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Nombre de programmes trouvés : 550
Conférences

le (1h5m18s)

COMMENT SE TISSE LA TOILE COSMIQUE ?

Les galaxies ne voguent pas de façon désordonnée dans l'Univers. Elles forment un véritable réseau en bulles de savon souvent appelé toile cosmique et composé de vides, de murs, de filaments et de noeuds dans lesquels les amas de galaxies résident. C'est un voyage au sein de la fabrique cosmique qui est proposé à l'occasion de cette conférence. L'Univers sera arpenté sur des milliards d'années lumière afin de comprendre comme se tisse cette toile cosmique, quelles sont ses origines, comment elle influence la naissance et l'évolution ...
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Conférences

le (50m57s)

Point processes, cost and the growth of rank for locally compact groups (workshop ERC Nemo Processus ponctuels et graphes aléatoires unimodulaires)

The cost of a vertex transitive graph is the infimum of the expected degree of an invariant random wiring of the graph. Similarly, one can define the cost of a point process on a homogeneous space, as the infimum of the average degree of a factor wiring on its points. It turns out that the cost of a Poisson process is maximal among point processes of the same density, by proving that all free processes weakly contain the Poisson. The cost is related to the growth ...
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Conférences

le (43m18s)

Spectral embedding for graph classification (workshop ERC Nemo Processus ponctuels et graphes aléatoires unimodulaires)

Learning on graphs requires a graph feature representation able to discriminate among different graphs while being amenable to fast computation. The graph isomorphism problem tells us that no fast representation of graphs is known if we require the representation to be both invariant to nodes permutation and able to discriminate two non-isomorphic graphs. Most graph representations explored so far require to be invariant. We explore new graph representations by relaxing this constraint. We present a generic embedding of graphs relying on spectral graph theory ...
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Conférences

le (39m53s)

Emergence of extended states at zero in the spectrum of sparse random graphs (workshop ERC Nemo Processus ponctuels et graphes aléatoires unimodulaires)

We confirm the long-standing prediction that c=e≈2.718 is the threshold for the emergence of a non-vanishing absolutely continuous part (extended states) at zero in the limiting spectrum of the Erdős-Renyi random graph with average degree c. This is achieved by a detailed second-order analysis of the resolvent (A−z)−1 near the singular point z=0, where A is the adjacency operator of the Poisson-Galton-Watson tree with mean offspring c. More generally, our method applies to arbitrary unimodular Galton-Watson trees, yielding explicit criteria for the presence or ...
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Conférences

le (55m56s)

A notion of entropy for limits of sparse marked graphs (workshop ERC Nemo Processus ponctuels et graphes aléatoires unimodulaires)

Bordenave and Caputo (2014) defined a notion of entropy for probability distributions on rooted graphs with finite expected degree at the root. When such a probability distribution \rho has finite BC entropy \Sigma(\rho), the growth in the number of vertices n of the number of graphs on n vertices whose associated rooted graph distribution is close to \rho is as d/2 n \log n + \Sigma(\rho) n + o(n), where d is expected degree of the root under \rho. We develop the parallel result for probability distributions on marked rooted graphs. Our graphs have vertex marks drawn from a finite ...
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