 Speaker:  Prof. Dan Christensen

Title: 
Finiteness and Positivity for the Lorentzian partition function 
Abstract: 
This talk gives an overview of recent results on the Lorentzian
BarrettCrane model, a spin foam model of quantum gravity. I will
begin with a concise proof of the finiteness of the Lorentzian 10j
symbol, which generalizes to other integral expressions of the same
form, such as causal models. I then describe work of my student Wade
Cherrington which uses the generalized finiteness result above to show
that the Lorentzian partition function for a fixed triangulation is
finite in the PerezRovelli normalization. Finally I will outline
joint work with Cherrington which shows that the Lorentzian partition
function is nonnegative. In fact, we show that the Lorentzian
BarrettCrane model can be reformulated as a model with nonnegative
amplitudes, and this leads to the possibility of efficient
computations of expectation values using statistical methods.

Talk: 
Transparencies, Recorded Talk

 