9 research outputs found
Time-Dependent Variational Principle for Field Theory: RPA Approximation and Renormalization (II)
The Gaussian-time-dependent variational equations are used to explored the
physics of field theory. We have investigated the static
solutions and discussed the conditions of renormalization. Using these results
and stability analysis we show that there are two viable non-trivial versions
of . In the continuum limit the bare coupling constant can
assume and , which yield well defined asymmetric and
symmetric solutions respectively. We have also considered small oscillations in
the broken phase and shown that they give one and two meson modes of the
theory. The resulting equation has a closed solution leading to a ``zero mode''
and vanished scattering amplitude in the limit of infinite cutoff.Comment: 29 pages, LaTex file, to appear in Annals of Physic
Gaussian Time-Dependent Variational Principle for Bosons I - Uniform Case
We investigate the Dirac time-dependent variational method for a system of
non-ideal Bosons interacting through an arbitrary two body potential. The
method produces a set of non-linear time dependent equations for the
variational parameters. In particular we have considered small oscillations
about equilibrium. We obtain generalized RPA equations that can be understood
as interacting quasi-bosons, usually mentioned in the literature as having a
gap. The result of this interaction provides us with scattering properties of
these quasi-bosons including possible bound-states, which can include zero
modes. In fact the zero mode bound state can be interpreted as a new
quasi-boson with a gapless dispersion relation. Utilizing these results we
discuss a straightforward scheme for introducing temperature.Comment: 28 pages, 1 figure to appear in Annals of Physic
A Complex Chemical Potential: Signature of Decay in a Bose-Einstein Condensate
We explore the zero-temperature statics of an atomic Bose-Einstein condensate
in which a Feshbach resonance creates a coupling to a second condensate
component of quasi-bound molecules. Using a variational procedure to find the
equation of state, the appearance of this binding is manifest in a collapsing
ground state, where only the molecular condensate is present up to some
critical density. Further, an excited state is seen to reproduce the usual
low-density atomic condensate behavior in this system, but the molecular
component is found to produce an underlying decay, quantified by the imaginary
part of the chemical potential. Most importantly, the unique decay rate
dependencies on density () and on scattering length () can be measured in experimental tests of this theory.Comment: 4 pages, 1 figur
Prospect of creating a composite fermi/bose superfluid
We show that composite fermi/bose superfluids can be created in cold-atom
traps by employing a Feshbach resonance or coherent photoassociation. The
bosonic molecular condensate created in this way implies a new fermion pairing
mechanism associated with the exchange of fermion pairs between the molecular
condensate and an atomic fermion superfluid. We predict macroscopically
coherent, Josephson-like oscillations of the atomic and molecular populations
in response to a sudden change of the molecular energy, and suggest that these
oscillations will provide an experimental signature of the pairing.Comment: Rejected by PR