Dr Michael Teper

Abstract:

We test a variety of blocking and smearing algorithms for constructing glueball and string wave-functionals, and find some with much improved overlaps onto the lightest states. We use these algorithms to obtain improved results on the tensions of k-strings in SU(4), SU(6), and SU(8) gauge theories. We emphasise the major systematic errors that still need to be controlled in calculations of heavier k-strings, and perform calculations in SU(4) on an anisotropic lattice in a bid to minimise one of these. All these results point to the k-string tensions lying part-way between the 'MQCD' and 'Casimir Scaling' conjectures, with the power in 1/N of the leading correction lying ∈ [1,2]. We also obtain some evidence for the presence of quasi-stable strings in calculations that do not use sources, and observe some near-degeneracies between (excited) strings in different representations. We also calculate the lightest glueball masses for N = 2,..., 8, and extrapolate to N = ∞, obtaining results compatible with earlier work. We show that the N = ∞ factorisation of the euclidean correlators that are used in such mass calculations does not make the masses any less calculable at large N. © SISSA/ISAS 2004.

Abstract:

We present our latest results on the glueball spectrum of SU(N) gauge theories in 2+1 dimensions for spins ranging from 0 to 6 inclusive, as well as preliminary results for SU(3) in 3+1 dimensions. Simple glueball models and the relation of the even-spin spectrum to the 'Pomeron' are discussed.

Abstract:

We investigate spontaneous chiral symmetry breaking in SU(N) gauge theories at large N using overlap fermions. The exact zero modes and the low-lying modes of the Dirac operator provide the tools to gain insight into the interplay between chiral symmetry breaking and topology. We find that topology indeed drives chiral symmetry breaking at N = 3 as well as at large N. By comparing the results on various volumes and at different lattice spacings we are able to show that our conclusions are not affected by finite volume effects and also hold in the continuum limit. We then address the question whether the topology can be usefully described in terms of instantons. © 2004 Elsevier B.V. All rights reserved.

Abstract:

We study the deconfinement phase transition in SU(N) gauge theories for N=2,3,4,6,8. The transition is first order for N ≥ 3, with the strength increasing as N increases. We extrapolate Tc/σ to the continuum limit for each N, and observe a rapid approach to the large N limit. As N increases the phase transition becomes clear-cut on smaller spatial volumes, indicating the absence of (non-singular) finite volume corrections at N = ∞ - reminiscent of large N reduction. The observed rapid increase of the inter-phase surface tension with N may indicate that for N = ∞ the deconfinement transition cannot, in practise, occur. © 2004 Published by Elsevier B.V.