97,716 research outputs found
Self-organized density patterns of molecular motors in arrays of cytoskeletal filaments
The stationary states of systems with many molecular motors are studied
theoretically for uniaxial and centered (aster-like) arrangements of
cytoskeletal filaments using Monte Carlo simulations and a two-state model.
Mutual exclusion of motors from binding sites of the filaments is taken into
account. For small overall motor concentration, the density profiles are
exponential and algebraic in uniaxial and centered filament systems,
respectively. For uniaxial systems, exclusion leads to the coexistence of
regions of high and low densities of bound motors corresponding to motor
traffic jams, which grow upon increasing the overall motor concentration. These
jams are insensitive to the motor behavior at the end of the filament. In
centered systems, traffic jams remain small and an increase in the motor
concentration leads to a flattening of the profile, if the motors move inwards,
and to the build-up of a concentration maximum in the center of the aster if
motors move outwards. In addition to motors density patterns, we also determine
the corresponding patterns of the motor current.Comment: 48 pages, 8 figure
Phase diagram of two-lane driven diffusive systems
We consider a large class of two-lane driven diffusive systems in contact
with reservoirs at their boundaries and develop a stability analysis as a
method to derive the phase diagrams of such systems. We illustrate the method
by deriving phase diagrams for the asymmetric exclusion process coupled to
various second lanes: a diffusive lane; an asymmetric exclusion process with
advection in the same direction as the first lane, and an asymmetric exclusion
process with advection in the opposite direction. The competing currents on the
two lanes naturally lead to a very rich phenomenology and we find a variety of
phase diagrams. It is shown that the stability analysis is equivalent to an
`extremal current principle' for the total current in the two lanes. We also
point to classes of models where both the stability analysis and the extremal
current principle fail
Traffic jams induced by rare switching events in two-lane transport
We investigate a model for driven exclusion processes where internal states are assigned to the particles. The latter account for diverse situations, ranging from spin states in spintronics to parallel lanes in intracellular or vehicular traffic. Introducing a coupling between the internal states by allowing particles to switch from one to another induces an intriguing polarization phenomenon. In a mesoscopic scaling, a rich stationary regime for the density profiles is discovered, with localized domain walls in the density profile of one of the internal states being feasible. We derive the shape of the density profiles as well as resulting phase diagrams analytically by a mean-field approximation and a continuum limit. Continuous as well as discontinuous lines of phase transition emerge, their intersections induce multi-critical behaviour
Gravitational-wave versus binary-pulsar tests of strong-field gravity
Binary systems comprising at least one neutron star contain strong
gravitational field regions and thereby provide a testing ground for
strong-field gravity. Two types of data can be used to test the law of gravity
in compact binaries: binary pulsar observations, or forthcoming
gravitational-wave observations of inspiralling binaries. We compare the
probing power of these two types of observations within a generic two-parameter
family of tensor-scalar gravitational theories. Our analysis generalizes
previous work (by us) on binary-pulsar tests by using a sample of realistic
equations of state for nuclear matter (instead of a polytrope), and goes beyond
a previous study (by C.M. Will) of gravitational-wave tests by considering more
general tensor-scalar theories than the one-parameter Jordan-Fierz-Brans-Dicke
one. Finite-size effects in tensor-scalar gravity are also discussed.Comment: 23 pages, REVTeX 3.0, uses epsf.tex to include 5 postscript figures
(2 paragraphs and a 5th figure added at the end of section IV + minor
changes
The Totally Asymmetric Simple Exclusion Process with Langmuir Kinetics
We discuss a new class of driven lattice gas obtained by coupling the
one-dimensional totally asymmetric simple exclusion process to Langmuir
kinetics. In the limit where these dynamics are competing, the resulting
non-conserved flow of particles on the lattice leads to stationary regimes for
large but finite systems. We observe unexpected properties such as localized
boundaries (domain walls) that separate coexisting regions of low and high
density of particles (phase coexistence). A rich phase diagram, with high an
low density phases, two and three phase coexistence regions and a boundary
independent ``Meissner'' phase is found. We rationalize the average density and
current profiles obtained from simulations within a mean-field approach in the
continuum limit. The ensuing analytic solution is expressed in terms of Lambert
-functions. It allows to fully describe the phase diagram and extract
unusual mean-field exponents that characterize critical properties of the
domain wall. Based on the same approach, we provide an explanation of the
localization phenomenon. Finally, we elucidate phenomena that go beyond
mean-field such as the scaling properties of the domain wall.Comment: 22 pages, 23 figures. Accepted for publication on Phys. Rev.
A Position-Space Renormalization-Group Approach for Driven Diffusive Systems Applied to the Asymmetric Exclusion Model
This paper introduces a position-space renormalization-group approach for
nonequilibrium systems and applies the method to a driven stochastic
one-dimensional gas with open boundaries. The dynamics are characterized by
three parameters: the probability that a particle will flow into the
chain to the leftmost site, the probability that a particle will flow
out from the rightmost site, and the probability that a particle will jump
to the right if the site to the right is empty. The renormalization-group
procedure is conducted within the space of these transition probabilities,
which are relevant to the system's dynamics. The method yields a critical point
at ,in agreement with the exact values, and the critical
exponent , as compared with the exact value .Comment: 14 pages, 4 figure
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