7,996 research outputs found
Controllable spiking patterns in long-wavelength VCSELs for neuromorphic photonics systems
Multiple controllable spiking patterns are obtained in a 1310 nm Vertical
Cavity Surface Emitting Laser (VCSEL) in response to induced perturbations and
for two different cases of polarized optical injection, namely parallel and
orthogonal. Achievement of reproducible spiking responses in VCSELs operating
at the telecom wavelengths offers great promise for future uses of these
devices in ultrafast neuromorphic photonic systems for non-traditional
computing applications.Comment: 10 pages, 6 figures, journal submissio
Test of the Additivity Principle for Current Fluctuations in a Model of Heat Conduction
The additivity principle allows to compute the current distribution in many
one-dimensional (1D) nonequilibrium systems. Using simulations, we confirm this
conjecture in the 1D Kipnis-Marchioro-Presutti model of heat conduction for a
wide current interval. The current distribution shows both Gaussian and
non-Gaussian regimes, and obeys the Gallavotti-Cohen fluctuation theorem. We
verify the existence of a well-defined temperature profile associated to a
given current fluctuation. This profile is independent of the sign of the
current, and this symmetry extends to higher-order profiles and spatial
correlations. We also show that finite-time joint fluctuations of the current
and the profile are described by the additivity functional. These results
suggest the additivity hypothesis as a general and powerful tool to compute
current distributions in many nonequilibrium systems.Comment: 4 pages, 4 figure
Spectral signatures of symmetry-breaking dynamical phase transitions
Large deviation theory provides the framework to study the probability of
rare fluctuations of time-averaged observables, opening new avenues of research
in nonequilibrium physics. One of the most appealing results within this
context are dynamical phase transitions (DPTs), which might occur at the level
of trajectories in order to maximize the probability of sustaining a rare
event. While the Macroscopic Fluctuation Theory has underpinned much recent
progress on the understanding of symmetry-breaking DPTs in driven diffusive
systems, their microscopic characterization is still challenging. In this work
we shed light on the general spectral mechanism giving rise to continuous DPTs
not only for driven diffusive systems, but for any jump process in which a
discrete symmetry is broken. By means of a symmetry-aided
spectral analysis of the Doob-transformed dynamics, we provide the conditions
whereby symmetry-breaking DPTs might emerge and how the different dynamical
phases arise from the specific structure of the degenerate eigenvectors. We
show explicitly how all symmetry-breaking features are encoded in the
subleading eigenvectors of the degenerate manifold. Moreover, by partitioning
configuration space into equivalence classes according to a proper order
parameter, we achieve a substantial dimensional reduction which allows for the
quantitative characterization of the spectral fingerprints of DPTs. We
illustrate our predictions in three paradigmatic many-body systems: (i) the 1D
boundary-driven weakly asymmetric exclusion process (WASEP), which exhibits a
particle-hole symmetry-breaking DPT for current fluctuations, (ii) the and
-state Potts model, which displays discrete rotational symmetry-breaking DPT
for energy fluctuations, and (iii) the closed WASEP which presents a continuous
symmetry-breaking DPT to a time-crystal phase characterized by a rotating
condensate
Proximity Drawings of High-Degree Trees
A drawing of a given (abstract) tree that is a minimum spanning tree of the
vertex set is considered aesthetically pleasing. However, such a drawing can
only exist if the tree has maximum degree at most 6. What can be said for trees
of higher degree? We approach this question by supposing that a partition or
covering of the tree by subtrees of bounded degree is given. Then we show that
if the partition or covering satisfies some natural properties, then there is a
drawing of the entire tree such that each of the given subtrees is drawn as a
minimum spanning tree of its vertex set
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