We have studied the wave dynamics and the Hawking radiation for a scalar field as well as a brane-localized gravitational field in the background of a brane-world black hole with a tidal charge containing information on the extra dimension. Comparing with four-dimensional black holes, we have observed the signature of the tidal charge which presents the signals of the extra dimension both in the wave dynamics and the Hawking radiation.

The linear relation between the entropy and area of a black hole can be derived from the Heisenberg principle, the energy-momentum dispersion relation of special relativity, and general considerations about black holes. There exist results in quantum gravity and related contexts suggesting the modification of the usual dispersion relation and uncertainty principle. One of these contexts is the gravity’s rainbow formalism. We analyze the consequences of such a modification for black hole thermodynamics from the perspective of two distinct rainbow realizations built from doubly special relativity. One is the proposal of Magueijo and Smolin and the other is based on a canonical implementation of doubly special relativity put forward recently by the authors. In these scenarios, we obtain modified expressions for the entropy and temperature of black holes. We show that, for a family of doubly special relativity theories satisfying certain properties, the temperature can vanish in the limit of zero black hole mass. For the Magueijo and Smolin proposal, this is only possible for some restricted class of models with bounded energy and unbounded momentum. With the proposal of a canonical implementation, on the other hand, the temperature may vanish for more general theories; in particular, the momentum may also be bounded, with bounded or unbounded energy. This opens new possibilities for the outcome of black hole evaporation in the framework of a gravity’s rainbow.

We explore a model of interacting dark energy where the dark energy density is related by the holographic principle to the Hubble parameter, and the decay of the dark energy into matter occurs at a rate comparable to the current value of the Hubble parameter. We find this gives a good fit to the observational data supporting an accelerating Universe, and the model represents a possible alternative interpretation of the expansion history of the Universe.

We calculate the power spectra of primordial curvature and isocurvature perturbations from a general two-field inflation model at next-to-leading order correction in a slow-roll expansion. In particular we calculate the spectral indices to second order in slow-roll parameters. We show that the cross correlation of the curvature and isocurvature perturbations at the time of Hubble exit during inflation is nonzero at first order in slow-roll parameters. We apply our results to different classes of inflation, including inflaton and curvaton scenarios. The spectrum of primordial gravitational waves, curvature and isocurvature perturbations obey generalized consistency relations in two-field inflation models. We give the first two consistency relations in an infinite hierarchy.

We calculate the one-loop flavor violating top quark decay $t\to cgg$ in the minimal supersymmetric standard model. We discuss the branching ratios obtained with minimal flavor violation, as well as with soft-supersymmetry induced general flavor violation. Based on this rate we calculate the cross section for the single top quark production via gluon fusion, $gg\to t\overline{c}$, and evaluate its contribution to the cross section for single top quark production in $pp$ collisions at the Large Hadron Collider. We calculate all contributions coming from the standard model and charged Higgs loops, as well as gluino (and neutralino)-up-type squarks, and chargino-down-type squarks loops. Our numerical results show that the gluino and the chargino contributions are largest over the whole parameter range in the unconstrained minimal supersymmetric standard model. While in general the gluino contributions dominate the cross section, this result depends on the supersymmetric flavor violating parameters in the up and down squark sector, the relative mass of the gauginos, and whether or not the grand unified theory relationships between gaugino masses are satisfied. In the most promising scenarios, the $pp\to t\overline{c}+\overline{t}c+X$ cross section at the Large Hadron Collider can reach a few hundred fb.

The existence of pentaquarks, namely, baryonic states made up of four quarks and one antiquark, became questionable, because the candidates, i.e. the ${\Theta }^{+}$ peak, are seen in certain reactions, i.e. $p+p$ collisions, but not in others, i.e. $e^{+}{e}^{-}$ annihilations. In this paper, we estimate the production of ${\Theta }^{+}(1540)$ and ${\Xi }^{--}(1860)$ in $e^{+}{e}^{-}$ annihilations at different energies using the Fermi statistical model as originally proposed in its microcanonical form. The results are compared with that from proton-proton (pp) collisions at SPS (CERN’s superconducting proton synchrotron) and RHIC (relativistic heavy ion collisions at Brookhaven) energies. We find that, if pentaquark states exist, the production is highly possible in $e^{+}{e}^{-}$ annihilations. For example, at LEP energy $\sqrt{s}=91.2\mathrm{GeV}$, both ${\Theta }^{+}(1540)$ and ${\Xi }^{--}(1860)$ yield more than in pp collisions at SPS and RHIC energy.

Sum rules are derived relating mean squared charge radii of the pseudoscalar mesons with the convergent integral of the difference of hadron photoproduction cross-sections on pseudoscalar mesons.

Braneworld inflation on the resolved warped deformed conifold is represented by the dynamics of a $D3$-brane probe with the world volume of a brane spanning the large dimensions of the observable Universe. This model was recently proposed as a string theory candidate for slow-roll inflationary cosmology [A. Dymarsky, I. R. Klebanov, and N. Seiberg, hep-th/0511254.]. During inflation, the scalar curvature of the Universe is determined by the Hubble scale. We argue that taking into account the curvature of the inflationary Universe renders dynamics of the $D3$-brane fast-roll deep inside the warped throat.

We discuss aspects of the problem of assigning probabilities in eternal inflation. In particular, we investigate a recent suggestion that the lowest energy de Sitter vacuum in the landscape is effectively stable. The associated proposal for probabilities would relegate lower energy vacua to unlikely excursions of a high entropy system. We note that it would also imply that the string theory landscape is experimentally ruled out. However, we extensively analyze the structure of the space of Coleman-De Luccia solutions, and we present analytic arguments, as well as numerical evidence, that the decay rate varies continuously as the false vacuum energy goes through zero. Hence, low-energy de Sitter vacua do not become anomalously stable; negative and zero-cosmological constant regions cannot be neglected.

Using the $1/N$ expansion, we study the influence of quantum instantons on the thermodynamics of the $\mathbb{C}{P}^{N-1}$ model in $1+1$ dimensions. We do this by calculating the pressure to next-to-leading order in $1/N$, without quantum instanton contributions. The fact that the $\mathbb{C}{P}^1$ model is equivalent to the $\mathrm{O}(3)$ nonlinear sigma model allows for a comparison to the full pressure up to $1/N^2$ corrections for $N=3$. Assuming validity of the $1/N$ expansion for the $\mathbb{C}{P}^1$ model makes it possible to argue that the pressure for intermediate temperatures is dominated by the effects of quantum instantons. A similar conclusion can be drawn for general $N$ values by using the fact that the entropy should always be positive.

Vacuum polarization in QED in a background gravitational field induces interactions which effectively modify the classical picture of light rays, as the null geodesics of spacetime. These interactions violate the strong equivalence principle and affect the propagation of light leading to superluminal photon velocities. Taking into account the QED vacuum polarization, we study the propagation of a bundle of rays in a background gravitational field. To do so we study the perturbative deformation of the Raychaudhuri equation through the influence of vacuum polarization on photon propagation. We analyze the contribution of the above interactions to the optical scalars, namely, shear, vorticity, and expansion using the Newman-Penrose formalism.

Nonminimal actions with matter represented by a scalar field coupled to gravity are considered in the context of a homogeneous and isotropic universe. The coupling is of the form $-\frac{1}{2}\xi {\varphi }^{2}R$. The possibility of successful inflation is investigated taking into account features of loop cosmology. For that end a conformal transformation is performed. That brings the theory into the standard minimally coupled form (Einstein frame) with some effective field and its potential. Both analytical and numerical estimates show that a negative coupling constant is preferable for successful inflation. Moreover, provided fixed initial conditions, larger $|\xi |$ leads to a greater number of $e$-folds. The latter is obtained for a reasonable range of initial conditions and the coupling parameter and indicates a possibility for successful inflation.

We study, in the multipolar coupling scheme, a uniformly accelerated multilevel hydrogen atom in interaction with the quantum electromagnetic field near a conducting boundary and separately calculate the contributions of the vacuum fluctuation and radiation reaction to the rate of change of the mean atomic energy. It is found that the perfect balance between the contributions of vacuum fluctuations and radiation reaction that ensures the stability of ground-state atoms is disturbed, making spontaneous transition of ground-state atoms to excited states possible in a vacuum with a conducting boundary. The boundary-induced contribution is effectively a nonthermal correction, which enhances or weakens the nonthermal effect already present in the unbounded case, thus possibly making the effect easier to observe. An interesting feature worth noting is that the nonthermal corrections may vanish for atoms on some particular trajectories.

The spin axes of gyroscopes experimentally define local nonrotating frames, i.e. the time evolution of axes of inertial frames. But what physical cause governs the time evolution of gyroscope axes? We consider linear perturbations of Friedmann-Robertson-Walker (FRW) cosmologies with $k=0$, i.e. spatially flat. We ask the following question: Will cosmological vector perturbations (i.e. vorticity or rotational perturbations) exactly drag the spin axes of gyroscopes relative to the directions of geodesics to quasars in the asymptotic unperturbed FRW space? Using Cartan’s formalism with local orthonormal bases, we cast the laws of linear cosmological gravitomagnetism into a form showing the close correspondence with the laws of ordinary magnetism. Our results, valid for any equation of state and any form of the energy-momentum tensor for cosmological matter, are as follows: (1) the dragging of a gyroscope axis by rotational perturbations of matter beyond the $H$-dot radius from the gyroscope is exponentially suppressed, where $H$ is the Hubble rate, and the dot is the derivative with respect to cosmic time. (2) If the perturbation of matter is a homogeneous rotation inside some radius around a gyroscope, then exact dragging of the gyroscope axis by the rotational perturbation is reached exponentially fast as the rotation radius gets larger than the $H$-dot radius. (3) For the most general linear cosmological perturbations, the time evolution of all gyroscope spin axes and the axis directions of all local inertial frames exactly follow a weighted average of the rotational motion of cosmological matter, i.e. there is exact frame-dragging everywhere. The weight function is the density of measured angular momentum of matter times ($1/r$) times the Yukawa force $(-d/dr)[(1/r)\exp (-\mu r)]$, where $r$ is the geodesic distance from the source to the gyroscope. The exponential cutoff is given by ${\mu }^2=-4(dH/dt)$. Except for the Yukawa cutoff the weight function is the same as in the integrated form of Ampère’s law. Our results demonstrate (in first-order perturbations of any type for FRW cosmologies with $k=0$) the validity of Mach’s hypothesis that axes of local nonrotating frames precisely follow an average of the motion of cosmic matter.

We present long-term ($\sim {10}^{4}M$) axisymmetric simulations of differentially rotating, magnetized neutron stars in the slow-rotation, weak magnetic field limit using a perturbative metric evolution technique. Although this approach yields results comparable to those obtained via nonperturbative (BSSN) evolution techniques, simulations performed with the perturbative metric solver require about $1/4$ the computational resources at a given resolution. This computational efficiency enables us to observe and analyze the effects of magnetic braking and the magnetorotational instability (MRI) at very high resolution. Our simulations demonstrate that (1) MRI is not observed unless the fastest-growing mode wavelength is resolved by $\gtrsim 10$ gridpoints; (2) as resolution is improved, the MRI growth rate converges, but due to the small-scale turbulent nature of MRI, the maximum growth amplitude increases, but does not exhibit convergence, even at the highest resolution; and (3) independent of resolution, magnetic braking drives the star toward uniform rotation as energy is sapped from differential rotation by winding magnetic fields.

We discuss the results of a global ${\chi }^2$ analysis of a simple $SO(10)$ supersymmetric grand unified theory (SUSY GUT) with $D_3$ family symmetry and low energy $R$ parity. The model describes fermion mass matrices with 14 parameters and gives excellent fits to 20 observable masses and mixing angles in both quark and lepton sectors, giving six predictions. Bi-large neutrino mixing is obtained with hierarchical quark and lepton Yukawa matrices, thus avoiding the possibility of large lepton flavor violation. The model naturally predicts small 1–3 neutrino mixing, with $\sin {\theta }_{13}\simeq 0.05–0.06$. In this paper we evaluate the predictions for the lepton flavor violating processes, $\mu \to e\gamma$, $\tau \to \mu \gamma$ and $\tau \to e\gamma$ and also the electric dipole moment of the electron ($d_e$), the muon, and the tau, assuming universal squark and slepton masses ($m_{16}$) and a universal soft SUSY breaking $A$ parameter ($A_0$) at the GUT scale. We find $\mathrm{Br}(\mu \to e\gamma )$ is naturally below present bounds, but may be observable by MEG. Similarly, $d_e$ is below present bounds, but it is within the range of future experiments. We also give predictions for the light Higgs mass (using FeynHiggs). We find an upper bound given by $m_h\le 127\mathrm{GeV}$, with an estimated $\pm 3\mathrm{GeV}$ theoretical uncertainty. Finally we present predictions for SUSY particle masses in the favored region of parameter space.

We study the lepton flavor violation (LFV) in tau decays in the framework of the supersymmetric seesaw mechanism with nonholomorphic terms for the lepton sector at a large $\tan \beta$. In particular, we analyze two new decay modes $\tau \to \ell f_0(980)$ and $\tau \to \ell K^{+}{K}^{-}$ arising from the scalar boson exchanges contrast to $\tau \to \ell {\eta }^{(\prime )}$ from the pseudoscalar ones. We find that the decay branching ratios of the two new modes could be not only as large as the current upper limits of $O({10}^{-7})$, but also larger than those of $\tau \to \ell {\eta }^{(\prime )}$. Experimental searches for the two modes are important for the LFV induced by the scalar-mediated mechanism. In addition, we show that the decay branching ratios of $\tau \to \ell {\mu }^{+}{\mu }^{-}$ are related to those of $\tau \to \ell \eta$ and $\tau \to \ell f_0(980)$.

The infrared limit of the lattice Landau gauge gluon propagator is studied. We show that the lattice data are compatible with the pure power law $(q^2{)}^{2\kappa }$ solution of the Dyson-Schwinger equations. Using various lattice volumes, the infinite volume limit for the exponent $\kappa$ is measured. Although, the results allow $\kappa =0.498–0.525$, the lattice data favor $\kappa \sim 0.52$, which would imply a vanishing zero momentum gluon propagator.

We analyze fall-apart decays of polyquark (tetra, penta and molecule type) hadrons within the constituent quark picture. For processes in which a polyquark hadron goes to final states containing a light pseudoscalar meson the constraints given by chiral symmetry are implemented. As an application of the approach developed, fall-apart decays of $a(980)$ and $X(3872)$ are studied, assuming these mesons are polyquark hadrons. Two extreme options—confined diquark-diquark states and molecular states—are considered. For $a^0(980)$, the observed width can be obtained assuming that this meson is a diquark-diquark composite with a relatively large size of around $1÷1.5\mathrm{fm}$. The pure $K\overline{K}$ molecular-type state, however, can be excluded. For the $X(3872)$, a sufficiently small width can be obtained if it is a dominantly isospin-0 diquark-diquark composite with a very large size of $\ge 2.5\mathrm{fm}$. The pure molecular option appears possible if the binding energy is tiny, $E_b\lesssim 0.2\mathrm{MeV}$, corresponding to a huge size.

Recently, the BES collaboration has published an extensive partial-wave analysis of experimental data on $J/\psi \to \varphi {\pi }^{+}{\pi }^{-}$, $J/\psi \to \omega {\pi }^{+}{\pi }^{-}$, $J/\psi \to \varphi K^{+}{K}^{-}$ and $J/\psi \to \omega K^{+}{K}^{-}$. These new results are analyzed here, with full account of detection efficiencies, in the framework of a chiral unitary description with coupled-channel final state interactions between $\pi \pi$ and $K\overline{K}$ pairs. The emission of a dimeson pair is described in terms of the strange and nonstrange scalar form factors of the pion and the kaon, which include the final state interaction and are constrained by unitarity and by matching to the next-to-leading-order chiral expressions. This procedure allows for a calculation of the $S$-wave component of the dimeson spectrum including the $f_0(980)$ resonance, and for an estimation of the low-energy constants of Chiral Perturbation Theory, in particular, the large $N_c$ suppressed constants $L_4^r$ and $L_6^r$. The decays in question are also sensitive to physics associated with OZI violation in the $0^{++}$ channel. It is found that the $S$-wave contributions to $\varphi {\pi }^{+}{\pi }^{-}$, $\varphi K^{+}{K}^{-}$ and $\omega {\pi }^{+}{\pi }^{-}$ given by the BES partial-wave analysis may be very well fitted up to a dimeson center-of-mass energy of $\sim 1.2\mathrm{GeV}$, for a large and positive value of $L_4^r$ and a value of $L_6^r$ compatible with zero. An accurate determination of the amount of OZI violation in the $J/\psi \to \varphi {\pi }^{+}{\pi }^{-}$ decay is achieved, and the $S$-wave contribution to $\omega K^{+}{K}^{-}$ near threshold is predicted.