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.
201234408
Geodesic motion on closed spaces: Two numerical examples
Abstract The geodesic structure is very closely related to the trace of the Laplace operator, involved in the calculation of the expectation value of the energy–momentum tensor in Universes with non-trivial topology. The purpose of this work is to provide concrete numerical examples of geodesic flows. Two manifolds with genus g = 0 are given. In one the chaotic regions, form sets of negligible or zero measure. In the second example the geodesic flow shows the presence of measurable chaotic regions. The approach is “experimental”, numerical, and there is no attempt to an analytical calculation.
119420912
Casimir energy in multiply connected static hyperbolic universes
We generalize a previously obtained result for the case of a few other static hyperbolic universes with manifolds of nontrivial topology as spatial sections.
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.
119676801
The power spectrum of the circular noise
The circular noise is important in connection to Mach's principle, and also as a possible probe of the Unruh effect. In this letter the power spectrum of the detector following the Trocheries-Takeno motion in the Minkowski vacuum is analytically obtained in the form of an infinite series. A mean distribution function and corresponding energy density are obtained for this particular detected noise. The analogous of a non constant temperature distribution is obtained. And in the end, a brief discussion about the equilibrium configuration is given.
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.
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.
18543905
Test of a conceptual prototype of the total internal reflection Cherenkov imaging detector (DIRC) with cosmic muons
The DIRC is a totally internally reflecting Cherenkov imaging detector proposed for particle identification at the asymmetric e/sup +/e/sup -/ B factories. First test results from a conceptual prototype using cosmic muons are reported. The photo-electron yield and the single Cherenkov photon resolution at various track dip angles and positions along the radiator bar have been measured. The results are consistent with estimates and Monte-Carlo simulations. >
120017490
QCD studies of hadronic decays of Z0 bosons by SLD
Z0 bosons have been produced by collisions of longitudinally polarized electrons with unpolarized positrons at the SLAC Linear Collider and their decays have been recorded by the SLD experiment. We present preliminary QCD results based on the first 6000 such decays. We find good agreement between the inclusive properties of these data and the predictions of perturbative QCD plus fragmentation models. The strong coupling, αs, has been measured by three methods: jet rates yield αs(MZ)=0.119±0.002(stat.)±0.003(exp. syst.)±0.014(theor.); energy‐energy correlations yield αs(MZ)=0.121±0.002±0.004±0.0160.009; and the energy‐energy correlation asymmetry gives αs(MZ)=0.108±0.003±0.005±0.0080.003.