1,498 research outputs found
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
Finite Nuclei in a Relativistic Mean-Field Model with Derivative Couplings
We study finite nuclei, at the mean-field level, using the Zimanyi-Moskowski
model and one of its variations (the ZM3 model). We calculate energy levels and
ground-state properties in nuclei where the mean-field approach is reliable.
The role played by the spin-orbit potential in sorting out mean-field model
descriptions is emphasized.Comment: 17 pages, 9 figures, 30 kbytes. Uses EPSF.TEX. To appear in Zeit. f.
Phys. A (Hadrons and Nuclei
Level spectroscopy of the square-lattice three-state Potts model with a ferromagnetic next-nearest-neighbor coupling
We study the square-lattice three-state Potts model with the ferromagnetic
next-nearest-neighbor coupling at finite temperature. Using the
level-spectroscopy method, we numerically analyze the excitation spectrum of
the transfer matrices and precisely determine the global phase diagram. Then we
find that, contrary to a previous result based on the finite-size scaling, the
massless region continues up to the decoupling point with criticality in the antiferromagnetic region. We also check the universal
relations among excitation levels to provide the reliability of our result.Comment: 4 pages, 2 figure
Sine-Gordon quantum field theory on the half-line with quantum boundary degrees of freedom
The sine-Gordon model on the half-line with a dynamical boundary introduced
by Delius and one of the authors is considered at quantum level. Classical
boundary conditions associated with classical integrability are shown to be
preserved at quantum level too. Non-local conserved charges are constructed
explicitly in terms of the field and boundary operators. We solve the
intertwining equation associated with a certain coideal subalgebra of
generated by these non-local charges. The corresponding
solution is shown to satisfy quantum boundary Yang-Baxter equations. Up to an
exact relation between the quantization length of the boundary quantum
mechanical system and the sine-Gordon coupling constant, we conjecture the
soliton/antisoliton reflection matrix and boundstates reflection matrices. The
structure of the boundary state is then considered, and shown to be divided in
two sectors. Also, depending on the sine-Gordon coupling constant a finite set
of boundary bound states are identified. Taking the analytic continuation of
the coupling, the corresponding boundary sinh-Gordon model is briefly
discussed. In particular, the particle reflection factor enjoys weak-strong
coupling duality.Comment: 15 pages, LaTeX file with amssymb, v2: references added, Comments
added, typos corrected. To appear in Nucl.Phys.
Universal amplitude ratios of two-dimensional percolation from field theory
We complete the determination of the universal amplitude ratios of
two-dimensional percolation within the two-kink approximation of the form
factor approach. For the cluster size ratio, which has for a long time been
elusive both theoretically and numerically, we obtain the value 160.2, in good
agreement with the lattice estimate 162.5 +/- 2 of Jensen and Ziff.Comment: 8 page
Haldane Gapped Spin Chains: Exact Low Temperature Expansions of Correlation Functions
We study both the static and dynamic properties of gapped, one-dimensional,
Heisenberg, anti-ferromagnetic, spin chains at finite temperature through an
analysis of the O(3) non-linear sigma model. Exploiting the integrability of
this theory, we are able to compute an exact low temperature expansion of the
finite temperature correlators. We do so using a truncated `form-factor'
expansion and so provide evidence that this technique can be successfully
extended to finite temperature. As a direct test, we compute the static
zero-field susceptibility and obtain an exact match to the susceptibility
derived from the low temperature expansion of the exact free energy. We also
study transport properties, computing both the spin conductance and the
NMR-relaxation rate, 1/T_1. We find these quantities to show ballistic
behaviour. In particular, the computed spin conductance exhibits a non-zero
Drude weight at finite temperature and zero applied field. The physics thus
described differs from the spin diffusion reported by Takigawa et al. from
experiments on the Haldane gap material, AgVP_2S_6.Comment: 51 pages, 5 figure
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
Kink Confinement and Supersymmetry
We analyze non-integrable deformations of two-dimensional N=1 supersymmetric
quantum field theories with kink excitations. As example, we consider the
multi-frequency Super Sine Gordon model. At weak coupling, this model is robust
with respect to kink confinement phenomena, in contrast to the purely bosonic
case. If we vary the coupling, the model presents a sequence of phase
transitions, where pairs of kinks disappear from the spectrum. The phase
transitions fall into two classes: the first presents the critical behaviors of
the Tricritical Ising model, the second instead those of the gaussian model. In
the first case, close to the critical point, the model has metastable vacua,
with a spontaneously supersymmetry breaking. When the life-time of the
metastable vacua is sufficiently long, the role of goldstino is given by the
massless Majorana fermion of the Ising model. On the contrary, supersymmetry
remains exact in the phase transition of the second type.Comment: 29 pages, 12 figure
Quasi-1D spin-1/2 Heisenberg magnets in their ordered phase: correlation functions
We study weakly coupled antiferromagnetic spin chains in their ordered phase
by combinining an exact solution of the single-chain problem with an RPA
analysis of the interchain interaction. A single chain is described by a
quantum Sine-Gordon model and dynamical staggered susceptibilities are
determined by employing the formfactor approach to quantum correlation
functions. We consider both antiferromagnetic order encountered in quasi-1D
materials like and spin-Peierls order as found in .Comment: 16 pages of revtex, 12 figure
Constraining relativistic models through heavy ion collisions
Relativistic models can be successfully applied to the description of compact
star properties in nuclear astrophysics as well as to nuclear matter and finite
nuclei properties, these studies taking place at low and moderate temperatures.
Nevertheless, all results are model dependent and so far it is unclear whether
some of them should be discarded. Moreover, in the regime of hot hadronic
matter very few calculations exist using these relativistic models, in
particular when applied to particle yields in heavy ion collisions.
In the present work we comment on the known constraints that can help the
selection of adequate models in this regime and investigate the main
differences that arise when the particle production during a Au+Au collision at
RHIC is calculated with different models.Comment: 9 pages, 1 figure, 3 table
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