Book Chapter in "Foundations of Space and Time"

Fri, 13 May 2011 17:44:50 +0100

We wrote a book chapter with a review of stochastic quantisation of causal quantum gravity to appear in “Foundations of Space and Time: Reflections on Quantum Gravity” edited by j. Murugan, A. Weltman and G. Ellis, to be published by Cambridge University Press in August 2011. Link to Amazon. Chapter in PDF.

Particles and Fields Seminar schedule

Mon, 2 May 2011 14:43:18 +0100

The organizers Subir Sarkar and Stefan Zohren invite everyone to attend the weekly seminar of the Oxford Particle Theory Group. Afterwards there will be a reception in the Dalitz Institute with cheese and wine.

Location: Dennis Sciama Lecture Theatre
Time: Thursdays 4.15 pm

Download the poster with the schedule for Trinity term 2011 here: poster.pdf

Visiting Scholar at Corpus Christi College, Oxford University

Mon, 3 Jan 2011 18:10:47 +0000

Before starting my position as post-doctoral research associate at the Rudolf Peierls Centre for Theoretical Physics at Oxford University, I spent Michaelmas term 2010 at Corpus Christi College in Oxford as a Visiting Scholar. I still remain Member of the SCR and I am enjoying being at Corpus at least twice a week.

PhD thesis as book

Mon, 5 Jan 2009 19:17:27 +0000

In November 2008 I defended my PhD thesis “A Causal Perspective on Random Geometry” and completed my PhD and DIC in theoretical and mathematical physics at Imperial College London. Following good examples from my Dutch colleagues I had my PhD thesis published as a book with an initial edition of one hundred copies. You can download a PDF copy from the arXiv.

From the back of the cover:

One of the biggest challenges of present day theoretical physics is to find a consistent theory of quantum gravity. There are however obvious problems in constructing a quantum theory of general relativity. It has already been shown in the seventies by 't Hooft and Veltman that perturbative quantum gravity is non-renormalizable in four dimensions. However, this does not mean that it is impossible to formulate quantum gravity by use of field theoretic techniques, on the contrary, it suggests that special, so-called non-perturbative methods have to be applied. In this thesis we investigate the importance of causality in such non-perturbative approaches to quantum gravity.
Firstly, causal sets are introduced as a simple kinematical model for causal geometry. It is shown how causal sets could account for the microscopic origin of the Bekenstein entropy bound. Holography and finite entropy emerge naturally from the interplay between causality and discreteness.
Going beyond causal set kinematics is problematic however. It is a hard problem to find the right amplitude to attach to each causal set that one needs to define the non-perturbative quantum dynamics of gravity. One approach which is ideally suited to define the non-perturbative gravitational path integral is dynamical triangulation. Without causality this method leads to unappealing features of the quantum geometry though. It is shown how causality is instrumental in regulating this pathological behavior. In two dimensions this approach of causal dynamical triangulations has been analytically solved by transfer matrix methods.
In this thesis considerable progress has been made in the development of more powerful techniques for this approach. The formulation through matrix models and a string field theory allow us to study interesting generalizations. Particularly, it has become possible to define the topological expansion. A surprising twist of the new matrix model is that it partially disentangles the large-N and continuum limit. This makes our causal model much closer in spirit to the original idea by 't Hooft than the conventional matrix models of non-critical string theory.
The power of the here introduced techniques greatly extends the scope of analytical calculations for causal quantum gravity. This ranges from simple matter coupling to a new causal perspective on non-critical string theory.

Research

Book Chapter in "Foundations of Space and Time"

Particles and Fields Seminar schedule

Visiting Scholar at Corpus Christi College, Oxford University

PhD thesis as book