165 research outputs found
An Effective Theory for the Four-Body System
We consider the non-relativistic four-body system with large scattering
length and short-range interactions within an effective theory with contact
interactions only. We compute the binding energies of the 4He tetramer and of
alpha-particle. The well-known linear correlation between the three-body
binding energies and the four-body binding energies of these physical systems
can be understood as a consequence of the absence of a four-body force at
leading order.Comment: 3 pages, 2 ps figures, oral contribution, 19th European Few-Body
Conference (EFB2004), Groningen, Netherlands, August 23 - August 27, 200
Universality in the triton charge form factor
We consider the three-nucleon system within an effective theory with contact
interactions at leading order in the large scattering length. We calculate the
charge form factor of the triton at low momentum transfer and extract the
triton charge radius. At this order, no two-body currents contribute and the
calculation can be performed in the impulse approximation. We also comment on
the power counting for higher orders. The requirement of a three-body force for
renormalization of the three-nucleon system explains the previously observed
correlation between the triton binding energy and charge radius for different
model potentials.Comment: 11 pages, 2 eps figures, revtex4, version to appear in Nucl. Phys.
Large-N droplets in two dimensions
Using lattice effective field theory, we study the ground state binding
energy of N distinct particles in two dimensions with equal mass interacting
weakly via an attractive SU(N)-symmetric short range potential. We find that in
the limit of zero range and large N, the ratio of binding energies
B_{N}/B_{N-1} approaches the value 8.3(6).Comment: 18 pages, 6 figures, version to appear in Phys. Rev.
Effective Range Corrections in Few-Body Systems with large Scattering Length
The effective field theory with contact interactions alone is a powerful tool
to compute low-energy observables for three-body systems with large scattering
length. Recent calculations including effective range corrections are discussed
and results are presented.Comment: 5 pages, 2 figures, talk given at the 18th International IUPAP
Conference on Few-Body Problems in Physics, August 21-26 2006, Santos, Sao
Paulo, Brazi
Threshold behavior of bosonic two-dimensional few-body systems
Bosonic two-dimensional self-bound clusters consisting of atoms
interacting through additive van der Waals potentials become unbound at a
critical mass m*(N); m*(N) has been predicted to be independent of the size of
the system. Furthermore, it has been predicted that the ground state energy
E(N) of the N-atom system varies exponentially as the atomic mass approaches
m*. This paper reports accurate numerical many-body calculations that allow
these predictions to be tested. We confirm the existence of a universal
critical mass m*, and show that the near-threshold behavior can only be
described properly if a previously neglected term is included. We comment on
the universality of the energy ratio E(N+1)/E(N) near threshold.Comment: 6 pages, 3 figure
Beyond universality in three-body recombination: an Effective Field Theory treatment
We discuss the impact of a finite effective range on three-body systems
interacting through a large two-body scattering length. By employing a
perturbative analysis in an effective field theory well suited to this scale
hierarchy we find that an additional three-body parameter is required for
consistent renormalization once range corrections are considered. This allows
us to extend previously discussed universal relations between different
observables in the recombination of cold atoms to account for the presence of a
finite effective range. We show that such range corrections allow us to
simultaneously describe the positive and negative scattering-length loss
features observed in recombination with Lithium-7 atoms by the Bar-Ilan group.
They do not, however, significantly reduce the disagreement between the
universal relations and the data of the Rice group on Lithium-7 recombination
at positive and negative scattering lengths.Comment: 15 pages, 4 figure
Universal Properties of the Four-Body System with Large Scattering Length
Few-body systems with large scattering length have universal properties that
do not depend on the details of their interactions at short distances. We study
the universal bound state properties of the four-boson system with large
scattering length in an effective quantum mechanics approach. We compute the
four-body binding energies using the Yakubovsky equations for positive and
negative scattering length. Moreover, we study the correlation between three-
and four-body energies and present a generalized Efimov plot for the four-body
system. These results are useful for understanding the cluster structure of
nuclei and for the creation of weakly-bound tetramers with cold atoms close to
a Feshbach resonance.Comment: 14 pages, 4 ps figures, minor changes, version to appear in EPJ
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