261 research outputs found
K\"ahlerian Twistor Spinors
On a K\"ahler spin manifold K\"ahlerian twistor spinors are a natural
analogue of twistor spinors on Riemannian spin manifolds. They are defined as
sections in the kernel of a first order differential operator adapted to the
K\"ahler structure, called K\"ahlerian twistor (Penrose) operator. We study
K\"ahlerian twistor spinors and give a complete description of compact K\"ahler
manifolds of constant scalar curvature admitting such spinors. As in the
Riemannian case, the existence of K\"ahlerian twistor spinors is related to the
lower bound of the spectrum of the Dirac operator.Comment: shorter version; to appear in Math.
The Secondary Transition Planning Process and Effective Outcomes for High School Graduates with Mild Disabilities
The secondary transition planning process and effective outcomes for high school graduates with mild disabilities
Regeneration of Cellulose from a Switchable Ionic Liquid: Toward More Sustainable Cellulose Fibers
A CO switchable solvent system is investigated to find an environmentally friendlier way to produce man‐made cellulose fibers. Cellulose solutions with concentrations from 2 wt% to 8 wt%, based on derivative and non‐derivative dissolution approaches, are investigated. Three different switchable solvent systems are tested. After accessing the stability of the produced cellulose solutions, their regeneration is investigated using different alcoholic coagulation media. In order to find a suitable coagulation medium and stable cellulose solution, a dissolution–regeneration cycle is investigated, while trying to minimize the amount of waste by recovering the employed solvents. The process is optimized and the resulting fibers are characterized by infrared (IR) spectroscopy, optical microscopy, as well as scanning electron microscopy
Symmetries of N=4 supersymmetric CP(n) mechanics
We explicitly constructed the generators of group which commute
with the supercharges of N=4 supersymmetric mechanics in the
background U(n) gauge fields. The corresponding Hamiltonian can be represented
as a direct sum of two Casimir operators: one Casimir operator on
group contains our bosonic and fermionic coordinates and momenta, while the
second one, on the SU(1,n) group, is constructed from isospin degrees of
freedom only.Comment: 10 pages, PACS numbers: 11.30.Pb, 03.65.-w; minor changes in
Introduction, references adde
A Simple Separable Exact C*-Algebra not Anti-isomorphic to Itself
We give an example of an exact, stably finite, simple. separable C*-algebra D
which is not isomorphic to its opposite algebra. Moreover, D has the following
additional properties. It is stably finite, approximately divisible, has real
rank zero and stable rank one, has a unique tracial state, and the order on
projections over D is determined by traces. It also absorbs the Jiang-Su
algebra Z, and in fact absorbs the 3^{\infty} UHF algebra. We can also
explicitly compute the K-theory of D, namely K_0 (D) = Z[1/3] with the standard
order, and K_1 (D) = 0, as well as the Cuntz semigroup of D.Comment: 16 pages; AMSLaTeX. The material on other possible K-groups for such
an algebra has been moved to a separate paper (1309.4142 [math.OA]
From the Dirac Operator to Wess-Zumino Models on Spatial Lattices
We investigate two-dimensional Wess-Zumino models in the continuum and on
spatial lattices in detail. We show that a non-antisymmetric lattice derivative
not only excludes chiral fermions but in addition introduces supersymmetry
breaking lattice artifacts. We study the nonlocal and antisymmetric SLAC
derivative which allows for chiral fermions without doublers and minimizes
those artifacts. The supercharges of the lattice Wess-Zumino models are
obtained by dimensional reduction of Dirac operators in high-dimensional
spaces. The normalizable zero modes of the models with N=1 and N=2
supersymmetry are counted and constructed in the weak- and strong-coupling
limits. Together with known methods from operator theory this gives us complete
control of the zero mode sector of these theories for arbitrary coupling.Comment: 39 pages, 3 figure
Extended Supersymmetries and the Dirac Operator
We consider supersymmetric quantum mechanical systems in arbitrary dimensions
on curved spaces with nontrivial gauge fields. The square of the Dirac operator
serves as Hamiltonian. We derive a relation between the number of supercharges
that exist and restrictions on the geometry of the underlying spaces as well as
the admissible gauge field configurations. From the superalgebra with two or
more real supercharges we infer the existence of integrability conditions and
obtain a corresponding superpotential. This potential can be used to deform the
supercharges and to determine zero modes of the Dirac operator. The general
results are applied to the Kahler spaces CP^n.Comment: 22 pages, no figure
Relative commutants of strongly self-absorbing C*-algebras
The relative commutant of a strongly self-absorbing
algebra is indistinguishable from its ultrapower . This
applies both to the case when is the hyperfinite II factor and to the
case when it is a strongly self-absorbing C*-algebra. In the latter case we
prove analogous results for and reduced powers
corresponding to other filters on . Examples of algebras with
approximately inner flip and approximately inner half-flip are provided,
showing the optimality of our results. We also prove that strongly
self-absorbing algebras are smoothly classifiable, unlike the algebras with
approximately inner half-flip.Comment: Some minor correction
Locally Trivial W*-Bundles
We prove that a tracially continuous W-bundle over a
compact Hausdorff space with all fibres isomorphic to the hyperfinite
II-factor that is locally trivial already has to be globally
trivial. The proof uses the contractibility of the automorphism group
shown by Popa and Takesaki. There is no
restriction on the covering dimension of .Comment: 20 pages, this version will be published in the International Journal
of Mathematic
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