Interdisciplinary Workshop on Fluctuations and Coherence: from Superfluids to Living Systems

We propose an interdisciplinary workshop bringing together experts from diverse fields to discuss a broad range of phenomena associated with the interplay of fluctuations and nonlinearity in complex systems. The underlying physics and concepts have much in common for such seemingly different phenomena as creation of quantized vortices in superfluids and flux lines in superconductors, mass transport in stochastic ratchets in biological cells and cold atom systems, mode switching in lasers, interstate switching in nano-mechanical resonators and in the Josephson bifurcation amplifiers used in quantum measurements, transitions between cardio-respiratory synchronization states, turbulence in He II, rogue waves on the ocean, and extinctions in population dynamics. Yet experts from the corresponding disciplines seldom, if ever, get together to study what in reality are problems of mutual interest where their expertise is likely to be complementary. The proposed conference seeks to address this deficiency and promises effective knowledge transfer between the disciplines.The topics to be addressed will include the hidden dynamics that underlies rare random events in both classical and quantum systems, with emphasis on systems far from thermal equilibrium. Generic features like rate-scaling will be discussed. Ways of controlling rare events in different types of system, e.g. increasing/decreasing the rates of the events, will be considered. The unusual role of quantum fluctuations far from thermal equilibrium, which has no analogue in equilibrium systems, will be explored. The mechanisms responsible for rare events will be discussed, ranging from the nano-scale (e.g. vortices in superfluids, cold atoms, and nano-mechanical resonators), through the mesoscopic (e.g. Josephson junctions), to the macroscopic (e.g. cardio-respiratory interaction and rogue waves on the ocean). These same mechanisms are also often responsible for loss of coherence in nonlinear systems. Other types of non-Gaussian fluctuations will be discussed, including full counting statistics, which is relevant to disciplines ranging from mesoscopic conductors to biosystems. The goal of the workshop is thus to advance understanding and develop new means of controlling fluctuating nonlinear systems far from thermal equilibrium by revealing the common and specific aspects of the behavior of different classes of system. To bring together the best experts in such different areas will involve careful planning and persuasion, as they will need to have it explained how their work fits into the broad context of the workshop. It will also require financial support for travel and subsistence, as many of the scientists we wish to attract are accustomed to invitations where most or all of their costs are covered. We envisage 15 keynote invited speakers in this category within a meeting of up to 60 participants in total, mostly invited, but with a wide range of seniority including some selected PhD students. There will be no parallel sessions. In addition to lectures, there will be round-table discussions of particular topics that transcend the disciplines, in order to identify the analogies and distinctions, and to promote knowledge transfer. Lancaster is in many ways a natural venue for such a workshop, as its Low Temperature and Nonlinear & Biomedical Physics research groups already encompass several of the topics to be studied including superfluidity, fluctuation theory, and cardiovascular dynamics. The Physics Department which will host the event has an excellent national and international reputation (e.g. best research profile in the 2008 UK national Research Assessment Exercise). The University's conference facilities are ideal for a workshop of this kind, with high quality meeting, eating and sleeping facilities all in close proximity on a compact and pleasant campus.

Beyond the participants in the workshop itself, there is also a much wider group of potential beneficiaries. The form of their benefits will vary markedly between the different areas, being largely academic in some cases and quite close to the industrial market in others. We consider two examples assuming, in each case, that the research in question will be enhanced by the workshop. A. Superfluidity and quantum turbulence. Most of the research in this area seeks basic scientific understanding. We anticipate that progress in understanding quantum turbulence will reflect back on classical turbulence, leading to an enhanced understanding of turbulence in general. Thus, given the universality and importance of turbulence, the work promises to have a powerful cultural and technological impact in the longer term. We envisage impact in the following areas - (a) Academic, as discussed under Academic Beneficiaries. (b) Public. Everybody is familiar with turbulence. It arises for water in e.g. sinks, baths, rivers, and the sea. It also arises in the atmosphere, and most people are familiar with e.g. storms, hurricanes, and admonitions to fasten their seat-belts on encountering turbulent conditions. Hence an improved understanding of turbulence promises to make a significant cultural contribution to the lives of ordinary people. One can readily imagine long-term benefits for museum displays, textbooks, and popular science writing. (c) Industry. Although immediate industrial applications are not envisaged, the research impinges on an area of enormous practical and financial importance. Much of the energy used in air or sea transport, for example, goes into the creation of turbulence. If improved understanding leads eventually to even a small reduction in turbulence production, the corresponding energy savings would pay for the cost of the proposed Workshop many times over. We note that the cooling of large superconducting magnets (e.g. for the LHC at CERN) is achieved through the forced flow of liquid He- 4 at about 1.9K. Here again, any advances in reducing the turbulent dissipation will increase the performance and reliability of the magnets. B. Research in biomedical physics. Activity here covers the full range, extending from the seeking of basic physical and physiological understanding to near-market research on practical devices. Improved modelling of interacting physiological oscillators is a likely outcome of the workshop, and it will bear on existing and ongoing applications to congestive heart failure, anaesthesia depth monitoring, hypertension, tetraplegia, diabetes mellitus, post-acute myocardial infarction, and healthy ageing. In both cases, and for the other research threads not mentioned explicitly, there will be impact through: collaborative research (e.g. the EPSRC/NSF Lancaster-Manchester-Birmingham-Florida-Yale Materials World Network programme on quantum turbulence, and the several clinical collaborations between Lancaster and the Royal Lancaster Infirmary and other hospitals); production of trained people (PhD students and PDRAs); and scientific publications and presentations of different kinds. Further details are given in the Pathways to Impact document.