25,975 research outputs found
Two dimensional XXZ-Ising model on square-hexagon lattice
We study a two dimensional XXZ-Ising on square-hexagon (4-6) lattice with
spin-1/2. The phase diagram of the ground state energy is discussed, shown two
different ferrimagnetic states and two type of antiferromagnetic states, beside
of a ferromagnetic state. To solve this model, it could be mapped into the
eight-vertex model with union jack interaction term. Imposing exact solution
condition we find the region where the XXZ-Ising model on 4-6 lattice have
exact solutions with one free parameter, for symmetric eight-vertex model
condition. In this sense we explore the properties of the system and analyze
the competition of the interaction parameters providing the region where it has
an exact solution. However the present model does not satisfy the \textit{free
fermion} condition, unless for a trivial situation. Even so we are able to
discuss their critical points region, when the exactly solvable condition is
ignored.Comment: 5 pages, 5 figure
Numerical Computation of Finite Size Scaling Functions: An Alternative Approach to Finite Size Scaling
Using single cluster flip Monte Carlo simulations we accurately determine new
finite size scaling functions which are expressed only in terms the variable , where is the correlation length in a finite system of
size . Data for the d=2 and d=3 Ising models, taken at different
temperatures and for different size lattices, show excellent data collapse over
the entire range of scaling variable for susceptibility and correlation length.
From these finite size scaling functions we can estimate critical temperatures
and exponents with rather high accuracy even though data are not obtained
extremely close to the critical point. The bulk values of the renormalized
four-point coupling constant are accurately measured and show strong evidence
for hyperscaling.Comment: RevTex. 19 page
On possible violation of the CHSH Bell inequality in a classical context
It has been shown that there is a small possibility to experimentally violate
the CHSH Bell inequality in a 'classical' context. The probability of such a
violation has been estimated in the framework of a classical probabilistic
model in the language of a random-walk representation.Comment: 9 pages, 1 figur
Remote sensing applications to hydrologic modeling
An energy balance snowmelt model for rugged terrain was devised and coupled to a flow model. A literature review of remote sensing applications to hydrologic modeling was included along with a software development outline
Constraining non-minimally coupled tachyon fields by Noether symmetry
A model for a spatially flat homogeneous and isotropic Universe whose
gravitational sources are a pressureless matter field and a tachyon field
non-minimally coupled to the gravitational field is analyzed. Noether symmetry
is used to find the expressions for the potential density and for the coupling
function, and it is shown that both must be exponential functions of the
tachyon field. Two cosmological solutions are investigated: (i) for the early
Universe whose only source of the gravitational field is a non-minimally
coupled tachyon field which behaves as an inflaton and leads to an exponential
accelerated expansion and (ii) for the late Universe whose gravitational
sources are a pressureless matter field and a non-minimally coupled tachyon
field which plays the role of dark energy and is the responsible of the
decelerated-accelerated transition period.Comment: 11 pages, 5 figures. Version accepted for publication in Classical
and Quantum Gravit
The monoclinic phase of PZT ceramics: Raman and phenomenological theory studies
This work reports on the first Raman detection of the tetragonal to
monoclinic phase transition in PZT ceramics near morphotropic phase boundary at
low temperatures. The transition is characterized by changes in the frequency
of lattice modes with the temperature. The results presented here confirm the
previous one recently reported by Noheda et al. using high-resolution
synchrotron X-ray powder diffraction technique and dielectric measurements. The
stability of the new phase is discussed within the framework of
phenomenological Landau-Devonshire Theory.Comment: 6 pages including 4 figures, Latex, submitted to Applied Physics
Letter
Components of multifractality in the Central England Temperature anomaly series
We study the multifractal nature of the Central England Temperature (CET)
anomaly, a time series that spans more than 200 years. The series is analyzed
as a complete data set and considering a sliding window of 11 years. In both
cases, we quantify the broadness of the multifractal spectrum as well as its
components defined by the deviations from the Gaussian distribution and the
influence of the dependence between measurements. The results show that the
chief contribution to the multifractal structure comes from the dynamical
dependencies, mainly the weak ones, followed by a residual contribution of the
deviations from Gaussianity. However, using the sliding window, we verify that
the spikes in the non-Gaussian contribution occur at very close dates
associated with climate changes determined in previous works by component
analysis methods. Moreover, the strong non-Gaussian contribution found in the
multifractal measures from the 1960s onwards is in agreement with global
results very recently proposed in the literature.Comment: 21 pages, 10 figure
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