145,231 research outputs found
Power Spectrum of Cosmic Momentum Field Measured from the SFI Galaxy Sample
We have measured the cosmic momentum power spectrum from the peculiar
velocities of galaxies in the SFI sample. The SFI catalog contains field spiral
galaxies with radial peculiar velocities derived from the I-band Tully-Fisher
relation. As a natural measure of the large-scale peculiar velocity field, we
use the cosmic momentum field that is defined as the peculiar velocity field
weighted by local number of galaxies. We have shown that the momentum power
spectrum can be derived from the density power spectrum for the constant linear
biasing of galaxy formation, which makes it possible to estimate \beta_S =
\Omega_m^{0.6} / b_S parameter precisely where \Omega_m is the matter density
parameter and b_S is the bias factor for optical spiral galaxies. At each
wavenumber k we estimate \beta_S(k) as the ratio of the measured to the derived
momentum power over a wide range of scales (0.026 h^{-1}Mpc <~ k <~ 0.157
h^{-1}Mpc) that spans the linear to the quasi-linear regimes. The estimated
\beta_S(k)'s have stable values around 0.5, which demonstrates the constancy of
\beta_S parameter at scales down to 40 h^{-1}Mpc. We have obtained
\beta_S=0.49_{-0.05}^{+0.08} or \Omega_m = 0.30_{-0.05}^{+0.09} b_S^{5/3}, and
the amplitude of mass fluctuation as
\sigma_8\Omega_m^{0.6}=0.56_{-0.21}^{+0.27}. The 68% confidence limits include
the cosmic variance. We have also estimated the mass density power spectrum.
For example, at k=0.1047 h Mpc^{-1} (\lambda=60 h^{-1}Mpc) we measure
\Omega_m^{1.2} P_{\delta}(k)=(2.51_{-0.94}^{+0.91})\times 10^3 (h^{-1}Mpc)^3,
which is lower compared to the high-amplitude power spectra found from the
previous maximum likelihood analyses of peculiar velocity samples like Mark
III, SFI, and ENEAR.Comment: 12 pages, 9 figures, accepted for publication in Ap
New Gauge Invariant Formulation of the Chern-Simons Gauge Theory: Classical and Quantal Analysis
Recently proposed new gauge invariant formulation of the Chern-Simons gauge
theory is considered in detail. This formulation is consistent with the gauge
fixed formulation. Furthermore it is found that the canonical (Noether)
Poincar\'e generators are not gauge invariant even on the constraints surface
and do not satisfy the Poincar\'e algebra contrast to usual case. It is the
improved generators, constructed from the symmetric energy-momentum tensor,
which are (manifestly) gauge invariant and obey the quantum as well as
classical Poincar\'e algebra. The physical states are constructed and it is
found in the Schr\"odinger picture that unusual gauge invariant longitudinal
mode of the gauge field is crucial for constructing the physical wavefunctional
which is genuine to (pure) Chern-Simons theory. In matching to the gauge fixed
formulation, we consider three typical gauges, Coulomb, axial and Weyl gauges
as explicit examples. Furthermore, recent several confusions about the effect
of Dirac's dressing function and the gauge fixings are clarified. The analysis
according to old gauge independent formulation a' la Dirac is summarized in an
appendix.Comment: No figures, 44 page
Connectivity and genus in three dimensions
Algorithms for labeling, counting, and computing connected objects in binary three dimensional arra
Comments on "Entropy of 2D Black Holes from Counting Microstates"
In a recent letter, Cadoni and Mignemi proposed a formulation for the
statistical computation of the 2D black holes entropy. We present a criticism
about their formulation.Comment: 5 pages, Latex, no figure
Statistical Mechanics of Three-dimensional Kerr-de Sitter Space
The statistical computation of the (2+1)-dimensional Kerr-de Sitter space in
the context of the {\it classical} Virasoro algebra for an asymptotic isometry
group has been a mystery since first, the degeneracy of the states has the
right value only at the infinite boundary which is casually disconnected from
our universe, second, the analyses were based on the unproven Cardy's formula
for complex central charge and conformal weight. In this paper, I consider the
entropy in Carlip's "would-be gauge" degrees of freedom approach instead. I
find that it agree with the Bekenstein-Hawking entropy but there are no the
above problems. Implications to the dS/CFT are noted.Comment: Added comments about diffeomorphism generators and Wheeler-de Witt
equation; Added references; Accpected in CQ
Electron Paramagnetic Resonance Linewidths and Lineshapes for the Molecular Magnets Fe8 and Mn12
We study theoretically Electron Paramagentic Resonance (EPR) linewidths for
single crystals of the molecular magnets Fe and Mn as functions of
energy eigenstates , frequency, and temperature when a magnetic field
along the easy axis is swept at fixed excitation frequency. This work was
motivated by recent EPR experiments. To calculate the linewidths, we use
density-matrix equations, including dipolar interactions and distributions of
the uniaxial anisotropy parameter and the Land\'{e} factor. Our
calculated linewidths agree well with the experimental data. We also examine
the lineshapes of the EPR spectra due to local rotations of the magnetic
anisotropy axes caused by defects in samples. Our preliminary results predict
that this effect leads to asymmetry in the EPR spectra.Comment: 2001 MMM conferenc
Low-temperature nucleation in a kinetic Ising model under different stochastic dynamics with local energy barriers
Using both analytical and simulational methods, we study low-temperature
nucleation rates in kinetic Ising lattice-gas models that evolve under two
different Arrhenius dynamics that interpose between the Ising states a
transition state representing a local energy barrier. The two dynamics are the
transition-state approximation [T. Ala-Nissila, J. Kjoll, and S. C. Ying, Phys.
Rev. B 46, 846 (1992)] and the one-step dynamic [H. C. Kang and W. H. Weinberg,
J. Chem. Phys. 90, 2824 (1989)]. Even though they both obey detailed balance
and are here applied to a situation that does not conserve the order parameter,
we find significant differences between the nucleation rates observed with the
two dynamics, and between them and the standard Glauber dynamic [R. J. Glauber,
J. Math. Phys. 4, 294 (1963)], which does not contain transition states. Our
results show that great care must be exercised when devising kinetic Monte
Carlo transition rates for specific physical or chemical systems.Comment: 14 pages RevTex, 6 embedded figures. Minor revisions. J. Chem. Phys.,
in pres
The quantization of the chiral Schwinger model based on the BFT-BFV formalism II
We apply an improved version of Batalin-Fradkin-Tyutin (BFT) Hamiltonian
method to the a=1 chiral Schwinger Model, which is much more nontrivial than
the a>1.\delta\xi$ in the measure. As a result, we explicitly
obtain the fully gauge invariant partition function, which includes a new type
of Wess-Zumino (WZ) term irrelevant to the gauge symmetry as well as usual WZ
action.Comment: 17 pages, To be published in J. Phys.
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