The vortex state in the BEC to BCS crossover: a path-integral description

We derive a path-integral description of the vortex state of a fermionic superfluid in the crossover region between the molecular condensate (BEC) regime and the Cooper pairing (BCS) regime. This path-integral formalism, supplemented by a suitable choice for the saddle point value of the pairing field in the presence of a vortex, offers a unified description that encompasses both the BEC and BCS limits. The vortex core size is studied as a function of the tunable interaction strength between the fermionic atoms. We find that in the BEC regime, the core size is determined by the molecular healing length, whereas in the BCS regime, the core size is proportional only to the Fermi wave length. The observation of such quantized vortices in dilute Fermi gases would provide an unambiguous proof of the realization of superfluidity in these gases.Comment: 10 pages, 2 figure

Die historiese Jesus as wonderwerker

The historical Jesus as miracle workerThis paper deals with some introductory aspects of the problem of the historical Jesus as miracle worker. After the attention that the words of Jesus have been receiving over the past few years, the deeds and especially the miracles of Jesus are now on the agenda of researchers. This paper surveys the sources that may be used in this research. It makes some comments on methods of research and finally gives a brief survey of the debate on the historicity of different types of miracle stories

S P J J van Rensburg, hoogleraar 1963-1972

S P J J van Rensburg, professor 1963-1972The aim of this article is to take a look at Van Rensburg as a theologian. He was a conservative theologian in the sense that he wanted to serve the church of Christby his scientific study of the Bible. He was greatly influenced by ‘Continental Theology’, especially as practiced by renowned German scholars. He was neither a fundamentalist nor over-enthusiastic about Bultmann’s idea of demythologising the New Testament

Kerklike tug volgens 1 Korintiërs 5 en 6

Ecclesiastical discipline according to 1 Cor 5 & 6According to Paul the believers in Jesus Christ form a community, being in certain aspects completely different from Jews or Gentiles. In order to be what they in principle already are, and for the ultimate benefit of the offenders, ecclesiastical discipline should be applied by this community of believers. The principle is put clear by Paul, but how should it be put into practice in present day circumstances and in each individual case? Do these chapters have any relevance for today’s church

BCS-to-BEC crossover from the exact BCS solution

The BCS-to-BEC crossover, as well as the nature of Cooper pairs, in a superconducting and Fermi superfluid medium is studied from the exact ground state wavefunction of the reduced BCS Hamiltonian. As the strength of the interaction increases, the ground state continuously evolves from a mixed-system of quasifree fermions and pair resonances (BCS), to pair resonances and quasibound molecules (pseudogap), and finally to a system of quasibound molecules (BEC). A single unified scenario arises where the Cooper-pair wavefunction has a unique functional form. Several exact analytic expressions, such as the binding energy and condensate fraction, are derived. We compare our results with recent experiments in ultracold atomic Fermi gases.Comment: 5 pages, 4 figures. Revised version with one figure adde

Postille 1955—1956, Boekencentrum N.V., ’s-Gravenhage

No Abstract

Short-coherence length superconductivity in the Attractive Hubbard Model in three dimensions

We study the normal state and the superconducting transition in the Attractive Hubbard Model in three dimensions, using self-consistent diagrammatics. Our results for the self-consistent $T$-matrix approximation are consistent with 3D-XY power-law critical scaling and finite-size scaling. This is in contrast to the exponential 2D-XY scaling the method was able to capture in our previous 2D calculation. We find the 3D transition temperature at quarter-filling and $U=-4t$ to be $T_c=0.207t$. The 3D critical regime is much narrower than in 2D and the ratio of the mean-field transition to $T_c$ is about 5 times smaller than in 2D. We also find that, for the parameters we consider, the pseudogap regime in 3D (as in 2D) coincides with the critical scaling regime.Comment: 4 pages, 5 figure