Quark dispersion relation and dilepton production in the quark-gluon plasma

Under very general assumptions we show that the quark dispersion relation in the quark-gluon plasma is given by two collective branches, of which one has a minimum at a nonvanishing momentum. This general feature of the quark dispersion relation leads to structures (van Hove singularities, gaps) in the low mass dilepton production rate, which might provide a unique signature for the quark-gluon plasma formation in relativistic heavy ion collisions.     

Lattice vibrations at ideal Si(111) surfaces

Surface vibrations at an ideal (111) silicon surface with vanishing wavevector components parallel to the surface are calculated within the shell-model for a simple model of surface force constants.     

The Existence of Helical Chirality in a Sterically Congested Naphtho [9]annulenone Preliminary Communication

The existence of the naphtho [9]annulenone 1 in two skeletally enantiomeric forms is demonstrated with the use of ¹H? NMR. spectroscopy in conjunction with a chiral «shift» reagent.     

Über unitäre Darstellungen abzählbarer,diskreter Gruppen

Ohne Zusammenfassung     

Eine Charakterisierung kompakter Untergruppen lokal-kompakter Gruppen

Ohne Zusammenfassung     

On some high accuracy difference schemes for solving elliptic equations

Summary Two well known high accuracy Alternating Direction Implicit difference schemes for solving Laplace's equation and the Biharmonic equation are considered. The set of iteration parameters of Douglas is used in both problems. More complete optimum values of the parameters involved are given.     

Optimal systems for equipment maintenance and replacement under Markovian deterioration

Deterioration of equipment is modeled as a multistate discrete time controlled Markov process. The states are classified according to the degree of deterioration. The problem of design of optimal systems for equipment maintenance and replacement is considered when the decision-maker may take, in each stage, one of many available maintenance actions, classified according to their “stochastic effectiveness”; no action and replacement are included as alternatives. It is assumed that the transition probabilities satisfy two conditions which effectively describe a trend for monotonically increasing expected deterioration and rate of deterioration. Under these assumptions it is proved in the paper that the optimal (cost minimizing) decision system in an infinite horizon is of the control limit rule type, rapidly obtained by policy improvement algorithms. A numerical example is presented for a specific practical application; detailed data are available from the authors on request.     

Darstellung von vollständigen Vektorverbänden durch vollständige Funktionenvektorverbände

Ohne Zusammenfassung     

Zur Reduktionstheorie in separablen Hilbert-Räumen

Ohne Zusammenfassung     

On comparing optimum Alternating Direction Preconditioning and Extrapolated Alternating Direction Implicit schemes

The purpose of this paper is to show the equivalence of Alternating Direction Preconditioning and Extrapolated Alternating Direction Implicit methods in the case of two-level one-parameter optimized schemes as far as convergence rates are concerned, and also to give optimum parameters for the numerical solution of the self-adjoint second-order elliptic partial differential equation and the biharmonic equation.