142,859 research outputs found
Scalable Multiagent Coordination with Distributed Online Open Loop Planning
We propose distributed online open loop planning (DOOLP), a general framework
for online multiagent coordination and decision making under uncertainty. DOOLP
is based on online heuristic search in the space defined by a generative model
of the domain dynamics, which is exploited by agents to simulate and evaluate
the consequences of their potential choices.
We also propose distributed online Thompson sampling (DOTS) as an effective
instantiation of the DOOLP framework. DOTS models sequences of agent choices by
concatenating a number of multiarmed bandits for each agent and uses Thompson
sampling for dealing with action value uncertainty. The Bayesian approach
underlying Thompson sampling allows to effectively model and estimate
uncertainty about (a) own action values and (b) other agents' behavior. This
approach yields a principled and statistically sound solution to the
exploration-exploitation dilemma when exploring large search spaces with
limited resources.
We implemented DOTS in a smart factory case study with positive empirical
results. We observed effective, robust and scalable planning and coordination
capabilities even when only searching a fraction of the potential search space
Dynamics of temporally interleaved percept-choice sequences: interaction via adaptation in shared neural populations
At the onset of visually ambiguous or conflicting stimuli, our visual system quickly âchoosesâ one of the possible percepts. Interrupted presentation of the same stimuli has revealed that each percept-choice depends strongly on the history of previous choices and the duration of the interruptions. Recent psychophysics and modeling has discovered increasingly rich dynamical structure in such percept-choice sequences, and explained or predicted these patterns in terms of simple neural mechanisms: fast cross-inhibition and slow shunting adaptation that also causes a near-threshold facilitatory effect. However, we still lack a clear understanding of the dynamical interactions between two distinct, temporally interleaved, percept-choice sequencesâa type of experiment that probes which feature-level neural network connectivity and dynamics allow the visual system to resolve the vast ambiguity of everyday vision. Here, we fill this gap. We first show that a simple column-structured neural network captures the known phenomenology, and then identify and analyze the crucial underlying mechanism via two stages of model-reduction: A 6-population reduction shows how temporally well-separated sequences become coupled via adaptation in neurons that are shared between the populations driven by either of the two sequences. The essential dynamics can then be reduced further, to a set of iterated adaptation-maps. This enables detailed analysis, resulting in the prediction of phase-diagrams of possible sequence-pair patterns and their response to perturbations. These predictions invite a variety of future experiments
A solvable model of the genesis of amino-acid sequences via coupled dynamics of folding and slow genetic variation
We study the coupled dynamics of primary and secondary structure formation
(i.e. slow genetic sequence selection and fast folding) in the context of a
solvable microscopic model that includes both short-range steric forces and and
long-range polarity-driven forces. Our solution is based on the diagonalization
of replicated transfer matrices, and leads in the thermodynamic limit to
explicit predictions regarding phase transitions and phase diagrams at genetic
equilibrium. The predicted phenomenology allows for natural physical
interpretations, and finds satisfactory support in numerical simulations.Comment: 51 pages, 13 figures, submitted to J. Phys.
Subshifts of quasi-finite type
We introduce subshifts of quasi-finite type as a generalization of the
well-known subshifts of finite type. This generalization is much less rigid and
therefore contains the symbolic dynamics of many non-uniform systems, e.g.,
piecewise monotonic maps of the interval with positive entropy. Yet many
properties remain: existence of finitely many ergodic invariant probabilities
of maximum entropy; lots of periodic points; meromorphic extension of the
Artin-Mazur zeta function.Comment: added examples, more precise estimates on periodic points and
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