We compute the boundary two point functions of operators corresponding to massive spin 1 and spin 2 de Sitter fields by an extension of the “S-matrix” approach developed for bulk scalars. In each case the two point functions are of the form required for conformal invariance of the dual boundary field theory. We emphasize that in the context of dS/CFT one should consider unitary representations of the Euclidean conformal group, without reference to analytic continuation of the boundary theory to the Lorentzian signature.

In the context of the braneworld inflation driven by a bulk scalar field, we study the energy dissipation from the bulk scalar field into the matter on the brane in order to understand the reheating after inflation. Deriving the late-time behavior of the bulk field with dissipation by using the Green’s function method, we give a rigorous justification of the statement that the standard reheating process is reproduced in this bulk inflaton model as long as the Hubble parameter on the brane and the mass of the bulk scalar field are much smaller than the five-dimensional inverse curvature scale. Our result supports the idea that the brane inflation model caused by a bulk scalar field is expected to be a viable alternative scenario of the early universe.

A single master equation is given describing spin $s<~2$ test fields that are gauge- and tetrad-invariant perturbations of the Kerr-Taub-NUT (Newman-Unti-Tamburino) spacetime representing a source with a mass M, gravitomagnetic monopole moment $-\mathcal{l},$ and gravitomagnetic dipole moment (angular momentum) per unit mass a. This equation can be separated into its radial and angular parts. The behavior of the radial functions at infinity and near the horizon is studied and used to examine the influence of $\mathcal{l}$ on the phenomenon of superradiance, while the angular equation leads to spin-weighted spheroidal harmonic solutions generalizing those of the Kerr spacetime. Finally, the coupling between the spin of the perturbing field and the gravitomagnetic monopole moment is discussed.

We consider a dynamical membrane world in a space-time with scalar bulk matter described by domain walls. Using the solutions to Einstein field equations and Israel conditions we investigate the possibility of having shortcuts for gravitons leaving the wall and returning subsequently. As it turns out, they usually appear under mild conditions. In the comparison with photons following a geodesic inside the brane, we verify that shortcuts exist. For some universes they are small, but there are cases where shortcuts are effective. In these cases we expect them to play a significant role in the solution of the horizon problem.

Measurements of radio emission from distant galaxies and quasars verify that the polarization vectors of these radiations are not randomly oriented as naturally expected. This peculiar phenomenon suggests that the spacetime intervening between the source and observer may be exhibiting some sort of optical activity, the origin of which is not known. In the present paper we provide a plausible explanation for this phenomenon by investigating the role played by a Chern-Simons-like term in the background of an ordinary or superconducting screwed cosmic string in a scalar-tensor gravity. We discuss the possibility that the excess in polarization of the light from radio galaxies and quasars can be understood as if the electromagnetic waves emitted by these cosmic objects interact with a scalar-tensor screwed cosmic string through a Chern-Simons coupling. We use current astronomical data to constrain possible values for the coupling constant of this theory, and show that it turns out to be $\lambda \sim {10}^{-26}\mathrm{eV},$ which is two orders of magnitude larger than in string-inspired theories.

A primary goal for cosmology and particle physics over the coming decade will be to unravel the nature of the dark energy that drives the accelerated expansion of the Universe. In particular, the determination of the equation-of-state of dark energy $w\equiv p/\rho$ and its time variation $dw/dz$ will be critical for developing a theoretical understanding of the new physics behind this phenomenon. Type Ia supernovae (SNe) and cosmic microwave background (CMB) anisotropy are each sensitive to the dark energy equation of state. SNe alone can determine $w\left(z\right)\mathrm{}$ with some precision, while CMB anisotropy alone cannot because of a strong degeneracy between the matter density ${\Omega }_M$ and $w.\mathrm{}$ However, we show that the Planck CMB mission can significantly improve the power of a deep SNe survey to probe w and especially $dw/dz.\mathrm{}$ Because CMB constraints are nearly orthogonal to SNe constraints in the ${\Omega }_M-w$ plane, for constraining $w\left(z\right)\mathrm{}$ Planck is more useful than precise determination of ${\Omega }_M.$ We discuss how the CMB/SNe complementarity impacts strategies for the redshift distribution of a supernova survey to determine $w\left(z\right)\mathrm{}$ and conclude that a well-designed sample should include a substantial number of supernovae out to redshifts $z\sim 2.$

We embed the supersymmetric standard model of hybrid inflation based on the next-to-minimal superpotential term $\lambda {\mathrm{NH}}_u{H}_d$ supplemented by an inflaton term $\kappa \phi N^2$ into an extra-dimensional framework, in which all the Higgs fields and singlets live in the bulk, while all the matter fields live on the brane. All the parameters of the effective 4D model can then be naturally understood in terms of a fundamental (“string”) scale $M_{*}\sim {10}^{13}\mathrm{GeV}$ and a brane supersymmetry breaking scale ${10}^8\mathrm{GeV},$ of the same order as the height of the inflaton potential during inflation. In particular, the very small Yukawa couplings $\lambda \sim \kappa \sim {10}^{-10},$ necessary for the model to solve the strong CP problem and to generate the correct effective $\mu$ term after inflation, can be naturally understood in terms of volume suppression factors. The brane scalar masses are naturally of order a TeV while the bulk inflaton mass is naturally in the MeV range sufficient to satisfy the slow roll constraints. Curvature perturbations are generated after inflation from the isocurvature perturbations of the supersymmetric Higgs field as discussed in a companion paper.

Recent work in two-brane Randall-Sundrum models has shown that the radion can drive parametric amplification of particles on the TeV brane leading to a stage of cosmology similar to preheating. We consider radion induced preheating as a mechanism for electroweak scale baryogenesis and estimate the baryon to entropy ratio for some regions of parameter space. We also predict an upper bound for the radion mass, which makes this baryogenesis mechanism testable. Finally, we verify some assumptions with numerical calculations of the 1+1 dimensional Abelian Higgs model.

We describe energy-momentum conservation in relativistic perturbation theory in general Friedmann-Robertson-Walker (FRW) backgrounds with causal source terms, such as the presence of cosmic defect networks. A prescription for a linear energy-momentum pseudotensor in a curved FRW universe is provided, and it is decomposed using eigenfunctions of the Helmholtz equation. Conserved vector densities are constructed from the conformal geometry of these spacetimes and related to our pseudotensor, demonstrating the equivalence of these two approaches. We also relate these techniques to the role played by residual gauge freedom in establishing matching conditions at early phase transitions, which we can express in terms of components of our pseudotensor. This formalism is concise and geometrically sound on both sub- and superhorizon scales, thus extending existing work to a physically (and numerically) useful context.

We study numerically the late-time tails of linearized fields with any spin s in the background of a spinning black hole. Our code is based on the ingoing Kerr coordinates, which allow us to penetrate through the event horizon. The late time tails are dominated by the mode with the least multipole moment $\mathcal{l}$ which is consistent with the equatorial symmetry of the initial data and is equal to or greater than the least radiative mode with s and the azimuthal number m.

The accelerating expansion of the universe suggests that an unknown component with strongly negative pressure, called dark energy, currently dominates the dynamics of the universe. Such a component makes up $\sim 70\%$ of the energy density of the universe yet has not been predicted by the standard model of particle physics. The best method for exploring the nature of this dark energy is to map the recent expansion history, at which type Ia supernovae have proved adept. We examine here the depth of survey necessary to provide a precise and qualitatively complete description of dark energy. A realistic analysis of parameter degeneracies, allowance for natural time variation of the dark energy equation of state, and systematic errors in astrophysical observations all demonstrate the importance of a survey covering the full range $0<z\lesssim 2$ for revealing the nature of dark energy.

We compare the latest observations of cosmic microwave background (CMB) anisotropies with the theoretical predictions of the standard scenario of structure formation. Assuming a primordial power spectrum of adiabatic perturbations we found that the total energy density is constrained to be ${\Omega }_{\mathrm{tot}}=1.03\mathrm{}\pm 0.06$ while the energy density in baryon and cold dark matter (CDM) are ${\Omega }_b{h}^2=0.021\mathrm{}\pm 0.03$ and ${\Omega }_{\mathrm{cdm}}{h}^2=0.12\mathrm{}\pm 0.02$ (all at 68% C.L.), respectively. The primordial spectrum is consistent with scale invariance ${(n}_s=0.97\mathrm{}\pm 0.04)$ and the age of the universe is $t_0=14.6\mathrm{}\pm 0.9\mathrm{Gyr}.$ Adding information from large scale structure and supernovae, we found strong evidence for a cosmological constant ${\Omega }_{\Lambda }{=0.70\mathrm{}}_{-0.05}^{+0.07\mathrm{}}$ and a value of the Hubble parameter $h=0.69\mathrm{}\pm \mathrm{0.07.}$ Restricting this combined analysis to flat universes, we put constraints on possible “extensions” of the standard scenario. A gravity waves contribution to the quadrupole anisotropy is limited to be $r<~0.42$ (95% C.L.). A constant equation of state for the dark energy component is bound to be $w_Q<~-\mathrm{0.87.}$ We constrain the effective relativistic degrees of freedom $N_{\nu }<~6.2$ and the neutrino chemical potential $-0.01<~{\xi }_e<~0.18$ and $|{\xi }_{\mu ,\tau }|<~2.3$ (massless neutrinos).

We calculate the QCD moments of the pion structure function using Drell-Yan data on the quark distributions in the pion and a phenomenological model for the resonance region. The extracted higher twist corrections are found to be larger than those for the nucleon, contributing around 50% of the lowest moment at $Q^2=1\mathrm{}{\mathrm{GeV}}^2.$

In view of the quark mass hierarchy and the assumption of up-down parallelism, we derive two phenomenologically favored patterns of Hermitian quark mass matrices from the quark flavor mixing matrix. We compare one of them with two existing Ansätze proposed by Rosner and Worah and by Roberts et al., and find that only the latter is consistent with the present experimental data.

We point out that some models with infinite additional dimension(s) of Randall-Sundrum type predict the disappearance of orthopositronium $(o-\mathrm{Ps})$ into additional dimension(s). The experimental signature of this effect is the $o-\mathrm{Ps}\to \mathrm{invisible}$ decay of orthopositronium which may occur at a rate within three orders of magnitude of the present experimental upper limit. This result enhances existing motivations for a more sensitive search for this decay mode and suggests additional directions for testing extra dimensions in nonaccelerator experiments.

We constrain some lepton flavor violating vertices in the context of the two Higgs doublet model type III, assuming that the lightest Higgs scalar mass $m_{h^0}$ is about 115 GeV. Specifically, based on the $g-2\mathrm{muon}$ factor and the decay width of $\overrightarrow{\mu }e\gamma ,$ the following quite general bounds are obtained: $7.62\times {10}^{-4}\lesssim {\xi }_{\mu \tau }^2\lesssim 4.44\times {10}^{-2};$ ${\xi }_{e\tau }^2\lesssim 2.77\times {10}^{-14}.$ Additionally, based on the processes $\overrightarrow{\tau }\mu \gamma ,$ and $\overrightarrow{\tau }\mu \mu \mu ,$ bounds on ${\xi }_{\tau \tau }$ and ${\xi }_{\mu \mu }$ are also obtained; such constraints on these parameters still give enough room for either a strong suppression or strong enhancement on the coupling of any Higgs boson to a pair of tau leptons or a pair of muons. Furthermore, upper limits on the decay widths of the leptonic decays $\overrightarrow{\tau }e\gamma$ and $\overrightarrow{\tau }\mathrm{eee}$ are calculated, finding them to stay far from the reach of near future experiments.

In the context of the brane-world scenarios with compactified large extra dimensions, we study the production of the possible massive brane oscillations (branons) in electron-positron colliders. We compute their contribution to the electroweak gauge bosons decay width and to the single-photon and single-Z processes. With CERN LEP-I results and assuming nonobservation at LEP-II we present exclusion plots for the brane tension $\tau {=f}^4$ and the branon mass M. Prospects for the next generation of electron-positron colliders are also considered.

We propose a spectral quark model which can be applied to low energy hadronic physics. The approach is based on a generalization of the Lehmann representation of the quark propagator. We work at the one-quark-loop level. Electromagnetic and chiral invariance are ensured with the help of the gauge technique which provides particular solutions to the Ward-Takahashi identities. General conditions on the quark spectral function follow from natural physical requirements. In particular, the function is normalized, its all positive moments must vanish, while the physical observables depend on negative moments and the so-called log moments. As a consequence, the model is made finite, dispersion relations hold, chiral anomalies are preserved, and the twist expansion is free from logarithmic scaling violations, as requested of a low-energy model. We study a variety of processes and show that the framework is very simple and practical. Finally, incorporating the idea of vector-meson dominance, we present an explicit construction of the quark spectral function which satisfies all the requirements. The corresponding momentum representation of the resulting quark propagator exhibits only cuts on the physical axis, with no poles present anywhere in the complex momentum space. The momentum-dependent quark mass compares very well with recent lattice calculations. A large number of predictions and relations, valid at the low-energy scale of the model, can be deduced from our approach for such quantities as the pion light-cone wave function, non-local quark condensate, pion transition form factor, pion valence parton distribution function, etc. These quantities, obtained at a low-energy scale of the model, have the correct properties, as requested by symmetries and anomalies. They also have pure twist expansion, free of logarithmic corrections, as requested by the QCD factorization property.

Two mechanisms for the ${\pi }_1{(J}^{\mathrm{PC}}{=1\mathrm{}}^{-+})$ hybrid meson decay processes ${\pi }_1\to \eta \pi ,{\eta }^{\prime }\pi$ are investigated. These mechanisms are applied to $\overrightarrow{\phi }\eta \gamma ,{\eta }^{\prime }\gamma$ and $J/\overrightarrow{\psi }\eta \gamma ,{\eta }^{\prime }\gamma$ decays to illustrate the validity of the decay mechanisms and to obtain independent information on the coupling of $\eta ,{\eta }^{\prime }$ to quark and gluonic operators. From this information, we find that $\Gamma ({\pi }_1\to \eta \pi )/\Gamma ({\pi }_1\to {\eta }^{\prime }\pi )$ is substantially different in the two decay mechanisms, and hence future experimental measurements of this ratio will provide valuable information for determining the mechanism for these hybrid decays.

We show that particle production in proton-nucleus (pA) collisions in the color glass condensate model can be related to deep inelastic scattering (DIS) of leptons on protons or nuclei. The common building block is the quark-antiquark (or gluon-gluon) dipole cross section which is present in both DIS and pA processes. This correspondence in a sense generalizes the standard leading twist approach to pA collisions based on collinear factorization and perturbative QCD, and allows one to express the pA cross sections in terms of a universal quantity (dipole cross section) which, in principle, can be measured in DIS or other processes. Therefore, using the parametrization of the dipole cross section at DESY HERA, one can calculate particle production cross sections in proton-nucleus collisions at high energies. Alternatively, one could use proton-nucleus experiments to further constrain models of the dipole cross section. We show that the McLerran-Venugopalan model predicts an enhancement of the cross sections at large $p_{\perp }$ (Cronin effect) and a suppression of the cross sections at low $p_{\perp }.$ The crossover depends on rapidity and moves to higher $p_{\perp }$ as one goes to more forward rapidities.