72,813 research outputs found
Factorised steady states for multi-species mass transfer models
A general class of mass transport models with Q species of conserved mass is
considered. The models are defined on a lattice with parallel discrete time
update rules. For one-dimensional, totally asymmetric dynamics we derive
necessary and sufficient conditions on the mass transfer dynamics under which
the steady state factorises. We generalise the model to mass transfer on
arbitrary lattices and present sufficient conditions for factorisation. In both
cases, explicit results for random sequential update and continuous time limits
are given.Comment: 11 page
Condensation transitions in a model for a directed network with weighted links
An exactly solvable model for the rewiring dynamics of weighted, directed
networks is introduced. Simulations indicate that the model exhibits two types
of condensation: (i) a phase in which, for each node, a finite fraction of its
total out-strength condenses onto a single link; (ii) a phase in which a finite
fraction of the total weight in the system is directed into a single node. A
virtue of the model is that its dynamics can be mapped onto those of a
zero-range process with many species of interacting particles -- an exactly
solvable model of particles hopping between the sites of a lattice. This
mapping, which is described in detail, guides the analysis of the steady state
of the network model and leads to theoretical predictions for the conditions
under which the different types of condensation may be observed. A further
advantage of the mapping is that, by exploiting what is known about exactly
solvable generalisations of the zero-range process, one can infer a number of
generalisations of the network model and dynamics which remain exactly
solvable.Comment: 23 pages, 8 figure
Rules for transition rates in nonequilibrium steady states
Just as transition rates in a canonical ensemble must respect the principle
of detailed balance, constraints exist on transition rates in driven steady
states. I derive those constraints, by maximum information-entropy inference,
and apply them to the steady states of driven diffusion and a sheared lattice
fluid. The resulting ensemble can potentially explain nonequilibrium phase
behaviour and, for steady shear, gives rise to stress-mediated long-range
interactions.Comment: 4 pages. To appear in Physical Review Letter
Modelling Citation Networks
The distribution of the number of academic publications as a function of
citation count for a given year is remarkably similar from year to year. We
measure this similarity as a width of the distribution and find it to be
approximately constant from year to year. We show that simple citation models
fail to capture this behaviour. We then provide a simple three parameter
citation network model using a mixture of local and global search processes
which can reproduce the correct distribution over time. We use the citation
network of papers from the hep-th section of arXiv to test our model. For this
data, around 20% of citations use global information to reference recently
published papers, while the remaining 80% are found using local searches. We
note that this is consistent with other studies though our motivation is very
different from previous work. Finally, we also find that the fluctuations in
the size of an academic publication's bibliography is important for the model.
This is not addressed in most models and needs further work.Comment: 29 pages, 22 figure
Studying a relativistic field theory at finite chemical potential with the density matrix renormalization group
The density matrix renormalization group is applied to a relativistic complex
scalar field at finite chemical potential. The two-point function and various
bulk quantities are studied. It is seen that bulk quantities do not change with
the chemical potential until it is larger than the minimum excitation energy.
The technical limitations of the density matrix renormalization group for
treating bosons in relativistic field theories are discussed. Applications to
other relativistic models and to nontopological solitons are also suggested.Comment: 9 pages, 5 figures; v2: title changed; references added, conclusions
expanded, to be published in PR
An exactly solvable dissipative transport model
We introduce a class of one-dimensional lattice models in which a quantity,
that may be thought of as an energy, is either transported from one site to a
neighbouring one, or locally dissipated. Transport is controlled by a
continuous bias parameter q, which allows us to study symmetric as well as
asymmetric cases. We derive sufficient conditions for the factorization of the
N-body stationary distribution and give an explicit solution for the latter,
before briefly discussing physically relevant situations.Comment: 7 pages, 1 figure, submitted to J. Phys.
Criterion for phase separation in one-dimensional driven systems
A general criterion for the existence of phase separation in driven
one-dimensional systems is proposed. It is suggested that phase separation is
related to the size dependence of the steady-state currents of domains in the
system. A quantitative criterion for the existence of phase separation is
conjectured using a correspondence made between driven diffusive models and
zero-range processes. Several driven diffusive models are discussed in light of
the conjecture
Isolation of Psoroptes scab mite microsatellite markers (Acari: Psoroptidae)
Nine microsatellite markers have been isolated from the scab mite,Psoroptes ovis. These markers have been tested for polymorphism in individual Psoroptes
mites originating from two hosts, the European rabbit,
Oryctolagus cuniculus, and sheep, Ovis aries. No
definitive picture of Psoroptes species’ status or interrelationships exists. This study provides the basis for a new molecular system to elucidate the systematics of groupings within the genus Psoroptes, allowing us to clarify the population dynamics and epidemiology of
the mites causing sheep scab world wide
Phase Transition in Two Species Zero-Range Process
We study a zero-range process with two species of interacting particles. We
show that the steady state assumes a simple factorised form, provided the
dynamics satisfy certain conditions, which we derive. The steady state exhibits
a new mechanism of condensation transition wherein one species induces the
condensation of the other. We study this mechanism for a specific choice of
dynamics.Comment: 8 pages, 3 figure
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