Can lattice data for two heavy-light mesons be understood in terms of simply two-quark potentials?

By comparing lattice data for the two heavy-light meson system (Q^2 qbar^2) with a standard many-body approach employing only interquark potentials, it is shown that the use of unmodified two-quark potentials leads to a gross overestimate of the binding energy.Comment: Contribution to LATTICE99 (Heavy Quarks). 3 pages, 2 ps figure

Searches for Compositeness at the Tevatron

Quark-quark and quark-lepton searches for compositenss at the Fermilab Tevatron are summarized. These are of the contact-interaction variety where sqrt(s-hat) < the hypothesized mass scales, Lambda. Tevatron experiments limit a variety of compositeness phenomena in the range from 1.9 to 8.3 TeV. These limits result from measurements of: the Ht spectrum (D0), dijet mass (D0), dijet angular distribution (CDF, D0), drell-yan production (CDF, D0), and the Neutral Current to Charged Current ratio (CCFR/NuTeV).Comment: Presented at VIIIth RENCONTRES DE BLOIS, with recent updates added. 7 Figure

Introduction to finite mixtures

Mixture models have been around for over 150 years, as an intuitively simple and practical tool for enriching the collection of probability distributions available for modelling data. In this chapter we describe the basic ideas of the subject, present several alternative representations and perspectives on these models, and discuss some of the elements of inference about the unknowns in the models. Our focus is on the simplest set-up, of finite mixture models, but we discuss also how various simplifying assumptions can be relaxed to generate the rich landscape of modelling and inference ideas traversed in the rest of this book.Comment: 14 pages, 7 figures, A chapter prepared for the forthcoming Handbook of Mixture Analysis. V2 corrects a small but important typographical error, and makes other minor edits; V3 makes further minor corrections and updates following review; V4 corrects algorithmic details in sec 4.1 and 4.2, and removes typo

The essential ideal is a Cohen-Macaulay module

Let G be a finite p-group which does not contain a rank two elementary abelian p-group as a direct factor. Then the ideal of essential classes in the mod-p cohomology ring of G is a Cohen-Macaulay module whose Krull dimension is the p-rank of the centre of G. This basically answers in the affirmative a question posed by J. F. Carlson.Comment: 6 page