario the standard model throat (together with SM brane) will be cloaked by a Schwarzschild horizon, produced by the Kaluza-Klein modes tunneling from the short throat. The black brane formation is dual to the first order chiral phase transition of the cascading gauge theory. We calculate the critical energy density corresponding the formation of the black hole (BH) horizon in the long throat. We discuss the duality between “black universe” cosmology and an expanding universe driven by the hot gauge theory radiation. We address the new problem of the hierarchical multiple-throat scenarios: SM brane disappearance after the decay of the BH horizon.

For many quantum models an apparent non-Hermiticity of observables just corresponds to their hidden Hermiticity in another, physical Hilbert space. For these models we show that the existence of observables which are manifestly time-dependent may require the use of a manifestly time-dependent representation of the physical Hilbert space of states.

We study the Hawking radiation of a $(4+n)$-dimensional Schwarzschild black hole imbedded in space-time with a positive cosmological constant. The greybody and energy emission rates of scalars, fermions, bosons, and gravitons are calculated in the full range of energy. Valuable information on the dimensions and curvature of space-time is revealed. Furthermore, we investigate the entropy radiated and lost by black holes. We find their ratio near 1 in favor of the Bekenstein’s conjecture.

In order for a modified gravity model to be a candidate for cosmological dark energy, it has to pass stringent local gravity experiments. We find that a Brans-Dicke (BD) theory with well-defined second order corrections that include the Gauss-Bonnet term possesses this feature. We construct the generic second order theory that gives, to linear order, a BD metric solution for a pointlike mass source. We find that the Eddington parameter $\gamma$, heavily constrained by time delay experiments, can be arbitrarily close to the general relativity value of 1, with an arbitrary BD parameter ${\omega }_{\mathrm{BD}}$. We find the region where the solution is stable to small timelike perturbations.

Motivated by the well-known Chamblin-Reall solutions of $n$-dimensional background spacetime in a dilaton gravity and the dynamics of a domain wall in the same backgrounds, we have tried to generalize those solutions by including an electromagnetic field in the bulk. The electromagnetic field is assumed to be coupled with the scalar field in an exponential way. Under the specific relations among the various parameters in our model, we have found five different types of solutions. For every case, the solution has singularity. In these backgrounds, we have also studied the dynamics of the domain wall. The energy densities, which play the role of these interesting dynamics, are known to be induced from the bulk fields through the Israel junction condition. In this more general background field configuration, we have found that static bulk spacetime exists consistently with the dynamic domain wall. In several cases, depending on the values of the parameters, in the early stage of evolution, the domain wall is found to have an inflationary phase for finite period of its proper time followed by usual decelerated expansion.

We study a set of universe models where the dark sector is described by a perfect fluid with an affine equation of state $P=P_0+\alpha \rho$, focusing specifically on cosmological perturbations in a flat universe. We perform a Monte Carlo Markov Chain analysis spanning the full parameter space of the model using the WMAP 5-yr data and the SDSS LRG4 survey. The affine fluid can either play the role of a unified dark matter, accounting for both dark matter and a cosmological constant, or work alongside cold dark matter (CDM), as a form of dark energy. A key ingredient is the sound speed, that depends on the nature of the fluid and that, for any given background model, adds a degree of freedom to the perturbations: in the barotropic case the square of the sound speed is simply equal to the affine parameter $\alpha$; if entropic perturbations are present the effective sound speed has to be specified as an additional parameter. In addition to the barotropic case, we consider the two limiting cases of effective sound speed equal to 0 or 1. For $\alpha =c_s^2=0$ our unified dark matter model is equivalent to the standard $\Lambda \mathrm{CDM}$ with adiabatic perturbations. Apart of a trivial subcase, all models considered satisfy the data constraints, with quite standard values for the usual cosmological parameters. In general our analysis confirms that cosmological data sets require both a collisionless massive and cold component to form the potential wells that lead to structure formation, and an effective cosmological constant that drives the late accelerated expansion.

We consider black holes resulting from binary black-hole mergers. By fitting to numerical results we construct analytic formulas that predict the mass and spin of the final black hole. Our formulas are valid for arbitrary initial spins and mass ratios and agree well with available numerical simulations. We use our spin formula in the context of two common merger scenarios for supermassive galactic black holes. We consider the case of isotropically distributed initial spin orientations (when no surrounding matter is present) and also the case when matter closely aligns the spins with the orbital angular momentum. The spin magnitude of black holes resulting from successive generations of mergers (with symmetric mass ratio $\eta$) has a mean of $1.73\eta +0.28$ in the isotropic case and 0.94 for the closely aligned case.