We demonstrate how to create artificial external non-Abelian gauge potentials acting on cold atoms in optical lattices. The method employs atoms with k internal states, and laser assisted state sensitive tunneling, described by unitary k x k matrices. The single-particle dynamics in the case of intense U2 vector potentials lead to a generalized Hofstadter butterfly spectrum which shows a complex mothlike structure. We discuss the possibility to realize non-Abelian interferometry (Aharonov-Bohm effect) and to study many-body dynamics of ultracold matter in external lattice gauge fields.

For the 3D gonihedric Ising models defined by Savvidy and Wegner the bare string tension is zero and the energy of a spin interface depends only on the number of bends and self-intersections, in antithesis to the standard nearest-neighbour 3D Ising action. When the parameter κ weighting the self-intersections is small the model has a first order transition and when it is larger the transition is continuous. In this paper we investigate the scaling of the renormalized string tension, which is entirely generated by fluctuations, using Monte Carlo simulations for κ = 0.0, 0.1, 0.5 and 1.0. The scaling of the string tension allows us to obtain an estimate for the critical exponents α and ν using both finite-size-scaling and data collapse for the scaling function. The behaviour of the string tension when the self-avoidance parameter κ is small also clearly demonstrates the first order nature of the transition in this case, in contrast to larger values. Direct estimates of α are in good agreement with those obtained from the scaling of the string tension. We have also measured γ/ν.(a) Permanent Address:

No abstract

No abstract