Transport properties of LaCu2Si2 and CeCu2Si2 between 1.5K and 300K

We report measurements of the electrical resistivity, the thermal conductivityk and the thermoelectric powerS between 1.5K and 300K on the anomalous CeCu₂Si₂ compound and on LaCu₂Si₂ as reference compound. For LaCu₂Si₂ the temperature dependences of andS are in accord with those found in otherd band metals. For CeCu₂Si₂ the observed resistivity (220 µ cm at 200K) leads to a very short electronic mean free path which is of the order of the Ce-Ce spacing. Correspondingly,k is almost identical with the phonon contributionk _p . Below 20K, resistivity and thermoelectric power strongly suggest Fermi liquid behavior with a degeneracy temperature between 20K and 40K. Above 200K, both andS decrease proportionally to –ln(T/1 K).Work performed within the research program of the Sonderforschungsbereich 125 Aachen/Jülich/KölnPart of this work will be presented at the Int. Conf. on Rare Earths in the Metallic State, St. Pierre de Chartreuse, Sept. 1978     

Electrons in disordered systems. Scaling near the mobility edge

Renormalization group arguments are applied to an ensemble of disordered electronic systems (without electron-electron interaction). The renormalization group procedure consists of a sequence of transformations of the length and the energy scales, and of orthogonal transformations of the electronic states. Homogeneity and power laws are obtained for various one and two-particle correlations and for the low-temperature conductivity in the vicinity of the mobility edge. Two types of fixed point ensembles are proposed, a homogeneous ensemble which is roughly approximated by a cell model, and an inhomogeneous ensemble.     

Functions of translation type and functorial properties of Segal algebras II

In this paper we investigate functorial properties of the Segal algebra which consists of all functionsf in Wiener's algebra onG with Fourier transform in Wiener's algebra on the dual group . Especially may serve as a very large and natural domain for Poisson's formula. Moreover, there is introduced a Segal algebraE ₀(G) containing as a subspace, but still eachfE ₀(S) satisfies Poisson's formula.     

Freeze-out conditions in ultrarelativistic heavy-ion collisions

We present recent results on single particle transverse momentum distributions of pions, kaons and protons, measured in CERN Experiment NA44, of 200 AGeV/c S+S and 158 AGeV/c Pb+Pb central collisions. By comparing these data with thermal and transport models, freeze-out parameters like the temperatureT _fo and the chemical potentials (μ _q ,μ _s ) are extracted and discussed.     

Transverse momentum distributions of neutral pions from central and peripheral16O+Au collisions at 200A·GeV

The production of neutral pions by the interaction of 200A·GeV p and¹⁶O projectiles with a Au target has been studied in the pseudorapidity range 1.5≦η≦2.1. Transverse momentum spectra have been measured between 0.4 GeV/c and 3.6 GeV/c and their dependence on the centrality of the collision has been investigated. The peripheral-collision spectra display a marked change of slope with a hard component starting at about 1.8 GeV/c, in contrast to central-collision data. The data are discussed in comparison to p+p and α+α data from the ISR.     

Consequences of the center–of–mass correction in nuclear mean–field models

We study the influence of the scheme for the correction for spurious center–of–mass motion on the fit of effective interactions for self–consistent nuclear mean–field calculations. We find that interactions with very simple center–of–mass correction have significantly larger surface coefficients than interactions for which the center–of–mass correction was calculated for the actual many–body state during the fit. The reason for that is that the effective interaction has to counteract the wrong trends with nucleon number of all simplified schemes for center–of–mass correction which puts a wrong trend with mass number into the effective interaction itself. The effect becomes clearly visible when looking at the deformation energy of largely deformed systems, e.g. superdeformed states or fission barriers of heavy nuclei. Received: 6 September 1999     

Kinetic energy spectrum and polarization of neutrons from the reaction 12C(p,n)X at 590 MeV

Abstact: The kinetic energy spectrum and the polarization of the PSI neutron beam produced in the reaction ¹²C(p,n)X at 0° with 590 MeV polarized protons were investigated. A strong energy dependence of the neutron beam polarization is observed which was not expected at the time the neutron beam was built. Received: 3 April 1998