404 research outputs found
Triton Binding Energy and Minimal Relativity
For relativistic three-body calculations, essentially two different
approaches are in use: field theory and relativistic direct interactions.
Results for relativistic corrections of the triton binding energy obtained from
the two approaches differ even in their sign, which is rather puzzling. In this
paper, we discuss the origin of such discrepancy. We show that the use of an
invariant two-body amplitude, as done in the field-theoretic approach,
increases the triton binding energy by about 0.30 MeV. This may explain a large
part of the discrepancy.Comment: 11 pages, LaTeX, no figure
Relativistic calculation of the triton binding energy and its implications
First results for the triton binding energy obtained from the relativistic
spectator or Gross equation are reported. The Dirac structure of the nucleons
is taken into account. Numerical results are presented for a family of
realistic OBE models with off-shell scalar couplings. It is shown that these
off-shell couplings improve both the fits to the two-body data and the
predictions for the binding energy.Comment: 5 pages, RevTeX 3.0, 1 figure (uses epsfig.sty
Few-Body Physics -- Then and Now
A summary of the XIV\underline{th} International Conference on Few-body
Problems In Physics is given, with an emphasis on the important problems solved
recently and the prognosis for the future of the field. Personal remarks and
``homework'' problem assignments are made.Comment: 17 pages, 1 fig., LA-UR-94-213
Nuclear Forces and Nuclear Structure
After a historical review, I present the progress in the field of realistic
NN potentials that we have seen in recent years. A new generation of very
quantitative (high-quality/high-precision) NN potentials has emerged. These
potentials will serve as reliable input for microscopic nuclear structure
calculations and will allow for a systematic investigation of off-shell
effects. The issue of three-nucleon forces is also discussed.Comment: Invited Talk presented at Nuclear Structure '98, Gatlinburg,
Tennessee, August 10-15, 1998; 15 pages, 6 figures, aipproc2.sty and
epsfig.st
Triton calculations with and exchange three-nucleon forces
The Faddeev equations are solved in momentum space for the trinucleon bound
state with the new Tucson-Melbourne and exchange three-nucleon
potentials. The three-nucleon potentials are combined with a variety of
realistic two-nucleon potentials. The dependence of the triton binding energy
on the cut-off parameter in the three-nucleon potentials is studied
and found to be reduced compared to the case with pure exchange. The
exchange parts of the three-nucleon potential yield an overall repulsive
effect. When the recommended parameters are employed, the calculated triton
binding energy turns out to be very close to its experimental value.
Expectation values of various components of the three-nucleon potential are
given to illustrate their significance for binding.Comment: 17 pages Revtex 3.0, 4 figures. Accepted for publication in Phys.
Rev.
Quantitative Relativistic Effects in the Three-Nucleon Problem
The quantitative impact of the requirement of relativistic invariance in the
three-nucleon problem is examined within the framework of Poincar\'e invariant
quantum mechanics. In the case of the bound state, and for a wide variety of
model implementations and reasonable interactions, most of the quantitative
effects come from kinematic factors that can easily be incorporated within a
non-relativistic momentum-space three-body code.Comment: 15 pages, 15 figure
Lorentz boosted NN potential for few-body systems: Application to the three-nucleon bound state
A Lorentz boosted two-nucleon potential is introduced in the context of equal time relativistic quantum mechanics. The dynamical input for the boosted nucleon-nucleon (NN) potential is based on realistic NN potentials, which by a suitable scaling of the momenta are transformed into NN potentials belonging to a relativistic two-nucleon Schrödinger equation in the c.m. system. This resulting Lorentz boosted potential is consistent with a previously introduced boosted two-body t matrix. It is applied in relativistic Faddeev equations for the three-nucleon bound state to calculate the 3H binding energy. Like in previous calculations the boost effects for the two-body subsystems are repulsive and lower the binding energy
Quantum Monte Carlo Studies of Relativistic Effects in Light Nuclei
Relativistic Hamiltonians are defined as the sum of relativistic one-body
kinetic energy, two- and three-body potentials and their boost corrections. In
this work we use the variational Monte Carlo method to study two kinds of
relativistic effects in the binding energy of 3H and 4He. The first is due to
the nonlocalities in the relativistic kinetic energy and relativistic one-pion
exchange potential (OPEP), and the second is from boost interaction. The OPEP
contribution is reduced by about 15% by the relativistic nonlocality, which may
also have significant effects on pion exchange currents. However, almost all of
this reduction is canceled by changes in the kinetic energy and other
interaction terms, and the total effect of the nonlocalities on the binding
energy is very small. The boost interactions, on the other hand, give repulsive
contributions of 0.4 (1.9) MeV in 3H (4He) and account for 37% of the
phenomenological part of the three-nucleon interaction needed in the
nonrelativistic Hamiltonians.Comment: 33 pages, RevTeX, 11 PostScript figures, submitted to Physical Review
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