Requirements for a Computerised Rail Passenger Service Information System – Results of Surveys at Doncaster, Woking, Euston, Halifax and Gatwick

The backround, survey methodology of this research project, and the results of surveys at Leeds City station have been discussed in Working paper 206. In this Paper we put forward the result of surveys at Doncaster, Woking, Euston, Halifax and Gatwick. For the most part, the results are similar to those given for Leeds in the earlier paper. Notable differences, however, are the much greater proportion of 'other station to other station' enquiries at Woking (37%), Euston (22%) and Gatwick (33%). Enquiries at Woking and Gatwick took longer to answer than elsewhere. Conversely, Halifax, with a higher proportion of enquiries relating to local journeys, produced the fastest answers. A summary of results from all the surveys, together with discussion of a survey on the use of the Prestel terminals provided for passengers at Kings Cross and overall conclusions from the study will be reported in a separate paper (Working Paper 208)

Sequentially Cohen-Macaulay matroidal ideals

Let $R=K[x_1,...,x_n]$ be the polynomial ring in $n$ variables over a field $K$ and let $J$ be a matroidal ideal of degree $d$ in $R$. In this paper, we study the class of sequentially Cohen-Macaulay matroidal ideals. In particular, all sequentially Cohen-Macaulay matroidal ideals of degree $2$ are classified. Furthermore, we give a classification of sequentially Cohen-Macaulay matroidal ideals of degree $d\geq 3$ in some special cases.Comment: 12 pages, Comments are welcome

Folding Branes

We study classical dynamics of a probe Dp-brane moving in a background sourced by a stack of Dp-branes. In this context the physics is similar to that of the effective action for open-string tachyon condensation, but with a power-law runaway potential. We show that small inhomogeneous ripples of the probe brane embedding grow with time, leading to folding of the brane as it moves. We give a full nonlinear analytical treatment of inhomogeneous brane dynamics, suitable for the Dirac-Born-Infeld + Wess-Zumino theory with arbitrary runaway potential, in the case where the source branes are BPS. In the near-horizon geometry, the inhomogeneous brane motion has a dual description in terms of free streaming of massive relativistic test particles originating from the initial hypersurface of the probe brane. We discuss limitations of the effective action description around loci of self-crossing of the probe brane (caustics). We also discuss the effect of brane folding in application to the theory of cosmological fluctuations in string theory inflation.Comment: 15 pages, 2 figures, LaTe