8,377 research outputs found

### Effective Range Corrections to Three-Body Recombination for Atoms with Large Scattering Length

Few-body systems with large scattering length a have universal properties
that do not depend on the details of their interactions at short distances. The
rate constant for three-body recombination of bosonic atoms of mass m into a
shallow dimer scales as \hbar a^4/m times a log-periodic function of the
scattering length. We calculate the leading and subleading corrections to the
rate constant which are due to the effective range of the atoms and study the
correlation between the rate constant and the atom-dimer scattering length. Our
results are applied to 4He atoms as a test case.Comment: 6 pages, 2 figures, improved discussion, final versio

### Efimov physics from a renormalization group perspective

We discuss the physics of the Efimov effect from a renormalization group
viewpoint using the concept of limit cycles. Furthermore, we discuss recent
experiments providing evidence for the Efimov effect in ultracold gases and its
relevance for nuclear systems.Comment: 22 pages, 4 figures (invited review submitted to Phil. Trans. Roy.
Soc. A

### Few-particle Green's functions for strongly correlated systems on infinite lattices

We show how few-particle Green's functions can be calculated efficiently for
models with nearest-neighbor hopping, for infinite lattices in any dimension.
As an example, for one dimensional spinless fermions with both nearest-neighbor
and second nearest-neighbor interactions, we investigate the ground states for
up to 5 fermions. This allows us not only to find the stability region of
various bound complexes, but also to infer the phase diagram at small but
finite concentrations.Comment: 4 pages with 4 figures + 7 pages with 2 figures of suppl. materia

### Ultracold three-body collisions near overlapping Feshbach resonances

We present a comprehensive collection of ultracold three-body collisions
properties near overlapping Feshbach resonances. Our results incorporate
variations of all scattering lengths and demonstrate novel collisional
behavior, such as atom-molecule interference effects. Taking advantage of the
unique ways in which these collisions reflect Efimov physics, new pathways to
control atomic and molecular losses open up. Further, we show that overlapping
resonances can greatly improve the chances of observing multiple Efimov
features in an ultracold quantum gas for nearly any system.Comment: 4 pages, 3 figures, 1 tabl

### Technological prerequisites for indistinguishability of a person and his/her computer replica

Some people wrongly believe that A. Turingâ€™s works that underlie all modern computer science never discussed â€śphysicalâ€ť robots. This is not so, since Turing did speak about such machines, though making a reservation that this discussion was still premature. In particular, in his 1948 report [8], he suggested that a physical intelligent machine equipped with motors, cameras and loudspeakers, when wandering through the fields of England, would present â€śthe danger to the ordinary citizen would be serious.â€ť [8, ]. Due to this imperfection of technology in the field of knowledge that we now call robotics, the methodology that he proposed was based on human speech, or rather on text. Other natural human skills were too difficult to implement, while the exchange of cues via written messages was much more accessible for engineering implementation in Turingâ€™s time. Nevertheless, since then, the progress of computer technology has taken forms that the founder of artificial intelligence could not have foreseen

### Condensates of Strongly-interacting Atoms and Dynamically Generated Dimers

In a system of atoms with large positive scattering length, weakly-bound
diatomic molecules (dimers) are generated dynamically by the strong
interactions between the atoms. If the atoms are modeled by a quantum field
theory with an atom field only, condensates of dimers cannot be described by
the mean-field approximation because there is no field associated with the
dimers. We develop a method for describing dimer condensates in such a model
based on the one-particle-irreducible (1PI) effective action. We construct an
equivalent 1PI effective action that depends not only on the classical atom
field but also on a classical dimer field. The method is illustrated by
applying it to the many-body behavior of bosonic atoms with large scattering
length at zero temperature using an approximation in which the 2-atom amplitude
is treated exactly but irreducible $N$-atom amplitudes for $N \ge 3$ are
neglected. The two 1PI effective actions give identical results for the atom
superfluid phase, but the one with a classical dimer field is much more
convenient for describing the dimer superfluid phase. The results are also
compared with previous work on the Bose gas near a Feshbach resonance.Comment: 10 figure

### Resonant Dimer Relaxation in Cold Atoms with a Large Scattering Length

Efimov physics refers to universal phenomena associated with a discrete
scaling symmetry in the 3-body problem with a large scattering length. The
first experimental evidence for Efimov physics was the recent observation of a
resonant peak in the 3-body recombination rate for 133Cs atoms with large
negative scattering length. There can also be resonant peaks in the atom-dimer
relaxation rate for large positive scattering length. We calculate the
atom-dimer relaxation rate as a function of temperature and show how
measurements of the relaxation rate can be used to determine accurately the
parameters that govern Efimov physics.Comment: 4 pages, 2 eps figures, normalization error in figures corrected,
equations unchange

### Linear correlations between 4He trimer and tetramer energies calculated with various realistic 4He potentials

In a previous work [Phys. Rev. A 85, 022502 (2012)] we calculated, with the
use of our Gaussian expansion method for few-body systems, the energy levels
and spatial structure of the 4He trimer and tetramer ground and excited states
using the LM2M2 potential, which has a very strong short-range repulsion. In
this work, we calculate the same quantities using the presently most accurate
4He-4He potential [M. Przybytek et al., Phys. Rev. Lett. 104, 183003 (2010)]
that includes the adiabatic, relativistic, QED and residual retardation
corrections. Contributions of the corrections to the tetramer
ground-(excited-)state energy, -573.90 (-132.70) mK, are found to be,
respectively, -4.13 (-1.52) mK, +9.37 (+3.48) mK, -1.20 (-0.46) mK and +0.16
(+0.07) mK. Further including other realistic 4He potentials, we calculated the
binding energies of the trimer and tetramer ground and excited states, B_3^(0),
B_3^(1), B_4^(0) and B_4^(1), respectively. We found that the four kinds of the
energies for the different potentials exhibit perfect linear correlations
between any two of them over the range of binding energies relevant for 4He
atoms (namely, six types of the generalized Tjon lines are given). The
dimerlike-pair model for 4He clusters, proposed in the previous work, predicts
a simple universal relation B_4^(1)/B_2 =B_3^(0)/B_2 + 2/3, which precisely
explains the correlation between the tetramer excited-state energy and the
trimer ground-state energy, with B_2 being the dimer binding energy.Comment: 10 pages, 3 figures, published version in Phys. Rev. A85, 062505
(2012), Figs. 2, 5, and 6 added, minor changes in the description of the
dimerlike-pair mode

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