185 research outputs found
Antisymmetrization of a Mean Field Calculation of the T-Matrix
The usual definition of the prior(post) interaction between
projectile and target (resp. ejectile and residual target) being contradictory
with full antisymmetrization between nucleons, an explicit antisymmetrization
projector must be included in the definition of the transition
operator, We derive the
suitably antisymmetrized mean field equations leading to a non perturbative
estimate of . The theory is illustrated by a calculation of forward
- scattering, making use of self consistent symmetries.Comment: 30 pages, no figures, plain TeX, SPHT/93/14
PT-symmetry and Integrability
We briefly explain some simple arguments based on pseudo Hermiticity,
supersymmetry and PT-symmetry which explain the reality of the spectrum of some
non-Hermitian Hamiltonians. Subsequently we employ PT-symmetry as a guiding
principle to construct deformations of some integrable systems, the
Calogero-Moser-Sutherland model and the Korteweg deVries equation. Some
properties of these models are discussed.Comment: Proceeding of the Micro conference Analytic and algebraic methods II,
Doppler Institute, Prague, April 200
Variational Schrieffer-Wolff transformations for quantum many-body dynamics
Building on recent results for adiabatic gauge potentials, we propose a variational approach for computing the generator of Schrieffer-Wolff transformations. These transformations consist of block diagonalizing a Hamiltonian through a unitary rotation, which leads to effective dynamics in a computationally tractable reduced Hilbert space. The generators of these rotations are computed variationally and thus go beyond standard perturbative methods, with error controlled by the locality of the variational ansatz. The method is demonstrated on two models. First, in the attractive Fermi-Hubbard model with onsite disorder, we find indications of a lack of observable many-body localization in the thermodynamic limit due to the inevitable mixture of different spinon sectors. Second, in the low-energy sector of the XY spin model with a broken U(1) symmetry, we analyze ground-state response functions by combining the variational Schrieffer-Wolf transformation with the truncated spectrum approach.Published versio
Higher Order Corrections in Minimal Supergravity Models of Inflation
We study higher order corrections in new minimal supergravity models of a
single scalar field inflation. The gauging in these models leads to a massive
vector multiplet and the D-term potential for the inflaton field with a
coupling g^{2} ~ 10^{-10}. In the de-Higgsed phase with vanishing g^2, the
chiral and vector multiplets are non-interacting, and the potential vanishes.
We present generic manifestly supersymmetric higher order corrections for these
models. In particular, for a supersymmetric gravity model -R+ R^2 we derive
manifestly supersymmetric corrections corresponding to R^n. The dual version
corresponds to a standard supergravity model with a single scalar and a massive
vector. It includes, in addition, higher Maxwell curvature/scalar interaction
terms of the Born-Infeld type and a modified D-term scalar field potential. We
use the dual version of the model to argue that higher order corrections do not
affect the last 60 e-foldings of inflation; for example the \xi R^4 correction
is irrelevant as long as \xi< 10^{24}.Comment: 25 pages, the version to appear in JCA
Classical Analysis of Phenomenological Potentials for Metallic Clusters
The classical trajectories of single particle motion in a Wodds-Saxon and a
modified Nilsson potential are studied for axial quadrupole deformation. Both
cases give rise to chaotic behaviour when the deformation in the Woods-Saxon
and the l**2 term in the modified Nilsson potential are turned on. Important
similarities, in particular with regard to the shortest periodic orbits, have
been found.Comment: 9 pages LaTex + 4 figures available via e-mail requests from the
authors, to appear in Phys.Rev.Let
A coordinate-dependent superspace deformation from string theory
Starting from a type II superstring model defined on in
a linear graviphoton background, we derive a coordinate dependent -deformed
, superspace. The chiral fermionic coordinates
satisfy a Clifford algebra, while the other coordinate algebra remains
unchanged. We find a linear relation between the graviphoton field strength and
the deformation parameter. The null coordinate dependence of the graviphoton
background allows to extend the results to all orders in .Comment: 14 pages, reference added, accepted for publication in JHE
The nucleus as a fluid of skyrmions: Energy levels and nucleon properties in the medium
A model of a fluid of skyrmions coupled to a scalar and to the \o meson
mean fields is developed. The central and spin-orbit potentials of a skyrmion
generated by the fields predict correct energy levels in selected closed shell
nuclei. The effect of the meson fields on the properties of skyrmions in nuclei
is investigated.Comment: Latex format, 6 figures, Journal of Physics G, to be publishe
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