837 research outputs found
Strength of Mechanical Memories is Maximal at the Yield Point of a Soft Glass
We show experimentally that both single and multiple mechanical memories can
be encoded in an amorphous bubble raft, a prototypical soft glass, subject to
an oscillatory strain. In line with recent numerical results, we find that
multiple memories can be formed sans external noise. By systematically
investigating memory formation for a range of training strain amplitudes
spanning yield, we find clear signatures of memory even beyond yielding. Most
strikingly, the extent to which the system recollects memory is largest for
training amplitudes near the yield strain and is a direct consequence of the
spatial extent over which the system reorganizes during the encoding process.
Our study further suggests that the evolution of force networks on training
plays a decisive role in memory formation in jammed packings.Comment: 13 pages, 4 Figure
Duality and phase diagram of one dimensional transport
The observation of duality by Mukherji and Mishra in one dimensional
transport problems has been used to develop a general approach to classify and
characterize the steady state phase diagrams. The phase diagrams are determined
by the zeros of a set of coarse-grained functions without the need of detailed
knowledge of microscopic dynamics. In the process, a new class of
nonequilibrium multicritical points has been identified.Comment: 6 pages, 2 figures (4 eps files
Nonequilibrium tricriticality in one dimension
We show the existence of a nonequilibrium tricritical point induced by a
repulsive interaction in one dimensional asymmetric exclusion process. The
tricritical point is associated with the particle-hole symmetry breaking
introduced by the repulsion. The phase diagram and the crossover in the
neighbourhood of the tricritical point for the shock formation at one of the
boundaries are determined.Comment: 6 pages; 4 figure
Nonlocality in kinetic roughening
We propose a phenomenological equation to describe kinetic roughening of a
growing surface in presence of long range interactions. The roughness of the
evolving surface depends on the long range feature, and several distinct
scenarios of phase transitions are possible. Experimental implications are
discussed.Comment: Replaced with the published version (Phys. Rev. Lett 79, 2502
(1997)). Eq. 1 written in a symmetrical form, references update
Scaling of fluctuation for Directed polymers with random interaction
Using a finite size scaling form for reunion probability, we show numerically
the existence of a binding-unbinding transition for Directed polymers with
random interaction. The cases studied are (A1) two chains in 1+1 dimensions,
(A2) two chains in 2+1 dimensions and (B) three chains in 1+1 dimensions. A
similar finite size scaling form for fluctuation establishes a disorder induced
transition with identical exponents for cases A2 and B. The length scale
exponents in all the three cases are in agreement with previous exact
renormalization group results.Comment: Revtex, 4 postscript figures available on request (email:
[email protected]); To appear in J. Phys. A Letter
A dynamically extending exclusion process
An extension of the totally asymmetric exclusion process, which incorporates
a dynamically extending lattice is explored. Although originally inspired as a
model for filamentous fungal growth, here the dynamically extending exclusion
process (DEEP) is studied in its own right, as a nontrivial addition to the
class of nonequilibrium exclusion process models. Here we discuss various
mean-field approximation schemes and elucidate the steady state behaviour of
the model and its associated phase diagram. Of particular note is that the
dynamics of the extending lattice leads to a new region in the phase diagram in
which a shock discontinuity in the density travels forward with a velocity that
is lower than the velocity of the tip of the lattice. Thus in this region the
shock recedes from both boundaries.Comment: 20 pages, 12 figure
Bose Condensation and the BTZ Black Hole
Although all popular approaches to quantum gravity are able to recover the
Bekenstein-Hawking entropy-area law in the thermodynamic limit, there are
significant differences in their descriptions of the microstates and in the
application of statistics. Therefore they can have significantly different
phenomenological implications. For example, requiring indistinguishability of
the elementary degrees of freedom should lead to changes in the black hole's
radiative porperties away from the thermodynamic limit and at low temperatures.
We demonstrate this for the Ba\~nados-Teitelboim-Zanelli (BTZ) black hole. The
energy eigenstates and statistical entropy in the thermodynamic limit of the
BTZ black hole were obtained earlier by us via symmetry reduced canonical
quantum gravity. In that model the BTZ black hole behaves as a system of
Bosonic mass shells moving in a one dimensional harmonic trap. Bose
condensation does not occur in the thermodynamic limit but this system
possesses a finite critical temperature, , and exhibits a large condensate
fraction below when the number of shells is finite.Comment: 5 pages, 5 figures. Published versio
Cosmological solutions, p-branes and the Wheeler-DeWitt equation
The low energy effective actions which arise from string theory or M-theory
are considered in the cosmological context, where the graviton, dilaton and
antisymmetric tensor field strengths depend only on time. We show that previous
results can be extended to include cosmological solutions that are related to
the E_N Toda equations. The solutions of the Wheeler-DeWitt equation in
minisuperspace are obtained for some of the simpler cosmological models by
introducing intertwining operators that generate canonical transformations
which map the theories into free theories. We study the cosmological properties
of these solutions, and also briefly discuss generalised Brans-Dicke models in
our framework. The cosmological models are closely related to p-brane solitons,
which we discuss in the context of the E_N Toda equations. We give the explicit
solutions for extremal multi-charge (D-3)-branes in the truncated system
described by the D_4 =O(4,4) Toda equations.Comment: 11 pages (2-column), Revte
Phase transitions and noise crosscorrelations in a model of directed polymers in a disordered medium
We show that effective interactions mediated by disorder between two directed
polymers can be modelled as the crosscorrelation of noises in the
Kardar-Parisi-Zhang (KPZ) equations satisfied by the respective free energies
of these polymers. When there are two polymers, disorder introduces attractive
interactions between them. We analyze the phase diagram in details and show
that these interactions lead to new phases in the phase diagram. We show that,
even in dimension , the two directed polymers see the attraction only if
the strength of the disorder potential exceeds a threshold value. We extend our
calculations to show that if there are polymers in the system then -body
interactions are generated in the disorder averaged effective free energy.Comment: To appear in Phys. Rev. E(2000
Scaling limit of vicious walks and two-matrix model
We consider the diffusion scaling limit of the one-dimensional vicious walker
model of Fisher and derive a system of nonintersecting Brownian motions. The
spatial distribution of particles is studied and it is described by use of
the probability density function of eigenvalues of Gaussian random
matrices. The particle distribution depends on the ratio of the observation
time and the time interval in which the nonintersecting condition is
imposed. As is going on from 0 to 1, there occurs a transition of
distribution, which is identified with the transition observed in the
two-matrix model of Pandey and Mehta. Despite of the absence of matrix
structure in the original vicious walker model, in the diffusion scaling limit,
accumulation of contact repulsive interactions realizes the correlated
distribution of eigenvalues in the multimatrix model as the particle
distribution.Comment: REVTeX4, 12 pages, no figure, minor corrections made for publicatio
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