118937097
Numerical Bianchi type I solutions in semiclassical gravitation
It is believed that soon after the Planck era, spacetime should have a semiclassical nature. In this context we consider quantum fields propagating in a classical gravitational field and study the backreaction of these fields, using the expected value of the energy-momentum tensor as source of the gravitational field. According to this theory, the escape from general relativity theory is unavoidable. Two geometric counter-term are needed to regularize the divergences which come from the expected value. There is a parameter associated to each counter-term and in this work we found numerical solutions of this theory to particular initial conditions, for general Bianchi Type I spaces. We show that even though there are spurious solutions some of them can be considered physical. These physical solutions include de Sitter and Minkowski that are obtained asymptotically.
119024485
A Semi-Analytical Method for the Evaluation of the Power Spectrum of a Rotating Observer
In this letter we propose a semi-analitical method of evaluation of the power spectrum of a circular moving Unruh-type detector using the method of residue and compare the spectrum with the already known result in the relativistic limit.
118576310
Gravitational Waves from Isotropisation process in Quadratic Gravity
It is believed that soon after the Planck era, spacetime should have a semi-classical nature. According to this idea, it is unavoidable to modify the General Relativity theory or look for alternative theories of gravitation. An interesting alternative found in the literature is to take into account two geometric counter-terms to regularize the divergences from the effective action. These counter-terms are responsible for a higher derivative metric theory of gravitation. In the present article, our main aim is to investigate if the process of isotropisation, which could well occur naturally in such a higher derivative metric theory, could generate gravitational waves. First of all, in order to proceed with such an investigation, we evaluate the time evolution of the resulting Weyl’s scalars. Then, we follow with a perturbative approach considering that the background metric is given by the Minkowski spacetime. Our entire analysis is restricted to the particular Bianchi I case.
18978265
Orbits in a Neighboring Dwarf Galaxy According to MOND
We study the orbits in the MOND theory within a dwarf galaxy of mass Md ∼ 108M⊙ at a distance of ∼ 100kpc from a neighboring galaxy of mass Mg = 5 × 1011M⊙, such as ours. It is assumed that a second mass m << Md is gravitationally bound to Md by a previously calculated potential for the MOND theory. This potential is obtained for a free falling mass Md in a constant external gravitational acceleration field ∇φg. The numerical technique of surfaces of section is used to study the stability of the phase-space orbits in the dwarf galaxy. Equatorial orbits with sufficiently small eccentricities e < 0.65 are found to be stable with respect to small changes in the initial conditions. (The equatorial plane is perpendicular to the direction of ∇φg, which is along the line joining Md and Mg.) For decreasing values of the conserved component of the angular momentum, in the direction of ∇φg, equatorial stability is lost. Subject headings: cosmology — gravitation — galaxies: dwarf.
119377344
Casimir Effect in Compact Universes
The Casimir effect in compact hyperbolic Universes was numerically obtained in previous publications. In this talk, I expose these results.
119495652
Casimir energy in a small volume multiply connected static hyperbolic preinflationary universe
A few years ago, Cornish, Spergel and Starkman (CSS) suggested that a multiply connected ''small'' universe could allow for classical chaotic mixing as a preinflationary homogenization process. The smaller the volume, the more important the process. Also, a smaller universe has a greater probability of being spontaneously created. Previously DeWitt, Hart and Isham (DHI) calculated the Casimir energy for static multiply connected flat space-times. Because of the interest in small volume hyperbolic universes (e.g., CSS), we generalize the DHI calculation by making a numerical investigation of the Casimir energy for a conformally coupled, massive scalar field in a static universe, whose spatial sections are the Weeks manifold, the smallest universe of negative curvature known. In spite of being a numerical calculation, our result is in fact exact. It is shown that there is spontaneous vacuum excitation of low multipolar components.
117111758
A study of jet handedness in hadronic Z0 decays
123690218
Identified hadron production at SLD and BABAR
We present measurements of identified hadron spectra in $e^+e^-\!\!\rightarrow$ hadrons from the BABAR and SLD experiments at respective c.m. energies of 10.54 GeV and 91.2 GeV. The scaling violations between the two energies are found to be large and described by hadronization models for charged pions, but not for heavier hadrons. SLD measurements show large differences between $b\bar{b}$, $c\bar{c}$ and light-flavor events that are qualitatively consistent with expectations. The light flavor events are somewhat more consistent with the predictions of MLLA QCD than are events of all flavors, but a discrepancy in the mass dependence remains. SLD have made several new and/or improved measurements of light leading particle production, paving the way for future tagging of u, d and s jets. They have also made a unique study of signed rapidity correlations, showing direct evidence for charge ordering of protons along the quark-antiquark axis.
119193340
The concept of phenomenological light-front wave functions -- Regge improved diquark model predictions
We introduce a classification scheme for parton distribution models and we model generalized parton distributions (GPDs), their form factors, and parton distribution functions (PDFs), integrated and unintegrated ones, in terms of unintegrated double distributions that are obtained from the parton number conserved overlap of effective light-front wave functions. For a so-called "spherical" model we present general expressions for all twist-two related non-perturbative quantities in terms of one effective light-front wave function, including chiral-odd GPDs. We also discuss the Regge improvement of such quark models from the $s$-channel point of view and study the relations between zero-skewness GPDs and unintegrated PDFs on a more general ground. Finally, we provide a few phenomenological applications that emphasize the role of orbital angular momenta.
119761219
a Measurement of the Average Lifetime of B Hadrons Using Vertex Reconstruction.
125346382
Precision tests of the Standard Model at electron colliders
We review electroweak physics studies in high-energy e + e − collisions at CERN and SLAC. Studies of couplings of the Z 0 boson to many of the fundamental fermions are now quite detailed, and those of the W ± bosons are well under way. Sensitivity to radiative corrections due to the massive top quark, the as yet undiscovered Higgs boson, and new physics at the TeV scale has been achieved. The Standard Model is consistent with all data, although further studies are indicated in several areas. In the absence of new physics, the Higgs mass is limited to <188 GeV/c2 at 95% C.L.