# Theoretical Physics in Sheffield

### Research Groups

Polymers and Soft Matter
We study, using analytical theory, computational methods and simulations a wide variety of phenomena that occur in polymers and other soft materials. Current projects are focussed on instabilities and pattern formation in thin films of mixtures driven by coupling between thermodynamics and kinetics, current/voltage characteristics in organic photovoltaics, templating nanoparticle self-assembly with block copolymers, and the anomolous dynamics of polymers in the presence of nanoparticles. Previous projects include mechanical properties of organogels and actin networks, blood flow through vein valves, phase separation and microstructure evolution in polymer blends and the coupling between phase transitions and flow. For more information, contact Nigel Clarke.

Biophysics
Working with experimental physicists and biologists in Sheffield and elsewhere, we use analytical theory and computation to model biological systems. Our aim is to construct simple models that capture the physical mechanisms involved. In particular we focus on the cell cytoskeleton, which is made up of protein filaments (actin, microtubules) and molecular motors. These biopolymers form a viscoelastic gel that is out of equilibrium due to the consumption of biochemical energy and is an example of what is known as an active gel. We are interested in how the properties of this material enable cells to carry out biological processes such as polarisation, migration, adhesion and endocytosis. For more information, contact Rhoda Hawkins.

Theory of Photonic Crystals and Microcavities
Most of the theoretical work in the group is concerned with the study of photonic crystals and planar semiconductor microcavities. We are currently developing an approach to calculating properties of photonic crystals based on Wannier functions from electronic structure theory. The main aim is to design high finesse optical cavities for studying cavity quantum electrodynamics and quantum information processing. Another major topic is understanding the properties of the Optical Parametric Oscillator (OPO) which is observed in resonantly pumped planar microcavity structures. Other interests include surface states on photonic crystals, THz emitters, and excitonic states in low dimensional structures. We also have strong links with the quantum dot work in the Department of Electronic & Electrical Engineering. For more information, contact David Whittaker.

Optical Quantum Information Processing
The research in this group focusses mainly on quantum information processing with optical systems. This encompasses how to build a quantum computer and quantum communication devices using light, quantum information extraction via metrology, and reseach in quantum imaging and lithography. In addition, we are interested in relativistic extensions of quantum information theory, in particular how quantum communication channel capacities are affected by curved spacetime. For more information, contact Pieter Kok.

Theoretical Magnetism
Research in theoretical magnetism supports the programme in experimental magnetism. Current topics include developing an understanding of the origins of magneto-optic properties of magnetic oxides and the behaviour of multiferroic manganites and also pseudo spin models for phase transitions in other materials, for example in liquid crystals. A computational study is underway on the properties of ferromagnetic nanoparticles embedded in a weakly magnetic oxide. A new project is available to expand on this topic to include the electron transport and hence to calculate magnetoresistance for granular materials and also tunnelling magnetoresistance between two such materials. The group works closely with collaborators in Russia, China and the UK (York). For more information please contact Gillian Gehring.

Astro-particle theory and cosmology
Our main research interests and activities include particle astrophysics: particle models for dark matter and prospects for its detection, formation and structure of dark matter halos; early Universe and brane world cosmology, inflation, particle relics; dark energy: cosmological consequences and observational constraints on diverse models; quantum gravity, black holes, quantum field theory in curved space; particle theory beyond the Standard Model, supersymmetry, grand and string unification, SUSY signatures in rare processes and in collider searches. For more information, contact Elizabeth Winstanley.

Theoretical astrophysics
As part of the astronomy group we study the formation and dynamical evolution of stars and star clusters. We are interested the hydrodynamics of star formation, especially multiple star formation, and the evolution of (planet-forming) discs in binary stars. We also study the pure gravitational phases of star cluster formation and binary destruction. We also investigate the statistical properties of both binary and multiple stars, and the distributions of young stellar systems. For more information contact Simon Goodwin

Quantum Dynamics
The research in this group focusses on the theoretical/computational study of chemical reactions using quantum dynamics. The systems studied vary from small fundamental gas-phase reactions, like H + O$_2$, an important combustion reaction to gas-surface reactions involving small molecules in the interstellar medium. The results of our calculations are compared to the results of sophisticated experiments performed by collaborators to obtain insight into the fundamentals of the reactions involved. Since our calculations are very time-consuming, we are also heavily involved in the development of new computational algorithms with a particular emphasis on parallellizability. For more information, contact Anthony Meijer.