The Physics Theory Group @ WarwickThe Physics Theory Group @ Warwickwww.warwick.ac.uk/go/theory

© RA Roemer 2005

Quantum PhysicsQuantum Physics

ApplicationsApplications

Academic StaffAcademic Staff

Prof Mike Allen

Prof Robin Ball

Dr Nick D'Ambrumenil

Dr John Dixon

Dr Boris Muzykantskii

Dr Mario Nicodemi

Dr Rudolf A Römer

Prof George Rowlands

Dr Ellak Somfai

Dr Marzena Szymanksa

Prof Julie Staunton

Dr Matthew Turner

The quantum mechanics of systems which are classically chaotic has been an intense focus of interest in recent years, particularly as experimental realisations as above can now be taylor-made.

Quantum ChaosQuantum Chaos

What controls the roughness and branching of crack propagation patterns?Experimentally based claims of universal behaviour suggest we should be able to understand this from computer simulations

Dynamical FractureDynamical Fracture

Diffusion Limited Diffusion Limited AggregationAggregation

This sort of growth we study by simulation and recently analytic theory. It is what makes snowflakes so varied, but it is also why your rechargeable batteries don’t last.Suppressing this sort of pattern when you inject water into an oil reservoir is a trillion dollar industry.

See the simulations on our website!

Wavefunctions amidst DisorderWavefunctions amidst Disorder

As material disorder gets stronger, the nature of particle wave functions changes from extended to localised, and what was a metal becomes an insulator.This image illustrates the subtlety observed at the metal-insulator transition.

Fermi Surface of Fermi Surface of CopperCopper

The key to understanding the electronic properties of metals is to view things in Momentum Space – a three dimensional Fourier Transform.

This image shows the states occupied by electrons. The greatest distortion from a sphere happens when the states come closest to the edge of the Brillouin Zone.

Quantum-Hall PhysicsQuantum-Hall PhysicsMeasuring a voltage difference in a thin layer of semiconductors allows us to observe quantum effects with astonishing accuracy. The quantum-Hall effect is currently used to define what we mean by the SI unit of “resistance”, it is among the most precise measurement of nature constants possible. At the heart of each measurement is the observational fact that h/e2 is quantized.

The picture shows a model for the electronic structure in a semiconductor.

metalmetal insulatorinsulator

MutY MutY

MutY MutY

Healthy DNA

Broken DNA

electron

Is DNA conducting?Is DNA conducting?Our genetic information is stored in large Deoxyribonucleicacid (DNA) molecules. Typically, billions of bases form one DNA molecule in mammals and base pairs are seperated by 0.34 billionth of a meter from each other. There is evidence that hese large chains might be used as nano-wires.

An issue of scientific concern is the exact way in which DNA and other biomolecules such as proteins signal one another in order to carry out the required operations. Both to scientists and to the untrained eye it seems fascinating how DNA-binding proteins find their way across thousands of bases in a DNA sequence and know exactly where to attach themselves to, i.e. their target, which could be a fragment as short as a few tens of bases. There is a signalling method, speculated to involve electrons, that guides processes like these.

Magnets and Nano-technologyMagnets and Nano-technologyThe main theme running through most of this research is a description of various properties of metallic materials via a careful account of their electronic `glue' or structure. This requires `state of the art' computing techniques and resources such as those available at the Centre for Scientific Computing at the University of Warwick. We study theoretical metallic magnetism in this way and also, with the same electronic basis, a theory for the types of alloys that can form when two or more metallic elements are combined. A strength of the work is that it is `first-principled' so that many aspects can be tested in quantitative detail by a range of experimental measurements.

Biological PhysicsBiological Physics

Myosin WalkersMyosin Walkers

To keep cells alive tiny molecular machines are needed to move cargo around. These can have efficiencies that are comparable to the best machines that engineers can build today but are only a few nanometres across and have to live in a very 'noisy' environment. They are highly evolved structures that use chemical energy to generate forces, and hence motion by exploiting cyclic reaction pathways. We are interested in understanding these theoretically, e.g. for two-legged 'walkers' (as shown) how is the rear leg 'told' when to detach and take a step forward ?

Granular Systems which are shaken rather than in thermal motion can develop unexpected patterns. In both of the above the shaking is from side to side and the view from above. The initially separated and initially mixed samples follow very different paths to similar end states. Challenge: understand the overall mechanism, timescales, and what so strongly selects the final state?

Pattern Formation in Granular SystemsPattern Formation in Granular Systems

Meiosis (dynamics of Meiosis (dynamics of sex)sex)

Meiosis is the specialized cell division necessary for the production of haploid gametes from diploid nuclei. In a crucial step, homologous (i.e. same number) chromosomes pair up, but how they recognize each other and come together are still mysterious. We studied a Statistical Mechanics Model for the regulation of such processes.

Bose-Einstein CondensationBose-Einstein CondensationAfter nearly a century of theoretical speculation, this is now an experimental reality. The first demonstration was in ultra-cold and ultra-dilute atoms, but above shows the evidence for condensation of polariton excitations in a solid. The nearer figures show occupation number as a function of momentum, with a macroscopic peak emerging. Our newest group member works on techniques to model these systems.

Classical PhysicsClassical Physics