Simulating non-commutative field theory

Non-commutative (NC) field theories can be mapped onto twisted matrix models. This mapping enables their Monte Carlo simulation, where the large N limit of the matrix models describes the continuum limit of NC field theory. First we present numeric results for 2d NC gauge theory of rank 1, which turns out to be renormalizable. The area law for the Wilson loop holds at small area, but at large area we observe a rotating phase, which corresponds to an Aharonov-Bohm effect. Next we investigate the NC phi^4 model in d=3 and explore its phase diagram. Our results agree with a conjecture by Gubser and Sondhi in d=4, who predicted that the ordered regime splits into a uniform phase and a phase dominated by stripe patterns.Comment: 6 pages, 7 figures, Lattice2002(theoretical

Large N reduction with overlap fermions

We revisit quenched reduction with fermions and explain how some old problems can be avoided using the overlap Dirac operator.Comment: Lattice2002(chiral) 3 pages, no figure

Supersymmetry on the lattice

Lattice results in supersymmetry are summarized. Past, present and future perspectives are discussed.Comment: 13 pages, 4 figures, Plenary Talk at Lattice 2002(plenary), MIT, USA. Typos correcte

The chaparral vegetation in Mexico under nonmediterranean climate: The convergence and Madrean-Tethyan hypotheses reconsidered

11 páginas, 4 figuras, 5 tablas.A comparative study between an unburned evergreen sclerophyllous vegetation located in south-central Mexico under a wet-summer climate, with mediterranean regions was conducted in order to re-analyze vegetation and plant characters claimed to converge under mediterranean climates. The comparison considered floristic composition, plant-community structure, and plant characters as adaptations to mediterranean climates and analyzed them by means of a correspondence analysis, considering a tropical spiny shrubland as the external group. We made a species register of the number of species that resprouted after a fire occurred in 1995 and a distribution map of the evergreen sclerophyllous vegetation in Mexico (mexical) under nonmediterranean climates. The Tehuacan mexical does not differ from the evergreen sclerophyllous areas of Chile, California, Australia, and the Mediterranean Basin, according to a correspondence analysis, which ordinated the Tehuacan mexical closer to the mediterranean areas than to the external group. All the vegetation and floristic characteristics of the mexical, as well as its distribution along the rain-shadowed mountain parts of Mexico, support its origin in the Madrean-Tethyan hypothesis of Axelrod. Therefore, these results allow to expand the convergence paradigm of the chaparral under an integrative view, in which a general trend to aridity might explain floristic and adaptive patterns detected in these environments.Peer reviewe