Propositional Dynamic Logic with Converse and Repeat for Message-Passing Systems

The model checking problem for propositional dynamic logic (PDL) over message sequence charts (MSCs) and communicating finite state machines (CFMs) asks, given a channel bound $B$, a PDL formula $\varphi$ and a CFM $\mathcal{C}$, whether every existentially $B$-bounded MSC $M$ accepted by $\mathcal{C}$ satisfies $\varphi$. Recently, it was shown that this problem is PSPACE-complete. In the present work, we consider CRPDL over MSCs which is PDL equipped with the operators converse and repeat. The former enables one to walk back and forth within an MSC using a single path expression whereas the latter allows to express that a path expression can be repeated infinitely often. To solve the model checking problem for this logic, we define message sequence chart automata (MSCAs) which are multi-way alternating parity automata walking on MSCs. By exploiting a new concept called concatenation states, we are able to inductively construct, for every CRPDL formula $\varphi$, an MSCA precisely accepting the set of models of $\varphi$. As a result, we obtain that the model checking problem for CRPDL and CFMs is still in PSPACE

Cohérence des données de bases RDF en évolution constante

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Determining the squark mass at the LHC

We propose a new way to determine the squark mass based on the shape of di-jet invariant mass distribution of supersymmetry (SUSY) di-jet events at the Large Hadron Collider (LHC). Our algorithm, which is based on event kinematics, requires that the branching ratio $B(\tilde{q} \rightarrow q \tilde{z}_1)$ is substantial for at least some types of squarks, and that $m_{\tilde{z}_1}^2/m_{\tilde{q}}^2 \ll 1$. We select di-jet events with no isolated leptons, and impose cuts on the total jet transverse energy, $E_T^{tot}=E_T(j_1)+E_T(j_2)$, on $\alpha = E_T(j_2)/m_{jj}$, and on the azimuthal angle between the two jets to reduce SM backgrounds. The shape of the resulting di-jet mass distribution depends sensitively on the squark mass, especially if the integrated luminosity is sufficient to allow a hard enough cut on $E_T^{tot}$ and yet leave a large enough signal to obtain the $m_{jj}$ distribution. We simulate the signal and Standard Model (SM) backgrounds for 100 fb$^{-1}$ integrated luminosity at 14 TeV requiring $E_T^{tot}> 700$ GeV. We show that it should be possible to extract $m_{\tilde{q}}$ to within about 3% at 95% CL --- similar to the precision obtained using $m_{T2}$ --- from the di-jet mass distribution if $m_{\tilde{q}} \sim 650$ GeV, or to within $\sim 5$% if $m_{\tilde{q}}\sim 1$ TeV.Comment: 20 pages, 9 figures. Footnote added, updated reference

Asynchronous Games over Tree Architectures

We consider the task of controlling in a distributed way a Zielonka asynchronous automaton. Every process of a controller has access to its causal past to determine the next set of actions it proposes to play. An action can be played only if every process controlling this action proposes to play it. We consider reachability objectives: every process should reach its set of final states. We show that this control problem is decidable for tree architectures, where every process can communicate with its parent, its children, and with the environment. The complexity of our algorithm is l-fold exponential with l being the height of the tree representing the architecture. We show that this is unavoidable by showing that even for three processes the problem is EXPTIME-complete, and that it is non-elementary in general

Aperçus de recherche : interroger efficacement un ensemble de bases RDF

In the context of information retrieval in the Web of Data, we propose a kind of compact version of a RDF triplestore, that acts as an overview on this base of RDF triples. An overview is not only more compact that the initial triplestore, but also SPARQL can be used on it. An overview is built in such a way that if a SPARQL query on overview has no result, then there is no result too to this query into the initial triplestore. So, querying overviews is a more efficient solution than querying the whole triplestores when the query has often no result from these RDF databases. It is usually the case when a user query triplestores on the web of data. Our solution has been evaluated using RDF bases extracted from DBPedia and queries extracted either from the most common used on DBPedia or because of their resolution complexity

Generalized squeezed-coherent states of the finite one-dimensional oscillator and matrix multi-orthogonality

A set of generalized squeezed-coherent states for the finite u(2) oscillator is obtained. These states are given as linear combinations of the mode eigenstates with amplitudes determined by matrix elements of exponentials in the su(2) generators. These matrix elements are given in the (N+1)-dimensional basis of the finite oscillator eigenstates and are seen to involve 3x3 matrix multi-orthogonal polynomials Q_n(k) in a discrete variable k which have the Krawtchouk and vector-orthogonal polynomials as their building blocks. The algebraic setting allows for the characterization of these polynomials and the computation of mean values in the squeezed-coherent states. In the limit where N goes to infinity and the discrete oscillator approaches the standard harmonic oscillator, the polynomials tend to 2x2 matrix orthogonal polynomials and the squeezed-coherent states tend to those of the standard oscillator.Comment: 18 pages, 1 figur