Juillet 2015

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Jeudi 2 Juillet
Heure: 12:30 - 13:30
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: Solving the quadratic shortest path problem
Description: Borzou Rostami Finding the shortest path in a directed graph is one of the
most important combinatorial optimization problems, having applications
in a wide range of fields. In its basic version, however, the problem
fails to represent situations in which the value of the objective function
is determined not only by the choice of each single arc, but also
by the combined presence of pairs of arcs in the solution. In this paper
we model these situations as a Quadratic Shortest Path Problem, which
calls for the minimization of a quadratic objective function subject to
shortest-path constraints. We prove strong NP-hardness of the problem
and analyze polynomially solvable special cases, obtained by restricting
the distance of arc pairs in the graph that appear jointly in a quadratic
monomial of the objective function. Based on this special case and problem
structure, we devise fast lower bounding procedures for the general
problem and show computationally that they clearly outperform other
approaches proposed in the literature in terms of their strength.
Heure: 14:30 - 15:30
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: Action synthesis for branching time logic: theory and applications
Description: Micha? Knapik Action-Restricted Computation Tree Logic (ARCTL) is a simple extension of CTL,
proposed by Pecheur and Raimondi, where the actions allowed along the considered
runs can be explicitly indicated by path selectors. ARCTL allows to
express properties
such as "a safe state is unavoidable for every path built from Forward
and Left actions",
denoted by AF{Forward,Safe}safe. By replacing the concrete sets of
actions with free
variables we obtain a parametric version of the logic pmARCTL, where
properties such
as AF{X}safe are allowed, where X is a parameter. We introduce a
fixed-point theory
that allows for the exhaustive synthesis of all the valuations of the
variables which make
the pmARTCL formulae hold in a given model. The theory has been
implemented in an
open source stand-alone tool and evaluated on scalable examples with
promising results.
Mardi 7 Juillet
Heure: 14:00 - 17:00
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: Nonlinear dynamics and complex systems [TBC]
Description: Joshua Socolar
Vendredi 24 Juillet
Heure: 11:00 - 12:00
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: Monetary Economics Simulation: Stock-Flow Consistent Invariance, Monadic Style
Description: Antoine Kaszczyc