We review the implications of having a nontrivial matter component in the Universe and the potential for detecting such a component through the matter power spectrum and integrated Sachs-Wolfe effect. We adopt a phenomenological approach and consider the mysterious dark energy to be a cosmic fluid. It is thus fully characterized, up to linear order, by its equation of state and its speed of sound. Whereas the equation of state has been widely studied in the literature, less interest has been devoted to the speed of sound. Its observational consequences come predominantly from very large scale modes of dark matter perturbations $(k<\mathrm{}0.01h{\mathrm{Mpc}}^{-1}).\mathrm{}$ Since these modes have hardly been probed so far by large scale galaxy surveys, we investigate whether joint constraints can be placed on those two quantities using the recent cosmic microwave background (CMB) fluctuations measurements by the Wilkinson Microwave Anisotropy Probe as well as the recently measured CMB large scale structure cross correlation. We find only a tentative 1 sigma detection of the speed of sound, from CMB alone, $c_s^2<0.04\mathrm{}$ at this low significance level. Furthermore, the current uncertainties in bias in the matter power spectrum preclude any constraints being placed using the cross correlation of CMB with the NRAO VLA Sky Survey radio survey.

Space-borne interferometric gravitational wave detectors, sensitive in the low-frequency (millihertz) band, will fly in the next decade. In these detectors the spacecraft-to-spacecraft light-travel-times will necessarily be unequal, time varying, and (due to aberration) have different time delays on up and down links. The reduction of data from moving interferometric laser arrays in solar orbit will in fact encounter nonsymmetric up- and down-link light time differences that are about 100 times larger than has previously been recognized. The time-delay interferometry (TDI) technique uses knowledge of these delays to cancel the otherwise dominant laser phase noise and yields a variety of data combinations sensitive to gravitational waves. Under the assumption that the (different) up- and down-link time delays are constant, we derive the TDI expressions for those combinations that rely only on four interspacecraft phase measurements. We then turn to the general problem that encompasses time dependence of the light-travel times along the laser links. By introducing a set of noncommuting time-delay operators, we show that there exists a quite general procedure for deriving generalized TDI combinations that account for the effects of time dependence of the arms. By applying our approach we are able to re-derive the “flex-free” expression for the unequal-arm Michelson combinations $X_1,$ and obtain the generalized expressions for the TDI combinations called relay, beacon, monitor, and symmetric Sagnac.

Following a baryogenesis scenario proposed by Lazarides, Panagiotakopoulos, and Shafi, we show how the observed baryon asymmetry can be explained via resonant leptogenesis in a class of supersymmetric models with an intermediate mass scale $M_I\lesssim {10}^9\mathrm{GeV}.$ It involves the out of equilibrium decay of heavy $(\lesssim M_I)$ right handed neutrinos at a temperature close to the TeV supersymmetry breaking scale. Such models can also resolve the MSSM μ problem.

The mass gap equation for spontaneous chiral symmetry breaking is studied directly in Minkowski space. In hadronic physics, spontaneous chiral symmetry breaking is crucial to generate a constituent mass for the quarks, and to produce the partially conserved axial vector current theorems, including a small mass for the pion. Here a class of finite kernels is used, expanded in Yukawa interactions. The Schwinger-Dyson equation is solved with an analytical approach. This improves the state of the art of solving the mass gap equation, which is usually solved with the equal-time approximation or with the Euclidean approximation. The mapping from Euclidean space to Minkowski space is also illustrated.

The observed branching ratios for $\overrightarrow{B}K{\eta }^{\prime }$ decays are much larger than factorization predictions in the standard model (SM). Many proposals have been made to reconcile the data and theoretical predictions. In this paper we study these decays within the SM using flavor SU(3) symmetry. Treating the singlet ${\eta }_1$ and octet $({\pi }^{\pm ,0\mathrm{}}{,K}^{\pm },K^0{,K}^0,{\eta }_8)$ pseudoscalar mesons as a nonet multiplet, we find that if small annihilation amplitudes are neglected only 11 hadronic parameters are needed to describe $\overrightarrow{B}\mathrm{PP}$ decays where P can be one of the $\pi ,$ K, $\eta$ and ${\eta }^{\prime }$ mesons. We find that existing data are consistent with the SM. We also predict several measurable branching ratios and CP asymmetries for $\overrightarrow{B}K\left(\pi \right)\eta \left({\eta }^{\prime }\right),$ $\eta \left({\eta }^{\prime }\right)\eta \left({\eta }^{\prime }\right)$ decays. Experiments in the near future can provide important tests for the standard model with flavor symmetry.

If strange quark matter is the true ground state of matter, it must have lower energy than nuclear matter. Simultaneously, two-flavor quark matter must have higher energy than nuclear matter, for otherwise the latter would convert to the former. We show, using an effective chiral Lagrangian, that the existence of a new lower energy ground state for two-flavor quark matter, the pion condensate, shrinks the window allowing strange quark matter to be the ground state of matter and sets new limits on the current strange quark mass.

The violation of Lorentz invariance has been invoked in a number of ways to explain issues dealing with ultrahigh energy cosmic ray (UHECR) production and propagation. These treatments, however, have mostly been limited to examples in the proton-neutron system and photon-electron system. In this paper we show how a broader violation of Lorentz invariance would allow for a series of previously forbidden decays to occur, and how that could lead to UHECR primaries being heavy baryonic states or Higgs bosons.

We study the braneworld solutions based on a solvable model of 5D gauged supergravity with two scalars of conformal dimension 3, which correspond to bilinear operators of fermions in the dual $\mathcal{N}=4\mathrm{}$ super Yang-Mills theory on the boundary. An accelerating braneworld solution is obtained when both scalars are taken as the form of deformations of the super Yang-Mills theory and the bulk supersymmetry is broken. This solution is smoothly connected to the Poincaré invariant brane in the limit of a vanishing cosmological constant. The stability of this brane solution and the correspondence to the gauge theory are addressed.

We study covariant entropy bounds in dynamical spacetimes with naked singularities. Specifically we study a spherically symmetric massless scalar field solution. The solution is an inhomogeneous cosmology with an initial spacelike singularity, and a naked timelike singularity at the origin. We construct the entropy flux 4-vector for the scalar field, and show by explicit computation that the generalized covariant bound $S_{{L(B,B}^{\prime })}<~\left[A\right(B\left)\mathrm{}-{A(B}^{\prime }\right)]/4\mathrm{}$ is violated for light sheets ${L(B,B}^{\prime })$ in the neighborhood of the (evolving) apparent horizon. We find no violations of the Bousso bound [for which ${A(B}^{\prime })=0\mathrm{}],$ even though certain sufficient conditions for this bound do not hold. This result therefore shows that these conditions are not necessary.

The differential rotation of r-modes is investigated within the nonlinear theory up to second order in the mode amplitude in the case of a slowly rotating, Newtonian, barotropic, perfect-fluid star. We find a nonlinear extension of the linear r-mode, which represents differential rotation that produces large scale drifts of fluid elements along stellar latitudes. This solution includes a piece induced by first-order quantities and another one that is a pure second-order effect. Since the latter is stratified on cylinders, it cannot cancel differential rotation induced by first-order quantities, which is not stratified on cylinders. It is shown that, unlike the situation in the linearized theory, r-modes do not preserve the vorticity of fluid elements at second order. It is also shown that the physical angular momentum and energy of the perturbation are, in general, different from the corresponding canonical quantities.

We investigate a new way of realizing a period of cosmological inflation in the context of brane gas cosmology. It is argued that a gas of codimension one branes, out of thermal equilibrium with the rest of the matter, has an equation of state which can—after stabilization of the dilaton—lead to power-law inflation of the bulk. The most promising implementation of this mechanism might be in type IIB superstring theory, with inflation of the three large spatial dimensions triggered by “stabilized embedded 2-branes.” Possible applications and problems with this proposal are discussed.

The recent observational evidence for the present accelerated stage of the Universe has stimulated renewed interest in alternative cosmologies. In general, such models contain an unknown negative-pressure dark component that explains the supernova results and reconciles the inflationary flatness prediction $({\Omega }_T=1)$ and the cosmic microwave background measurements with the dynamical estimates of the quantity of matter in the Universe $({\Omega }_m\simeq 0.3\pm 0.1).$ In this paper we study some observational consequences of a dark energy candidate, the so-called generalized Chaplygin gas, which is characterized by an equation of state $p_C=-A/{\rho }_C^{\alpha },$ where A and $\alpha$ are positive constants. We investigate the prospects for constraining the equation of state of this dark energy component by combining Chandra observations of the x-ray luminosity of galaxy clusters, independent measurements of the baryonic matter density, the latest measurements of the Hubble parameter as given by the HST Key Project, and data of the Supernova Cosmology Project. We show that very stringent constraints on the model parameters can be obtained from this combination of observational data.

We show that stationary dyonic black holes with static and counterrotating horizons exist in Einstein-Maxwell-dilaton theory when the dilaton coupling constant exceeds the Kaluza-Klein value. The black holes with a static horizon bifurcate from the static black holes. Their mass decreases with increasing angular momentum; their horizons are prolate.

The supersymmetric QCD and the supersymmetric electroweak loop corrections to the violations of weak isospin to Yukawa couplings are investigated. Specifically it involves an analysis of the supersymmetric (SUSY) loop corrections to the Higgs couplings to the third generation quarks and leptons. Here we analyze the SUSY loop corrections to the charged Higgs couplings which are then compared with the supersymmetric loop corrections to the neutral Higgs couplings previously computed. It is found that the weak isospin violations can be quite significant, i.e., as much as 40–50% or more of the total loop correction to the Yukawa coupling. The effects of CP phases are also studied and it is found that these effects can either enhance or suppress the weak isospin violations. We also investigate the weak isospin violation effects on the branching ratio ${BR(H}^{-}\to \overline{t}{b)/BR(H}^{-}\to {\overline{\nu }}_{\tau }{\tau }^{-})$ and show that the effects are sensitive to CP phases. Thus an accurate measurement of this branching ratio along with the branching ratio of the neutral Higgs boson decays can provide a measure of weak isospin violation along with providing a clue to the presence of supersymmetry.

One-loop matching of heavy-light currents is carried out for a highly improved lattice action, including the effects of mixings with dimension $4O(1/M)\mathrm{}$ and $O\left(a\right)\mathrm{}$ operators. We use the NRQCD action for heavy quarks, the Asqtad improved naive action for light quarks, and the Symanzik improved glue action. As part of the matching procedure we also present results for the NRQCD self-energy and for massless Asqtad quark wave function renormalization with improved glue.

Decays of the $\psi \mathrm{}\left(2S\right)\mathrm{}$ into vector plus tensor meson final states have been studied with 14 million $\psi \mathrm{}\left(2S\right)\mathrm{}$ events collected with the BESII detector. The branching fractions of $\psi \mathrm{}\left(2S\right)\mathrm{}\to \omega f_2\mathrm{}\left(1270\right),$ $\rho a_2\mathrm{}\left(1320\right),$ $K^{*}{\mathrm{}\left(892\right)\mathrm{}}^0{K}_2^{*}{\mathrm{}\left(1430\right)\mathrm{}}^0+\mathrm{c}.\mathrm{c}.\mathrm{},$ and $\phi f_2^{\prime }\mathrm{}\left(1525\right)\mathrm{}$ are determined. They improve upon previous BESI results and confirm the violation of the “12%” rule for $\psi \mathrm{}\left(2S\right)\mathrm{}$ decays to $\mathrm{VT}$ channels with higher precision.

We report a measurement of the production ratio of charged and neutral B mesons from ${\rm Y}\mathrm{}\left(4S\right)\mathrm{}$ decays based on the ratio of efficiency-corrected yields for the charmonium modes $J/\psi K^{+}$ and $J/\psi K_s^0$ with 81.9 ${\mathrm{fb}}^{\mathrm{-}1}$ of data collected with the BABAR detector on the ${\rm Y}\mathrm{}\left(4S\right)\mathrm{}$ resonance at 10.580 GeV. We find a value of $1.006\pm 0.036\left(\mathrm{stat}\right)\pm 0.031\left(\mathrm{syst}\right)$ for the ratio $R^{+/0\mathrm{}}=\Gamma \left({\rm Y}\mathrm{}\right(4S)\mathrm{}\to B^{+}{B}^{-})/\Gamma \left({\rm Y}\mathrm{}\right(4S)\mathrm{}\to B^0{B}^0).$

We consider Neveu-Schwarz (NS) pp waves with spacetime supersymmetry. Upon compactification of a spacelike direction, these backgrounds develop closed null curves (CNCs) and closed timelike curves (CTCs), and are U dual to supersymmetric Gödel type universes. We study classical and quantum strings in this background, with emphasis on the strings winding around the compact direction. We consider two types of strings: long strings stabilized by NS flux and rotating strings which are stabilized against collapse by angular momentum. Some of the latter strings wrap around CNCs and CTCs, and are thus a potential source of pathology. We analyze the partition function, and in particular discuss the effects of these string states. Although our results are not conclusive, the partition function seems to be dramatically altered due to the presence of CNCs and CTCs. We discuss some interpretations of our results, including a possible sign of unitary violation.

The scalar dark matter candidate in a prototypical theory space little Higgs model is investigated. We review all details of the model pertinent to a relic density calculation. We perform a thermal relic density calculation including couplings to the gauge and Higgs sectors of the model. We find two regions of parameter space that give acceptable dark matter abundances. The first region has a dark matter candidate with a mass $O\left(100\mathrm{}\mathrm{GeV}\right),$ the second region has a candidate with a mass greater than $O\left(500\mathrm{}\mathrm{GeV}\right).\mathrm{}$ The dark matter candidate in either region is an admixture of an $\mathrm{SU}\left(2\right)\mathrm{}$ triplet and an $\mathrm{SU}\left(2\right)\mathrm{}$ singlet, thereby constituting a possible weakly interacting massive particle.

The existence of phantom energy in a universe which evolves to eventually show a big rip doomsday is a possibility which is not excluded by present observational constraints. In this paper it is argued that the field theory associated with a simple quintessence model is compatible with a field definition that is interpretable in terms of a rank-3 axionic tensor field, whenever we consider a perfect-fluid equation of state that corresponds to the phantom energy regime. Explicit expressions for the axionic field and its potential, both in terms of an imaginary scalar field, are derived, which show that these quantities both diverge at the big rip, and that the onset of phantom-energy dominance must take place just at present.