5 research outputs found
Chiral Logs in Quenched QCD
The quenched chiral logs are examined on a lattice with
Iwasaki gauge action and overlap fermions. The pion decay constant is
used to set the lattice spacing, . With pion mass as low
as , we see the quenched chiral logs clearly in
and , the pseudoscalar decay constant. We analyze the data
to determine how low the pion mass needs to be in order for the quenched
one-loop chiral perturbation theory (PT) to apply. With the constrained
curve-fitting method, we are able to extract the quenched chiral log parameter
together with other low-energy parameters. Only for do we obtain a consistent and stable fit with a constant
which we determine to be 0.24(3)(4) (at the chiral scale ). By comparing to the lattice, we estimate the
finite volume effect to be about 2.7% for the smallest pion mass. We also
fitted the pion mass to the form for the re-summed cactus diagrams and found
that its applicable region is extended farther than the range for the one-loop
formula, perhaps up to MeV. The scale independent
is determined to be 0.20(3) in this case. We study the quenched
non-analytic terms in the nucleon mass and find that the coefficient
in the nucleon mass is consistent with the prediction of one-loop PT\@.
We also obtain the low energy constant from . We conclude from
this study that it is imperative to cover only the range of data with the pion
mass less than in order to examine the chiral behavior of
the hadron masses and decay constants in quenched QCD and match them with
quenched one-loop PT\@.Comment: 37 pages and 24 figures, pion masses are fitted to the form for the
re-summed cactus diagrams, figures added, to appear in PR
Interacting new agegraphic viscous dark energy with varying
We consider the new agegraphic model of dark energy with a varying
gravitational constant, , in a non-flat universe. We obtain the equation of
state and the deceleration parameters for both interacting and noninteracting
new agegraphic dark energy. We also present the equation of motion determining
the evolution behavior of the dark energy density with a time variable
gravitational constant. Finally, we generalize our study to the case of viscous
new agegraphic dark energy in the presence of an interaction term between both
dark components.Comment: 12 pages, accepted for publication in IJTP (2010
Black Holes in Bulk Viscous Cosmology
We investigate the effects of the accretion of phantom energy with non-zero
bulk viscosity onto a Schwarzschild black hole and show that black holes
accreting viscous phantom energy will lose mass rapidly compared to the
non-viscous case. When matter is incorporated along with the phantom energy,
the black holes meet with the same fate as bulk viscous forces dominate matter
accretion. If the phantom energy has large bulk viscosity, then the mass of the
black hole will reduce faster than in the small viscosity case.Comment: 20 pages, 3 figures, accepted for publication in Int. J. Theor. Phy