Quantum field theory and gravity

The research of Jan Willem van Holten involves the question how to construct quantum field-theoretical models incorporating new symmetries (such as supersymmetry) one the one hand, and gravity in a consistent manner on the other. He also investigates the physics of black holes, and gravitational waves.

String theory

String theory is the subject of Bert Schellekens' research, in particular its relation to conformal field theory. There have been exciting recent developments in string theory, involving surprising connections (dualities) between apparently unrelated theories. His recent research focusses in particular on the open string sector.

The exploration of flavour physics and CP violation, with a focus on decays of B mesons, is the main research topic of Robert Fleischer. Here the goal is to perform precision tests of the flavour structure of the Standard Model by means of rare, strongly suppressed processes that are caused by virtual quantum effects and are sensitive probes for contributions from physics beyond the Standard Model. There is a strong interaction with Nikhef's experimental B-physics group working on the LHCb experiment at CERN.

The phase structure of Quantum Chromodynamics (QCD), the quantum field theory that provides a microscopic description of the strong force, has received a lot of attention in recent years. This field is investigated by Justus Koch. Understanding the possible phases of this theory, besides having intrinsic interestes, is relevant for describing the universe up to one microsecond after the Big Bang. There is much experimental research into this area by means for ultra-relativistic heavy-ion collisions at CERN and Brookhaven, with the goal of turning the heavy nuclei for a moment after their collision into a quark-gluon plasma. Describing this physics combines particle physics with statistical physics, thermodynamics, and finite temperature quantum field theory.

Eric Laenen investigates, from a perturbation theory approach, fundamental and phenomenological aspects of the aforementioned QCD, a highly nontrivial non-abelian gauge theory. He is especially interested in the sector involving the heavy quark flavors charm, bottom and top. These flavors can be individually identified in high-energy collisions, thereby allowing a more detailed study of the strong interaction itself. The phenomenology of these heavy quarks often allows a description by appropiate effective field theories, yielding further insight. In this context he investigates the possibility of accounting for high orders in perturbation theory. Such "resummation" studies can also provide insight into non-perturbative aspects of the theory.
Also Jos Vermaseren's research concentrates on the perturbative approach to the computation of QCD observables. By means of a powerful computeralgebra program (FORM) that he developed, and that is in worldwide use, he can perform very complicated calculations, which are impossible to do by hand. Besides much quantum field theory fine points, these computations involve the mathematics of harmonic sums, Mellin transformations, etc. The results of these calculations are of great practical importance for a correct interpretation of measurements at the HERA, Tevatron and LHC accelerators.