982 research outputs found
Broken Symmetries from Minimally Doubled Fermions
Novel chirally symmetric fermion actions containing the minimum amount of
fermion doubling have been recently proposed in the literature. We study the
symmetries and renormalization of these actions and find that in each case,
discrete symmetries, such as parity and time-reversal, are explicitly broken.
Consequently, when the gauge interactions are included, these theories
radiatively generate relevant and marginal operators. Thus the restoration of
these symmetries and the approach to the continuum limit require the
fine-tuning of several parameters. With some assumptions, we show that this
behavior is unavoidable for actions displaying minimal fermion doubling.Comment: 13 pages, 3 figures, published version, analysis reorganized and
condense
Universal Equation for Efimov States
Efimov states are a sequence of shallow 3-body bound states that arise when
the 2-body scattering length is large. Efimov showed that the binding energies
of these states can be calculated in terms of the scattering length and a
3-body parameter by solving a transcendental equation involving a universal
function of one variable. We calculate this universal function using effective
field theory and use it to describe the three-body system of 4He atoms. We also
extend Efimov's theory to include the effects of deep 2-body bound states,
which give widths to the Efimov states.Comment: 8 pages, revtex4, 2 ps figures, table with numerical values of
universal function adde
Universality in the Three-Body Problem for 4He Atoms
The two-body scattering length a for 4He atoms is much larger than their
effective range r_s. As a consequence, low-energy few-body observables have
universal characteristics that are independent of the interaction potential.
Universality implies that, up to corrections suppressed by r_s/a, all
low-energy three-body observables are determined by a and a three-body
parameter \Lambda_*. We give simple expressions in terms of a and \Lambda_* for
the trimer binding energy equation, the atom-dimer scattering phase shifts, and
the rate for three-body recombination at threshold. We determine \Lambda_* for
several 4He potentials from the calculated binding energy of the excited state
of the trimer and use it to obtain the universality predictions for the other
low-energy observables. We also use the calculated values for one potential to
estimate the effective range corrections for the other potentials.Comment: 23 pages, revtex4, 6 ps figures, references added, universal
expressions update
Liberating Efimov physics from three dimensions
When two particles attract via a resonant short-range interaction, three
particles always form an infinite tower of bound states characterized by a
discrete scaling symmetry. It has been considered that this Efimov effect
exists only in three dimensions. Here we review how the Efimov physics can be
liberated from three dimensions by considering two-body and three-body
interactions in mixed dimensions and four-body interaction in one dimension. In
such new systems, intriguing phenomena appear, such as confinement-induced
Efimov effect, Bose-Fermi crossover in Efimov spectrum, and formation of
interlayer Efimov trimers. Some of them are observable in ultracold atom
experiments and we believe that this study significantly broadens our horizons
of universal Efimov physics.Comment: 17 pages, 5 figures, contribution to a special issue of Few-Body
Systems devoted to Efimov Physic
Three-body problem in Fermi gases with short-range interparticle interaction
We discuss 3-body processes in ultracold two-component Fermi gases with
short-range intercomponent interaction characterized by a large and positive
scattering length . It is found that in most cases the probability of 3-body
recombination is a universal function of the mass ratio and , and is
independent of short-range physics. We also calculate the scattering length
corresponding to the atom-dimer interaction.Comment: 4 pages, 2 figure
Weakly bound atomic trimers in ultracold traps
The experimental three-atom recombination coefficients of the atomic states
Na, Rb and Rb,
together with the corresponding two-body scattering lengths, allow predictions
of the trimer bound state energies for such systems in a trap. The
recombination parameter is given as a function of the weakly bound trimer
energies, which are in the interval for large
positive scattering lengths, . The contribution of a deep-bound state to our
prediction, in the case of Rb, for a particular trap, is
shown to be relatively small.Comment: 5 pages, 1 figur
Quantum Corrections to Dilute Bose Liquids
It was recently shown (A. Bulgac. Phys. Rev. Lett. {\bf 89}, 050402 (2002))
that an entirely new class of quantum liquids with widely tunable properties
could be manufactured from bosons (boselets), fermions (fermilets) and their
mixtures (ferbolets) by controlling their interaction properties by the means
of a Feshbach resonance. We extend the previous mean--field analysis of these
quantum liquids by computing the lowest order quantum corrections to the ground
state energy and the depletion of the Bose--Einstein condensate and by
estimating higher order corrections as well. We show that the quantum
corrections are relatively small and controlled by the diluteness parameter
, even though strictly speaking in this case there is no
low density expansion.Comment: final published version, typos corrected, updated references and
added one referenc
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