1,182 research outputs found
On the Control of Asynchronous Automata
The decidability of the distributed version of the Ramadge and Wonham
controller synthesis problem,where both the plant and the controllers are
modeled as asynchronous automataand the controllers have causal memoryis a
challenging open problem.There exist three classes of plants for which the
existence of a correct controller with causal memory has been shown decidable:
when the dependency graph of actions is series-parallel, when the processes are
connectedly communicating and when the dependency graph of processes is a tree.
We design a class of plants, called decomposable games, with a decidable
controller synthesis problem.This provides a unified proof of the three
existing decidability results as well as new examples of decidable plants
Blackwell-Optimal Strategies in Priority Mean-Payoff Games
We examine perfect information stochastic mean-payoff games - a class of
games containing as special sub-classes the usual mean-payoff games and parity
games. We show that deterministic memoryless strategies that are optimal for
discounted games with state-dependent discount factors close to 1 are optimal
for priority mean-payoff games establishing a strong link between these two
classes
Two-Player Perfect-Information Shift-Invariant Submixing Stochastic Games Are Half-Positional
We consider zero-sum stochastic games with perfect information and finitely
many states and actions. The payoff is computed by a payoff function which
associates to each infinite sequence of states and actions a real number. We
prove that if the the payoff function is both shift-invariant and submixing,
then the game is half-positional, i.e. the first player has an optimal strategy
which is both deterministic and stationary. This result relies on the existence
of -subgame-perfect equilibria in shift-invariant games, a second
contribution of the paper
Pushing undecidability of the isolation problem for probabilistic automata
This short note aims at proving that the isolation problem is undecidable for
probabilistic automata with only one probabilistic transition. This problem is
known to be undecidable for general probabilistic automata, without restriction
on the number of probabilistic transitions. In this note, we develop a
simulation technique that allows to simulate any probabilistic automaton with
one having only one probabilistic transition
Crossover from quasi-static to dense flow regime in compressed frictional granular media
We investigate the evolution of multi-scale mechanical properties towards the
macroscopic mechanical instability in frictional granular media under
multiaxial compressive loading. Spatial correlations of shear stress
redistribution following nucleating contact sliding events and shear strain
localization are investigated. We report growing correlation lengths associated
to both shear stress and shear strain fields that diverge simultaneously as
approaching the transition to a dense flow regime. This shows that the
transition from quasi static to dense flow regime can be interpreted as a
critical phase transition. Our results suggest that no shear band with a
characteristic thickness has formed at the onset of instability
Determinacy and Decidability of Reachability Games with Partial Observation on Both Sides
We prove two determinacy and decidability results about two-players
stochastic reachability games with partial observation on both sides and
finitely many states, signals and actions
Deciding the value 1 problem for probabilistic leaktight automata
The value 1 problem is a decision problem for probabilistic automata over
finite words: given a probabilistic automaton, are there words accepted with
probability arbitrarily close to 1? This problem was proved undecidable
recently; to overcome this, several classes of probabilistic automata of
different nature were proposed, for which the value 1 problem has been shown
decidable. In this paper, we introduce yet another class of probabilistic
automata, called leaktight automata, which strictly subsumes all classes of
probabilistic automata whose value 1 problem is known to be decidable. We prove
that for leaktight automata, the value 1 problem is decidable (in fact,
PSPACE-complete) by constructing a saturation algorithm based on the
computation of a monoid abstracting the behaviours of the automaton. We rely on
algebraic techniques developed by Simon to prove that this abstraction is
complete. Furthermore, we adapt this saturation algorithm to decide whether an
automaton is leaktight. Finally, we show a reduction allowing to extend our
decidability results from finite words to infinite ones, implying that the
value 1 problem for probabilistic leaktight parity automata is decidable
Les MatemĂ tiques de GOOGLE: l'algorisme PageRank
En aquest article presentem i analitzem l'algorisme PageRank, emprat per
Google en l'ordenació dels seus resultats de cerca. La seva fonamentació teòrica ens
duu a interrelacionar diferents parts de la matemĂ tica, com la teoria de matrius no
negatives, la teoria de grafs i les cadenes de Markov. Cal dir que hi ha altres algorismes
de valoració de pà gines web, basats en el còmput de vectors propis, com l'algorisme
HITS, el qual exposem breument al final del treball.The mathematics of Google: The PageRank algorithm.
In this paper we present and analyze the PageRank algorithm, used by Google
to rank its search results. We focus on the mathematical background of this
algorithm, which involves nonnegative matrices, graphs and Markov chains.
There are some other web ranking algorithms, based on the computation of
eigenvectors, like the HITS algorithm, which we briefly explain at the end of the
paper
Etude de l'influence de voies électroniques mortes ou bruyantes sur les performances du système de déclenchement dimuons de l'expérience ALICE
ALICE, rapport JANU
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