Condensed Matter Physics

Chen Cheng
In the summer of 2008 a third year MSci undergraduate Chen Cheng Lin undertook a UROP project with Professor Adrian Sutton and Dr Alvin Chua. The project consisted of the development of a genetic algorithm to model the structures of grain boundaries in strontium titanate. The project was immensely challenging and exciting and we are now writing two papers, one intended for Science. Chen Cheng Lin’s contribution was essential to the success of this work, and he will be a principal author of both papers.

Alvin Chua
"Exact enumeration of the critical states in the Oslo model"
Alvin Chua and Kim Christensen
BSc project 1999-2000 by Alvin Chua
Although not published in a research journal, it is a well-know paper and well cited.

Ole Peters and Christopher Hertlein
"A complexity view of rainfall"
Ole Peters, Christopher Hertlein, and Kim Christensen
Phys. Rev. Lett. 88, 018701, 1-4 (2002).
BSc project 2000-2001 by Ole Peters and Christopher Hertlein
Work featured in New Scientists news article May 2002.
No. citations: 249

Leon Danon and Tim Scanlon
"Unified scaling law for earthquakes"
Per Bak, Kim Christensen, Leon Danon, and Tim Scanlon
Phys. Rev. Lett. 88, 178501, 1-4 (2002).
MSci project 2000-2001 by Leon Danon, and Tim Scanlon
Work featured in Scientific American news scan article "Scaling the Quakes", June 2002.
No. citations: 536

Matthew Stapleton and Martin Dingler
"Sensitivity to initial conditions in self-organized critical systems"
Matthew Stapleton, Martin Dingler, and Kim Christensen
J. Stat. Phys, Vol. 117, Nos. 5/6, (2004).
MSci project 2002-2003 by Matthew Stapleton and Martin Dingler

Peter Welinder
"Multiscaling in the sequence of areas enclosed by coalescing random walkers"
Peter Welinder, Gunnar Pruessner, and Kim Christensen
New Journal of Physics 9, 149 (2007).
UROP project by Peter Welinder 2006.

Michael Thomas
Working at the Rutherford Appleton Laboratory in summer 2011 with Dr Oleg Kirichek, Michael helped conduct an investigation into the adhesive properties of solid methane. The objective was to determine why the methane moderator used by the ISIS neutron source was broken during use. Michael was involved in designing the experimental setup, doing the experimental work, and assisting in results interpretation. The experimental write up was published in the journal Cryogenics under the title "Adhesion, plasticity and other peculiar properties of solid methane"

Dario Papavassiliou and Alexandre de Figueiredo
"Universality in Ant Behaviour"
Kim Christensen, Dario Papavassiliou, Alexandre de Figueiredo, Nigel R. Franks and Ana B. Sendova-Franks
Journal of The Royal Society Interface (2015)
Work initiated as 4th year MSci Project. Completed and published in 2015.

Kishan A. Manani
"Simple model for identifying critical regions in atrial fibrillation"
Kim Christensen, Kishan A. Manani, and Nicholas S. Peters
Physical review letters 114 (2), 028104 (2015)
Work initiated as 4th year MSci Project. Completed and published during Kishan Manani's PhD.

Andrew Warwick and Eliot Banks
Andrew Warwick and Eliot Banks undertook their MSci project with Professor Adrian Sutton and co-authored a paper published in the Proceedings of the Royal Society.
The five-dimensional space of grain boundaries”, A P Sutton, E P Banks and A R Warwick, Proc. R. Soc. A, 471 20150442 (2015)

Crystalline matter almost always comprises an agglomeration of many separate crystals differing in the orientations of their crystal axes. Where two such misorieneted crystals meet there is an interface called a grain boundary. Five independent variables are required to specify the misorientation (3) and plane (2) of each grain boundary. This paper asked the question “how similar are two boundaries with different misorinentations and boundary planes?”. The answer to this question involves the definition of a metric in the 5D space associated with the boundaries. It is complicated by the presence of point group rotational symmetries in the crystal lattice which leave the boundary structure  invariant but which alter its misorientation. This paper addressed these questions using Rodrigues vectors to represent rotations.

Andrew Warwick subsequently decided to undertake a PhD in the Centre for Doctoral Training on Theory and Simulation of Materials at Imperial College London.

Nick Blunt, Tom Rogers and Francine (Min-Hui) Foo
These students have worked with Professor Matthew Foulkes on the following papers:

Density-matrix quantum Monte Carlo method N.S. Blunt, T.W. Rogers, J.S. Spencer, and W.M.C. Foulkes Phys. Rev. B 89, 245124 (2014)

Quantum-classical simulations of the electronic stopping force and charge on slow heavy channelling ions in metals C.P. Race, D.R. Mason, M.H.F. Foo, W.M.C. Foulkes, A.P. Horsfield, and A.P. Sutton J. Phys.: Condens. Matter 25, 125501 (2013)

The sign problem and population dynamics in the full configuration interaction quantum Monte Carlo method J.S. Spencer, N.S. Blunt, and W.M.C. Foulkes J. Chem. Phys.  136, 054110 (2012)

D.R. Mason, C.P. Race, M.H.F. Foo, A.P. Horsfield, W.M.C. Foulkes, and A.P. Sutton Resonant charging and stopping power of slow channelling atoms in a crystalline metal New J. Phys. 14, 073009 (2012)

Jonathan Lee and Alex Leonard

Together with two MSci students, Jonathan Lee and Alex Leonard, and an academic visitor to the department, Simon Morgan, we have analyzed these networks on the chorionic plate (the fetal side of the placenta) in two cohorts: a population cohort representative of the United States, and a cohort from newborns with an elevated risk of developing autistic spectrum disorder. Our analysis is based on scaling theory – a pillar of modern statistical mechanics that reveals common aspects of diverse systems from a suitable choice of variables.  Each chorionic plate is partitioned into contiguous polygonal regions, called Voronoi cells, that measure the region served by each blood vessel. The cell areas of each placenta are then divided by the average cell area for that placenta to obtain the variables used for a scaling plot. The resulting distributions of re-scaled Voronoi cell areas in the two cohorts collapse onto a single distribution, that is, they “scale”.  This means that the differences between the vasculatures in the two cohorts are due only to the average cell area and, in particular, indicates that the formation mechanism of the vasculature at the level of vessel segments is the same in both cohorts. The lower branching density seen in the at-risk placentas suggests that this mechanism is less active in this cohort. The possibility that this conclusion to all placentas, that is, that this mechanism is “universal", is the subject of another MSci project.

This research was published as a Rapid Communication in Physical Review E: A. S. Leonard, et al., Scaling of the surface vasculature on the human placenta,