Wednesday, April 30, 2014 - 9:00am - 9:50am
Victor Chepoi (Aix-Marseille Université)
In the talk, after an introduction of the cop and robber game and Gromov hyperbolicity, we will outline the proof that all cop-win graphs G in the game in which the robber and the cop move at different speeds s and s' with s'for any r>0, this establishes a new --game-theoretical-- characterization of Gromov hyperbolicity.
Monday, April 28, 2014 - 3:15pm - 4:05pm
Blair Sullivan (North Carolina State University)
In this talk, we discuss recent work on Gromov's delta-hyperbolicity in the context of random graph models, tree-decompositions, and empirical evaluation of network structure. Specifically, we characterize when random intersection graphs have bounded hyperbolicity, give general theoretical bounds on delta in terms of tree-width, and describe a relationship to local measurement of the core structure. More generally, we describe empirical results on tree-like structure in complex networks and suggest several open problems.
Tuesday, February 11, 2014 - 10:15am - 11:05am
Thomas Wanner (George Mason University)
Homology has long been accepted as an important computational tool for
quantifying complex structures. In many applications these structures arise as
nodal domains or excursion sets of real-valued functions, and are therefore
amenable to a numerical study based on suitable discretizations. Such an
approach immediately raises the question of how accurately the resulting
homology can be computed. In this talk we present a probabilistic algorithm for
correctly determining the topology of two-dimensional excursion sets. The
Tuesday, December 10, 2013 - 10:15am - 11:05am
Christian Reidys (Syddansk Universitet (University of Southern Denmark))
In this talk we introduce the basic construction of topological RNA structures.
We introduce shapes and the associated shape polynomial and its connection to
RNA folding. We then establish the connection to unicellular maps and outline
the combinatorial constructions that facilitate genus induction. We furthermore
show applications of this framework to the uniform generation of RNA structures
of fixed topological genus and how to deal with RNA-RNA interaction structures.
Wednesday, December 11, 2013 - 9:00am - 9:50am
Zhe (Sage) Chen (Massachusetts Institute of Technology)
The hippocampus plays an important role in representing space (for spatial navigation) and time (for episodic memory). Spatial representation of the environment is pivotal for navigation in rodents and primates. Two types of maps, topographical and topological, may be used for spatial representation. Rodent hippocampal place cells exhibit spatially-selective firing patterns in an environment that can be decoded to determine the animal’s location, heading, and past and future trajectory.
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