1 July - 31 December 1994

**Organisers**: T W B Kibble (*Imperial College*), A J Bray (*Manchester*), R M Ward (*Durham*)

Topological defects appear in a vast array of physical situations, ranging from unified theories of elementary particles at the very highest energy scales to low temperature laboratory phenomena near absolute zero. These defects exhibit remarkably similar behaviour, whether it be the reconnection of cosmic strings or of superfluid vortices, or the evolution of a defect network in a liquid crystal or in an expanding universe. Despitethis very substantial overlap, there has been surprisingly little interaction between particle physicists and condensed-matter theorists. Indeed, it is not difficult to cite examples of closely related advances which were arrived at independently, a notable example being the simultaneous recognition of the relevance of homotopy theory for classifying topological defects. This programme aims to rectify this deficiency, while furthering the mathematical study of topological defects in each of their primary contexts. The programme will bring together experts in field theory, cosmology, geometry, condensed-matter physics and high-energy particle physics.

There will be a regular seminar programme throughout the period. Additional topical meetings have been arranged as follows:

14--15 July:

**Topological Defects in Superfluids, Superconductors and Liquid Crystals**Principal lecturers:

A. Leggett, P. McClintock, M. Moore, J. Toner, H. Toyoki, A. Dorsey, P. Shah

21 August--3 September:

**Advanced Study Institute on Formation and Interactions of Topological Defects**Principal lecturers:

A Bray, B Carter, R Durrer, N Goldenfeld, T Kibble, M Kleman, H Kleinert, N Manton, G Mazenko, R Rivers, P Shellard, J Toner, N Turok, B Yurke, W Zurek.

- 12--13 September:
**Defects in First-order Phase Transitions** - 19 September: Spitalfields Day, sponsored by the London Mathematical Society, on
**Soliton Dynamics and Moduli Spaces** - 12--13 October: Numerical Approaches to Defect Evolution

The following are expected to participate in the programme for the periods indicated:

**Ach A** 21 Aug--3 Sep, 1 Nov--19 Nov, **Albrecht, B** 17 Jul--31 Jul, 21 Aug--3 Sep, **Allen, B** 17 Sep--16 Dec, **Bhattacharjee, P** 14 Aug--10 Sep, **Bogolubsky, I** 21 Aug--17 Sep, **Borrill, J** 21 Aug--3 Sep, 18 Sep--29 Oct, **Boyanovsky, D** 21 Aug--3 Sep, 9 Oct--29 Oct, **Brandenburger, R** 7 Jul--31 Aug, 1 Nov--16 Dec, **Bray, A** 21 Aug--17 Dec, **Caldwell, R** 14 Jul--7 Aug, **Carter, B** 21 Aug--17 Sep, **Chudnovsky, E** 1 Aug--21 Aug, **Chuong, N** 30 Oct--16 Dec, **Copeland, E** 2 Oct--16 Dec, **Davis, A** 7 Jul--16 Dec, **De Vega, H** 7--15 Jul, 28 Aug--3 Sep, 16--30 Oct, **Dorsey, A** 7 Jul--31 Jul, **Duff, M** 1 Sep--17 Dec, **Gleiser, M** 1 Dec--10 Dec, **Gottlieb, D** 31 Oct--26 Nov, **Hindmarsh, M** 30 Oct--16 Dec, **Holman, R** 24 Jul--28 Aug, **Jackiw, R**21 Aug--3 Sep, **Kephart, T** 2 Oct--29 Oct, **Kibble, T** 7 Jul--17 Dec, **Kleman M** 21 Aug--30 Sep, **Lee, C** 15 Aug--30 Aug, **Lee, K** 7 Jul--30 Jul, **Leggett, A** 7 Jul--30 Jul, **Letelier, P** 2 Oct--16 Dec, **Liddle, A** 21 Aug--3 Sep, 30 Oct--19 Nov, **Lyth, D** 1 Oct--17 Dec, **Maharana, J** 2 Oct--29 Oct, **Mazenko, G** 15 Aug--16 Sep, **Monastyrsky, M** 21 Aug--15 Oct, **Montgomery, R** 1 Aug--16 Dec, **Nattermann, T** 1 Aug--14 Aug, **Nunes, J** 17 Jul--30 Jul, **Pi, S** 21 Aug--3 Sep, **Pranevicius, L** 7 Jul--13 Aug, **Puri, S** 1 Oct--7 Dec, **Rey, S** 7 Jul--23 Jul, 14 Aug--3 Sep, **Rivers, R** 22 Aug--30 Sep, **Rivier, N** 21 Aug--30 Sep, **Rutenberg, A** 2 Oct--16 Dec, **Sakellariadou, M** 7 Aug--3 Sep, **Salomaa, M** 21 Aug--17 Sep, **Sasaki, M** 2 Oct--29 Oct, **Schroers, B** 7 Aug--3 Sep, 27 Nov--16 Dec, **Schwarz, A** 1 Jul--17 Jul, 1 Aug--20 Sep, **Shafi, Q** 27 Jul--20 Aug, **Sikivie, P** 14 Nov--16 Dec, **Sluckin, T** 16 Oct--12 Nov, **Stebbins, A** 17 Jul--15 Oct, **Toner, J** 7 Jul--30 Jul, 21 Aug--3 Sep, **Toyoki, H** 16 Jul--15 Sep, **Trebin, H** 25 Jul--31 Oct, **Turok, N** 7 Jul--16 Dec, **Vachaspati, T** 7 Jul--16 Dec, **Vilenkin, A** 1 Aug--3 Sep, **Ward, R** 7 Jul--17 Dec, **Weinberg, E** 7 Jul--31 Jul, **Zakrzewski, W** 1 Aug--30 Sep, **Zurek, W** 18 Aug--3 Sep, 11 Sep--1 Oct

Topological defects appear in a vast array of physical situations, ranging from unified theories of elementary particles at the very highest energy scales to low temperature laboratory phenomena near absolute zero. These defects exhibit remarkably similar behaviour, whether it be the reconnection of cosmic strings or of superfluid vortices, or the evolution of a defect network in a liquid crystal or in an expanding universe. Despite this very substantial overlap, there has been surprisingly little interaction between particle physicists and condensed-matter theorists. Indeed, it is not difficult to cite examples of closely related advances which were arrived at independently, a notable example being the simultaneous recognition of the relevance of homotopy theory for classifying topological defects. This programme aims to rectify this deficiency, while furthering the mathematical study of topological defects in each of their primary contexts. The programme will bring together experts in field theory, cosmology, geometry, condensed-matter physics and high-energy particle physics.