875 research outputs found
A construction of symplectic connections through reduction
We give an elementary construction of symplectic connections through
reduction. This provides an elegant description of a class of symmetric spaces
and gives examples of symplectic connections with Ricci type curvature, which
are not locally symmetric; the existence of such symplectic connections was
unknown.Comment: 16 pages, Plain TeX fil
Phase Space Reduction for Star-Products: An Explicit Construction for CP^n
We derive a closed formula for a star-product on complex projective space and
on the domain using a completely elementary
construction: Starting from the standard star-product of Wick type on and performing a quantum analogue of Marsden-Weinstein
reduction, we can give an easy algebraic description of this star-product.
Moreover, going over to a modified star-product on ,
obtained by an equivalence transformation, this description can be even further
simplified, allowing the explicit computation of a closed formula for the
star-product on \CP^n which can easily transferred to the domain
.Comment: LaTeX, 17 page
Dirac Operators on Coset Spaces
The Dirac operator for a manifold Q, and its chirality operator when Q is
even dimensional, have a central role in noncommutative geometry. We
systematically develop the theory of this operator when Q=G/H, where G and H
are compact connected Lie groups and G is simple. An elementary discussion of
the differential geometric and bundle theoretic aspects of G/H, including its
projective modules and complex, Kaehler and Riemannian structures, is presented
for this purpose. An attractive feature of our approach is that it
transparently shows obstructions to spin- and spin_c-structures. When a
manifold is spin_c and not spin, U(1) gauge fields have to be introduced in a
particular way to define spinors. Likewise, for manifolds like SU(3)/SO(3),
which are not even spin_c, we show that SU(2) and higher rank gauge fields have
to be introduced to define spinors. This result has potential consequences for
string theories if such manifolds occur as D-branes. The spectra and
eigenstates of the Dirac operator on spheres S^n=SO(n+1)/SO(n), invariant under
SO(n+1), are explicitly found. Aspects of our work overlap with the earlier
research of Cahen et al..Comment: section on Riemannian structure improved, references adde
A construction of integer-valued polynomials with prescribed sets of lengths of factorizations
For an arbitrary finite set S of natural numbers greater 1, we construct an
integer-valued polynomial f, whose set of lengths in Int(Z) is S. The set of
lengths of f is the set of all natural numbers n, such that f has a
factorization as a product of n irreducibles in Int(Z)={g in Q[x] | g(Z)
contained in Z}.Comment: To appear in Monatshefte f\"ur Mathematik; 11 page
Identification of Berezin-Toeplitz deformation quantization
We give a complete identification of the deformation quantization which was
obtained from the Berezin-Toeplitz quantization on an arbitrary compact Kaehler
manifold. The deformation quantization with the opposite star-product proves to
be a differential deformation quantization with separation of variables whose
classifying form is explicitly calculated. Its characteristic class (which
classifies star-products up to equivalence) is obtained. The proof is based on
the microlocal description of the Szegoe kernel of a strictly pseudoconvex
domain given by Boutet de Monvel and Sjoestrand.Comment: 26 page
On invariants of almost symplectic connections
We study the irreducible decomposition under Sp(2n, R) of the space of
torsion tensors of almost symplectic connections. Then a description of all
symplectic quadratic invariants of torsion-like tensors is given. When applied
to a manifold M with an almost symplectic structure, these instruments give
preliminary insight for finding a preferred linear almost symplectic connection
on M . We rediscover Ph. Tondeur's Theorem on almost symplectic connections.
Properties of torsion of the vectorial kind are deduced
Non-formal deformation quantizations of solvable Ricci-type symplectic symmetric spaces
Ricci-type symplectic manifolds have been introduced and extensively studied
by M. Cahen et al.. In this note, we describe their deformation quantizations
in the split solvable symmetric case. In particular, we introduce the notion of
non-formal tempered deformation quantization on such a space. We show that the
set of tempered deformation quantizations is in one-to-one correspondence with
the space of Schwartz operator multipliers on the real line. Moreover we prove
that every invariant formal star product on a split Ricci-type solvable
symmetric space is an asymptotic expansion of a tempered non-formal
quantization. This note illustrates and partially reviews through an example a
problematic studied by the author regarding non-formal quantization in presence
of large groups of symmetries
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