Pure Mathematics Seminars

This term is jointly organised by Yiftach Barnea and Christian Elsholtz.

1st May 2007
Ed Godolphin (RHUL)
Title: Specification of trend and seasonal components for time series data. Abstract:

There has been much attention in the literature devoted to the modelling and decomposition of time series observations, recorded at roughly equal intervals of time, into independent trend and seasonal component time series. This presentation will consider several recent developments in this area, involving both the model-based SARIMA specification and the state-space structural representation, and the results will be illustrated by topical examples.

8th May 2007
Stefanie Gerke (RHUL)
Title: Connectivity of addable graph classes
A non-empty class A of labelled graphs that is closed under isomorphism is weakly addable if for each graph G in A and any two distinct components of G, any graph that can be obtain by adding an edge between the two components is also in A. For a weakly addable graph class A, we consider a random element R_n chosen uniformly from the set of all graph in A on the vertex set {1,...,n}. McDiarmid, Steger and Welsh conjecture that the probability that R_n is connected is at least e^{-1/2}+o(1) and showed that it is at least e^{-1} for sufficiently large n. We improve the latter result and show that this probability is at least e^{-0.7983} for sufficiently large n.
We also consider 2-addable graph classes B where for each graph G in B and for any two distinct components of G, the graphs that can be obtained by adding at most 2 edges between the components are in B. We show that a random element of a 2-addable graph class on n vertices is connected with probability tending to 1 as n tends to infinity.
This is joined work with Paul Ballister and Bela Bollobas.

15th May 2007
Peter Wild (RHUL)
"Identity based public key cryptography using symmetric primitives"

Friday 1st June 2007, 4pm
Svante Janson (Uppsala)
"Graph limits and exchangeable random infinite graphs"
Lovasz and a number of coworkers (Borgs, Chayse, Sos, Szegedy, Vesztergombi) have introduced and studied a notion of graph limits; these are not graphs, but can be regarded as limits of sequences of (dense) graphs. We study this notion further, considering random graph limits, and convergence in distribution of random graphs (with arbitrary distributions) to random graph limits. As a result we find that the characterization of Lovasz et al of the graph limits is essentially equivalent to the characterization of exchangeable random infinite graphs by Aldous and Hoover. (This is joint work with Persi Diaconis.)

12th June 2007
Teo Sharia (RHUL)
Title: Asymptotically efficient parameter estimation procedures

19th June 2007 IN ROOM C336 (!)
Paul Balister (Memphis)
Title: Cycle decompositions
Abstract: The Alspach conjecture proposes necessary and sufficient conditions for a complete graph K_n (n odd) on n vertices , or a complete graph minus a 1-factor (n even) to be decomposable as an edge-disjoint union of cycles of prescribed lengths. We discuss various results on this and some related problems. In particular we show that the obvious necessary conditions are sufficient if the cycle lengths are bounded by a linear function of the number of vertices n, or in general if we only require closed trails of prescribed lengths rather than cycles. We also describe some similar results for complete bipartite graphs, dense graphs, and complete digraphs.

Wednesday 18th July 2007, room C229
Jon Gonzalez-Sanchez (Netherlands)
Title: Lie theory for p-groups and pro-p groups
Abstract: In his works of 1954 and 1965 Michelle Lazard established an equivalence of categories between p-groups and finite Z_p-Lie algebras of nilpotency class smaller than p, and between p-saturable pro-p groups and p-saturable Lie algebras. The latter was reinterpreted by Alex Lubotzky and Avinoam Mann using uniformly powerful groups and Lie algebras. The aim of this talk is to extend Lazard's correspondence to more families of finite p-groups and to explain the differences between p-saturable groups and uniformly powerful groups. Finally, we would like to explain how Kirillov's orbit method can be applied to p-saturable groups.

31 July 2007, room C229
Doug Stinson (Waterloo, Canada)
Title: A Combinatorial Approach to Key Predistribution for Distributed Sensor Networks


This page lists this term's Pure Mathematics Seminars. All are welcome. All seminars will take place in the McCrea Building, Room 219, at 4.00pm, unless stated otherwise. Tea is served before the seminar at 3.30 in Room 237 of the McCrea Building.

Seminars of the past years.

Useful links:
Info for the speaker.
National Rail enquiries.
An interactive local street map. (In the right corner is Egham station, in the left corner is Royal Holloway. You can zoom the map, or go the left/right etc..., and print.) Note that the official college recommendation is to go via Station Road to the roundabout and walk up Egham Hill (A30). Even though this appears to be a detour it may be the fastest way. If you try, on your risk, the direct route make sure you reach Ripley avenue and enter the College at the end of Lynwood avenue.
For other directions (car, bus, taxi or from Heathrow see the following directions.)

Campus Map (The maths department is in no 17)
For other maps.

For any further information, please contact Dr Christian Elsholtz,
Tel: 01784 414021,
email: christian.elsholtz_at_rhul.ac.uk