201 research outputs found
Spectral asymmetries in nucleon sum rules at finite density
Apparent inconsistencies between different formulations of nucleon sum rules
at finite density are resolved through a proper accounting of asymmetries in
the spectral functions between positive- and negative-energy states.Comment: 10 pages in RevTeX, OSU-090
The Axial-Vector Current in Nuclear Many-Body Physics
Weak-interaction currents are studied in a recently proposed effective field
theory of the nuclear many-body problem. The Lorentz-invariant effective field
theory contains nucleons, pions, isoscalar scalar () and vector
() fields, and isovector vector () fields. The theory exhibits a
nonlinear realization of chiral symmetry and has three
desirable features: it uses the same degrees of freedom to describe the
axial-vector current and the strong-interaction dynamics, it satisfies the
symmetries of the underlying theory of quantum chromodynamics, and its
parameters can be calibrated using strong-interaction phenomena, like hadron
scattering or the empirical properties of finite nuclei. Moreover, it has
recently been verified that for normal nuclear systems, it is possible to
systematically expand the effective lagrangian in powers of the meson fields
(and their derivatives) and to reliably truncate the expansion after the first
few orders. Here it is shown that the expressions for the axial-vector current,
evaluated through the first few orders in the field expansion, satisfy both
PCAC and the Goldberger--Treiman relation, and it is verified that the
corresponding vector and axial-vector charges satisfy the familiar chiral
charge algebra. Explicit results are derived for the Lorentz-covariant,
axial-vector, two-nucleon amplitudes, from which axial-vector meson-exchange
currents can be deduced.Comment: 32 pages, REVTeX 4.0 with 12pt.rtx, aps.rtx, revsymb.sty,
revtex4.cls, plus 14 figures; two sentences added in Summary; two references
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Corrections to nuclear energies and radii in finite oscillator spaces
We derive corrections to the ground-state energies and radii of atomic nuclei
that result from the limitations of finite oscillator spaces.Comment: 6 pages, 6 figure
Nuclei in a chiral SU(3) model
Nuclei can be described satisfactorily in a nonlinear chiral SU(3)-framework,
even with standard potentials of the linear -model. The condensate
value of the strange scalar meson is found to be important for the properties
of nuclei even without adding hyperons. By neglecting terms which couple the
strange to the nonstrange condensate one can reduce the model to a Walecka
model structure embedded in SU(3). We discuss inherent problems with chiral
SU(3) models regarding hyperon optical potentials.Comment: 25 pages, RevTe
QCD Sum Rules, Scattering Length and the Vector Mesons in Nuclear Medium
Critical examination is made on the relation between the mass shift of vector
mesons in nuclear medium and the vector-meson nucleon scattering length. We
give detailed comparison between the QCD sum rule approach by two of the
present authors (Phys. Rev. {\bf C46} (1992) R34) and the scattering-length
approach by Koike (Phys. Rev. {\bf C51} (1995) 1488). It is shown that the
latter approach is mortally flawed both technically and conceptually.Comment: 16 pages, latex, 4 figures appended as uu-encoded fil
Static properties of nuclear matter within the Boson Loop Expansion
The use of the Boson Loop Expansion is proposed for investigating the static
properties of nuclear matter. We explicitly consider a schematic dynamical
model in which nucleons interact with the scalar-isoscalar sigma meson. The
suggested approximation scheme is examined in detail at the mean field level
and at the one- and two-loop orders. The relevant formulas are provided to
derive the binding energy per nucleon, the pressure and the compressibility of
nuclear matter. Numerical results of the binding energy at the one-loop order
are presented for Walecka's sigma-omega model in order to discuss the degree of
convergence of the Boson Loop Expansion.Comment: 40 pages, 13 figure
Phase transition from quark-meson coupling hyperonic matter to deconfined quark matter
We investigate the possibility and consequences of phase transitions from an
equation of state (EOS) describing nucleons and hyperons interacting via mean
fields of sigma, omega, and rho mesons in the recently improved quark-meson
coupling (QMC) model to an EOS describing a Fermi gas of quarks in an MIT bag.
The transition to a mixed phase of baryons and deconfined quarks, and
subsequently to a pure deconfined quark phase, is described using the method of
Glendenning. The overall EOS for the three phases is calculated for various
scenarios and used to calculate stellar solutions using the
Tolman-Oppenheimer-Volkoff equations. The results are compared with recent
experimental data, and the validity of each case is discussed with consequences
for determining the species content of the interior of neutron stars.Comment: 12 pages, 14 figures; minor typos correcte
Local Projections of Low-Momentum Potentials
Nuclear interactions evolved via renormalization group methods to lower
resolution become increasingly non-local (off-diagonal in coordinate space) as
they are softened. This inhibits both the development of intuition about the
interactions and their use with some methods for solving the quantum many-body
problem. By applying "local projections", a softened interaction can be reduced
to a local effective interaction plus a non-local residual interaction. At the
two-body level, a local projection after similarity renormalization group (SRG)
evolution manifests the elimination of short-range repulsive cores and the flow
toward universal low-momentum interactions. The SRG residual interaction is
found to be relatively weak at low energy, which motivates a perturbative
treatment
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