We introduce a $\mathrm{}(5+m)-\mathrm{dimensional}$ vacuum description of five-dimensional bulk inflaton models with exponential potentials that makes an analysis of cosmological perturbations simple and transparent. We show that various solutions, including the power-law inflation model recently discovered by Koyama and Takahashi, are generated from known $\mathrm{}(5+m)\mathrm{}-\mathrm{d}\mathrm{i}\mathrm{m}\mathrm{e}\mathrm{n}\mathrm{s}\mathrm{i}\mathrm{o}\mathrm{n}\mathrm{a}\mathrm{l}$ vacuum solutions of pure gravity. We derive master equations for all types of perturbations, and each of them becomes a second order differential equation for one master variable supplemented by simple boundary conditions on the brane. One exception is the case for massive modes of scalar perturbations. In this case, there are two independent degrees of freedom, and in general it is difficult to disentangle them into two separate sectors.

The general-covariant Z4 formalism is further analyzed. The gauge conditions are generalized with a view to numerical relativity applications and the conditions for obtaining strongly hyperbolic evolution systems are given both at the first and the second order levels. A symmetry-breaking mechanism is proposed that allows one, when applied in a partial way, to recover previously proposed strongly hyperbolic formalisms, like the BSSN and the Bona-Massó formulas. When applied in its full form, the symmetry-breaking mechanism allows one to recover the full five-parameter family of first order KST systems. Numerical codes based in the proposed formalisms are tested. A robust stability test is provided by evolving random noise data around Minkowski space-time. A strong field test is provided by the collapse of a periodic background of plane gravitational waves, as described by the Gowdy metric.

We derive a new regularization method for the calculation of the (massless) scalar self-force in curved spacetime. In this method, the scalar self-force is expressed in terms of the difference between two retarded scalar fields: the massless scalar field and an auxiliary massive scalar field. This field difference combined with a certain limiting process gives the expression for the scalar self-force. This expression provides a new self-force calculation method.

We investigate the ultrarelativistic boost of a Schwarzschild black hole immersed in an external electromagnetic field, described by an exact solution of the Einstein-Maxwell equations found by Ernst (the “Schwarzschild-Melvin” metric). Following the classical method of Aichelburg and Sexl, the gravitational field generated by a black hole moving “with the speed of light” and the transformed electromagnetic field are determined. The corresponding exact solution describes an impulsive gravitational wave propagating in the static, cylindrically symmetric, electrovac universe of Melvin, and for a vanishing electromagnetic field it reduces to the well known Aichelburg-Sexl pp wave. In the boosting process, the original Petrov type I of the Schwarzschild-Melvin solution simplifies to type II on the impulse, and to type D elsewhere. The geometry of the wave front is studied, in particular its nonconstant Gauss curvature. In addition, a more general class of impulsive waves in the Melvin universe is constructed by means of a six-dimensional embedding formalism adapted to the background. A coordinate system is also presented in which all the impulsive metrics take a continuous form. Finally, it is shown that these solutions are a limiting case of a family of exact gravitational waves with an arbitrary profile. This family is identified with a solution previously found by Garfinkle and Melvin. We thus complement their analysis, in particular demonstrating that such spacetimes are of type II and belong to the Kundt class.

We present the expressions of the three- and four-point correlation functions of a self-interacting light scalar field in a de Sitter spacetime at tree order, respectively, for a cubic and a quartic potential. Exact expressions are derived and their limiting behavior on superhorizon scales are presented. Their essential features are shown to be similar to those obtained in a classical approach.

The evolution of slow-roll inflation in a five-dimensional brane world model with two boundary branes and a bulk scalar field is studied. Assuming that the inflationary scale is below the brane tension, we can employ the moduli space approximation to study the dynamics of the system. Detuning the brane tension results in a potential for the moduli fields which we show will not support a period of slow-roll inflation. We then study an inflaton field, confined to the positive tension brane, to which the moduli fields are nonminimally coupled. We discuss in detail the two cases of $V\left(\chi \right)=\frac{1}{2}{m}^2{\chi }^2$ and $V\left(\chi \right)=\lambda {\chi }^4$ and demonstrate that increasing the coupling results in spectra which are further away from scale invariance and in an increase in the tensor mode production, while entropy perturbations are subdominant. Finally, we point out that the five-dimensional spacetime is unstable during inflation because the negative tension brane collapses.

We show that if color superconducting quark matter forms in hybrid or quark stars it is possible to satisfy most of the recent observational boundaries on the masses and radii of compact stellar objects. An energy of the order of ${10}^{53}$ erg is released in the conversion from a (metastable) hadronic star into a (stable) hybrid or quark star in the presence of a color superconducting phase. If the conversion occurs immediately after the deleptonization of the protoneutron star, the released energy can help supernovae to explode. If the conversion is delayed the energy released can power a gamma-ray burst. A delay between the supernova and the subsequent gamma-ray burst is possible, in agreement with the delay proposed in the recent analysis of astrophysical data.

We study the indication of different large branching ratios between $B^{-}\to D^{\left(*\right)0\mathrm{}}{K}^{-}{K}^0$ and $B_d\to D^{\left(*\right)+}{K}^{-}{K}^0$ observed by Belle. Interestingly, the same situation is not found in the decays $\overrightarrow{B}{D}^{\left(*\right)}{K}^{-}{K}^{*0}.$ If no intermediate resonances exists in the decays $B^{-}\to D^{\left(*\right)0\mathrm{}}{K}^{-}{K}^0,$ a puzzle will arise. We find that the color-suppressed processes $B^{-}\to D^{\left(*\right)0\mathrm{}}{a}_0^{-}\mathrm{}\left(1450\right)\mathrm{}$ with $a_0^{-}\mathrm{}\left(1450\right)\mathrm{}\to K^{-}{K}^0$ could be one of the candidates to enhance the BRs of $B^{-}\to D^{\left(*\right)0\mathrm{}}{K}^{-}{K}^0.$ Our conjecture can be examined by the Dalitz plot technique and the analysis of the angular dependence of the $K^{-}{K}^0$ state at B factories.

The third moment $d_2$ of the twist-3 part of the nucleon spin structure function $g_2$ is generalized to arbitrary momentum transfer $Q^2$ and is evaluated in heavy baryon chiral perturbation theory up to order ${O(p}^4)$ and in a unitary isobar model (MAID). We show how to link $d_2$ as well as higher moments of the nucleon spin structure functions $g_1$ and $g_2$ to nucleon spin polarizabilities. We compare our results with the most recent experimental data, and find a good description of these available data within the unitary isobar model. We proceed to extract the twist-4 matrix element $f_2$ which appears in the ${1/Q}^2$ suppressed term in the twist expansion of the spin structure function $g_1$ for the proton and neutron.

We study the subleading corrections originating from the three-parton $\left(q\overline{q}g\right)$ Fock states of final-state mesons in B decays. The corrections could give significant contributions to decays involving an $\omega$ or ${\eta }^{{(}^{\prime })}$ in the final states. Our results indicate the similarity of $\omega K$ and $\omega {\pi }^{-}$ rates, of order $5\times {10}^{-6},$ consistent with the recent measurements. We obtain $a_2(\overrightarrow{B}J/\psi K)\approx 0.27+0.05i,$ in good agreement with data. Without resorting to the unknown singlet annihilation effects, three-parton Fock state contributions can enhance the branching ratios of $K{\eta }^{\prime }$ to a level above $50\times {10}^{-6}.$

Parton distributions in a valon in the next-to-leading order are used to determine the parton distributions in a pion and kaon. The validity of the valon model is tested and it is shown that the partonic content of the valon is universal and independent of the valon type. We evaluate the valon distribution in the pion and kaon, and in particular it is shown that the results are in good agreement with the experimental data on the pion structure in a wide range of $x=[{10}^{-4},1\mathrm{}].$

Nonleptonic B to charmonium decays generally show deviations from the factorization predictions. For example, the mode $B^{-}\to K^{-}{\chi }_{c0\mathrm{}}$ has been experimentally observed with a sizable branching fraction while its factorized amplitude vanishes. We investigate the role of rescattering effects mediated by intermediate charmed meson production in this class of decay modes, and consider $B^{-}\to K^{-}{h}_c$ with $h_c$ the $J^{\mathrm{PC}}{=1\mathrm{}}^{+-}\overline{c}c$ meson. Using an effective Lagrangian describing interactions of pairs of heavy-light $Q\overline{q}$ mesons with a quarkonium state, we relate this mode to the analogous mode with ${\chi }_{c0\mathrm{}}$ in the final state. We find $\mathcal{B}{(B}^{-}\to K^{-}{h}_c)$ large enough to be measured at B factories, so that this decay mode could be used to study the poorly known $h_c.$

We carry out an analysis of the pentaquark ${\Theta }^{+}$ photoproduction with polarized photon beams. Kinematical and dynamical aspects are examined for the purpose of determining ${\Theta }^{+}\mathrm{’}\mathrm{s}$ spin and parity. It shows that the polarized photon beam asymmetry in association with certain dynamical properties of the production mechanism would provide further information on its quantum numbers. Facilities at SPring-8, JLab, ELSA, and ESRF will have access to them.

We argue that a modification of the super-AdS algebras which accounts for the presence of D-branes requires not only the inclusion of bosonic brane charges but also the inclusion of new fermionic ones. We show that such fermionic brane charges are indeed present in the matrix model and the supermembrane in the pp-wave limit of the corresponding backgrounds. We briefly comment on an AdS version of Sezgin’s M- algebra inspired by this observation.

An experimetnt is proposed to measure the post-Maxwellian parameters of the nonlinear electrodynamics of a vacuum. It is shown that the system for recording small differences of optical paths used in the Laser Interferometer Gravitational-Wave Observatory (LIGO) and in other laser interferometers for gravitational wave detectors permits us to measure the nonlinear electrodynamics corrections predicted by quantum electrodynamics. However, the use of LIGO or other full-scale laser interferometers of the gravitational wave detectors for this purpose does not seem sensible. Therefore it is suggested to perform this experiment on one of the laboratory prototypes used to develop interferometry for gravitational wave detection. The sensitivity of these laboratory prototypes is about the same as the sensitivity of the full-scale instruments, and the other parameters are most similar to the optimal values allowing us to observe the considered effect: the arm length $l_0$ of these prototypes is about several meters and in the Fabry-Perot interferometer about $N\sim 2\times {10}^5$ bounces can be realized. A further increase in the detector sensitivity is noted to offer also an opportunity of experimentally studying the nonlinearly electrodynamic corrections predicted by the Born-Infeld theory.

We consider a massless scalar field obeying Dirichlet boundary conditions on the walls of a two-dimensional $L\times b$ rectangular box, divided by a movable partition (piston) into two compartments of dimensions $a\times b$ and $\left(L-a\right)\times b.\mathrm{}$ We compute the Casimir force on the piston in the limit $\overrightarrow{L}\infty .$ Regardless of the value of $a/b,$ the piston is attracted to the nearest end of the box. Asymptotic expressions for the Casimir force on the piston are derived for $a\ll b$ and $a\gg b.\mathrm{}$

We carry out an investigation into the possibility of developing a Bohmian interpretation based on the continuous motion of point particles for noncommutative quantum mechanics. The conditions for such an interpretation to be consistent are determined, and the implications of its adoption for noncommutativity are discussed. A Bohmian analysis of the noncommutative harmonic oscillator is carried out in detail. By studying the particle motion in the oscillator orbits, we show that small-scale physics can have influence at large scales, something similar to the IR-UV mixing.

It is known that the imaginary parts of the quasinormal mode (QNM) frequencies for the Schwarzschild black hole are evenly spaced with a spacing that depends only on the surface gravity. On the other hand, for massless minimally coupled scalar fields, there exist no QNMs in the pure de Sitter spacetime. It is not clear what the structure of the QNMs would be for the Schwarzschild–de Sitter (SDS) spacetime, which is characterized by two different surface gravities. We provide a simple derivation of the imaginary parts of the QNM frequencies for the SDS spacetime by calculating the scattering amplitude in the first Born approximation and determining its poles. We find that, for the usual set of boundary conditions in which the incident wave is scattered off the black hole horizon, the imaginary parts of the QNM frequencies have an equally spaced structure with the level spacing depending on the surface gravity of the black hole. Several conceptual issues related to the QNM are discussed in the light of this result and a comparison with previous work is presented.

We describe the first convergent numerical method to determine static black hole solutions (with an $S^3$ horizon) in 5D compactified spacetime. We obtain a family of solutions parametrized by the ratio of the black hole size and the size of the compact extra dimension. The solutions satisfy the demanding integrated first law. For small black holes our solutions approach the 5D Schwarzschild solution and agree very well with new theoretical predictions for the small corrections to thermodynamics and geometry. The existence of such black holes is thus established. We report on thermodynamical (temperature, entropy, mass and tension along the compact dimension) and geometrical measurements. Most interestingly, for large masses (close to the Gregory-Laflamme critical mass) the scheme destabilizes. We interpret this as evidence for an approach to a physical tachyonic instability. Using extrapolation we speculate that the system undergoes a first order phase transition.