8,197 research outputs found
Universal Properties of the Four-Boson System in Two Dimensions
We consider the nonrelativistic four-boson system in two dimensions
interacting via a short-range attractive potential. For a weakly attractive
potential with one shallow two-body bound state with binding energy B_2, the
binding energies B_N of shallow N-body bound states are universal and thus do
not depend on the details of the interaction potential. We compute the
four-body binding energies in an effective quantum mechanics approach. There
are exactly two bound states: the ground state with B_4^(0)=197.3(1)B_2 and one
excited state with B_4^(1)=25.5(1)B_2. We compare our results to recent
predictions for N-body bound states with large N>>1.Comment: 7 pages, 1 ps figure, references and discussion added, final versio
Efimov Physics around the neutron rich Calcium-60 isotope
We calculate the neutron-Calcium-60 S-wave scattering phase shifts using
state of the art coupled-cluster theory combined with modern ab initio
interactions derived from chiral effective theory. Effects of three-nucleon
forces are included schematically as density dependent nucleon-nucleon
interactions. This information is combined with halo effective field theory in
order to investigate the Calcium-60-neutron-neutron system. We predict
correlations between different three-body observables and the two-neutron
separation energy of Calcium-62. This provides evidence of Efimov physics along
the Calcium isotope chain. Experimental key observables that facilitate a test
of our findings are discussed.Comment: 5 pages, 4 figure
Coherent polychotomous waves from an attractive well
A novel effect of a wave packet scattering off an attractive one- dimensional
well is found numerically and analytically. For a wave packet narrower than the
width of the well, the scattering proceeds through a quasi-bound state of
almost zero energy. The wave reflected from the well is a polychotomous
(multiple peak) monochromatic and coherent train. The transmitted wave is a
spreading smooth wave packet. The effect is strong for low average speeds of
the packet, and it disappears for wide packets.Comment: Latex, 8 eps figure
Comment on "Measurement of time of arrival in quantum mechanics"
The analysis of the model quantum clocks proposed by Aharonov et al. [Phys.
Rev. A 57 (1998) 4130 - quant-ph/9709031] requires considering evanescent
components, previously ignored. We also clarify the meaning of the operational
time of arrival distribution which had been investigated.Comment: 3 inlined figures; comment on quant-ph/970903
Wave packet scattering from an attractive well
Wave packet scattering off an attractive well is investigated in two spatial
dimensions numerically. The results confirm what was found previously for the
one dimensional case. The wave scattered at large angles is a polychotomous
(multiple peak) coherent train. Large angle scattering is extremely important
for low impinging velocities and at all impact parameters. The effect
disappears for packets more extended than the well. Experiments to detect the
polychotomous behavior are suggested.Comment: Final version, Journal of Physics A, to be publishe
Generalized Swiss-cheese cosmologies: Mass scales
We generalize the Swiss-cheese cosmologies so as to include nonzero linear
momenta of the associated boundary surfaces. The evolution of mass scales in
these generalized cosmologies is studied for a variety of models for the
background without having to specify any details within the local
inhomogeneities. We find that the final effective gravitational mass and size
of the evolving inhomogeneities depends on their linear momenta but these
properties are essentially unaffected by the details of the background model.Comment: 10 pages, 14 figures, 1 table, revtex4, Published form (with minor
corrections
Direct calculation of the probability of pionium ionization in the target
We performed the first direct calculation of the probability of pionium
(pi+pi- atom) ionization in the target. The dependence of the probability of
pionium ionization in the target as a function of the pionium lifetime is
established. These calculations are of interest of the DIRAC experiment at
CERN, which aims to measure the pionium lifetime with high precision.Comment: 11 pages, 4 figures; submitted to "Physics of Atomic Nuclei"
("Yadernaya Fizika"
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