427 research outputs found
Estimating Bandwidth Requirements using Flow-level Measurements
Bandwidth provisioning is an important task of network management and it is done aiming to meet desired levels of quality of service. Current practices of provisioning are mostly based on rules-of-thumb and use coarse traffic measurements that may lead to problems of under and over dimensioning of links. Several solutions have already been proposed, in which link provisioning is done by measuring and analyzing network traffic at the packet-level. However, high-speed traffic rates as observed nowadays demand scalable measurement solutions. In this regard, flow monitoring seems to be a promising approach. Many software tools and network equipment already provide flow monitoring. But, flows result in inherent information loss due to the aggregation of packets details, i.e. only a summary of traffic characteristics is provided. The poster will present a flow-based approach that overcomes the problem of traffic information loss and enable the use of flows in place of packet measurements for bandwidth provisioning. Among other results we will show that outcomes from the proposed flow-based approach can be as good as the ones obtained with packet-level measurements
Trees with Given Stability Number and Minimum Number of Stable Sets
We study the structure of trees minimizing their number of stable sets for
given order and stability number . Our main result is that the
edges of a non-trivial extremal tree can be partitioned into stars,
each of size or , so that every vertex is included in at most two
distinct stars, and the centers of these stars form a stable set of the tree.Comment: v2: Referees' comments incorporate
On Relevant Equilibria in Reachability Games
We study multiplayer reachability games played on a finite directed graph
equipped with target sets, one for each player. In those reachability games, it
is known that there always exists a Nash equilibrium (NE) and a subgame perfect
equilibrium (SPE). But sometimes several equilibria may coexist such that in
one equilibrium no player reaches his target set whereas in another one several
players reach it. It is thus very natural to identify "relevant" equilibria. In
this paper, we consider different notions of relevant equilibria including
Pareto optimal equilibria and equilibria with high social welfare. We provide
complexity results for various related decision problems
On the Sets of Real Numbers Recognized by Finite Automata in Multiple Bases
This article studies the expressive power of finite automata recognizing sets
of real numbers encoded in positional notation. We consider Muller automata as
well as the restricted class of weak deterministic automata, used as symbolic
set representations in actual applications. In previous work, it has been
established that the sets of numbers that are recognizable by weak
deterministic automata in two bases that do not share the same set of prime
factors are exactly those that are definable in the first order additive theory
of real and integer numbers. This result extends Cobham's theorem, which
characterizes the sets of integer numbers that are recognizable by finite
automata in multiple bases.
In this article, we first generalize this result to multiplicatively
independent bases, which brings it closer to the original statement of Cobham's
theorem. Then, we study the sets of reals recognizable by Muller automata in
two bases. We show with a counterexample that, in this setting, Cobham's
theorem does not generalize to multiplicatively independent bases. Finally, we
prove that the sets of reals that are recognizable by Muller automata in two
bases that do not share the same set of prime factors are exactly those
definable in the first order additive theory of real and integer numbers. These
sets are thus also recognizable by weak deterministic automata. This result
leads to a precise characterization of the sets of real numbers that are
recognizable in multiple bases, and provides a theoretical justification to the
use of weak automata as symbolic representations of sets.Comment: 17 page
Language Emptiness of Continuous-Time Parametric Timed Automata
Parametric timed automata extend the standard timed automata with the
possibility to use parameters in the clock guards. In general, if the
parameters are real-valued, the problem of language emptiness of such automata
is undecidable even for various restricted subclasses. We thus focus on the
case where parameters are assumed to be integer-valued, while the time still
remains continuous. On the one hand, we show that the problem remains
undecidable for parametric timed automata with three clocks and one parameter.
On the other hand, for the case with arbitrary many clocks where only one of
these clocks is compared with (an arbitrary number of) parameters, we show that
the parametric language emptiness is decidable. The undecidability result
tightens the bounds of a previous result which assumed six parameters, while
the decidability result extends the existing approaches that deal with
discrete-time semantics only. To the best of our knowledge, this is the first
positive result in the case of continuous-time and unbounded integer
parameters, except for the rather simple case of single-clock automata
Computer aided synthesis: a game theoretic approach
In this invited contribution, we propose a comprehensive introduction to game
theory applied in computer aided synthesis. In this context, we give some
classical results on two-player zero-sum games and then on multi-player non
zero-sum games. The simple case of one-player games is strongly related to
automata theory on infinite words. All along the article, we focus on general
approaches to solve the studied problems, and we provide several illustrative
examples as well as intuitions on the proofs.Comment: Invitation contribution for conference "Developments in Language
Theory" (DLT 2017
Molecular spintronics: Coherent spin transfer in coupled quantum dots
Time-resolved Faraday rotation has recently demonstrated coherent transfer of
electron spin between quantum dots coupled by conjugated molecules. Using a
transfer Hamiltonian ansatz for the coupled quantum dots, we calculate the
Faraday rotation signal as a function of the probe frequency in a pump-probe
setup using neutral quantum dots. Additionally, we study the signal of one
spin-polarized excess electron in the coupled dots. We show that, in both
cases, the Faraday rotation angle is determined by the spin transfer
probabilities and the Heisenberg spin exchange energy. By comparison of our
results with experimental data, we find that the transfer matrix element for
electrons in the conduction band is of order 0.08 eV and the spin transfer
probabilities are of order 10%.Comment: 13 pages, 6 figures; minor change
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