98 research outputs found
Exact Solution of the Discrete (1+1)-dimensional RSOS Model in a Slit with Field and Wall Interactions
We present the solution of a linear Restricted Solid--on--Solid (RSOS) model
confined to a slit. We include a field-like energy, which equivalently weights
the area under the interface, and also include independent interaction terms
with both walls. This model can also be mapped to a lattice polymer model of
Motzkin paths in a slit interacting with both walls and including an osmotic
pressure. This work generalises previous work on the RSOS model in the
half-plane which has a solution that was shown recently to exhibit a novel
mathematical structure involving basic hypergeometric functions .
Because of the mathematical relationship between half-plane and slit this work
hence effectively explores the underlying -orthogonal polynomial structure
to that solution. It also generalises two other recent works: one on Dyck paths
weighted with an osmotic pressure in a slit and another concerning Motzkin
paths without an osmotic pressure term in a slit
Exact Solution of Semi-Flexible and Super-Flexible Interacting Partially Directed Walks
We provide the exact generating function for semi-flexible and super-flexible
interacting partially directed walks and also analyse the solution in detail.
We demonstrate that while fully flexible walks have a collapse transition that
is second order and obeys tricritical scaling, once positive stiffness is
introduced the collapse transition becomes first order. This confirms a recent
conjecture based on numerical results. We note that the addition of an
horizontal force in either case does not affect the order of the transition. In
the opposite case where stiffness is discouraged by the energy potential
introduced, which we denote the super-flexible case, the transition also
changes, though more subtly, with the crossover exponent remaining unmoved from
the neutral case but the entropic exponents changing
Dyck Paths, Motzkin Paths and Traffic Jams
It has recently been observed that the normalization of a one-dimensional
out-of-equilibrium model, the Asymmetric Exclusion Process (ASEP) with random
sequential dynamics, is exactly equivalent to the partition function of a
two-dimensional lattice path model of one-transit walks, or equivalently Dyck
paths. This explains the applicability of the Lee-Yang theory of partition
function zeros to the ASEP normalization.
In this paper we consider the exact solution of the parallel-update ASEP, a
special case of the Nagel-Schreckenberg model for traffic flow, in which the
ASEP phase transitions can be intepreted as jamming transitions, and find that
Lee-Yang theory still applies. We show that the parallel-update ASEP
normalization can be expressed as one of several equivalent two-dimensional
lattice path problems involving weighted Dyck or Motzkin paths. We introduce
the notion of thermodynamic equivalence for such paths and show that the
robustness of the general form of the ASEP phase diagram under various update
dynamics is a consequence of this thermodynamic equivalence.Comment: Version accepted for publicatio
Exact Scaling Functions for Self-Avoiding Loops and Branched Polymers
It is shown that a recently conjectured form for the critical scaling
function for planar self-avoiding polygons weighted by their perimeter and area
also follows from an exact renormalization group flow into the branched polymer
problem, combined with the dimensional reduction arguments of Parisi and
Sourlas. The result is generalized to higher-order multicritical points,
yielding exact values for all their critical exponents and exact forms for the
associated scaling functions.Comment: 5 pages; v2: factors of 2 corrected; v.3: relation with existing
theta-point results clarified, some references added/update
The Grand-Canonical Asymmetric Exclusion Process and the One-Transit Walk
The one-dimensional Asymmetric Exclusion Process (ASEP) is a paradigm for
nonequilibrium dynamics, in particular driven diffusive processes. It is
usually considered in a canonical ensemble in which the number of sites is
fixed. We observe that the grand-canonical partition function for the ASEP is
remarkably simple. It allows a simple direct derivation of the asymptotics of
the canonical normalization in various phases and of the correspondence with
One-Transit Walks recently observed by Brak et.al.Comment: Published versio
Relaxation time in a non-conserving driven-diffusive system with parallel dynamics
We introduce a two-state non-conserving driven-diffusive system in
one-dimension under a discrete-time updating scheme. We show that the
steady-state of the system can be obtained using a matrix product approach. On
the other hand, the steady-state of the system can be expressed in terms of a
linear superposition Bernoulli shock measures with random walk dynamics. The
dynamics of a shock position is studied in detail. The spectrum of the transfer
matrix and the relaxation times to the steady-state have also been studied in
the large-system-size limit.Comment: 10 page
Boundary correlation functions of the six-vertex model
We consider the six-vertex model on an square lattice with the
domain wall boundary conditions. Boundary one-point correlation functions of
the model are expressed as determinants of matrices, generalizing
the known result for the partition function. In the free fermion case the
explicit answers are obtained. The introduced correlation functions are closely
related to the problem of enumeration of alternating sign matrices and domino
tilings.Comment: 20 pages, 2 figures, typos correcte
Raise and Peel Models of fluctuating interfaces and combinatorics of Pascal's hexagon
The raise and peel model of a one-dimensional fluctuating interface (model A)
is extended by considering one source (model B) or two sources (model C) at the
boundaries. The Hamiltonians describing the three processes have, in the
thermodynamic limit, spectra given by conformal field theory. The probability
of the different configurations in the stationary states of the three models
are not only related but have interesting combinatorial properties. We show
that by extending Pascal's triangle (which gives solutions to linear relations
in terms of integer numbers), to an hexagon, one obtains integer solutions of
bilinear relations. These solutions give not only the weights of the various
configurations in the three models but also give an insight to the connections
between the probability distributions in the stationary states of the three
models. Interestingly enough, Pascal's hexagon also gives solutions to a
Hirota's difference equation.Comment: 33 pages, an abstract and an introduction are rewritten, few
references are adde
Refined Razumov-Stroganov conjectures for open boundaries
Recently it has been conjectured that the ground-state of a Markovian
Hamiltonian, with one boundary operator, acting in a link pattern space is
related to vertically and horizontally symmetric alternating-sign matrices
(equivalently fully-packed loop configurations (FPL) on a grid with special
boundaries).We extend this conjecture by introducing an arbitrary boundary
parameter. We show that the parameter dependent ground state is related to
refined vertically symmetric alternating-sign matrices i.e. with prescribed
configurations (respectively, prescribed FPL configurations) in the next to
central row.
We also conjecture a relation between the ground-state of a Markovian
Hamiltonian with two boundary operators and arbitrary coefficients and some
doubly refined (dependence on two parameters) FPL configurations. Our
conjectures might be useful in the study of ground-states of the O(1) and XXZ
models, as well as the stationary states of Raise and Peel models.Comment: 11 pages LaTeX, 8 postscript figure
- …