Tue, 14 Jun 2016
14:30
L6

Limits of Some Combinatorial Problems

Endre Csóka
(Budapest)
Abstract

We purify and generalize some techniques which were successful in the limit theory of graphs and other discrete structures. We demonstrate how this technique can be used for solving different combinatorial problems, by defining the limit problems of the Manickam--Miklós--Singhi Conjecture, the Kikuta–Ruckle Conjecture and Alpern's Caching Game.

Tue, 04 May 2010

16:30 - 17:30
SR2

Multigraph limits and aging of the edge reconnecting model

Balázs Ráth
(Budapest)
Abstract

We define the edge reconnecting model, a random multigraph evolving in time. At each time step we change one endpoint of a uniformly chosen edge: the new endpoint is chosen by linear preferential attachment. We consider a sequence of edge reconnecting models where the sequence of initial multigraphs is convergent in a sense which is a natural generalization of the Lovász-Szegedy notion of convergence of dense graph sequences. We investigate how the limit objects evolve under the edge reconnecting dynamics if we rescale time properly: we give the complete characterization of the time evolution of the limiting object from its initial state up to the stationary state using the theory of exchangeable arrays, the Pólya urn model, queuing and diffusion processes. The number of parallel edges and the degrees evolve on different timescales and because of this the model exhibits “aging”.

Thu, 29 May 2008
16:00
L3

Elliptic curves with prime order

Antal Balog
(Budapest)
Abstract

Let E be an elliptic curve over the rationals. To get an asymptotic to the number of primes p

Mon, 03 Mar 2008
14:45
Oxford-Man Institute

Some new results on 1-d self-repelling random walks

Prof. Balint Toth
(Budapest)
Abstract

I will present two new results in the context of the title. Both are joint work with B. Veto.

1. In earlier work a limit theorem with $t^{2/3}$ scaling was established for a class of self repelling random walks on $\mathbb Z$ with long memory, where the self-interaction was defined in terms of the local time spent on unoriented edges. For combinatorial reasons this proof was not extendable to the natural case when the self-repellence is defined in trems of local time on sites. Now we prove a similar result for a *continuous time* random walk on $\mathbb Z$, with self-repellence defined in terms of local time on sites.

2. Defining the self-repelling mechanism in terms of the local time on *oriented edges* results in totally different asymptotic behaviour than the unoriented cases. We prove limit theorems for this random walk with long memory.

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