1,255 research outputs found
Statistical Mechanical Calculation of Anisotropic Step Stiffness of a Two-Dimensional Hexagonal Lattice Gas Model with Next-Nearest-Neighbor Interactions: Application to Si(111) Surface
We study a two-dimensional honeycomb lattice gas model with both nearest- and
next-nearest-neighbor interactions in a staggered field, which describes the
surface of stoichiometrically binary crystal.
We calculate anisotropic step tension, step stiffness, and equilibrium island
shape, by an extended random walk method. We apply the results to Si(111)
77 reconstructed surface and high-temperature Si(111) 11
surface. We also calculate inter-step interaction coefficient.Comment: revised on May 29 1999: RevTeX v3.1, 10 pages with 9 figures (one
figure added
Non-universal equilibrium crystal shape results from sticky steps
The anisotropic surface free energy, Andreev surface free energy, and
equilibrium crystal shape (ECS) z=z(x,y) are calculated numerically using a
transfer matrix approach with the density matrix renormalization group (DMRG)
method. The adopted surface model is a restricted solid-on-solid (RSOS) model
with "sticky" steps, i.e., steps with a point-contact type attraction between
them (p-RSOS model). By analyzing the results, we obtain a first-order shape
transition on the ECS profile around the (111) facet; and on the curved surface
near the (001) facet edge, we obtain shape exponents having values different
from those of the universal Gruber-Mullins-Pokrovsky-Talapov (GMPT) class. In
order to elucidate the origin of the non-universal shape exponents, we
calculate the slope dependence of the mean step height of "step droplets"
(bound states of steps) using the Monte Carlo method, where p=(dz/dx,
dz/dy)$, and represents the thermal averag |p| dependence of , we
derive a |p|-expanded expression for the non-universal surface free energy
f_{eff}(p), which contains quadratic terms with respect to |p|. The first-order
shape transition and the non-universal shape exponents obtained by the DMRG
calculations are reproduced thermodynamically from the non-universal surface
free energy f_{eff}(p).Comment: 31 pages, 21 figure
Vicinal Surface with Langmuir Adsorption: A Decorated Restricted Solid-on-solid Model
We study the vicinal surface of the restricted solid-on-solid model coupled
with the Langmuir adsorbates which we regard as two-dimensional lattice gas
without lateral interaction. The effect of the vapor pressure of the adsorbates
in the environmental phase is taken into consideration through the chemical
potential. We calculate the surface free energy , the adsorption coverage
, the step tension , and the step stiffness by
the transfer matrix method combined with the density-matrix algorithm. Detailed
step-density-dependence of and is obtained. We draw the roughening
transition curve in the plane of the temperature and the chemical potential of
adsorbates. We find the multi-reentrant roughening transition accompanying the
inverse roughening phenomena. We also find quasi-reentrant behavior in the step
tension.Comment: 7 pages, 12 figures (png format), RevTeX 3.1, submitted to Phys. Rev.
Non semi-simple sl(2) quantum invariants, spin case
Invariants of 3-manifolds from a non semi-simple category of modules over a
version of quantum sl(2) were obtained by the last three authors in
[arXiv:1404.7289]. In their construction the quantum parameter is a root of
unity of order where is odd or congruent to modulo . In this
paper we consider the remaining cases where is congruent to zero modulo
and produce invariants of -manifolds with colored links, equipped with
generalized spin structure. For a given -manifold , the relevant
generalized spin structures are (non canonically) parametrized by
.Comment: 13 pages, 16 figure
Multi-Colour Braid-Monoid Algebras
We define multi-colour generalizations of braid-monoid algebras and present
explicit matrix representations which are related to two-dimensional exactly
solvable lattice models of statistical mechanics. In particular, we show that
the two-colour braid-monoid algebra describes the Yang-Baxter algebra of the
critical dilute A-D-E models which were recently introduced by Warnaar,
Nienhuis, and Seaton as well as by Roche. These and other solvable models
related to dense and dilute loop models are discussed in detail and it is shown
that the solvability is a direct consequence of the algebraic structure. It is
conjectured that the Yang-Baxterization of general multi-colour braid-monoid
algebras will lead to the construction of further solvable lattice models.Comment: 32 page
Flexible construction of hierarchical scale-free networks with general exponent
Extensive studies have been done to understand the principles behind
architectures of real networks. Recently, evidences for hierarchical
organization in many real networks have also been reported. Here, we present a
new hierarchical model which reproduces the main experimental properties
observed in real networks: scale-free of degree distribution (frequency
of the nodes that are connected to other nodes decays as a power-law
) and power-law scaling of the clustering coefficient
. The major novelties of our model can be summarized as
follows: {\it (a)} The model generates networks with scale-free distribution
for the degree of nodes with general exponent , and arbitrarily
close to any specified value, being able to reproduce most of the observed
hierarchical scale-free topologies. In contrast, previous models can not obtain
values of . {\it (b)} Our model has structural flexibility
because {\it (i)} it can incorporate various types of basic building blocks
(e.g., triangles, tetrahedrons and, in general, fully connected clusters of
nodes) and {\it (ii)} it allows a large variety of configurations (i.e., the
model can use more than copies of basic blocks of nodes). The
structural features of our proposed model might lead to a better understanding
of architectures of biological and non-biological networks.Comment: RevTeX, 5 pages, 4 figure
Product Wave Function Renormalization Group: construction from the matrix product point of view
We present a construction of a matrix product state (MPS) that approximates
the largest-eigenvalue eigenvector of a transfer matrix T, for the purpose of
rapidly performing the infinite system density matrix renormalization group
(DMRG) method applied to two-dimensional classical lattice models. We use the
fact that the largest-eigenvalue eigenvector of T can be approximated by a
state vector created from the upper or lower half of a finite size cluster.
Decomposition of the obtained state vector into the MPS gives a way of
extending the MPS, at the system size increment process in the infinite system
DMRG algorithm. As a result, we successfully give the physical interpretation
of the product wave function renormalization group (PWFRG) method, and obtain
its appropriate initial condition.Comment: 8 pages, 8 figure
Primordial Gravitational Waves Enhancement
We reconsider the enhancement of primordial gravitational waves that arises
from a quantum gravitational model of inflation. A distinctive feature of this
model is that the end of inflation witnesses a brief phase during which the
Hubble parameter oscillates in sign, changing the usual Hubble friction to
anti-friction. An earlier analysis of this model was based on numerically
evolving the graviton mode functions after guessing their initial conditions
near the end of inflation. The current study is based on an equation which
directly evolves the normalized square of the magnitude. We are also able to
make a very reliable estimate for the initial condition using a rapidly
converging expansion for the sub-horizon regime. Results are obtained for the
energy density per logarithmic wave number as a fraction of the critical
density. These results exhibit how the enhanced signal depends upon the number
of oscillatory periods; they also show the resonant effects associated with
particular wave numbers.Comment: 25 pages, 14 figure
Colored Vertex Models, Colored IRF Models and Invariants of Trivalent Colored Graphs
We present formulas for the Clebsch-Gordan coefficients and the Racah
coefficients for the root of unity representations (-dimensional
representations with ) of . We discuss colored vertex
models and colored IRF (Interaction Round a Face) models from the color
representations of . We construct invariants of trivalent colored
oriented framed graphs from color representations of .Comment: 39 pages, January 199
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