One of the fundamental contributions of mathematical logic has been the precise definition and study of algorithms and the closely associated study of recursively enumerable sets. A subset A £ co is recursive (decidable) if there is an algorithm for computing its characteristic function cA and recursively enumerable (r.e.) if there is an algorithm for generating its members. Nonrecursive r.e. s...

DENSLOW M. W. (Department of Biology, Appalachian State University, Boone, NC 28608), M. W. PALMER (Department of Botany, Oklahoma State University, Stillwater, OK 74078), AND Z. E. MURRELL (Department of Biology, Appalachian State University, Boone, NC 28608). Patterns of native and exotic vascular plant richness along an elevational gradient from sea level to the summit of the Appalachian Mou...

I discuss gauge coupling unification in a class of superstring standard–like models, which are derived in the free fermionic formulation. Recent calculations indicate that the superstring unification scale is at O(10GeV ) while the minimal supersymmetric standard model is consistent with LEP data if the unification scale is at O(10)GeV . A generic feature of the superstring standard–like models...

We show that a modification of the BRST lattice quantization allows to circumvent an old paradox, formulated by Neuberger, related to lattice Gribov copies and nonperturbative BRST invariance. In the continuum limit the usual BRST formulation is recovered. ⋆ Address until August 31st, 1998. ⋆⋆ Permanent address.

In this talk I review some aspects of the idea that there is an infra-red conformal fixedpoint at the TeV scale. In particular, it is shown how gauge coupling unification can be achieved by TeV unification in a semi-simple gauge group.

This Letter addresses a provocative question: “Can the standard electroweak Higgs doublets and their color-triplet partners be the messengers of a low energy gaugemediated SUSY breaking?” Such a possibility does not seem to be immediately ruled out. If so, it can lead to a very economical scheme with clear-cut predictions quite distinct from those of the conventional gauge-mediated scenario. Na...

We analyze the bound on gauge couplings e ≥ m/mp, suggested by Arkani-Hamed et.al. We show this bound can be derived from simple semi-classical considerations and holds in spacetime dimensions greater than or equal to four. Non abelian gauge symmetries seem to satisfy the bound in a trivial manner. We comment on the case of discrete symmetries and close by performing some checks for the bound i...

A gauge invariant procedure for extracting combined SO(3)-Z2 monopoles in positive-plaquette SU(2) lattice gauge theory is shown. When these monopoles are eliminated through a constraint, the theory deconfines for all β on 12 and 20 lattices even in the strong coupling limit, despite a rather strong average plaquette of around 0.64. This corresponds to an effective Wilson β of 2.45, at which Wi...