96 research outputs found

### Cooper-Mesons in the Color-Flavor-Locked Superconducting Phase of Dense QCD

QCD superconductors in the color-flavor-locked (CFL) phase sustain
excitations (``Cooper'' mesons) that can be described as pairs of particles or
holes around a gapped Fermi surface. In weak coupling and to leading logarithm
accuracy the masses, decay constants and form factors of the scalar,
pseudoscalar, vector and axial-vector excitations, which explicitly are of
finite size, can be calculated exactly. Furthermore, the constraints of this
microscopic calculation on the effective-lagrangian description and the
computation of the generalized triangle anomaly are discussed.Comment: 8 pages, LaTeX, 3 figures.eps, uses sprocl.sty, invited talk for
Bologna 200

### Electric dipole moments of the nucleon and light nuclei

The electric dipole moments of the nucleon and light ions are discussed and
strategies for disentangling the underlying sources of CP violation beyond the
Kobayashi-Maskawa quark-mixing mechanism of the Standard Model are indicated.
Contribution to "45 years of nuclear theory at Stony Brook: a tribute to Gerald
E. Brown".Comment: 14 pages, 2 figures, contribution to "45 years of nuclear theory at
Stony Brook: a tribute to Gerald E. Brown

### S-wave Meson-Nucleon Interactions and the Meson Mass in Nuclear Matter from Chiral Effective Lagrangians

Chiral effective lagrangians may differ in their prediction of meson-nucleon
scattering amplitudes off-meson-mass-shell, but must yield identical S-matrix
elements. We argue that the effective meson mass in nuclear matter obtained
from chiral effective lagrangians is also unique. Off-mass-shell amplitudes
obtained using the PCAC choice of pion field must therefore not be viewed as
fundamental constraints on the dynamics, the determination of the effective
meson mass in nuclear matter or the possible existence of meson condensates in
the ground state of nuclear matter. This hypothesis is borne out by a
calculation of the effective mass in two commonly employed formulations of
chiral perturbation theory which yield different meson-nucleon scattering
amplitudes off-meson-mass-shell.Comment: 23 pages, LaTeX, 2 Postscript figures (fig1.ps, fig2.ps

### Permanent Electric Dipole Moments of Single-, Two-, and Three-Nucleon Systems

A nonzero electric dipole moment (EDM) of the neutron, proton, deuteron or
helion, in fact, of any finite system necessarily involves the breaking of a
symmetry, either by the presence of external fields (i.e. electric fields
leading to the case of induced EDMs) or explicitly by the breaking of the
discrete parity and time-reflection symmetries in the case of permanent EDMs.
We discuss two theorems describing these phenomena and report about the
cosmological motivation for an existence of CP breaking beyond what is
generated by the Kobayashi-Maskawa mechanism in the Standard Model and what
this might imply for the permanent electric dipole moments of the nucleon and
light nuclei by estimating a window of opportunity for physics beyond what is
currently known. Recent - and in the case of the deuteron even unpublished -
results for the relevant matrix elements of nuclear EDM operators are presented
and the relevance for disentangling underlying New Physics sources are
discussed.Comment: 20 pages, chapter for the memorial book "Gerry Brown 90", final
version, some typos correcte

### Casimir Interaction among Objects Immersed in a Fermionic Environment

Using ensembles of two, three and four spheres immersed in a fermionic
background we evaluate the (integrated) density of states and the Casimir
energy. We thus infer that for sufficiently smooth objects, whose various
geometric characteristic lengths are larger then the Fermi wave length one can
use the simplest semiclassical approximation (the contribution due shortest
periodic orbits only) to evaluate the Casimir energy. We also show that the
Casimir energy for several objects can be represented fairly accurately as a
sum of pairwise Casimir interactions between pairs of objects.Comment: 4 pages, 5 figures, version to appear in PR

### A direct link between the quantum-mechanical and semiclassical determination of scattering resonances

We investigate the scattering of a point particle from n non-overlapping,
disconnected hard disks which are fixed in the two-dimensional plane and study
the connection between the spectral properties of the quantum-mechanical
scattering matrix and its semiclassical equivalent based on the semiclassical
zeta function of Gutzwiller and Voros. We rewrite the determinant of the
scattering matrix in such a way that it separates into the product of n
determinants of 1-disk scattering matrices - representing the incoherent part
of the scattering from the n disk system - and the ratio of two mutually
complex conjugate determinants of the genuine multi-scattering kernel, M, which
is of Korringa-Kohn-Rostoker-type and represents the coherent multi-disk aspect
of the n-disk scattering. Our result is well-defined at every step of the
calculation, as the on-shell T-matrix and the kernel M-1 are shown to be
trace-class. We stress that the cumulant expansion (which defines the
determinant over an infinite, but trace class matrix) imposes the curvature
regularization scheme to the Gutzwiller-Voros zeta function and thus leads to a
new, well-defined and direct derivation of the semiclassical spectral function.
We show that unitarity is preserved even at the semiclassical level.Comment: 23 pages, latex with IOP journal preprint style, no figures; final
version - considerably shortene

### In-medium effective chiral lagrangians and the pion mass in nuclear matter

We argue that the effective pion mass in nuclear matter obtained from chiral
effective lagrangians is unique and does not depend on off-mass-shell
extensions of the pion fields as e.g. the PCAC choice. The effective pion mass
in isospin symmetric nuclear matter is predicted to increase slightly with
increasing nuclear density, whereas the effective time-like pion decay constant
and the magnitude of the density-dependent quark condensate decrease
appreciably. The in-medium Gell-Mann-Oakes-Renner relation as well as other
in-medium identities are studied in addition. Finally, several constraints on
effective lagrangians for the description of the pion propagation in isospin
symmetric, isotropic and homogenous nuclear matter are discussed. (Talk
presented at the workshop ``Hirschegg '95: Hadrons in Nuclear Matter'',
Hirschegg, Kleinwalsertal, Austria, January 16-21, 1995)Comment: 14 pages, LaTeX, some typographical errors correcte

### Scalar Casimir effect between Dirichlet spheres or a plate and a sphere

We present a simple formalism for the evaluation of the Casimir energy for
two spheres and a sphere and a plane, in case of a scalar fluctuating field,
valid at any separations. We compare the exact results with various
approximation schemes and establish when such schemes become useful. The
formalism can be easily extended to any number of spheres and/or planes in
three or arbitrary dimensions, with a variety of boundary conditions or
non-overlapping potentials/non-ideal reflectors.Comment: published version; 13 pages, 2 figures; add. material (in Sec.VI) and
corrections (esp. in App.B

### Fermionic Casimir Effect in Case of Andreev Reflection

We describe the Fermionic Casimir effect in the case of two spherical
superfluid scatterers immersed in a normal Fermi system. It is shown that due
to the focusing property of Andreev reflection this new Casimir-like energy is
significantly enhanced when compared to the case of normal scatterers with
specular reflection.Comment: 7 pages, 4 eps figures, latex (with epl.cls

### Application of the diffraction trace formula to the three disk scattering system

The diffraction trace formula ({\em Phys. Rev. Lett.} {\bf 73}, 2304 (1994))
and spectral determinant are tested on the open three disk scattering system.
The system contains a generic and exponentially growing number of diffraction
periodic orbits. In spite of this it is shown that even the scattering
resonances with large imaginary part can be reproduced semiclassicaly. The
non-trivial interplay of the diffraction periodic orbits with the usual
geometrical orbits produces the fine structure of the complicated spectrum of
scattering resonances, which are beyond the resolution of the conventional
periodic orbit theory.Comment: Latex article + 3 ps figure

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