5,885 research outputs found
Amplification of Quantum Meson Modes in the Late Time of Chiral Phase Transition
It is shown that there exists a possibility of amplification of amplitudes of
quantum pion modes with low momenta in the late time of chiral phase transition
by using the Gaussian wave functional approximation in the O(4) linear sigma
model. It is also shown that the amplification occurs in the mechanism of the
resonance by forced oscillation as well as the parametric resonance induced by
the small oscillation of the chiral condensate. These mechanisms are
investigated in both the case of spatially homogeneous system and the spatially
expanded system described by the Bjorken coordinate.Comment: 17 pages, 16 figure
Novel Lifshitz point for chiral transition in the magnetic field
Based on the generalized Ginzburg-Landau theory, chiral phase transition is
discussed in the presence of magnetic field. Considering the chiral density
wave we show chiral anomaly gives rise to an inhomogeneous chiral phase for
nonzero quark-number chemical potential. Novel Lifshitz point appears on the
vanishing chemical potential line, which may be directly explored by the
lattice QCD simulation.Comment: 4pages,2figure
Multicriticality of the (2+1)-dimensional gonihedric model: A realization of the (d,m)=(3,2) Lifshitz point
Multicriticality of the gonihedric model in 2+1 dimensions is investigated
numerically. The gonihedric model is a fully frustrated Ising magnet with the
finely tuned plaquette-type (four-body and plaquette-diagonal) interactions,
which cancel out the domain-wall surface tension. Because the
quantum-mechanical fluctuation along the imaginary-time direction is simply
ferromagnetic, the criticality of the (2+1)-dimensional gonihedric model should
be an anisotropic one; that is, the respective critical indices of real-space
(\perp) and imaginary-time (\parallel) sectors do not coincide. Extending the
parameter space to control the domain-wall surface tension, we analyze the
criticality in terms of the crossover (multicritical) scaling theory. By means
of the numerical diagonalization for the clusters with N\le 28 spins, we
obtained the correlation-length critical indices
(\nu_\perp,\nu_\parallel)=(0.45(10),1.04(27)), and the crossover exponent
\phi=0.7(2). Our results are comparable to
(\nu_{\perp},\nu_{\parallel})=(0.482,1.230), and \phi=0.688 obtained by Diehl
and Shpot for the (d,m)=(3,2) Lifshitz point with the \epsilon-expansion method
up to O(\epsilon^2)
Comment on ``Density Matrix Renormalization Group Study of the Haldane Phase in Random One-Dimensional Antiferromagnets"
In a recent Letter (PRL 83, 3297 (1999)), Hida presented numerical results
indicating that the Haldane phase of the Heisenberg antiferromagnetic spin-1
chain is stable against bond randomness, for box distributions of the bond
strength, even when the box distribution stretches to zero bond strength. The
author thus concluded that the Haldane phase is stable against bond randomness
for any distribution of the bond strength, no matter how broad. In this
Comment, we (i) point out that the randomness distributions studied in this
Letter do not represent the broadest possible distributions, and therefore
these numerical results do not lead to the conclusion that the Haldane phase is
stable against any randomness; and (ii) provide a semiquantitative estimate of
the critical randomness beyond which the Haldane phase yields to the Random
Singlet phase, in a specific class of random distribution functions for the
bond strength.Comment: A comment on PRL 83, 3297 (1999). One pag
Density Matrix Renormalization Group Study of the Haldane Phase in Random One-Dimensional Antiferromagnets
It is conjectured that the Haldane phase of the S=1 antiferromagnetic
Heisenberg chain and the ferromagnetic-antiferromagnetic alternating
Heisenberg chain is stable against any strength of randomness, because of
imposed breakdown of translational symmetry. This conjecture is confirmed by
the density matrix renormalization group calculation of the string order
parameter and the energy gap distribution.Comment: 4 Pages, 7 figures; Considerable revisions are made in abstract and
main text. Final accepted versio
High resolution observations of Cen A: Yellow and red supergiants in a region of jet-induced star formation?
We present the analysis of near infrared (NIR), adaptive optics (AO) Subaru
and archived HST imaging data of a region near the northern middle lobe (NML)
of the Centaurus A (Cen A) jet, at a distance of kpc north-east (NE)
from the center of NGC5128. Low-pass filtering of the NIR images reveals strong
-- above the background mean -- signal at the expected position of
the brightest star in the equivalent HST field. Statistical analysis of the NIR
background noise suggests that the probability to observe signal at
the same position, in three independent measurements due to stochastic
background fluctuations alone is negligible () and, therefore,
that this signal should reflect the detection of the NIR counterparts of the
brightest HST star. An extensive photometric analysis of this star yields
, visual-NIR, and NIR colors expected from a yellow supergiant (YSG) with
an estimated age Myr. Furthermore, the second and third
brighter HST stars are, likely, also supergiants in Cen A, with estimated ages
Myr and Myr, respectively. The ages of
these three supergiants are in good agreement with the ages of the young
massive stars that were previously found in the vicinity and are thought to
have formed during the later phases of the jet-HI cloud interaction that
appears to drive the star formation (SF) in the region for the past
Myr.Comment: 11 pages, 6 figures, 2 tables, accepted for publication in Ap
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