We address the localization of gravity on the Friedmann-Robertson-Walker type brane embedded in either ${\mathrm{AdS}}_5$ or ${\mathrm{dS}}_5$ bulk space, and derive two definite limits between which the value of the bulk cosmological constant has to lie in order to localize the graviton on the brane. The lower limit implies that the brane should be either ${\mathrm{dS}}_4$ or 4D Minkowski in the ${\mathrm{AdS}}_5$ bulk. The positive upper limit indicates that the gravity can be trapped also on a curved brane in the ${\mathrm{dS}}_5$ bulk space. Some implications for recent cosmological scenarios are also discussed.

I find the most general spherically symmetric nonsingular black hole solution in a special class of teleparallel theory of gravitation. If r is large enough, the general solution coincides with the Schwarzschild solution. Whereas, if r is small, the general solution behaves in a manner similar to that of a de Sitter solution. Otherwise it describes a spherically symmetric black hole singularity free everywhere. Moreover, the energy associated with the general solution is calculated using the superpotential given by Møller.

We discuss thermalization through perturbative inflaton decay at the end of inflation. We find that a thermal plasma should form well before all inflatons have decayed, unless all gauge symmetries are badly broken during that epoch. However, before they thermalize, the very energetic inflaton decay products can contribute to the production of massive stable particles, either through collisions with the thermal plasma, or through collisions with each other. If such reactions exist, the same massive particles can also be produced directly in inflaton decay, once higher-order processes are included. We show that these new, nonthermal production mechanisms often significantly strengthen constraints on the parameters of models containing massive stable particles; for example, stable charged particles with mass below the inflaton mass seem to be essentially excluded.

The equations of motion and junction conditions for a gravidilaton brane world scenario are studied in the string frame. It is shown that they allow Kasner-like solutions on the brane, which makes the dynamics of the brane very similar to the low curvature phase of pre-big-bang cosmology. Analogies and differences of this scenario with the Randall-Sundrum one and with the standard bulk pre-big-bang dynamics are also discussed.

We reexamine the issue of cosmological parameter estimation in light of current and upcoming high-precision measurements of the cosmic microwave background power spectrum. Physical quantities which determine the power spectrum are reviewed, and their connection to familiar cosmological parameters is explicated. We present a set of physical parameters, analytic functions of the usual cosmological parameters, upon which the microwave background power spectrum depends linearly (or with some other simple dependence) over a wide range of parameter values. With such a set of parameters, microwave background power spectra can be estimated with a high accuracy and negligible computational effort, vastly increasing the efficiency of the cosmological parameter error determination. The techniques presented here allow calculation of microwave background power spectra ${10}^5$ times faster than comparably accurate direct codes (after precomputing a handful of power spectra). We discuss various issues of parameter estimation, including parameter degeneracies, numerical precision, mapping between physical and cosmological parameters, systematic errors, and illustrate these considerations with an idealized model of the Microwave Anisotropy Probe experiment.

We consider the problem of detecting a burst signal of unknown shape in the data from gravitational wave interferometric detectors. We introduce a statistic which generalizes the excess power statistic proposed first by Flanagan and Hughes, and then extended by Anderson et al. to the multiple detector case. The statistic that we propose is shown to be optimal for an arbitrary noise spectral characteristic, under the two hypotheses that the noise is Gaussian, albeit colored, and that the prior for the signal is uniform. The statistic derivation is based on the assumption that a signal affects only $N_{\Vert }$ samples in the data stream, but that no other information is a priori available, and that the value of the signal at each sample can be arbitrary. This is the main difference from previous works, where different assumptions were made, such as a signal distribution uniform with respect to the metric induced by the (inverse) noise correlation matrix. The two choices are equivalent if the noise is white, and in that limit the two statistics do indeed coincide. In the general case, we believe that the statistic we propose may be more appropriate, because it does not reflect the characteristics of the noise affecting the detector on the supposed distribution of the gravitational wave signal. Moreover, we show that the proposed statistic can be easily implemented in its exact form, combining standard time-series analysis tools which can be efficiently implemented. We generalize this version of an excess power statistic to the multiple detector case, considering first a noise uncorrelated among the different instruments, and then including the effect of correlated noise. We discuss exact and approximate forms of the statistic; the choice depends on the characteristics of the noise and on the assumed length of the burst event. As an example, we show the sensitivity of the network of interferometers to a $\delta$-function burst.

We comment on the recent paper published by the Obelix Collaboration on protonium annihilation into ${\pi }^0{\pi }^0$ at rest in a liquid hydrogen target [Phys. Rev. D 65, 012001 (2002)], with particular reference to the discrepancy with the results obtained by the Crystal Barrel Collaboration.

We discuss the mixing between the sigma meson $\sigma$ and the “pure” glueball field H and study the decays of the scalar glueball candidates $f_0\mathrm{}\left(1370\right),$ $f_0\mathrm{}\left(1500\right),$ and $f_0\mathrm{}\left(1710\right)\mathrm{}$ (a linear combination of $\sigma$ and $H)$ into two pions in an effective linear sigma model.

We show that, in ${\nu }_{\mu }\overrightarrow{N}{\mu }^{-}\Lambda X$ at NOMAD energies, it is impossible to separate the products of the fragmentation of the struck quark from those of the nucleon remnant. The latter has a large contribution even in the current fragmentation region and has to be taken into account in calculating $\Lambda$ polarization using different pictures. Based on this, we make a rough estimation for the longitudinal $\Lambda$ polarization in ${\nu }_{\mu }\overrightarrow{N}{\mu }^{-}\Lambda X$ at NOMAD energies. A comparison with the data is given and predictions for ${\nu }_{\mu }\overrightarrow{N}{\mu }^{-}{\Sigma }^{+}X$ are presented.

A simple and consistent real time analysis of the long-wavelength chiral condensate fields in the background of hard thermal modes is presented in the framework of the linear sigma model. Effective evolution equations are derived for the inhomogeneous condensate fields coupled to a heat bath. The multiple effects of the thermal background on the disoriented chiral condensate are studied using linear response theory. I determine the temperature dependence of the equilibrium condensate, and examine the modification of the sigma and pion dispersion relations as these mesons traverse a hot medium. I calculate the widths by determining the dissipative coefficients at nonzero temperature at one- and two-loop order with resummed meson masses. My results show that not only decay processes, but elastic scattering processes are significant at high temperatures, yielding to short relaxation times in the phase transition region. The relaxation times obtained are shorter than in previous estimates, making the observation of disoriented chiral condensate signals questionable. Throughout this work Goldstone’s theorem is satisfied when chiral symmetry is spontaneously broken.

We discuss the fermion mass hierarchy and flavor mixing in the fat brane scenario of a five dimensional SUSY theory. Assuming that the matter fields live in the bulk, their zero mode wave functions are Gaussians, and Higgs fields are localized on the brane, we find various simple types of the matter configurations generating the mass matrices consistent with experimental data. The sfermion mass spectrum is also discussed using the matter configurations found above. Which type of squark mass spectra (the degeneracy, the decoupling and the alignment) is realized depends on the relative locations of the SUSY breaking brane and the brane where Higgs fields are localized.

We perform a comprehensive study of the Higgs sector of the minimal supersymmetric extension of the standard model in the case where all Higgs bosons are rather light, with masses of $\mathcal{O}\left(100\mathrm{}\mathrm{GeV}\right),$ and couple maximally to electroweak gauge bosons and strongly to standard third generation fermions, i.e. for large values of the ratio of the vacuum expectation values of the two Higgs doublet fields, $\tan \beta .$ We first summarize the main phenomenological features of this “intense-coupling” scenario and discuss the available constraints from direct searches of Higgs bosons at CERN LEP2 and the Fermilab Tevatron as well as the indirect constraints from precision measurements such as the $\rho$ parameter, the $\mathrm{Zb}\overline{b}$ vertex, the muon $\left(g-2\right)$ and the decay $\overrightarrow{b}s\gamma .$ We then analyze the decay branching fractions of the neutral Higgs particles in this regime and their production cross sections at the upcoming colliders, the Tevatron run II, the CERN Large Hadron Collider, a 500 GeV $e^{+}{e}^{-}$ linear collider (in the $e^{+}{e}^{-}$ and $\gamma \gamma$ options) as well as at a ${\mu }^{+}{\mu }^{-}$ collider.

Nonresonant three-body decays of D and B mesons are studied. It is pointed out that if heavy meson chiral perturbation theory (HMChPT) is applied to the heavy-light strong and weak vertices and assumed to be valid over the whole kinematic region, then the predicted decay rates for nonresonant charmless 3-body B decays will be too large, and especially $B^{-}\to {\pi }^{-}{K}^{+}{K}^{-}$ greatly exceeds the current experimental limit. This can be understood as chiral symmetry has been applied there twice beyond its region of validity. If HMChPT is applied only to the strong vertex and the weak transition is accounted for by the form factors, the dominant $B^{*}$ pole contribution to the tree-dominated direct three-body B decays will become small and the branching ratio will be of the order of ${10}^{-6}.$ The decay modes $B^{-}\to {(K}^{-}{h}^{+}{h}^{-}{)}_{\mathrm{NR}}$ and $B^0\to (K^0{h}^{+}{h}^{-}{)}_{\mathrm{NR}}$ for $h=\pi ,K$ are penguin dominated. We apply HMChPT in two different cases to study the direct 3-body D decays and compare the results with experiment. The preliminary FOCUS measurement of the direct decay $D_s^{+}\to ({\pi }^{+}{\pi }^{+}{\pi }^{-}{)}_{\mathrm{NR}}$ may provide the first indication of the importance of final-state interactions for the weak annihilation process in nonresonant D decays. Theoretical uncertainties are discussed.

We study QCD hard processes at scales of order ${\mathbf{k}}^2\gg {\Lambda }^2$ in the limit in which the beta-function coefficient b is taken to be small, but ${\overline{\alpha }}_s\left({\mathbf{k}}^2\right)$ is kept fixed. The (nonperturbative) Pomeron is exponentially suppressed in this limit, making it possible to define purely perturbative high-energy Green’s functions. The hard Pomeron exponent acquires diffusion and running coupling corrections which can be expanded in the b parameter and turn out to be dependent on the effective coupling $b{\overline{\alpha }}_s^{2}Y,$ where Y is rapidity of the process. We provide a general setup for this b expansion and we calculate the first few terms both analytically and numerically.

We study the first observed charmless $\overrightarrow{B}\mathrm{VV}$ modes, the $\overrightarrow{B}\phi K^{*}$ decays, in perturbative QCD formalism. The obtained branching ratios $B\left(\overrightarrow{B}\phi K^{*}\right)\sim 15\times {10}^{-6}$ are larger than $\sim 9\times {10}^{-6}$ from QCD factorization. The comparison of the predicted magnitudes and phases of the different helicity amplitudes, and branching ratios with experimental data can test the power counting rules, the evaluation of annihilation contributions, and the mechanism of dynamical penguin enhancement in perturbative QCD, respectively.

Up to now, the only known exact Foldy-Wouthuysen transformation (FWT) in curved space is that concerning Dirac particles coupled to static spacetime metrics. Here we construct the exact FWT related to a real spin-0 particle for the aforementioned spacetimes. This exact transformation exists independently of the value of the coupling between the scalar field and gravity. Moreover, the gravitational Darwin term written for the conformal coupling is one-third of the corresponding term in the fermionic case. There are some arguments in the literature that seem to favor the choice $\lambda =\frac{1}{6}.$ We rehearse a number of claims of these works.

We present an alternative quantization for irreducible open gauge theories. The method relies on the possibility of modifying the classical Becchi-Rouet-Stora-Tyutin (BRST) operator and the gauge-fixing action written as in Yang-Mills type theories in order to obtain an on-shell invariant quantum action by using equations characterizing the full gauge algebra. From this then follows the construction of an off-shell version of the theory. We show how it is possible to build off-shell BRST algebra together with an invariant extension of the classical action. This is realized via a systematic prescription for the introduction of auxiliary fields.

We extensively develop a perturbation theory for nonlinear cosmological dynamics, based on the Lagrangian description of hydrodynamics. We solve the hydrodynamic equations for a self-gravitating fluid with pressure, given by a polytropic equation of state, using a perturbation method up to second order. This perturbative approach is an extension of the usual Lagrangian perturbation theory for a pressureless fluid, in view of the inclusion of the pressure effect, which should be taken into account on the occurrence of velocity dispersion. We obtain the first-order solutions in generic background universes and the second-order solutions in a wider range of a polytropic index, whereas our previous work gives the first-order solutions only in the Einstein–de Sitter background and the second-order solutions for the polytropic index $4/3.$ Using the perturbation solutions, we present illustrative examples of our formulation in one- and two-dimensional systems, and discuss how the evolution of inhomogeneities changes for the variation of the polytropic index.

Modeling the potential by an inverse square law in terms of the tachyon field $\left[V\right(T)=\beta T^{-2}]$ we find an exact solution for a spatially flat isotropic universe. We show that for $\beta >2\mathrm{}\sqrt{3}/3\mathrm{}$ the model undergoes power-law inflation. A way to construct other exact solutions is specified and exemplified.