4,559 research outputs found
Critical curves in conformally invariant statistical systems
We consider critical curves -- conformally invariant curves that appear at
critical points of two-dimensional statistical mechanical systems. We show how
to describe these curves in terms of the Coulomb gas formalism of conformal
field theory (CFT). We also provide links between this description and the
stochastic (Schramm-) Loewner evolution (SLE). The connection appears in the
long-time limit of stochastic evolution of various SLE observables related to
CFT primary fields. We show how the multifractal spectrum of harmonic measure
and other fractal characteristics of critical curves can be obtained.Comment: Published versio
Phase Structure in a Hadronic Chiral Model
We study the phase diagram of a hadronic chiral flavor-SU(3) model. Heavy
baryon resonances can induce a phase structure that matches current results
from lattice-QCD calculations at finite temperature and baryon density.
Furthermore, we determine trajectories of constant entropy per net baryon in
the phase diagram.Comment: 4 pages, 5 figure
Hypermatter in chiral field theory
We investigate the properties of hadronic matter and nuclei be means of a
generalized model with broken scale invariance. In
mean-field approximation, vector and scalar interactions yield a saturating
nuclear equation of state. Finite nuclei can be reasonably described, too. The
condensates and the effective baryon masses at finite baryon density and
temperature are discussed.Comment: uses IOP style, to be published in Journal of Physics, Proceedings of
the International Symposium on Strangeness in Quark Matter 1997, April 14-18,
Thera (Santorini), Hella
Neutron stars within the SU(2) parity doublet model
The equation of state of beta-stable and charge neutral nucleonic matter is
computed within the SU(2) parity doublet model in mean field and in the
relativistic Hartree approximation. The mass of the chiral partner of the
nucleon is assumed to be 1200 MeV. The transition to the chiral restored phase
turns out to be a smooth crossover in all the cases considered, taking place at
a baryon density of just . The mass-radius relations of compact stars
are calculated to constrain the model parameters from the maximum mass limit of
neutron stars. It is demonstrated that chiral symmetry starts to be restored,
which in this model implies the appearance of the chiral partners of the
nucleons, in the center of neutron stars. However, the analysis of the decay
width of the assumed chiral partner of the nucleon poses limits on the validity
of the present version of the model to describe vacuum properties.Comment: 14 pages, 9 figures, 2 tables, version accepted for publication in
EJP
Relativistic field theories in a magnetic background as noncommutative field theories
We study the connection of the dynamics in relativistic field theories in a
strong magnetic field with the dynamics of noncommutative field theories
(NCFT). As an example, the Nambu-Jona-Lasinio models in spatial dimensions are considered. We show that this connection is rather sophisticated.
In fact, the corresponding NCFT are different from the conventional ones
considered in the literature. In particular, the UV/IR mixing is absent in
these theories. The reason of that is an inner structure (i.e., dynamical
form-factors) of neutral composites which plays an important role in providing
consistency of the NCFT. An especially interesting case is that for a magnetic
field configuration with the maximal number of independent nonzero tensor
components. In that case, we show that the NCFT are finite for even and
their dynamics is quasi-(1+1)-dimensional for odd . For even , the NCFT
describe a confinement dynamics of charged particles. The difference between
the dynamics in strong magnetic backgrounds in field theories and that in
string theories is briefly discussed.Comment: 19 pages, REVTeX4, clarifications added, references added, to appear
in Phys. Rev.
The cosmic growth of the active black hole population at 1<z<2 in zCOSMOS, VVDS and SDSS
We present a census of the active black hole population at 1<z<2, by
constructing the bivariate distribution function of black hole mass and
Eddington ratio, employing a maximum likelihood fitting technique. The study of
the active black hole mass function (BHMF) and the Eddington ratio distribution
function (ERDF) allows us to clearly disentangle the active galactic nuclei
(AGN) downsizing phenomenon, present in the AGN luminosity function, into its
physical processes of black hole mass downsizing and accretion rate evolution.
We are utilizing type-1 AGN samples from three optical surveys (VVDS, zCOSMOS
and SDSS), that cover a wide range of 3 dex in luminosity over our redshift
interval of interest. We investigate the cosmic evolution of the AGN population
as a function of AGN luminosity, black hole mass and accretion rate. Compared
to z = 0, we find a distinct change in the shape of the BHMF and the ERDF,
consistent with downsizing in black hole mass. The active fraction or duty
cycle of type-1 AGN at z~1.5 is almost flat as a function of black hole mass,
while it shows a strong decrease with increasing mass at z=0. We are witnessing
a phase of intense black hole growth, which is largely driven by the onset of
AGN activity in massive black holes towards z=2. We finally compare our results
to numerical simulations and semi-empirical models and while we find reasonable
agreement over certain parameter ranges, we highlight the need to refine these
models in order to match our observations.Comment: 31 pages, 28 figures, accepted for publication in MNRA
The Length of an SLE - Monte Carlo Studies
The scaling limits of a variety of critical two-dimensional lattice models
are equal to the Schramm-Loewner evolution (SLE) for a suitable value of the
parameter kappa. These lattice models have a natural parametrization of their
random curves given by the length of the curve. This parametrization (with
suitable scaling) should provide a natural parametrization for the curves in
the scaling limit. We conjecture that this parametrization is also given by a
type of fractal variation along the curve, and present Monte Carlo simulations
to support this conjecture. Then we show by simulations that if this fractal
variation is used to parametrize the SLE, then the parametrized curves have the
same distribution as the curves in the scaling limit of the lattice models with
their natural parametrization.Comment: 18 pages, 10 figures. Version 2 replaced the use of "nu" for the
"growth exponent" by 1/d_H, where d_H is the Hausdorff dimension. Various
minor errors were also correcte
On the temperature dependence of correlation functions in the space like direction in hot QCD
We study the temperature dependence of quark antiquark correlations in the
space like direction. In particular, we predict the temperature dependence of
space like Bethe-Salpeter amplitudes using recent Lattice gauge data for the
space like string potential. We also investigate the effect of the space like
string potential on the screening mass and discuss possible corrections which
may arise when working with point sources.Comment: 15 pages 8 figures (not included, will be sent on request),
(SUNY-NTG-94-3
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