Gravitational wave solutions to Einstein’s equations and their generation are examined in D-dimensional flat spacetimes. First the plane wave solutions are analyzed; then the wave generation is studied with the solution for the metric tensor being obtained with the help of retarded D-dimensional Green’s functions. Because of the difficulties in handling the wave tails in odd dimensions we concentrate our study on even dimensions. We compute the metric quantities in the wave zone in terms of the energy-momentum tensor at retarded time. Some special cases of interest are studied. First we study the slow motion approximation, where the D-dimensional quadrupole formula is deduced. Within the quadrupole approximation, we consider two cases of interest: a particle in circular orbit and a particle falling radially into a higher dimensional Schwarzschild black hole. Then we turn our attention to the gravitational radiation emitted during collisions lasting zero seconds, i.e., hard collisions. We compute the gravitational energy radiated during the collision of two point particles, in terms of a cutoff frequency. In the case in which at least one of the particles is a black hole, we argue that this cutoff frequency should be close to the lowest gravitational quasinormal frequency. In this context, we compute the scalar quasinormal frequencies of higher dimensional Schwarzschild black holes. Finally, as an interesting new application of this formalism, we compute the gravitational energy release during the quantum process of black hole pair creation. These results might be important in light of the recent proposal that there may exist extra dimensions in the Universe, one consequence of which may be black hole creation at the Large Hadron Collider at CERN.

We study theoretical aspects of rotating black hole production and evaporation in extra dimension scenarios with TeV scale gravity, within the mass range in which the higher dimensional Kerr solution provides a good description. We evaluate the production cross section of black holes, taking their angular momenta into account. We find that it becomes larger than the Schwarzschild radius squared, which is conventionally utilized in the literature, and our result nicely agrees with the recent numerical study by Yoshino and Nambu within a few percent error for the higher dimensional case. In the same approximation used to obtain the above result, we find that the production cross section becomes larger for a black hole with larger angular momentum. Second, we derive the generalized Teukolsky equation for spin 0, 1/2, and 1 brane fields in higher dimensional Kerr geometry and explicitly show that it is separable in any dimensions. For a five-dimensional (Randall-Sundrum) black hole, we obtain analytic formulas for the greybody factors in the low frequency expansion and we present the power spectra of the Hawking radiation as well as their angular dependence. The phenomenological implications of our results are briefly sketched.

The consensus of opinion in cosmology is that the Universe is currently undergoing a period of accelerated expansion. With current and proposed high precision experiments it offers the hope of being able to discriminate between the two competing models that are being suggested to explain the observations, namely a cosmological constant or a time dependent “quintessence” model. The latter suffers from a plethora of scalar field potentials all leading to similar late time behavior of the universe and, hence, to a lack of predictability. In this paper, we develop a model independent approach which simply involves parametrizing the dark energy equation of state in terms of known observables. This allows us to analyze the impact dark energy has had on cosmology without the need to refer to particular scalar field models and opens up the possibility that future experiments will be able to constrain the dark energy equation of state in a model independent manner.

We investigate in detail the question of whether a nonvanishing cosmological constant is required by the present-day cosmic microwave background and large scale structure data when general isocurvature initial conditions are taken into account. We also discuss the differences between the usual Bayesian and the frequentist approaches in data analysis. We show that the Cosmic Background Explorer (COBE)-normalized matter power spectrum is dominated by the adiabatic mode and therefore breaks the degeneracy between initial conditions which is present in the cosmic microwave background anisotropies. We find that in a flat universe the Bayesian analysis requires ${\Omega }_{\Lambda }\ne 0$ to more than $3\sigma ,$ while in the frequentist approach ${\Omega }_{\Lambda }=0\mathrm{}$ is still within $3\sigma$ for a value of $h<~\mathrm{0.48.}$ Both conclusions hold regardless of the initial conditions.

We analyze the CP asymmetry of the $\overrightarrow{B}\phi K_S$ process in general supersymmetric models. In the framework of the mass insertion approximation, we derive model independent limits for the mixing CP asymmetry. We show that a chromomagnetic type of operator may play an important role in accounting for the deviation of the mixing CP asymmetry between $\overrightarrow{B}\phi K_S$ and $\overrightarrow{B}J/\psi K_S$ processes observed by the Belle and BaBar experiments. A possible correlation between the direct and mixing CP asymmetry is also discussed. Finally, we apply our result in the minimal supergravity model and supersymmetric models with nonuniversal soft terms.

We calculate the $\overrightarrow{B}{D}^{\left(*\right)}$ form factors in the heavy-quark and large-recoil limits in the perturbative QCD framework based on the $k_T$ factorization theorem, assuming the hierachy $M_B\gg M_{D^{\left(*\right)}}\gg \overline{\Lambda },$ with the B meson mass $M_B,$ the $D^{\left(*\right)}$ meson mass $M_{D^{\left(*\right)}},$ and the heavy meson and heavy quark mass difference $\overline{\Lambda }.$ The qualitative behavior of the light-cone $D^{\left(*\right)}$ meson wave function and the associated Sudakov resummation are derived. The leading-power contributions to the $\overrightarrow{B}{D}^{\left(*\right)}$ form factors, characterized by the scale $\overline{\Lambda }\sqrt{M_B{/M}_{D^{\left(*\right)}}},$ respect the heavy-quark symmetry. The next-to-leading-power corrections in ${1/M}_B$ and ${1/M}_{D^{\left(*\right)}},$ characterized by a scale larger than $\sqrt{\overline{\Lambda }{M}_B},$ are estimated to be less than 20%. The $D^{\left(*\right)}$ meson wave function is determined from the fit to the observed $\overrightarrow{B}{D}^{\left(*\right)}l\nu$ decay spectrum, which can be employed to make predictions for nonleptonic decays, such as $\overrightarrow{B}{D}^{\left(*\right)}\pi \left(\rho \right).\mathrm{}$

The $\overrightarrow{B}\pi \pi$ hadronic matrix element of the chromomagnetic dipole operator $O_{8g}$ (gluonic penguin operator) is calculated using the QCD light-cone sum rule approach. The resulting sum rule for $〈\pi \pi |O_{8g}|B〉$ contains, in addition to the $O\left({\alpha }_s\right)$ part induced by hard-gluon exchanges, a contribution due to soft gluons. We find that in the limit $m_b\to \infty$ the soft-gluon contribution is suppressed as a second power of ${1/m}_b$ with respect to the leading-order factorizable $\overrightarrow{B}\pi \pi$ amplitude, whereas the hard-gluon contribution has only an ${\alpha }_s$ suppression. Nevertheless, at finite $m_b,$ the soft and hard effects of the gluonic penguin operator in $\overrightarrow{B}\pi \pi$ are of the same order. Our result indicates that soft contributions are indispensable for an accurate counting of nonfactorizable effects in charmless B decays. On the phenomenological side we predict that the impact of gluonic penguin operators on $B_d^0\to {\pi }^{+}{\pi }^{-}$ is very small, but is noticeable for $B_d^0\to {\pi }^0{\pi }^0.$

A dipole-dipole scattering amplitude is calculated exactly in the first two orders of perturbation theory. This amplitude is an analytic function of the relative energy and the dipoles’ sizes. The cross section of the dipole-dipole scattering approaches the high-energy Balitskii-Fadin-Kuraev-Lipatov (BFKL) asymptotics starting from a relatively large rapidity $\sim 5.$

We consider synchrotronlike radiation in QCD by generalizing Schwinger’s treatment of quantum synchrotron radiation in QED to the case of a constant chromomagnetic field. We suggest a novel mechanism for jet quenching in heavy ion collisions, whereby high-$p_t$ partons get depleted through strong (classical) color fields. The latter are encountered in the color glass condensate or in the form of expanding shells of exploding sphalerons. Unlike bremsstrahlung radiation through multiple soft rescattering, synchrotron radiation converts a jet into a wide shower of soft gluons. We estimate the energy loss through this mechanism and suggest that it contributes significantly to the unexpectedly strong jet quenching observed at BNL RHIC.

A prescription for the short-distance expansion of Euclidean current correlators based on a delocalized modification of the multipole expansion of perturbative short-distance coefficient functions is proposed that appreciates the presence of nonlocal physics in the nonperturbative QCD vacuum. This expansion converges better than the local Wilson OPE, which is recovered in the limit of infinite resolution. As a consequence, the usual local condensates in the Wilson OPE become condensates that depend on a resolution parameter and that can be expressed as an infinite series of local condensates with increasing dimension. In a calculation of the nonperturbative correction to the ground state energy level of heavy quarkonia the improved convergence properties of the delocalized expansion are demonstrated. Phenomenological evidence is gathered that the gluon condensate, often being the leading nonperturbative parameter of the Wilson OPE, is indeed a function of resolution. The delocalized expansion is applied to derive a leading order scaling relation for $f_D{/f}_B$ in the heavy mass expansion.

The proposed neutrino factory based on a muon storage ring (MSR) is an ideal place to look for heavy quark production via neutral current and charged current interactions. In this article, we address the issue of contributions coming from mediating leptoquarks (LQs) in ${\nu }_{\mu }$ $\left({\overline{\nu }}_e\right)$-N scattering, leading to the production of b $\left(\overline{b}\right)$ at a MSR, and investigate the region where LQ interactions are significant in the near-site experiments.

The dc electrical conductivity of an ultrarelativistic QED plasma is studied in real time by implementing the dynamical renormalization group. The conductivity is obtained from the real-time dependence of a dissipative kernel closely related to the retarded photon polarization. Pinch singularities in the imaginary part of the polarization are manifest as secular terms that grow in time in the perturbative expansion of this kernel. The leading secular terms are studied explicitly and it is shown that they are insensitive to the anomalous damping of hard fermions as a result of a cancellation between self-energy and vertex corrections. The resummation of the secular terms via the dynamical renormalization group leads directly to a renormalization group equation in real time, which is the Boltzmann equation for the (gauge invariant) fermion distribution function. A direct correspondence between the perturbative expansion and the linearized Boltzmann equation is established, allowing a direct identification of the self-energy and vertex contributions to the collision term. We obtain a Fokker-Planck equation in momentum space that describes the dynamics of the departure from equilibrium to leading logarithmic order in the coupling. This equation determines that the transport time scale is given by $t_{\mathrm{tr}}=24\mathrm{}\pi {/e}^{4}T\ln \mathrm{}(1/e).$ The solution of the Fokker-Planck equation approaches asymptotically the steady-state solution as $\sim e^{-t/\left(4.038\mathrm{}\dots t_{\mathrm{tr}}\right)}.$ The steady-state solution leads to the conductivity $\sigma =15.698\mathrm{}{T/e}^2\ln \mathrm{}(1/e)\mathrm{}$ to leading logarithmic order. We discuss the contributions beyond leading logarithms as well as beyond the Boltzmann equation. The dynamical renormalization group provides a link between linear response in quantum field theory and kinetic theory.

In this paper we define a causal Lorentz covariant noncommutative (NC) classical electrodynamics. We obtain an explicit realization of the NC theory by solving perturbatively the Seiberg-Witten map. The action is polynomial in the field strength F, allowing us to preserve both causality and Lorentz covariance. The general structure of the Lagrangian is studied to all orders in the perturbative expansion in the NC parameter θ. We show that monochromatic plane waves are solutions of the equations of motion to all orders. An iterative method has been developed to solve the equations of motion and has been applied to the study of the corrections to the superposition law and to the Coulomb law.

Emitted radiation can be reprocessed in curved spacetimes, due to the breakdown of the Huyghens principle. A maximization procedure for the energy diffusion allows one to obtain wave packets (gravitational and electromagnetic) that are particularly strongly backscattered. Examples are shown with the backscattered part exceeding by one order the remnants of the initial signals. A robust ringing can be observed, with amplitudes exceeding the leftovers of the main radiation pulse. An analysis of the results obtained allows one to set demands on some parameters in the numerical description of a realistic process of the collapse of two black holes.

In Einstein gravity there is a simple procedure to build D-dimensional spacetimes starting from $\left(D-1\right)$-dimensional ones, by stacking any $\left(D-1\right)$-dimensional Ricci-flat metric into the extra dimension. We analyze this procedure in the context of Einstein-Gauss-Bonnet gravity, and find that it can be applied only to metrics with a constant Krestschmann scalar. For instance, we show that solutions of the black-string type are not allowed in this framework.

We discuss various features and details of two versions of the Barrett-Crane spin foam model of quantum gravity: first of the Spin(4)-symmetric Riemannian model and second of the $SL(2,C)$-symmetric Lorentzian version in which all tetrahedra are spacelike. Recently, Livine and Oriti proposed to introduce a causal structure into the Lorentzian Barrett-Crane model from which one can construct a path integral that corresponds to the causal (Feynman) propagator. We show how to obtain convergent integrals for the $10j$ symbols and how a dimensionless constant can be introduced into the model. We propose a “Wick rotation” which turns the rapidly oscillating complex amplitudes of the Feynman path integral into positive real and bounded weights. This construction does not yet have the status of a theorem, but it can be used as an alternative definition of the propagator and makes the causal model accessible by standard numerical simulation algorithms. In addition, we identify the local symmetries of the models and show how their four-simplex amplitudes can be reexpressed in terms of the ordinary relativistic $10j$ symbols. Finally, motivated by possible numerical simulations, we express the matrix elements that are defined by the model, in terms of the continuous connection variables and determine the most general observable in the connection picture. Everything is done on a fixed two complex.

It is proven that the equations for the time-independent, negative-parity, gravitational and electromagnetic perturbations of the Reissner-Nordström geometry have (for each angular momentum) one solution in the form of a finite power series in the (Schwarzschild-like) radial coordinate r. The explicit form of these solutions is given. Therefrom the second fundamental solutions of these equations, and the positive-parity perturbations, can also be constructed explicitly.

The relic abundance and the scalar cross section off the nucleon for light neutralinos (of mass below about 45 GeV) are evaluated in an effective MSSM model without GUT-inspired relations among the gaugino masses. It is shown that these neutralinos may provide a sizable contribution to the matter density in the Universe and produce measurable effects in WIMP direct detection experiments. These properties are elucidated in terms of simple analytical arguments.

We analyze the curvaton scenario in the context of supersymmetry. Supersymmetric theories contain many scalars, and therefore many curvaton candidates. To obtain a scale invariant perturbation spectrum, the curvaton mass should be small during inflation $m\ll H.\mathrm{}$ This can be achieved by invoking symmetries, which suppress the soft masses and nonrenormalizable terms in the potential. Other constraints on the curvaton model come from nucleosynthesis, gravitino overproduction, and thermal evaporation. The curvaton coupling to matter should be very small to satisfy these constraints (e.g., $h\lesssim {10}^{-8}$ for typical soft masses $m\sim \mathrm{TeV}).\mathrm{}$

Filters developed in order to detect short bursts of gravitational waves in interferometric detector outputs are compared according to three main points. Conventional receiver operating characteristics (ROC) are first built for all the considered filters and for three typical burst signals. Optimized ROC are shown for a simple pulse signal in order to estimate the best detection efficiency of the filters in the ideal case, while realistic ones obtained with filters working with several “templates” show how detection efficiencies can be degraded in a practical implementation. Second, estimations of biases and statistical errors on the reconstruction of the time of arrival of pulse-like signals are then given for each filter. Such results are crucial for future coincidence studies between gravitational wave detectors but also with neutrino or optical detectors. As most of the filters require a pre-whitening of the detector noise, the sensitivity to a nonperfect noise whitening procedure is finally analyzed. For this purpose lines of various frequencies and amplitudes are added to a Gaussian white noise and the outputs of the filters are studied in order to monitor the excess of false alarms induced by the lines. The comparison of the performances of the different filters finally show that they are complementary rather than competitive.