Imperial College London

Emeritus Professor Ray Rivers

Faculty of Natural SciencesDepartment of Physics

Distinguished Research Fellow
 
 
 
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Contact

 

+44 (0)20 7594 7830r.rivers Website

 
 
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Location

 

509Huxley BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

104 results found

Rivers R, Evans T, 2020, How do we avoid imposing the present on the past when modelling spatial interactions?, Documenta Praehistorica, Vol: 47, Pages: 462-475, ISSN: 1318-6701

Theoretical archaeological modelling for describing spatial interactions often adopts contemporary socioeconomic ideas whose C20th language gets translated into historical behaviour with the simplest of lexicons. This can lead to the impression that the past is like the present. Our intention in this paper is that, when this happens, to strip out as much of the contemporary context as we can, to bring modelling back to basic epistemic propositions. We suggest that although the underlying ontology may be specific to contemporary society the epistemology has much greater generality, leading to essentially the same conclusions without the carapace of intricate economics.

Journal article

Lee D-S, Lin C-Y, Rivers RJ, 2020, Large phonon time-of-flight fluctuations in expanding flat condensates of cold Fermi gases, JOURNAL OF PHYSICS-CONDENSED MATTER, Vol: 32, ISSN: 0953-8984

Journal article

Rivers R, Knitter D, Bilger M, Faupel F, Filet C, Girotto C, Grammer B, Hamer W, Hinz M, Nakoinz O, Radloff K, Raese H, Roe J, Roth G, Tietze C, Watson Jet al., 2018, CRC1266-A2/moin: Release after Moin Summer School

This release contains all the code created during the moin Summer School, jointly organized by CRC1266 project A2 and ISAAKiel.It is a major refactoring of all previous code of moin. However, concept and general wording remains the same.Please note that the different new methods implemented needs proper testing! This release is intended to be the starting point of all these tests and corresponding code changes.

Software

Rivers RJ, Steer DA, Lin C-Y, Lee D-S, Weir DJet al., 2018, When are two fermions a simple boson? New Gross-Pitaevskii actions for cold Fermi condensates, ANNALS OF PHYSICS, Vol: 396, Pages: 495-516, ISSN: 0003-4916

Journal article

Hsiang J-T, Lee D-S, Lin C-Y, Rivers RJet al., 2015, Quantum sound-cone fluctuations in cold Fermi gases: Phonon propagation, PHYSICAL REVIEW A, Vol: 91, ISSN: 1050-2947

Journal article

Evans TS, Rivers RJ, 2014, New approaches to Archaic Greek Settlement Structure, Les Nouvelles de l'archéologie, Vol: 135, Pages: 21-27, ISSN: 0242-7702

Recent developments in network theory have led to the creation of new Spatial Interaction Models (SIMs) and a reappraisal of existing models. Although not directed at the archaeology community, these models generalise the familiar gravitational models and Proximal Point Analysis (PPA) used by archaeologists for many years to help explain the archaeological record. However, a problem arises in archaeology that, with the increasing suite of plausible models that now exist, it is unclear how to choose one model over another. This can lead to the criticism that, if we hunt hard enough, we may be doing no more than finding a model which can be manipulated to conform to our preconceptions. In recent articles we have begun to address this criticism (Evans 2014, in press) with particular reference to the maritime networks of the MBA Aegean (Rivers 2014, in press). Different historical periods require different approaches and in this paper we continue this analysis by re-examining the onset of centralisation in mainland Greek city states of the 9th and 8th centuries BCE. Pioneering work on this archaic settlement structure was performed in 1987 by Rihll and Wilson (Rihll & Wilson 1987, 2: 5-32; 1991: 59-95), adapting a 'retail' model devised originally for urban planning. One alternative approach is given by a recent cost-benefit model termed ariadne, developed by ourselves (Evans, Knappett & Rivers 2009, 7: 451-79; Knappett, Evans & Rivers 2008, 82: 1009-84; 2011, 85: 1008-23), initially designed for Bronze Age maritime networks. A comparison of these models and other simpler SIMs for archaic settlements highlights the problems of modelling archaeological data. In particular we examine what constitutes model 'robustness' and the way in which different models handle 'contingency' when handling periods of rapid change.

Journal article

Hsiang J-T, Lin C-Y, Lee D-S, Rivers RJet al., 2013, The role of causality in tunable Fermi gas condensates, JOURNAL OF PHYSICS-CONDENSED MATTER, Vol: 25, ISSN: 0953-8984

Journal article

Weir DJ, Monaco R, Koshelets VP, Mygind J, Rivers RJet al., 2013, Gaussianity revisited: exploring the Kibble-Zurek mechanism with superconducting rings, JOURNAL OF PHYSICS-CONDENSED MATTER, Vol: 25, ISSN: 0953-8984

Journal article

Weir DJ, Monaco R, Rivers RJ, 2013, Defect Formation in Superconducting Rings: External Fields and Finite-Size Effects, JOURNAL OF LOW TEMPERATURE PHYSICS, Vol: 171, Pages: 788-796, ISSN: 0022-2291

Journal article

Rivers R, Knappett C, Evans T, 2013, Network Models and Archaeological Spaces, Computational Approaches to Archaeological Spaces, Editors: Bevan, Lake, Publisher: Left Coast Press, ISBN: 978-1-61132-346-7

Book chapter

Rivers R, Knappett C, Evans T, 2013, What makes a site important? Centrality, gateways and gravity, Network Analysis in Archaeology: New Approaches to Regional Interaction, Editors: Knappett, Publisher: OUP, Pages: 125-150

Book chapter

Lin C-Y, Lee D-S, Rivers RJ, 2012, Nonequilibrium damping of the collective motion of homogeneous cold Fermi condensates with Feshbach resonances, PHYSICAL REVIEW A, Vol: 85, ISSN: 1050-2947

Collisionless damping of a condensate of cold Fermi atoms, whose scattering is controlled by a Feshbach resonance, is explored throughout the BCS and Bose-Einstein condensate (BEC) regimes when small perturbations on its phase and amplitude modes are turned on to drive the system slightly out of equilibrium. Using a one-loop effective action, we first recreate the known result that for a broad resonance the amplitude of the condensate decays as t(-1/2) at late times in the BCS regime, whereas it decays as t(-3/2) in the BEC regime. We then examine the case of an idealized narrow resonance, and find that this collective mode decays as t(-3/2) throughout both the BCS and BEC regimes. Although this seems to contradict earlier results that damping is identical for both broad and narrow resonances, the breakdown of the narrow resonance limit restores this universal behavior. More measurably, the phase perturbation may give a shift on the saturated value to which the collective amplitude mode decays, which vanishes only in the deep BCS regime when the phase and amplitude modes are decoupled.

Journal article

Evans TS, Rivers RJ, 2012, Interactions in Space for Archaeological Models, Advances in Complex Systems, Vol: 15

In this article we examine a variety of quantitative models for describingarchaeological networks, with particular emphasis on the maritime networksof the Aegean Middle Bronze Age. In particular, we discriminate betweenthose gravitational networks that are most likely (maximum entropy) andmost efficient (best cost/benefit outcomes).

Journal article

Knappett C, Rivers R, Evans T, 2011, The Theran eruption and Minoan palatial collapse: new interpretations gained from modelling the maritime network, ANTIQUITY, Vol: 85, Pages: 1008-1023, ISSN: 0003-598X

Journal article

Rivers RJ, Evans TS, Knappett C, 2011, Modelling maritime interaction in the Aegean Bronze Age, II. The Theran eruption and Minoan palatial collapse, Antiquity: a quarterly review of archaeology, Vol: 85, Pages: 1008-1023

What was the effect on Late Minoan civilisation of the catastrophic destruction of Akrotiri on Thera (Santorini) by volcanic eruption? Not much, according to the evidence for continuing prosperity on Crete. But the authors mobilise their ingenious mathematical model (published in Antiquity 82: 1009–1024), this time to show that the effects of removing a major port of call could have impacted after an interval, as increased costs of transport gradually led to ever fewer routes and eventual economic collapse.

Journal article

Lin C-Y, Lee D-S, Rivers RJ, 2011, Spontaneous vortex production in driven condensates with narrow Feshbach resonances, PHYSICAL REVIEW A, Vol: 84, ISSN: 1050-2947

Journal article

Rivers RJ, 2011, PATH INTEGRALS FOR QUASI-HERMITIAN HAMILTONIANS, INTERNATIONAL JOURNAL OF MODERN PHYSICS D, Vol: 20, Pages: 919-932, ISSN: 0218-2718

Journal article

Rivers RJ, 2011, Path Integrals for Pseudo-Hermitian Hamiltonians, International Conference on Pseudo-Hermitian Hamiltonians in Quantum Physics, Publisher: SPRINGER/PLENUM PUBLISHERS, Pages: 1081-1096, ISSN: 0020-7748

Conference paper

Weir DJ, Rivers RJ, 2011, Fluxoid formation: size effects and non-equilibrium universality, Conference on Condensed Matter and Materials Physics (CMMP10), Publisher: IOP PUBLISHING LTD, ISSN: 1742-6588

Conference paper

Rivers RJ, 2011, Path Integrals for (Complex) Classical andQuantum Mechanics, AAMP7, Pages: 83-89

An analysis of classical mechanics in a complex extension of phase space shows thata particle in such a space can behave in a way redolant of quantum mechanics; addi-tional degrees of freedom permit 'tunnelling' without recourse to instantons and lead totime/energy uncertainty. In practice, 'classical' particle trajectories with additional de-grees of freedom have arisen in several di®erent formulations of quantum mechanics. Inthis talk we compare the extended phase space of the closed time-path formalism withthat of complex classical mechanics, to suggest that ~ has a role in our understanding ofthe latter. However, di®erences in the way that trajectories are used make a deeper com-parison problematical. We conclude with some thoughts on quantisation as dimensionalreduction.

Conference paper

Monaco R, Mygind J, Rivers RJ, Koshelets VPet al., 2009, Spontaneous fluxoid formation in superconducting loops, PHYSICAL REVIEW B, Vol: 80, ISSN: 2469-9950

Journal article

Lin C-Y, Lee D-S, Rivers RJ, 2009, Nonuniversal behavior of cold Fermi condensates with narrow Feshbach resonances, PHYSICAL REVIEW A, Vol: 80, ISSN: 1050-2947

Journal article

Jones HF, Rivers RJ, 2009, Which Green functions does the path integral for quasi-Hermitian Hamiltonians represent?, PHYSICS LETTERS A, Vol: 373, Pages: 3304-3308, ISSN: 0375-9601

Journal article

Evans TS, Knappett C, Rivers RJ, 2009, Using Statistical Physics To Understand Relational Space: A Case Study From Mediterranean Prehistory, Complexity Perspectives on Innovation and Social Change, Editors: Lane, Pumain, Leeuw, West, Lane, Pumain, Leeuw, West, Publisher: Springer Science + Business Media, Pages: 451-479, ISBN: 9781402096624

Book chapter

Rivers RJ, Monaco R, Mygind J, Aaroe M, Koshelets VPet al., 2008, Do superconductors change as fast as possible when quenched?, Phil. Trans. R. Soc. A, Vol: 366, Pages: 2871-2880

If superconductors change as fast as possible as they pass through a phase transition,then the initial domain structure is constrained by causality. We shall see that Josephson junctions do, indeed, display such behaviour. However, we shall argue that causal bounds arise through the Gaussian nature of the order parameter, which can be thought of as a consequence of instabilities growing as fast as possible.

Journal article

Rivers RJ, Steer DA, 2008, Statistical mechanics of strings with Y-junctions, PHYSICAL REVIEW D, Vol: 78, ISSN: 1550-7998

Journal article

Monaco R, Aaroe M, Mygind J, Rivers RJ, Koshelets VPet al., 2008, Spontaneous fluxon production in annular Josephson tunnel junctions in the presence of a magnetic field, PHYSICAL REVIEW B, Vol: 77, ISSN: 2469-9950

Journal article

Rivers RJ, Lee D-S, Lin C-Y, 2008, EFFECTIVE FIELD THEORY FOR THE BEC/BCS TRANSITION, 9th International Conference on Path Integrals, Publisher: WORLD SCIENTIFIC PUBL CO PTE LTD, Pages: 368-+

Conference paper

Aaroe M, Monaco R, Rivers R, Koshelets V, Mygind Jet al., 2008, Quench-induced trapping of magnetic flux in annular Josephson junctins, Journal of Physics; Conference series, 8th European Conference on Applied Superconductivity

Conference paper

Knappett C, Evans TS, Rivers RJ, 2008, Modelling Maritime Interaction In The Aegean Bronze Age, Antiquity, Vol: 82, Pages: 1009-1024

The authors raise spatial analysis to a new level of sophistication – and insight – in proposing a mathematical model of imperfect optimisation to describe maritime networks. This model encodes, metaphorically, the notion of gravitational attraction between objects in space. The space in which this interaction occurs is the southern Aegean in the Middle Bronze Age, and the objects some of the main 34 sites we know about. The gravitational potential, more sophisticated than in Newtonian physics, is interpreted as a social potential whose equilibria, sampled statistically, determine networks with settlements of particular sizes and links of particular strengths. The model can be tweaked by giving different relative importance to the cultivation of local resources or to trade, and to show what happens when a member of the network suddenly disappears.

Journal article

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