My current research interests are mainly from a field called
"few-nucleon dynamics".
At present I am working on certain types of three-nucleon forces, and
on a relativistic description of the three-nucleon system and its
interaction with electromagnetic probes. Below is a short description
of few-nucleon dynamics, and of the basic ideas of a current research
project on the relativistic three-nucleon problem.
Few-Nucleon Dynamics
Introduction
Although Quantum chromodynamics (QCD) is widely believed to be the
fundamental theory of the strong interaction, it cannot be used directly
to explain the structure of nuclei or the features of nuclear reactions
observed in the laboratory at low and medium energies. This is due to
the strong coupling of its fundamental constituents, quarks and gluons,
which prevents the use of the almost only tool available to solve
quantum field theories, namely perturbation theory.
At energies relevant to nuclear physics away from extreme conditions,
quarks and gluons appear to be confined into hadrons, namely baryons
and mesons. It is therefore sensible, and has met with considerable
success, to describe nuclear phenomena in terms of nucleons (protons
and neutrons) and mesons, occasionally allowing for the formation of
more exotic baryons. In particular, the interaction between nucleons at
low energies can be described accurately through meson exchange
theories.
Research in few-nucleon dynamics deals with processes involving a small
number of nucleons, which can be analyzed with exact computational
methods. Since calculational approximations are avoided, the comparison
of theoretical predictions and experimental data makes it possible to
draw reliable conclusions about the quality of the employed dynamical
model.
It is of particular current interest to find out at which energies and
in which reactions these effective hadronic theories of nuclear
phenomena break down and have to be abandoned in favor of a quark-gluon
description. However, from the theoretical side, calculations at higher
energies are more complicated, because a nonrelativistic framework, such
as the Schrödinger equation with instantaneous potentials, is no
longer a good approximation. It is therefore important to find
relativistic alternatives that are still calculable.
Relativity in few-nucleon systems
One of several approaches to the relativistic few-body problem is the
so-called Spectator (or Gross) formalism. It leads to few-body
equations not too much more complicated than its nonrelativistic
counterpart, while maintaining relativistic covariance exactly. It has
been applied in recent years to a variety of few-nucleon problems, such
as two-nucleon scattering, the deuteron bound state, elastic
electron-deuteron scattering, and the three-nucleon bound state. Already
a number of interesting relativistic effects have been discovered in
these studies.
This research project continues the work on the relativistic
three-nucleon bound state within the Spectator framework. Given the
obtained relativistic 3He and 3H wave functions, elastic and inelastic
electron scattering from these light nuclei will be calculated and
compared to existing data and new experiments that are being performed
at Jefferson Lab. The results should provide a very good basis to test
our understanding of the short-distance properties of the nuclear
interaction as well as the electromagnetic structure of light nuclei.
Extensive analytic and numerical calculations, as well as collaboration
with and advice from foreign colleagues are required to accomplish
these tasks. Two students are planned to obtain their Ph.D. through
their participation in this project.