32161871
Thermally induced density perturbations in the inflation era.
The possibility of thermally induced initial density perturbations in inflationary cosmology is examined. The fluctuation dynamics of a scalar field plus a thermal bath system during slow roll is described by a Langevin-like equation. Fluctuation-dissipation arguments show that for a wide parameter range within the standard inflation model, the thermal fluctuations of the scalar field can dominate its quantum fluctuations. The initial amplitude of density perturbations is found to lie in a range which is consistent with the recent observations of cosmic temperature fluctuations.
44885425
EVIDENCE FOR SCALE-SCALE CORRELATIONS IN THE COSMIC MICROWAVE BACKGROUND RADIATION
We perform a discrete wavelet analysis of the Cosmic Background Explorer differential microwave radiometer (DMR) 4-yr sky maps and find a significant scale-scale correlation on angular scales from about 11\ifmmode^\circ\else\textdegree\fi{} to 22\ifmmode^\circ\else\textdegree\fi{}, only in the DMR face centered on the north galactic pole. This non-Gaussian signature does not arise either from the known foregrounds or the correlated noise maps, nor is it consistent with upper limits on the residual systematic errors in the DMR maps. Either the scale-scale correlations are caused by an unknown foreground contaminate or systematic errors on angular scales as large as 22\ifmmode^\circ\else\textdegree\fi{}, or the standard inflation plus cold dark matter paradigm is ruled out at the $g99%$ confidence level.
119432175
A Statistical Comparison of Cluster Mass Estimates from Optical/X-Ray Observations and Gravitational Lensing
We present a statistical comparison of three different estimates of cluster mass, namely, the dynamical masses obtained from the velocity dispersion of optical galaxies, the X-ray masses measured from the temperature of X-ray-emitting gas under the assumption of isothermal hydrostatic equilibrium, and the gravitational lensing masses derived from the strong/weak distortions of background galaxy images. Using a sample of 29 lensing clusters available in literature, we show that the dynamical masses are in agreement with the gravitational lensing masses while the X-ray method has systematically underestimated cluster masses by a factor of 2-3 as compared with the others. These results imply that galaxies indeed trace the gravitational potential of their clusters and that there is no bias between the velocities of the dark matter particles and the galaxies in clusters. The X-ray cluster mass discrepancy probably arises from the simplification in the models for the X-ray gas distribution and dynamical evolution.
16427302
The Local Power Spectrum and Correlation Hierarchy of the Cosmic Mass Field
We analyze the power spectrum of a QSO's Lyα-transmitted flux in the discrete wavelet transform (DWT) representation. Although the mean DWT power spectrum is consistent with its counterpart in Fourier representation, the spatial distribution of the local power varies greatly; i.e., the local DWT power spectra show remarkably spiky structures on small scales. To measure these spiky features, we introduce the quantities roughness of the local power spectrum and correlation between spikes on different scales. We then test the predictions made by the correlation hierarchy model on the roughness and the scale-scale correlations of the local power spectrum. Using the Lyα-transmitted flux of the QSO HS 1700, we find that the underlying cosmic mass field of the transmitted flux at redshift around z 2.2 can be described by the hierarchical clustering model on physical scales from 2.5 h-1 Mpc to a few tens h-1 kpc in an Einstein-de Sitter universe. However, the nonlinear features of the clustering show differences on different scale ranges: (1) On physical scales larger than ~1.3 h-1 Mpc, the field is almost Gaussian. (2) On scales 1.3-0.3 h-1 Mpc, the field is consistent with the correlation hierarchy with a constant value for the coefficient Q4. (3) On scales less than 300 h-1 kpc, the field is no longer Gaussian but essentially intermittent. In this case, the field can still be fitted by the correlation hierarchy, but the coefficient, Q4, should be scale dependent. These three points are strongly supported by the following result: the scale dependencies of Q4 given by two statistically independent measures, i.e., Q by roughness and Q by scale-scale correlation, are the same in the entire scale range considered.
17575002
Environmental Effect on the Associations of Background Quasars with Foreground Objects. II. Numerical Simulations
Using numerical simulations of cluster formation in the standard cold dark matter (CDM) model and in a low-density, flat CDM model with a cosmological constant, we investigate the gravitational lensing explanation for the reported associations between background quasars and foreground clusters. Under the thin-lens approximation and the unaffected-background hypothesis, we show that the recently detected quasar overdensity around clusters of galaxies on scales of ~10' cannot be interpreted as a result of gravitational lensing by cluster matter or by their environmental and projected matter along the line of sight, which is consistent with the analytical result based on the observed cluster and galaxy correlations. It appears very unlikely that uncertainties in the modeling of the gravitational lensing can account for the disagreement between the theoretical predictions and the observations. We conclude that either the detected signal of the quasar-cluster associations is a statistical fluke or the associations are generated by mechanisms other than the magnification bias.
15746639
Time-dependent correlations of inflationary perturbations
We show that if the primordial classical perturbations were generated by the gravitational particle creation during inflation, and followed by an evolution of quantum-to-classical transition, the time-dependent correlation of these perturbations is long-tailed with a correlation time larger than the Hubble time. Consequently, the inflationary perturbations are locally scale-scale correlated. Hence, the interaction of the fields during inflation can be explored via the detection of the local scale-scale correlation of the CMB fluctuations.
33113460
Studies of xi (2230) in J/ psi radiative decays.
30514138
Search for a vector glueball by a scan of the J/ psi resonance.
The cross section for {ital e}{sup +}{ital e}{sup {minus}}{r_arrow}{rho}{pi} has been measured by the BES detector at BEPC at center-of-mass energies covering a 40 MeV interval spanning the {ital J}/{psi} resonance. The data are used to search for the vector gluonium state hypothesized by Brodsky, Lepage, and Tuan as an explanation of the {rho}{pi} puzzle in charmonium physics. The shape of the {rho}{pi} cross section is compatible with that of the total hadronic cross section. No distortions indicating the presence of a vector glueball are seen. {copyright} {ital 1996 The American Physical Society.}
125927421
Measurement of the mass of the tau lepton.
Author(s): Bai, JZ; Bardon, O; Becker-Szendy, RA; Blum, I; Breakstone, A; Burnett, T; Chen, GP; Chen, HF | Abstract: A data-driven energy scan in the immediate vicinity of the τ pair production threshold has been performed using the Beijing Spectrometer at the Beijing Electron-Positron Collider. Approximately 5pb-1of data, distributed over 12 scan points, have been collected. A previous mass value for the τ lepton, obtained using only the eµ final state, has been published. In this paper, the final BES result on the mass measurement is presented. The analysis is based on the combined data from the ee, eµ, eh, µµ, µh, and hh final states, where h denotes a charged Π or K. A maximum likelihood fit to the τ pair production cross section data yields the value mT=1776.96-0.21-0.17+0.18+0.25. © 1995 The American Physical Society.