Decoherence properties of arbitrarily long histories

Within the decoherent histories formulation of quantum mechanics, we consider arbitrarily long histories constructed from a fixed projective partition of a finite-dimensional Hilbert space. We review some of the decoherence properties of such histories including simple necessary decoherence conditions and the dependence of decoherence on the initial state. Here we make a first step towards generalization of our earlier results [Scherer and Soklakov, e-print: quant-ph/0405080, (2004) and Scherer et al., Phys. Lett. A, vol. 326, 307, (2004)] to the case of approximate decoherence.Comment: 8 pages, no figure

Reassessing Public Meetings As Participation in Risk Management Decisions

Using a U.S. case study, Ms. McComas and Dr. Scherer discuss how reliance on public meetings as tools for risk communication in public policy decisions affects relationships between stakeholders and risk managers

Strict Positivstellens\"atze for matrix polynomials with scalar constraints

We extend Krivine's strict positivstellensatz for usual (real multivariate) polynomials to symmetric matrix polynomials with scalar constraints. The proof is an elementary computation with Schur complements. Analogous extensions of Schm\" udgen's and Putinar's strict positivstellensatz were recently proved by Hol and Scherer using methods from optimization theory.Comment: 6 pages, to appear in Linear Algebra and its Application

Interpretation of a low-lying excited state of the reaction center of Rb.sphaeroides as a double triplet

The recently observed transient absorption of the lowest excited state of the special pair P* at 2710 cm-1 is assigned as a singlet which arises from the coupling of the two lowest triplets from the two dimer halves. INDO calculations are used to predict its intensity. The analogy of the coupling mechanism to the trip-doublet spectrum from P+ is shown and the influence of the double triplet on the Stark effect of P* is investigated.Comment: 10 pages Latex, 1 figure, to be published in Chemical Physics Letters 199

Generalized polarizabilities and the chiral structure of the nucleon

We discuss the virtual Compton scattering reaction $e^-p\to e^-p\gamma$ at low energies. We present results for the generalized polarizabilities of the nucleon obtained in heavy baryon chiral perturbation theory at $O(p^3)$.Comment: 5 pages, LaTex file, 1 postscript figure, uses ``espcrc1.sty'', talk given by S. Scherer at the 15th International Conference on Few Body Problems in Physics, Groningen, The Netherlands, 22-26 July 1997, to appear in the proceedings (Nucl. Phys. A

Initial states and decoherence of histories

We study decoherence properties of arbitrarily long histories constructed from a fixed projective partition of a finite dimensional Hilbert space. We show that decoherence of such histories for all initial states that are naturally induced by the projective partition implies decoherence for arbitrary initial states. In addition we generalize the simple necessary decoherence condition [Scherer et al., Phys. Lett. A (2004)] for such histories to the case of arbitrary coarse-graining.Comment: 10 page

Archimedean operator-theoretic Positivstellens\"atze

We prove a general archimedean positivstellensatz for hermitian operator-valued polynomials and show that it implies the multivariate Fejer-Riesz Theorem of Dritschel-Rovnyak and positivstellens\"atze of Ambrozie-Vasilescu and Scherer-Hol. We also obtain several generalizations of these and related results. The proof of the main result depends on an extension of the abstract archimedean positivstellensatz for *-algebras that is interesting in its own right.Comment: 17 pages, revised version, to appear in the Journal of Functional Analysi

A Finite Element Model of Multi-Layered Laser Sintered Parts

Afinite element heat transfer analysis is applied to the selective laser sinteringofa layered part made frompolyroerpowder. The sinteringsubroutine in the code is based on the analyses of Scherer [l t2] and Mackenzie and Shuttleworth [3]. The density and conductivity of the particle bed are treated as functions of the void fraction of the bed. The Yagi - Kunii [4] thermal characterization of the powder bed is used to calculate the effective conductivity of the bed. An example is worked for ABS powder.Mechanical Engineerin