**Members**

Rajat K. Bhaduri | Melvin A. Preston |

Cliff Burgess | Donald W.L. Sprung |

Yukihisa Nogami | Wytse van Dijk |

**Research**

Members of the theory group have varied interests and while they work on different
topics, they tend to use similar general techniques in their work. The efforts
in theoretical astrophysics and theoretical condensed matter physics are described
under those headings. A wide range of more general theoretical investigations
are ongoing within the department.

Bhaduri
is broadly interested in the connection between quantum theory and classical
periodic orbits in non-integrable dynamical systems. He also works on low-dimensional
physics and quantum statistics, including Bose-Einstein condensation of dilute
gases in traps.

Burgess
is a high-energy particle theorist whose current interests lie at the interface
between string theory and lower-energy physics, with a particular emphasis on
how the discovery of D-branes (and the realization that we may be trapped on
one) may have observable consequences in experiments and in cosmology.

Nogami
has been interested in the propagation of wave packets and solitons in nonrelativistic
as well as relativistic quantum mechanics. With van
Dijk, he has been studying quantum tunnelling of wave packets through potential
barriers. This has led to applications on the alpha decay problem in nuclei.
Nogami's other work relates to the field theoretical description of the vacuum
in relation to fractional fermion numbers. van
Dijk and Sprung
also study two-nucleon scattering, and its implications on the nuclear force.

Preston
has been active recently in the area of quantisation under constraints, and
applied the theory to topological solitons. The correct procedure leads to the
stability of the Skyrmion with a simpler Lagrangian, and a consistent description
of the nucleon.

Sprung,
in collaboration with Hua Wu and J.
Martorell (Barcelona) has been interested in nanometer scale electron devices.
They have studied electron transport through quantum wires with a variety of
bends and cavities attached to them, and have developed an elegant formalism
for scattering in a finite periodic system. Electron confinement in heterostructures
has been studied using the self-consistent Thomas Fermi method. Through the
QUADRANT project, funded
through the European Union, the group has been attempting to implement the Quantum
Cellular Automaton (QCA) paradigm in semiconductor materials using analytical
as well as computational methods.