36454783
Casimir energy density in closed hyperbolic universes
The original Casimir effect results from the difference in the vacuum energies of the electromagnetic field, between that in a region of space with boundary conditions and that in the same region without boundary conditions. In this paper we develop the theory of a similar situation, involving a scalar field in spacetimes with closed spatial sections of negative curvature.
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.
118472353
BIANCHI I SOLUTIONS OF EFFECTIVE QUADRATIC GRAVITY
It is believed that soon after the Planck time, Einstein's general relativity theory should be corrected to an effective quadratic theory. Numerical solutions for the anisotropic generalization of the Friedmann "flat" model E3 for this effective gravity are given. It must be emphasized that although numeric, these solutions are exact in the sense that they depend only on the precision of the machine. The solutions are identified asymptotically in a certain sense. It is found solutions which asymptote de Sitter space, Minkowski space and a singularity. This work is a generalization for nondiagonal spatial metrics of a previous result obtained by one of us and a collaborator for Bianchi I spaces.
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.
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.
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.
56136446
Hadron production in e+e- annihilation at BaBar, and implication for the muon anomalous magnetic moment.
The BABAR collaboration has an intensive program of studying hadroni c cross sections in lowenergyee collisions, accessible at BABAR via initial-state radiation. Our measurements allow significant improvements in the precision of the predicted v alue of the muon anomalous magnetic moment. These improvements are necessary for shedding ligh t on t e current ∼3.5σ difference between the predicted and experimental values. We have publ ished results on a number of processes with two to six hadrons in the final state. We report her e the results of recent studies of the processese+e−→K+K− ande+e− → 4 hadrons, which constitute the main contribution to the hadronic cross section in the energy region between 1 and 3 Ge V.
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.
1646135
THE DIRC COUNTER: A NEW TYPE OF PARTICLE IDENTIFICATION DEVICE FOR B FACTORIES*
A very thin, solid radiator, totally internally reflecting, imaging Cherenkov counter (DIRC) is described. This device is well matched to requirements at an asymmetric e+e- B Factory. the hadronic charged particle identification 1. INTR~IXJ~TI~N Particle identification at a B factory is difficult, and highly constrained by the machine environment and the need for good energy measurement of soft photons in the calorimeter which surrounds the particle identification device [l]. Because of the high beam crossing rate and the potential for large backgrounds, the particle identification detector must be robust and relatively fast. Good r~‘dK separation is required over a wide momentum range between about 0.25 and 4 GeV/c. Most detectors measure dE/dx in the tracking chamber which allows good X/K separation up to about 600 MeV/c, but a specific identification device is required over most of the momentum region [2]. The amount of material in the device should be small (preferably less than 10% LRAD) and should be distributed as close as possible to the calorimeter in order to avoid degradation in the resolution performance of the calorimeter, and the loss of low energy conversion electrons in the magnetic field. In addition, the cost of the high quality calorimeter scales roughly like the radius squared and there will be substantial cost savings if the particle identification device can be made thin.
42652971
Hadron Production in Quark and Antiquark Jets
We present a number of jet fragmentation measurements e{sup +}e{sup -} --> hadrons. The ALEPH collaboration measures inclusive rho{sup 0}(770), f{sub 0}(980) and f{sub 2}(1270) production rates, improving the world averages. The SLD collaboration measures pi{sup {+-}}, K{sup {+-}} and p/anti-p production in light-, c- and b-flavor Z{sup 0} decays, as well as leading hadrons in light-quark jets, precisely. The DELPHI collaboration measures the average charged multiplicity in light- and b-flavor events at 183 and 189 GeV, verifying a precise prediction of QCD and excluding flavor-independent fragmentation.
119112341
Measurement of Inclusive Production of Light Charged Hadrons at BaBar
Inclusive hadron production cross sections in e+e-collisions shed light on the fundamental fragmentation and hadronization processes. We present measurements of the inclusive spectra of charged pions, kaons and protons in hadronic events at a center-of-mass energy of 10.54 \gev. These results are compared with theoretical predictions and the predictions of three hadronization models. Along with previous measurements at higher energies, they are also used to study the scaling properties of hadron production.