Exact characterization of O(n) tricriticality in two dimensions

We propose exact expressions for the conformal anomaly and for three critical exponents of the tricritical O(n) loop model as a function of n in the range $-2 \leq n \leq 3/2$. These findings are based on an analogy with known relations between Potts and O(n) models, and on an exact solution of a 'tri-tricritical' Potts model described in the literature. We verify the exact expressions for the tricritical O(n) model by means of a finite-size scaling analysis based on numerical transfer-matrix calculations.Comment: submitted to Phys. Rev. Let

Resonances for coupled Bose-Einstein Condensates

We study some effects arising from periodic modulation of the asymmetry and the barrier height of a two-well potential containing a Bose-Einstein condensate. At certain modulation frequencies the system exhibits resonances, which may lead to enhancement of the tunneling rate between the wells and which can be used to control the particle distribution among the wells. Some of the effects predicted for a two-well system can be carried over to the case of a Bose-Einstein condensate in an optical lattice

Angular spectrum of quantized light beams

We introduce a generalized angular spectrum representation for quantized light beams. By using our formalism, we are able to derive simple expressions for the electromagnetic vector potential operator in the case of: {a)} time-independent paraxial fields, {b)} time-dependent paraxial fields, and {c)} non-paraxial fields. For the first case, the well known paraxial results are fully recovered.Comment: 3 pages, no figure

Modes of a rotating astigmatic optical cavity

Nuevamente sacado à luz, y de muchos errores purgadoMarca tip. en port.Texto a dos columnasDatos de ed. preceden a "segunda parte

Analogy between a two-well Bose-Einstein condensate and atom diffraction

We compare the dynamics of a Bose-Einstein condensate in two coupled potential wells with atoms diffracting from a standing light wave. The corresponding Hamiltonians have an identical appearance, but with a different set of commutation rules. Well-known diffraction phenomena as Pendellosung oscillations between opposite momenta in the case of Bragg diffraction, and adiabatic transitions between momentum states are shown to have analogies in the two-well case. They represent the collective exchange of a fixed number of atoms between the wells

Phase dynamics of a multimode Bose condensate controlled by decay

The relative phase between two uncoupled BE condensates tends to attain a specific value when the phase is measured. This can be done by observing their decay products in interference. We discuss exactly solvable models for this process in cases where competing observation channels drive the phases to different sets of values. We treat the case of two modes which both emit into the input ports of two beam splitters, and of a linear or circular chain of modes. In these latter cases, the transitivity of relative phase becomes an issue

Diffraction and trapping in circular lattices

When a single two-level atom interacts with a pair of Laguerre-Gaussian beams with opposite helicity, this leads to an efficient exchange of angular momentum between the light field and the atom. When the radial motion is trapped by an additional potential, the wave function of a single localized atom can be split into components that rotate in opposite direction. This suggests a novel scheme for atom interferometry without mirror pulses. Also atoms in this configuration can be bound into a circular lattice