## Past Events at the University of British Columbia

### Past Events

- 16-May-07

Oscillating random walk on Z driven by its occupation time at zero

I will consider a nearest-neighbor random walk X_n on integers with the drift at time n (conditional on the past expectation of $X_{n+1}-X_n$) equals to $-sign(X_n)f^{-1}(eta_n),$ where eta_n is the number of visits to zero by time n and f(n) is a more››

Scientific Event

- 15-May-07

- 9-May-07

Boundary Value Problems for Elliptic PDEs and the Morse Index

A symplectic view of linearized elliptic problems leads naturally to the formulation of an appropriate Maslov Index. This is well-known in one space dimension and is generalized here to domains in higher space dimensions. The result is a Morse Ind more››

Scientific Event

- 9-May-07

Gamma-Convergence and Saddle Points

We prove a theorem asserting, roughly speaking, that if a sequence of functionals converges to a limiting functional (in the sense of Gamma-convergence, a natural and widely-used notion in the calculus of variations), and if the limiting functiona more››

Scientific Event

- 7-May-07

We analyze portfolio credit risk in light of dynamic "frailty," in the form of incompletely observed covariates. Common dependence by firms on unobservable time-varying default covariates is estimated to cause large changes in conditiona more››

Scientific Event

- 4-May-07

In these two lectures I will survey my recent work with Lupercio and Xicotencatl on the properties of the homology of the free loop space of an orbifold. In the first lecture I will review the work of Chas and Sullivan on string topology and I wil more››

Scientific Event

- 2-May-07

Spanning Trees, Random Graphs, and Random Walks

In the usual Erdõs-Rényi model of random graphs, each pair of n vertices is connected by an edge independently with probability c/n for some constant c. When c > 1, it has a unique 'giant' component. How quickly does the number of spannin more››

Scientific Event

- 2-May-07

In these two lectures I will survey my recent work with Lupercio and Xicotencatl on the properties of the homology of the free loop space of an orbifold. In the first lecture I will review the work of Chas and Sullivan on string topology and I wil more››

Scientific Event

- 30-Apr-07

Modular tensor categories from semisimple algebras

Modular tensor categories are finitely semisimple Abelian categories with some additional structure that allows us to obtain combinatorial invariants of oriented framed tangles. Reshetikhin and Turaev invented them in order to construct their 3-ma more››

Scientific Event

- 26-Apr-07

Evolutionary and Population Dynamics of Bacteria and Phage

Bacterial viruses, aka bacteriophage or phage, are ubiquitous in nature, yet many central aspects of host-phage biology have not been integrated into mathematical models. In this talk I present a series of theoretical efforts to understand the div more››

Scientific Event

- 25-Apr-07

Prandtl Conjecture and von Neumann Paradox for Shock Reflections

We plan to discuss the two fundamental problems, the Prandtl Conjecture and von Neumann Paradox, in the theory of supersonic flows with shock waves. These problems were raised in the first half of the 20th century and clearly formulated in the cla more››

Scientific Event

- 24-Apr-07

Mathematical analysis of models for chemotaxis: parabolic, hyperbolic, kinetic

TBA more››

Scientific Event

- 21-Apr-07
- 22-Apr-07

The 40th Cascade Topology Seminar is a bi-annual gathering of topologists from the US Pacific Northwest and Southwestern Canada. All talks will be at the Pacific Institute for the Mathematical Sciences in Room 110 West Mall A more››

Scientific Event

- 18-Apr-07

- 18-Apr-07

Random walk on the incipient infinite cluster for oriented percolation

We consider simple random walk on the incipient infinite cluster for the spread-out model of oriented percolation in d spatial dimensions and one time dimension. For d>6, we obtain bounds on exit times, transition probabilities, and the range o more››

Scientific Event

- 17-Apr-07

- 16-Apr-07

Algebraic Topology and Geometric Pattern Recognition

With the "blizzard" of data being generated by scientists in all disciplines, the development of tools for analyzing it has become a very high priority task. In particular, methods for quick qualitative analysis are of particular value. more››

Scientific Event

- 12-Apr-07

Gerbes in orbifold cohomology and mirror symmetry

I will explain why twisting by a gerbe is a natural operation in both orbifold cohomology and mirror symmetry, and show how many examples of Calabi-Yau orbifolds whose twisted orbifold Hodge numbers are mirror to each other may be easily constructed. more››

Scientific Event

- 5-Apr-07

Evolutionary branching is sympatric speciation driven by competition between dominant species and their mutants. The traditional approach to study evolutionary branching is to use pairwise-invasibility plot (PIP). However, PIP is only suitable for more››

Scientific Event

- 4-Apr-07

Two Dimensional Lotka-Volterra Models and Superprocesses

Neuhauser and Pacala (99) introduced a particle system to model the dynamics of two competing types on an integer lattice. We study the model near the parameter values for which there is a cross-over from preference of one's own type to preference more››

Scientific Event