Theory

Theoretical Physics

Marko Ivin and Mathias Möbius
Their MSci project supervised by Dr. Tim Evans applied a novel non-perturbative approach to calculations in quantum field theory. Marko and Mathias looked at phase transitions in a simplified model of the Higgs field. It was published in Nuclear Physics B as An Optimised Perturbation Expansion for a Global O(2) Theory in 2000.


Edmund Hunt
For his BSc project Edmund looked at a network model used to study interactions in the Minoan Aegean. He applied concepts from statistical physics to produce models of interest to archaeologists. His results formed part of a presentation at the European Conference on Complex Systems in 2007 (ECCS 07). This appeared in the proceedings as Modelling Cultural Dynamics: A Macroscopic Approach To Cultural Transmission In The Prehistoric Aegean coauthored with two physicists, Dr. Tim Evans and Prof. Ray Rivers, and an archaeologist, Prof. Carl Knappett.


Tevong You
As part of his MSci project, Tevong looked at a statistical physics model of cultural transmission, that is how are ideas (memes) are exchanged in human society. In particular he asked how results are changed when the exchange is done on a variety of different types of network. His work formed part of a presentation at the European Conference on Mathematics for Industry (ECMI) in 2008. Tevong's results were used in an article for the proceedings entitled Are Copying and Innovation Enough?, coauthored with an MSc student Doug Plato (who gave the presentation) and his project supervisor Dr. Tim Evans.


Andrea Giometto
A visiting Erasmus student, Andrea looked at the statistics of top 10 lists in models of cultural transmission. That is if we look a list of the y most popular items of one type, such as music downloads or baby names, and the list is updated on a regular basis, how large are the changes to the list every week? This result can be used to fix the parameters used in models of cultural transmission. This was written up as a paper on the arXiv entitled Turnover Rate of Popularity Charts in Neutral Models, coauthored with his project supervisor Dr. Tim Evans.


Toby Clemson
In his MSci project Toby looked at a simple model of markets known as the Minority Game. His study looked at the effect on markets of introducing a more realistic social network between the brokers as this controls the flow of information between agents. His results formed the basis for a paper published in 2012 in Physica A, The Emergence of Leadership in Social Networks.


Nicola Hopkins and Ben Kaube
Nicola and Ben worked in successive years as summer students with Dr. Tim Evans funded by aNuffield Undergraduate Research Bursary and an Imperial College UROP bursary respectively. They looked at ways to characterise the quality of research papers which were better than a straight count of the number of citations a paper receives. This involved data on citations drawn from a research institute and from the arXiv. Their work appeared as Universality of Performance Indicators based on Citation and Reference Counts which was published in Scientometrics in 2012.


Annabel Downs and Anna Hashagen, together with PhD student James Yearsley, supervised by Prof Jonathan Halliwell, co-authored a paper based on their MSci project, in which an idealized clock model was used to derive formulas for the arrival time and dwell time of the free particle.
“Quantum Arrival and Dwell Times via Idealised Clocks”
J.M.YearsleyD.A.DownsJ.J.HalliwellA.K.Hashagen
Phys. Rev. A 84, 022109 (2011),arXiv:1106.4767.


Rhian Hartshorn and Ariadne Whitby, together with PhD student James Yearsley, supervised by Prof Jonathan Halliwell, co-authored a paper based on their MSci project, exploring the quantum-mechanical phenomenon of backflow, in which a state of entirely positive momenta can have negative current, so that the probability flows "backwards’’.
“Analytic Examples, Measurement Models and Classical Limit of Quantum Backflow”
J.M.YearsleyJ J.HalliwellR.HartshornA.Whitby
Phys. Rev. A 86, 042116 (2012), arXiv:1202.1783.


Edward Gillman, Olivier Lennon, Meera Patel and Ivan Ramirez, supervised by Prof Jonathan Halliwell, co-authored a paper based on their MSci project, exploring the quantum-mechanical phenomenon of backflow an determining a wide class of states exhibiting it.
“Quantum Backflow States from Eigenstates of the Regularized Current Operator”
J.J.HalliwellE.GillmanO.LennonM.PatelI.Ramirez
J. Phys. A 46, 475303 (2013), arXiv:1309.2909.


Jonas Evaeus, Jonathan London and Yasmin Malik, supervised by Prof Jonathan Halliwell, co-authored a paper based on their MSci project in which a new physically motivated self-adjoint time operator was derived, and also a discussion of why the conventional arrival time operator is not self-adjoint was given.
"A self-adjoint arrival time operator inspired by measurement models”
J.J. HalliwellJ. EvaeusJ. LondonY. Malik
Phys. Lett. A 379, 2445 (2015), arXiv:1504.02509.


Sophia Goldberg and Hannah Anthony
From June 2012 to May 2013, Sophia and Hannah worked with Dr Tim Evans on their final year MSci project. This was looking at the way that the distribution of number of citations to papers published on one topic in the same year always seems to have the same shape, once you scale out the growth in the average number of citations over time. However most simple models fail to capture this feature. It showed that a relatively simple model, involving some copying of citations read in other papers, led to the correct behaviour. This work was published as Modelling Citation Networks in Scientometrics 105 (2015) 1577-1604, one of the leading journals for bibliometrics, DOI 10.1007/s11192-015-1737-9 [arXiv:1408.2970]. The work was presented as a poster, Do We Need Global and Local Knowledge of the Citation Network? at the ISSI 2015 conference and a summary appears in the ISSI 2015 conference proceedings.


Tamar Loach
Tamar worked on a summer project with Dr Tim Evans from June to September 2013. They looked at data from altmetric.com which showed when an academic paper was mentioned in social media, traditional media web sites. They showed how you could use this information to rate different journals based on the attention their papers gained in such alternative (non-traditional) media. This work was presented at the ISSI 2015 conference,Ranking Journals Using Altmetrics (the slides for Ranking Journals Using Altmetrics are on figshare.com) and the accompanying paper appears in the ISSI 2015 conference proceedings [arXiv:1507.00451].


James Clough, Jamie Gollings and Tamar Loach
James, Jamie and Tamar did their final year project with Dr Tim Evans from June 2011 to May 2013 as part of their MSci degree in Physics at Imperial. They looked at a particular type of network in which the vertices (nodes) are constrained by time (or an equivalent ordering). These are known as DAGs - Directed Acyclic Graphs. They did this both on theoretical models, some of which are used in the causal sets approach to quantum gravity, and on real data - a citation network derived from the arXiv preprint database. The paper is Transitive Reduction of Citation Networks, published with open access in The Journal of Complex Networks 3 (2015) 189-203, DOI 10.1093/comnet/cnu039 [arXiv:1310.8224].


Dominic Reiss and Joshua Price

Dominic and Joshua were students on the Imperial College Physics BSc course. Their final year project over the Spring term of 2013 tried to convert mathematical models used in complexity science into 3D printed objects. This was much harder than we expected for various technical reasons so it was all the more to their credit that they pushed this through to produce an actual 3D printed object based on a modified version of the forest fire model. Their project reports and code are online at figshare.com. A paper based on this work appeared as Scuplexity: Sculpture of Complexity using 3D Printing, European Physics Letters 104 (2013) 48001, doi: 10.1209/0295-5075/104/48001 (see also 3D printing used as a tool to explain theoretical physics and Sculplexity: sculptures of complexity using 3D printing).


Zhenghao Zhong

For his UROP project, Zhenghao Zhong and PhD student Santiago Cabrera, supervised by Professor Amihay Hanany, looked at various quiver gauge theories. These are 3d N=4 gauge theories whose matter content and gauge groups can be encoded in graphs called quiver diagrams. Their research focused on 3d mirror symmetry and the choice of orthogonal and special orthogonal gauge groups in the quiver diagrams and can be found here.