2,033 research outputs found
Nuclear Matter Properties in Derivative Coupling Models Beyond Mean - Field Approximation
The structure of infinite nuclear matter is studied with two of the Zimanyi -
Moszkowski (ZM) models in the framework of a relativistic approximation which
takes into account Hartree terms and beyond and is compared with the results
which come out of the relativistic Hartree - Fock approach in the linear
Walecka model. The simple treatment applied to these models can be used in
substitution to the more complicated Dirac - Brueckner - Hartree - Fock method
to perform future calculations in finite nuclei.Comment: 11 pages including 1 table, 1 figure (available upon request
Phase transition of the nucleon-antinucleon plasma at different ratios
We investigate phase transitions for the Walecka model at very high
temperatures. As is well known, depending on the parametrization of this model
and for the particular case of a zero chemical potential (), a first
order phase transition is possible \cite{theis}. We investigate this model for
the case in which . It turns out that, in this situation, phases
with different values of antinucleon-nucleon ratios and net baryon densities
may coexist. We present the temperature versus antinucleon-nucleon ratio as
well as the temperature versus the net baryon density for the coexistence
region. The temperature versus chemical potential phase diagram is also
presented.Comment: 5 pages, 8 figure
Mass Generation in Perturbed Massless Integrable Models
We extend form-factor perturbation theory to non--integrable deformations of
massless integrable models, in order to address the problem of mass generation
in such systems. With respect to the standard renormalisation group analysis
this approach is more suitable for studying the particle content of the
perturbed theory. Analogously to the massive case, interesting information can
be obtained already at first order, such as the identification of the operators
which create a mass gap and those which induce the confinement of the massless
particles in the perturbed theory
Form factors in the Bullough-Dodd related models: The Ising model in a magnetic field
We consider particular modification of the free-field representation of the
form factors in the Bullough-Dodd model. The two-particles minimal form factors
are excluded from the construction. As a consequence, we obtain convenient
representation for the multi-particle form factors, establish recurrence
relations between them and study their properties. The proposed construction is
used to obtain the free-field representation of the lightest particles form
factors in the perturbed minimal models. As a significant example
we consider the Ising model in a magnetic field. We check that the results
obtained in the framework of the proposed free-field representation are in
agreement with the corresponding results obtained by solving the bootstrap
equations.Comment: 20 pages; v2: some misprints, textual inaccuracies and references
corrected; some references and remarks adde
Long range correlations generated by phase separation. Exact results from field theory
We consider near-critical planar systems with boundary conditions inducing phase separation. While order parameter correlations decay exponentially in pure phases, we show by direct field theoretical derivation how phase separation generates long range correlations in the direction parallel to the interface, and determine their exact analytic form. The latter leads to specific contributions to the structure factor of the interface
Boundary form factors of the sinh-Gordon model with Dirichlet boundary conditions at the self-dual point
In this manuscript we present a detailed investigation of the form factors of
boundary fields of the sinh-Gordon model with a particular type of Dirichlet
boundary condition, corresponding to zero value of the sinh-Gordon field at the
boundary, at the self-dual point. We follow for this the boundary form factor
program recently proposed by Z. Bajnok, L. Palla and G. Takaks in
hep-th/0603171, extending the analysis of the boundary sinh-Gordon model
initiated there. The main result of the paper is a conjecture for the structure
of all n-particle form factors of two particular boundary operators in terms of
elementary symmetric polynomials in certain functions of the rapidity
variables. In addition, form factors of boundary "descendant" fields have been
constructedComment: 14 pages LaTex. Version to appear in J. Phys.
Hadronic Entropy Enhancement and Low Density QGP
Recent studies show that for central collisions the rising of the incident
energy from AGS to RHIC decreases the value of the chemical potential in the
Hadron-QGP phase diagram. Thus, the formation of QGP at RHIC energies in
central collisions may be expected to occur at very small values of the
chemical potential. Using many different relativistic mean-field hadronic
models (RMF) at this regime we show that the critical temperature for the
Hadron-QGP transition is hadronic model independent. We have traced back the
reason for this and conclude that it comes from the fact that the QGP entropy
is much larger than the hadronic entropy obtained in all the RMF models. We
also find that almost all of these models present a strong entropy enhancement
in the hadronic sector coming from the baryonic phase transition to a
nucleon-antinucleon plasma. This result is in agreement with the recent data
obtained in the STAR collaboration at RHIC where it was found a rich
proton-antiproton matter
Universal Ratios in the 2-D Tricritical Ising Model
We consider the universality class of the two-dimensional Tricritical Ising
Model. The scaling form of the free-energy naturally leads to the definition of
universal ratios of critical amplitudes which may have experimental relevance.
We compute these universal ratios by a combined use of results coming from
Perturbed Conformal Field Theory, Integrable Quantum Field Theory and numerical
methods.Comment: 4 pages, LATEX fil
Proposal to improve the behaviour of self-energy contributions to the S-matrix
A simple modification of the definition of the S-matrix is proposed. It is
expected that the divergences related to nonzero self-energies are considerably
milder with the modified definition than with the usual one. This conjecture is
verified in a few examples using perturbation theory. The proposed formula is
written in terms of the total Hamiltonian operator and a free Hamiltonian
operator and is therefore applicable in any case when these Hamiltonian
operators are known.Comment: 24 pages, 1 figure; v2: revised version; v3: section 3 improved.
Accepted for publication in Central European Journal of Physics; v4: minor
text misprints correcte
Interface localization near criticality
The theory of interface localization in near-critical planar systems at phase
coexistence is formulated from first principles. We show that mutual delocalization of two
interfaces, amounting to interfacial wetting, occurs when the bulk correlation length crit-
ical exponent \u3bd is larger than or equal to 1. Interaction with a boundary or defect line
involves an additional scale and a dependence of the localization strength on the distance
from criticality. The implications are particularly rich in the boundary case, where de-
localization proceeds through different renormalization patterns sharing the feature that
the boundary field becomes irrelevant in the delocalized regime. The boundary delocal-
ization (wetting) transition is shown to be continuous, with surface specific heat and layer
thickness exponents which can take values that we determine
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