We study the quantum stress tensor correlation function for a massless scalar field in a flat two-dimensional spacetime containing a moving mirror. We construct the correlation functions for right-moving and left-moving fluxes for an arbitrary trajectory, and then specialize them to the case of a mirror trajectory for which the expectation value of the stress tensor describes a pair of delta-function pulses, one of negative energy and one of positive energy. The flux correlation function describes the fluctuations around this mean stress tensor, and reveals subtle changes in the correlations between regions where the mean flux vanishes.

We present a calculation of the zeta function and of the functional determinant for a Laplace-type differential operator, corresponding to a scalar field in a higher-dimensional de Sitter brane background, which consists of a higher-dimensional anti de Sitter bulk spacetime bounded by a de Sitter section, representing a brane. Contrary to the existing examples, which all make use of conformal transformations, we evaluate the zeta function working directly with the higher-dimensional wave operator. We also consider a generic mass term and coupling to curvature, generalizing previous results. The massless, conformally coupled case is obtained as a limit of the general result and compared with known calculations. In the limit of large anti de Sitter radius, the zeta determinant for the ball is recovered in perfect agreement with known expressions, providing an interesting check of our result and an alternative way of obtaining the ball determinant.

We study the sensitivity of weak lensing by large scale structures as a probe of the evolution of dark energy. We explore a two-parameters model of dark energy evolution, inspired by tracking quintessence models. To this end, we compute the likelihood of a few fiducial models with varying and nonvarying equation of states. For the different models, we investigate the dark energy parameter degeneracies with the mass power spectrum shape $\Gamma$, normalization ${\sigma }_8$, and with the matter mean density ${\Omega }_M$. We find that degeneracies are such that weak lensing turns out to be a good probe of dark energy evolution, even with limited knowledge on $\Gamma$, ${\sigma }_8$, and ${\Omega }_M$. This result is a strong motivation for performing large scale structure simulations beyond the simple constant dark energy models, in order to calibrate the nonlinear regime accurately. Such calibration could then be used for any large scale structure tests of dark energy evolution. Prospective for the Canada France Hawaii Telescope Legacy Survey and Super-Novae Acceleration Probe are given. These results complement nicely the cosmic microwave background and supernovae constraints.

We study particle production at the collision of two domain walls in 5-dimensional Minkowski spacetime. This may provide the reheating mechanism of an ekpyrotic (or cyclic) brane universe, in which two BPS branes collide and evolve into a hot big bang universe. We evaluate a production rate of particles confined to the domain wall. The energy density of created particles is given as $\rho \approx 20{\overline{g}}^4{N}_b{m}_{\eta }^4$ where $\overline{g}$ is a coupling constant of particles to a domain-wall scalar field, $N_b$ is the number of bounces at the collision and $m_{\eta }$ is the fundamental mass scale of the domain wall. It does not depend on the width $d$ of the domain wall, although the typical energy scale of created particles is given by $\omega \sim 1/d$. The reheating temperature is evaluated as $T_{\mathrm{R}}\approx 0.88\overline{g}{N}_b^{1/4}$. In order to have the baryogenesis at the electro-weak energy scale, the fundamental mass scale is constrained as $m_{\eta }\gtrsim 1.1\times {10}^7\mathrm{G}\mathrm{e}\mathrm{V}$ for $\overline{g}\sim {10}^{-5}$.

We discuss spatial fluctuations in the gravitational wave background arising from unresolved Galactic binary sources, such as close white dwarf binaries, due to the fact the galactic binary source distribution is anisotropic. We introduce a correlation analysis of the two data streams of the Laser Interferometer Space Antenna (LISA) to extract spherical harmonic coefficients of the hexadecapole moment ($l=4$) related to the projected two-dimensional density distribution of the binary source population in an independent manner. In this analysis, we use a free parameter with which we can effectively control the frequency of the cartwheel rotation of LISA. The proposed technique complements and improves over previous suggestions in the literature to measure the gravitational wave background anisotropy based on the time modulation of data as LISA orbits around the Sun. Such techniques, however, are restricted only to certain combinations of spherical harmonic coefficients of the galaxy with no ability to separate them individually. With LISA, $m=2,3$ and 4 coefficients of the hexadecapole ($l=4$) can be measured with signal-to-noise ratios at the level of ten and above in a certain coordinate system. In addition to the hexadecapole coefficients, when combined with the time modulation analysis, the correlation study also can be used, in principle, to measure quadrupole coefficients of the binary distribution.

Captures of compact objects (COs) by massive black holes (MBHs) in galactic nuclei will be an important source for LISA, the proposed space-based gravitational wave (GW) detector. However, a large fraction of captures will not be individually resolvable—either because they are too distant, have unfavorable orientation, or have too many years to go before final plunge—and so will constitute a source of “confusion noise,” obscuring other types of sources. In this paper we estimate the shape and overall magnitude of the GW background energy spectrum generated by CO captures. This energy spectrum immediately translates to a spectral density ${\mathcal{S}}_h^{\mathrm{c}\mathrm{a}\mathrm{p}\mathrm{t}}(f)$ for the amplitude of capture-generated GWs registered by LISA. The overall magnitude of ${\mathcal{S}}_h^{\mathrm{c}\mathrm{a}\mathrm{p}\mathrm{t}}(f)$ is linear in the CO capture rates, which are rather uncertain; therefore we present results for a plausible range of rates. ${\mathcal{S}}_h^{\mathrm{c}\mathrm{a}\mathrm{p}\mathrm{t}}(f)$ includes the contributions from both resolvable and unresolvable captures, and thus represents an upper limit on the confusion noise level. We then estimate what fraction of ${\mathcal{S}}_h^{\mathrm{c}\mathrm{a}\mathrm{p}\mathrm{t}}(f)$ is due to unresolvable sources and hence constitutes confusion noise. We find that almost all of the contribution to ${\mathcal{S}}_h^{\mathrm{c}\mathrm{a}\mathrm{p}\mathrm{t}}(f)$ coming from white dwarf and neutron star captures, and at least $\sim 30\%$ of the contribution from black hole captures, is from sources that cannot be individually resolved. Nevertheless, we show that the impact of capture confusion noise on the total LISA noise curve ranges from insignificant to modest, depending on the rates. Capture rates at the high end of estimated ranges would raise LISA’s overall (effective) noise level $[f{S}_h^{\mathrm{e}\mathrm{f}\mathrm{f}}(f){]}^{1/2}$ by at most a factor $\sim 2$ in the frequency range $1–10\mathrm{m}\mathrm{H}z$, where LISA is most sensitive. While this slightly elevated noise level would somewhat decrease LISA’s sensitivity to other classes of sources, we argue that, overall, this would be a pleasant problem for LISA to have: It would also imply that detection rates for CO captures were at nearly their maximum possible levels (given LISA’s baseline design and the level of confusion noise from galactic white dwarf binaries). This paper also contains, as intermediate steps, several results that should be useful in further studies of LISA capture sources, including (i) a calculation of the total GW energy output from generic inspirals of COs into Kerr MBHs, (ii) an approximate GW energy spectrum for a typical capture, and (iii) an estimate showing that in the population of detected capture sources, roughly half the white dwarfs and a third of the neutron stars will be detected when they still have $\gtrsim 10$ years to go before final plunge.

An interesting extension of the standard model is based on the electroweak gauge group $\mathrm{S}\mathrm{U}(3{)}_L\times \mathrm{U}(1)$. It requires three generations to cancel anomalies, treats the third generation differently than the first two, and has a rich phenomenology. There are several models, distinguished by the embedding of the charge operator into the $\mathrm{S}\mathrm{U}(3{)}_L$ group and by the choice of fermion representations. In this brief report, we consider flavor-changing neutral currents in these models, concentrating on the $P-\overline{P}$ mass difference, where $P=(K,D,B,B_s)$, as well as $B\to K{l}^{+}{l}^{-}$, $B\to {\mu }^{+}{\mu }^{-}$, and $B_s\to {\mu }^{+}{\mu }^{-}$ decays. Although the $P-\overline{P}$ mass difference has been considered previously in some models, the rare $B$ decays are new. We find that the strongest bounds come from the $B-\overline{B}$ and $B_s-{\overline{B}}_s$ mass difference.

We present an update of the Hagedorn hypothesis of the exponential growth of the number of hadronic resonances with mass. We use the newest available experimental data for the nonstrange mesons and baryons, as well as fill in some missing states according to the observation that the high-lying states form chiral multiplets. The results show, especially for the case of the mesons, that the Hagedorn growth continues with the increasing mass, with the new states lining up along the exponential growth.

Adopting the complete ${\alpha }_s^4$ approach of the perturbative QCD and the updated parton distribution functions, we have estimated the hadronic production of the $P$-wave excited $B_c$ states ($B_{cJ,L=1}^{*}$). In the estimate, special care has been paid to the dependence of the production amplitude on the derivative of the wave function at origin which is obtained by the potential model. For experimental references, main theoretical uncertainties are discussed, and the total cross section as well as the distributions of the production with reasonable cuts at the energies of Tevatron and CERN LHC are computed and presented properly. The results show that the $P$-wave production may contribute to the $B_c$-meson production indirectly by a factor of about 0.5 of the direct production, and according to the estimated cross section, it is further worthwhile to study the possibility of observing the $P$-wave production itself experimentally.

We calculate production cross sections of a forward quark-gluon pair and of two gluons at midrapidity in deep inelastic scattering and in high energy proton-nucleus collisions. The calculation is performed in the framework of the color glass condensate formalism. We first calculate the cross sections in the quasiclassical approximation, which includes multiple rescatterings in the target. We then proceed to include the effects of nonlinear small-$x$ evolution in the production cross sections. It is interesting to note that our result for the two-gluon production cross section appears to be in direct violation of Abramovsky-Gribov-Kanchelli cutting rules, which is the first example of such violation in QCD. The calculated quark-gluon and gluon-gluon production cross sections can be used to construct theoretical predictions for two-particle azimuthal correlations at the Relativistic Heavy Ion Collider and LHC ($I^{p(d)A}$) as well as for deep inelastic scattering experiments at the Hadron Electron Ring Accelerator and the Electron-Relativistic Heavy Ion Collider.

We present the renormalized Taylor expansion of the chiral condensate with chemical potential. The relation with the Taylor coefficients of meson susceptibilities and the quark mass dependence of the quark number susceptibilities are obtained through chiral Ward identities and Maxwell relations. The continuum limit is obtained in quenched and two flavor QCD. In $N_f=2$ QCD, the quadratic response coefficients of the chiral condensate to chemical potential indicate that pion fluctuations decrease at finite chemical potential toward the critical end point. We discuss how these observables can be used to test other features of the QCD phase diagram.

For neutrinos of $\mathcal{O}(10\mathrm{k}\mathrm{e}\mathrm{V})$ energies, their oscillation lengths are less than a few hundred meters, thereby suggesting the fascinating idea of oscillation experiments of small geometrical size. To help in evaluating this idea, a formalism is developed for calculating the neutrino ionization cross sections for H as well as the noble atoms. This formalism is based on the use of spin-independent atomic wave functions and should very accurately describe the ionization spectra for H, He, Ne, and Ar. The accuracy is considerably reduced for the Xe case though, where the spin dependence in the wave functions is non-negligible. Nevertheless, even for Xe the results remain qualitatively correct. In all cases, the atomic ionizations cross section per electron is found to be smaller than the neutrino cross section off free electrons, approaching it from below as the energy increases to the 100 keV region. At the 10–20 keV range though, the atomic binding effects in the cross sections and the spectra are very important and increasing with the atomic number. They are canceling out though, when total ionization cross section ratios, like ${\nu }_{\mu }/{\nu }_e$ or ${\overline{\nu }}_{\mu }/{\overline{\nu }}_e$, are considered.

In most supersymmetic models, neutralino dark matter particles are predicted to accumulate in the Galactic center and annihilate generating, among other products, gamma rays. The Energetic Gamma Ray Experiment Telescope has made observations in this region, and is sensitive to gamma rays from 30 MeV to $\sim 30\mathrm{G}\mathrm{e}\mathrm{V}$. We have used an improved point source analysis including an energy dependent point spread function and an unbinned maximum likelihood technique, which has allowed us to lower the limits on gamma ray flux from the Galactic center by more than 1 order of magnitude. We find that the present Energetic Gamma Ray Experiment Telescope data can limit many supersymmetric models if the density of the Galactic dark matter halo is cuspy or spiked toward the Galactic center. We also discuss the ability of the Gamma ray Large Area Space Telescope to test these models.

We construct a fuzzy $S^4$, utilizing the fact that ${\mathbf{C}\mathbf{P}}^3$ is an $S^2$ bundle over $S^4$. We find that the fuzzy $S^4$ can be described by a block-diagonal form whose embedding square matrix represents a fuzzy ${\mathbf{C}\mathbf{P}}^3$. We discuss some pending issues on fuzzy $S^4$, i.e., precise matrix-function correspondence, associativity of the algebra, and, etc. Similarly, we also obtain a fuzzy $S^8$, using the fact that ${\mathbf{C}\mathbf{P}}^7$ is a ${\mathbf{C}\mathbf{P}}^3$ bundle over $S^8$.

We investigate nondilatonic $p$-branes in the near-extremal, near-horizon regime. A two-dimensional gravity model, obtained from dimensional reduction, gives an effective description of the brane. We show that the ${\mathrm{A}\mathrm{d}\mathrm{S}}_{p+2}$/${\mathrm{C}\mathrm{F}\mathrm{T}}_{p+1}$ correspondence at finite temperature admits an effective description in terms of a ${\mathrm{A}\mathrm{d}\mathrm{S}}_2$/${\mathrm{C}\mathrm{F}\mathrm{T}}_1$ duality endowed with a scalar field, which breaks the conformal symmetry and generates a nonvanishing central charge. The entropy of the ${\mathrm{C}\mathrm{F}\mathrm{T}}_1$ is computed using Cardy formula. Fixing in a natural way a free, dimensionless, parameter introduced in the model by a renormalization procedure, we find exact agreement between the ${\mathrm{C}\mathrm{F}\mathrm{T}}_1$ entropy and the Bekenstein-Hawking entropy of the brane.

We propose that under certain conditions heterotic string compactifications on half-flat and nearly Kähler manifolds are equivalent. Based on this correspondence we argue that the moduli space of the nearly Kähler manifolds under discussion consists only of the Kähler deformations moduli space and there is no correspondent for the complex structure deformations.

The theory of statistical mechanics is studied in the presence of Lorentz-violating background fields. The analysis is performed using the Standard-Model Extension (SME) together with a Jaynesian formulation of statistical inference. Conventional laws of thermodynamics are obtained in the presence of a perturbed hamiltonian that contains the Lorentz-violating terms. As an example, properties of the nonrelativistic ideal gas are calculated in detail. To lowest order in Lorentz violation, the scalar thermodynamic variables are only corrected by a rotationally invariant combination of parameters that mimics a (frame dependent) effective mass. Spin-couplings can induce a temperature-independent polarization in the classical gas that is not present in the conventional case. Precision measurements in the residual expectation values of the magnetic moment of Fermi gases in the limit of high temperature may provide interesting limits on these parameters.

Hamiltonian dynamics of a gravitational field contained in a spacetime region with boundary $S$ being a null-like hypersurface (a wave front) is discussed. A complete Hamiltonian formula for the dynamics (with no surface integrals neglected) is derived. A quasilocal proof of the first law of black holes thermodynamics is obtained as a consequence, in the case when $S$ is a nonexpanding horizon. The zeroth law and Penrose inequalities are discussed from this point of view.