**What do you expect from your Lorentz Professorship?**

'I am very pleased with the Lorentz Professorship. To me this is one of the most valuable awards: Lorentz is my hero in physics. I hope to be able to present lectures which will live up to expectations. This is a challenge. I also hope to meet many interesting people during my stay in Leiden and particularly during the workshop which I hope will be very productive.'

**About your work: you study the cosmological implications of string theory. Is it possible to explain this in words?**

'I study the cosmological implications of string theory and supergravity. We are closing in on the first 10

^{-35}seconds of the universe, using General Relativity and Quantum Field Theory. Supergravity and a more advanced version of it —superstring theory— are the only advanced forms known to us of General Relativity and Quantum Field Theory which we may test by cosmological observations in the early universe. And by the way, the fundamentals of supergravity were to a large extent developed in The Netherlands, by Bernard de Wit, Eric Bergshoeff and Mees de Roo, and in application to cosmology by a younger generation of people in The Netherlands like Ana Achucarro and Diederik Roest.'

**To outsiders, string theory is famous for being a theory that is impossible to prove. Will string theory shrug off this image?**

'I don’t have an answer to your question, but at present I see that string theory ideas help us to build cosmological models which fit the data from observations. Moreover, we have produced relatively simple predictions from string theory and related theories which will be testable with future detectors of primordial gravity waves (gravitational waves from the Big Bang, edit.)'

**What is the most promising upcoming observation regarding confirming your theoretical work?**

'Future ground based or satellite missions will either detect primordial gravity waves or reduce the current bound on the ratio of tensor to scalar perturbations (amount of gravitational waves, edit.) during early universe inflation. Both of these outcomes will be of a significant importance for theoretical physics in general, and for my work in particular.'

**As a student, what attracted you to cosmology in general and string theory in particular?**

'I was working on supergravity and string theory during most of my career in physics since I was always interested in mathematical methods in physics. More recently I became involved into studies of cosmology and I found it gratifying to see that the results of my formal theoretical studies are known and discussed in the context of observational cosmology, for example in the Planck satellite comparison of theory with experiment and in upcoming experiments on the Cosmic Microwave Background.'

**You will be in a long list of Lorentz Professors since 1955. Whose work do you admire most?**

'I admire Lorentz and I greatly respect all people in the list. Wheeler, Wigner, Klein, Yang, Wess, Wilczek, Susskind, Thorne and Penrose strongly affected my work and I admire them.'