20,293 research outputs found
Gluon propagators and center vortices at finite temperature
We study influence of center vortices on infrared properties of gluons in the
deconfinement phase of quenched QCD. We observe a significant suppression of
the magnetic component of the gluon propagator in the low-momentum region after
the vortices are removed from the gluon configurations. The propagator of the
electric gluon stays almost unaffected by the vortex removal. Our results
demonstrate that the center vortices are responsible for important
nonperturbative properties of the magnetic component of the quark-gluon plasma.Comment: 7 pages, 8 figures, talk presented at 27th International Symposium on
Lattice Field Theory (Lattice 2009), Beijing, 26-31 Jul 200
A new measure of using the lensing dispersion in high- type Ia SNe
The gravitational lensing magnification or demagnification due to large-scale
structures induces a scatter in peak magnitudes of high redshift type Ia
supernovae (SNe Ia). The amplitude of the lensing dispersion strongly depends
on that of density fluctuations characterized by the parameter.
Therefore the value of is constrained by measuring the dispersion in
the peak magnitudes. We examine how well SN Ia data will provide a constraint
on the value of using a likelihood analysis method. It is found that
the number and quality of SN Ia data needed for placing a useful constraint on
is attainable with Next Generation Space Telescope.Comment: 9 pages, 3 figures. Accepted for publication in The Astrophysical
Journa
New criterion for direct black hole formation in rapidly rotating stellar collapse
We study gravitational collapse of rapidly rotating relativistic polytropes
of the adiabatic index and 2, in which the spin parameter where and are total angular momentum and
gravitational mass, in full general relativity.
First, analyzing initial distributions of the mass and the spin parameter
inside stars, we predict the final outcome after the collapse. Then, we perform
fully general relativistic simulations on assumption of axial and equatorial
symmetries and confirm our predictions. As a result of simulations, we find
that in contrast with the previous belief, even for stars with , the
collapse proceeds to form a seed black hole at central region, and the seed
black hole subsequently grows as the ambient fluids accrete onto it. We also
find that growth of angular momentum and mass of the seed black hole can be
approximately determined from the initial profiles of the density and the
specific angular momentum. We define an effective spin parameter at the central
region of the stars, , and propose a new criterion for black hole
formation as q_{c} \alt 1. Plausible reasons for the discrepancy between our
and previous results are clarified.Comment: submitted to PR
Dynamical Model of Coherent Pion Production in Neutrino-Nucleus Scattering
We study coherent pion production in neutrino-nucleus scattering in the
energy region relevant to neutrino oscillation experiments of current interest.
Our approach is based on a combined use of the Sato-Lee model of electroweak
pion production on a nucleon and the Delta-hole model of pion-nucleus
reactions. Thus we develop a model which describes pion-nucleus scattering and
electroweak coherent pion production in a unified manner. Numerical
calculations are carried out for the case of the 12C target. All the free
parameters in our model are fixed by fitting to both total and elastic
differential cross sections for pi-12C scattering. Then we demonstrate the
reliability of our approach by confronting our prediction for the coherent pion
photo-productions with data. Finally, we calculate total and differential cross
sections for neutrino-induced coherent pion production, and some of the results
are (will be) compared with the recent (forthcoming) data from K2K, SciBooNE
and MiniBooNE. We also study effect of the non-locality of the
Delta-propagation in the nucleus, and compare the elementary amplitudes used in
different microscopic calculations.Comment: 42 pages, 21 figure
Gluon propagators and center vortices in gluon plasma
We study electric and magnetic components of the gluon propagators in
quark-gluon plasma in terms of center vortices by using a quenched simulation
of SU(2) lattice theory. In the Landau gauge, the magnetic components of the
propagators are strongly affected in the infrared region by removal of the
center vortices, while the electric components are almost unchanged by this
procedure. In the Coulomb gauge, the time-time correlators, including an
instantaneous interaction, also have an essential contribution from the center
vortices. As a result, one finds that magnetic degrees of freedom in the
infrared region couple strongly to the center vortices in the deconfinement
phase.Comment: 12 pages, 11 figure
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