104 research outputs found
Three-Body Interactions in Many-Body Effective Field Theory
This contribution is an advertisement for applying effective field theory
(EFT) to many-body problems, including nuclei and cold atomic gases. Examples
involving three-body interactions are used to illustrate how EFT's quantify and
systematically eliminate model dependence, and how they make many-body
calculations simpler and more powerful.Comment: 5 pp, 9 figs, invited parallel talk at 17th International IUPAP
Conference on Few-Body Problems in Physics, June 5-10, 2003, Durham, North
Carolina, US
Pionic contribution to relativistic Fermi Liquid parameters
We calculate pionic contribution to the relativistic Fermi Liquid parameters
(RFLPs) using Chiral Effective Lagrangian. The RFLPs so determined are then
used to calculate chemical potential, exchange and nuclear symmetry energies
due to interaction. We also evaluate two loop ring diagrams involving
, and meson exchanges and compare results with what one
obtains from the relativistic Fermi Liquid theory (RFLT).Comment: 6 pages, 2 figures, Published in Canadian Journal of Physics, vol.
88, issue 8, pp. 585-59
Relativistic Point-Coupling Models as Effective Theories of Nuclei
Recent studies have shown that concepts of effective field theory such as
naturalness can be profitably applied to relativistic mean-field models of
nuclei. Here the analysis by Friar, Madland, and Lynn of naturalness in a
relativistic point-coupling model is extended. Fits to experimental nuclear
data support naive dimensional analysis as a useful principle and imply a
mean-field expansion analogous to that found for mean-field meson models.Comment: 26 pages, REVTeX 3.0 with epsf.sty, plus 5 figure
Three-Body Forces Produced by a Similarity Renormalization Group Transformation in a Simple Model
A simple class of unitary renormalization group transformations that force
hamiltonians towards a band-diagonal form produce few-body interactions in
which low- and high-energy states are decoupled, which can greatly simplify
many-body calculations. One such transformation has been applied to
phenomenological and effective field theory nucleon-nucleon interactions with
success, but further progress requires consistent treatment of at least the
three-nucleon interaction. In this paper we demonstrate in an extremely simple
model how these renormalization group transformations consistently evolve two-
and three-body interactions towards band-diagonal form, and introduce a
diagrammatic approach that generalizes to the realistic nuclear problem.Comment: 25 pages, 18 figures, minor typos corrected and references update
Density Functional Theory for a Confined Fermi System with Short-Range Interaction
Effective field theory (EFT) methods are applied to density functional theory
(DFT) as part of a program to systematically go beyond mean-field approaches to
medium and heavy nuclei. A system of fermions with short-range, natural
interactions and an external confining potential (e.g., fermionic atoms in an
optical trap) serves as a laboratory for studying DFT/EFT. An effective action
formalism leads to a Kohn-Sham DFT by applying an inversion method
order-by-order in the EFT expansion parameter. Representative results showing
the convergence of Kohn-Sham calculations at zero temperature in the local
density approximation (LDA) are compared to Thomas-Fermi calculations and to
power-counting estimates.Comment: 36 pages, 20 figures, RevTeX
Are Occupation Numbers Observable?
The question of whether occupation numbers and momentum distributions of
nucleons in nuclei are observables is considered from an effective field theory
perspective. Field redefinitions lead to variations that imply the answer is
negative, as illustrated in the interacting Fermi gas at low density.
Implications for the interpretation of (e,e'p) experiments with nuclei are
discussed.Comment: 8 pages, revtex4, 4 ps figure
Collective modes of asymmetric nuclear matter in Quantum HadroDynamics
We discuss a fully relativistic Landau Fermi liquid theory based on the
Quantum Hadro-Dynamics () effective field picture of Nuclear Matter
({\it NM}).
From the linearized kinetic equations we get the dispersion relations of the
propagating collective modes. We focus our attention on the dynamical effects
of the interplay between scalar and vector channel contributions. A beautiful
``mirror'' structure in the form of the dynamical response in the
isoscalar/isovector degree of freedom is revealed, with a complete parallelism
in the role respectively played by the compressibility and the symmetry energy.
All that strongly supports the introduction of an explicit coupling to the
scalar-isovector channel of the nucleon-nucleon interaction. In particular we
study the influence of this coupling (to a -meson-like effective field)
on the collective response of asymmetric nuclear matter (). Interesting
contributions are found on the propagation of isovector-like modes at normal
density and on an expected smooth transition to isoscalar-like oscillations at
high baryon density. Important ``chemical'' effects on the neutron-proton
structure of the mode are shown. For dilute we have the isospin
distillation mechanism of the unstable isoscalar-like oscillations, while at
high baryon density we predict an almost pure neutron wave structure of the
propagating sounds.Comment: 18 pages (LATEX), 8 Postscript figures, uses "epsfig
Perturbative Effective Field Theory at Finite Density
An accurate description of nuclear matter starting from free-space nuclear
forces has been an elusive goal. The complexity of the system makes
approximations inevitable, so the challenge is to find a consistent truncation
scheme with controlled errors. Nonperturbative effective field theories could
be well suited for the task. Perturbative matching in a model calculation is
used to explore some of the issues encountered in extending effective field
theory techniques to many-body calculations.Comment: 21 pages, 5 figure
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