4,034 research outputs found
Fedosov supermanifolds: II. Normal coordinates
The study of recently introduced Fedosov supermanifolds is continued. Using
normal coordinates, properties of even and odd symplectic supermanifolds
endowed with a symmetric connection respecting given sympletic structure are
studied.Comment: 12 pages, Late
Boson-fermion mapping of collective fermion-pair algebras
We construct finite Dyson boson-fermion mappings of general collective
algebras extended by single-fermion operators. A key element in the
construction is the implementation of a similarity transformation which
transforms boson-fermion images obtained directly from the supercoherent state
method. In addition to the general construction, we give detailed applications
to SO(2N), SU(l+1), SO(5), and SO(8) algebras.Comment: 22 pages, latex, no figure
SDG fermion-pair algebraic SO(12) and Sp(10) models and their boson realizations
It is shown how the boson mapping formalism may be applied as a useful
many-body tool to solve a fermion problem. This is done in the context of
generalized Ginocchio models for which we introduce S-, D-, and G-pairs of
fermions and subsequently construct the sdg-boson realizations of the
generalized Dyson type. The constructed SO(12) and Sp(10) fermion models are
solved beyond the explicit symmetry limits. Phase transitions to rotational
structures are obtained, also in situations where there is no underlying SU(3)
symmetry.Comment: 25 LaTeX pages, 4 uuencoded postscript figures included, Preprint
IFT/8/94 & STPHY-TH/94-
Quantum properties of general gauge theories with composite and external fields
The generating functionals of Green's functions with composite and external
fields are considered in the framework of BV and BLT quantization methods for
general gauge theories. The corresponding Ward identities are derived and the
gauge dependence is investigatedComment: 24 pages, LATEX, slightly changed to clarify the essential new aspect
concerning composite fields depending on external ones; added formulas
showing lack of (generalized) nilpotence of operators appearing in the Ward
identitie
Analysis of the Strong Coupling Limit of the Richardson Hamiltonian using the Dyson Mapping
The Richardson Hamiltonian describes superconducting correlations in a
metallic nanograin. We do a perturbative analysis of this and related
Hamiltonians, around the strong pairing limit, without having to invoke Bethe
Ansatz solvability. Rather we make use of a boson expansion method known as the
Dyson mapping. Thus we uncover a selection rule that facilitates both
time-independent and time-dependent perturbation expansions. In principle the
model we analise is realised in a very small metalic grain of a very regular
shape. The results we obtain point to subtleties sometimes neglected when
thinking of the superconducting state as a Bose-Einstein condensate. An
appendix contains a general presentation of time-independent perturbation
theory for operators with degenerate spectra, with recursive formulas for
corrections of arbitrarily high orders.Comment: New final version accepted for publication in PRB. 17 two-column
pages, no figure
Boson-fermion mappings for odd systems from supercoherent states
We extend the formalism whereby boson mappings can be derived from
generalized coherent states to boson-fermion mappings for systems with an odd
number of fermions. This is accomplished by constructing supercoherent states
in terms of both complex and Grassmann variables. In addition to a known
mapping for the full so(2+1) algebra, we also uncover some other formal
mappings, together with mappings relevant to collective subspaces.Comment: 40 pages, REVTE
Dynamical stabilization of classical multi electron targets against autoionization
We demonstrate that a recently published quasiclassical M\oller type approach
[Geyer and Rost 2002, J. Phys. B 35 1479] can be used to overcome the problem
of autoionization, which arises in classical trajectory calculations for many
electron targets. In this method the target is stabilized dynamically by a
backward--forward propagation scheme. We illustrate this refocusing and present
total cross sections for single and double ionization of helium by electron
impact.Comment: LaTeX, 6 pages, 2 figures; submitted to J. Phys.
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