3,241 research outputs found
Nickel hydrogen low Earth orbit test program update and status
The current status of nickel-hydrogen (NiH2) testing ongong at NWSC, Crane In, and The Aerospace Corporation, El Segundo, Ca are described. The objective of this testing is to develop a database for NiH2 battery use in Low Earth Orbit (LEO) and support applications in Medium Altitude Orbit (MAO). Individual pressure vessel-type cells are being tested. A minimum of 200 cells (3.5 in diameter and 4.5 in diameter) are included in the test, from four U.S. vendors. As of this date (Nov. 18, 1986) approximately 60 cells have completed preliminary testing (acceptance, characterization, and environmental testing) and have gone into life cycling
There are No Causality Problems for Fermi's Two Atom System
A repeatedly discussed gedanken experiment, proposed by Fermi to check
Einstein causality, is reconsidered. It is shown that, contrary to a recent
statement made by Hegerfeldt, there appears no causality paradoxon in a proper
theoretical description of the experiment.Comment: 6 pages, latex, DESY 94-02
Canonical Quantization Inside the Schwarzschild Black Hole
We propose a scheme for quantizing a scalar field over the Schwarzschild
manifold including the interior of the horizon. On the exterior, the timelike
Killing vector and on the horizon the isometry corresponding to restricted
Lorentz boosts can be used to enforce the spectral condition. For the interior
we appeal to the need for CPT invariance to construct an explicitly positive
definite operator which allows identification of positive and negative
frequencies. This operator is the translation operator corresponding to the
inexorable propagation to smaller radii as expected from the classical metric.
We also propose an expression for the propagator in the interior and express it
as a mode sum.Comment: 8 pages, LaTex. Title altered. One reference added. A few typos esp.
eq.(7),(38) corrected. To appear in Class.Q.Gra
Localization of dexamethasone within dendritic core-multishell (CMS) nanoparticles and skin penetration properties studied by multi-frequency electron paramagnetic resonance (EPR) spectroscopy
The skin and especially the stratum corneum (SC) act as a barrier and protect epidermal cells and thus the whole body against xenobiotica of the external environment. Topical skin treatment requires an efficient drug delivery system (DDS). Polymer-based nanocarriers represent novel transport vehicles for dermal application of drugs. In this study dendritic core-multishell (CMS) nanoparticles were investigated as promising candidates. CMS nanoparticles were loaded with a drug (analogue) and were applied to penetration studies of skin. We determined by dual-frequency electron paramagnetic resonance (EPR) how dexamethasone (Dx) labelled with 3-carboxy-2,2,5,5-tetramethyl-1-pyrrolidinyloxy (PCA) is associated with the CMS. The micro-environment of the drug loaded to CMS nanoparticles was investigated by pulsed high-field EPR at cryogenic temperature, making use of the fact that magnetic parameters (g-, A-matrices, and spin-lattice relaxation time) represent specific probes for the micro-environment. Additionally, the rotational correlation time of spin-labelled Dx was probed by continuous wave EPR at ambient temperature, which provides independent information on the drug environment. Furthermore, the penetration depth of Dx into the stratum corneum of porcine skin after different topical applications was investigated. The location of Dx in the CMS nanoparticles is revealed and the function of CMS as penetration enhancers for topical application is shown
Localized Endomorphisms of the Chiral Ising Model
Based on the treatment of the chiral Ising model by Mack and Schomerus, we
present examples of localized endomorphisms and
. It is shown that they lead to the same
superselection sectors as the global ones in the sense that unitary equivalence
and holds. Araki's formalism of the selfdual CAR algebra is
used for the proof. We prove local normality and extend representations and
localized endomorphisms to a global algebra of observables which is generated
by local von Neumann algebras on the punctured circle. In this framework, we
manifestly prove fusion rules and derive statistics operators.Comment: 41 pages, latex2
Effective quantum gravity observables and locally covariant QFT
Perturbative algebraic quantum field theory (pAQFT) is a mathematically
rigorous framework that allows to construct models of quantum field theories on
a general class of Lorentzian manifolds. Recently this idea has been applied
also to perturbative quantum gravity, treated as an effective theory. The
difficulty was to find the right notion of observables that would in an
appropriate sense be diffeomorphism invariant. In this article I will outline a
general framework that allows to quantize theories with local symmetries (this
includes infinitesimal diffeomorphism transformations) with the use of the BV
(Batalin-Vilkovisky) formalism. This approach has been successfully applied to
effective quantum gravity in a recent paper by R. Brunetti, K. Fredenhagen and
myself. In the same paper we also proved perturbative background independence
of the quantized theory, which is going to be discussed in the present work as
well.Comment: 16 pages, based on a plenary talk given at the 14th Marcel Grossmann
Meeting in Rome (July 2015
Measurement-induced localization of relative degrees of freedom
Published versio
CFT fusion rules, DHR gauge groups, and CAR algebras
It is demonstrated that several series of conformal field theories, while
satisfying braid group statistics, can still be described in the conventional
setting of the DHR theory, i.e. their superselection structure can be
understood in terms of a compact DHR gauge group. Besides theories with only
simple sectors, these include (the untwisted part of) c=1 orbifold theories and
level two so(N) WZW theories. We also analyze the relation between these models
and theories of complex free fermions.Comment: 22 pages, LaTeX2
The Modular Group, Operator Ordering, and Time in (2+1)-Dimensional Gravity
A choice of time-slicing in classical general relativity permits the
construction of time-dependent wave functions in the ``frozen time''
Chern-Simons formulation of -dimensional quantum gravity. Because of
operator ordering ambiguities, however, these wave functions are not unique. It
is shown that when space has the topology of a torus, suitable operator
orderings give rise to wave functions that transform under the modular group as
automorphic functions of arbitrary weights, with dynamics determined by the
corresponding Maass Laplacians on moduli space.Comment: 8 pages, LaTe
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