537 research outputs found
A Comment on Jones Inclusions with infinite Index
Given an irreducible inclusion of infinite von-Neumann-algebras \cn \subset
\cm together with a conditional expectation E : \cm \rightarrow \cm such
that the inclusion has depth 2, we show quite explicitely how \cn can be
viewed as the fixed point algebra of \cm w.r.t. an outer action of a compact
Kac-algebra acting on \cm. This gives an alternative proof, under this
special setting of a more general result of M. Enock and R. Nest, [E-N], see
also S. Yamagami, [Ya2].Comment: latex, 40 page
Looking beyond the Thermal Horizon: Hidden Symmetries in Chiral Models
In thermal states of chiral theories, as recently investigated by H.-J.
Borchers and J. Yngvason, there exists a rich group of hidden symmetries. Here
we show that this leads to a radical converse of of the Hawking-Unruh
observation in the following sense. The algebraic commutant of the algebra
associated with a (heat bath) thermal chiral system can be used to reprocess
the thermal system into a ground state system on a larger algebra with a larger
localization space-time. This happens in such a way that the original system
appears as a kind of generalized Unruh restriction of the ground state sytem
and the thermal commutant as being transmutated into newly created ``virgin
space-time region'' behind a horizon. The related concepts of a ``chiral
conformal core'' and the possibility of a ``blow-up'' of the latter suggest
interesting ideas on localization of degrees of freedom with possible
repercussion on how to define quantum entropy of localized matter content in
Local Quantum Physics.Comment: 17 pages, tcilatex, still more typos removed and one reference
correcte
Weak Hopf Algebras and Reducible Jones Inclusions of Depth 2. I: From Crossed products to Jones towers
We apply the theory of finite dimensional weak C^*-Hopf algebras A as
developed by G. B\"ohm, F. Nill and K. Szlach\'anyi to study reducible
inclusion triples of von-Neumann algebras N \subset M \subset (M\cros\A). Here
M is an A-module algebra, N is the fixed point algebra and \M\cros\A is the
crossed product extension. ``Weak'' means that the coproduct \Delta on A is
non-unital, requiring various modifications of the standard definitions for
(co-)actions and crossed products. We show that acting with normalized positive
and nondegenerate left integrals l\in\A gives rise to faithful conditional
expectations E_l: M-->N, where under certain regularity conditions this
correspondence is one-to-one. Associated with such left integrals we construct
``Jones projections'' e_l\in\A obeying the Jones relations as an identity in
M\cros\A. Finally, we prove that N\subset M always has finite index and depth 2
and that the basic Jones construction is given by the ideal M_1:=M e_l M
\subset M\cros\A, where under appropriate conditions M_1 = M\cros\A. In a
subsequent paper we will show that converseley any reducible finite index and
depth-2 Jones tower of von-Neumann factors (with finite dimensional centers)
arises in this way.Comment: Latex, 63 page
Modular Groups of Quantum Fields in Thermal States
For a quantum field in a thermal equilibrium state we discuss the group
generated by time translations and the modular action associated with an
algebra invariant under half-sided translations. The modular flows associated
with the algebras of the forward light cone and a space-like wedge admit a
simple geometric description in two dimensional models that factorize in
light-cone coordinates. At large distances from the domain boundary compared to
the inverse temperature the flow pattern is essentially the same as time
translations, whereas the zero temperature results are approximately reproduced
close to the edge of the wedge and the apex of the cone. Associated with each
domain there is also a one parameter group with a positive generator, for which
the thermal state is a ground state. Formally, this may be regarded as a
certain converse of the Unruh-effect.Comment: 28 pages, 4 figure
An algebraic Haag's theorem
Under natural conditions (such as split property and geometric modular action
of wedge algebras) it is shown that the unitary equivalence class of the net of
local (von Neumann) algebras in the vacuum sector associated to double cones
with bases on a fixed space-like hyperplane completely determines an algebraic
QFT model. More precisely, if for two models there is unitary connecting all of
these algebras, then --- without assuming that this unitary also connects their
respective vacuum states or spacetime symmetry representations --- it follows
that the two models are equivalent. This result might be viewed as an algebraic
version of the celebrated theorem of Rudolf Haag about problems regarding the
so-called "interaction-picture" in QFT.
Original motivation of the author for finding such an algebraic version came
from conformal chiral QFT. Both the chiral case as well as a related conjecture
about standard half-sided modular inclusions will be also discussed
Comment on: Modular Theory and Geometry
In this note we comment on part of a recent article by B. Schroer and H.-W.
Wiesbrock. Therein they calculate some new modular structure for the
U(1)-current-algebra (Weyl-algebra). We point out that their findings are true
in a more general setting. The split-property allows an extension to
doubly-localized algebras.Comment: 13 pages, corrected versio
Poly(hydroxy alkanoate)s in Medical Applications
This review summarizes the state-of-the-art knowledge of the usage of poly(hydroxy alkanoate)s in medical and sanitary applications. Depending on the monomers incorporated into the polymers and copolymers, this class of polymers exhibits a broad range of (thermo-)plastic properties, enabling their processing by, e.g., solution casting
or melt extrusion. In this review, strategies for the polymer analogous modification of these materials and their surfaces are highlighted and correlated with the potential applications of the corresponding materials and blends. While the commercial availability of purified PHAs is addressed in brief, special focus is put on the (bio-)degradability of these polymers and ways to influence the degradation mechanism and/or the duration of degradation
UV-Induced Crosslinking of Poly[2-(2’-Norbornenyl)-2-Oxazoline]s
A 2-oxazoline monomer bearing a norbornenyl functionality in the side-chain was prepared from the reaction of 5-norbornene-2-carbonitrile and 2-ethanol amine. This monomer could be successfully polymerized using a 2-oxazolinium-based macroinitiator that was in-situ generated from the methyl cation-initiated oligomerization of 2-ethyl-2-oxazoline. This polymer could be subjected to polymeranalogous reactions involving the alkene groups of the norbornenyl side-chains: A proof-of-concept was established by utilizing the polymers in photoresists that were crosslinked by thiol-ene reactions involving bisfunctional thiols. Photoinitiators for the UV-induced thiol-ene reaction were required in catalytic amounts only. After development, the resists exhibited reproduction of the geometric patterns with a resolution of 30 ÎĽm
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