Einstein's cosmic model of 1931 revisited: an analysis and translation of a forgotten model of the universe

We present a translation and analysis of a cosmic model published by Einstein in 1931. The paper, which is not widely known, features a model of a universe that undergoes an expansion followed by a contraction, quite different to his static model of 1917 or the monotonic Einstein-de Sitter model of 1932. The paper offers many insights into the cosmology of Albert Einstein in the light of the first evidence for an expanding universe, and we discuss his views of issues such as the curvature of space, the cosmological constant, the singularity and the timespan of the expansion. We argue that retrospective descriptions of this model as cyclic or periodic are not historically or mathematically accurate. We find that calculations in the paper of the matter density and radius of the universe contain a numerical error, a finding that is supported by writing on a blackboard used by Einstein during a lecture at Oxford University in May 1931. Our article concludes with a general discussion of his philosophy of cosmology.Comment: Accepted for publication in the European Physical Journal (H). The article includes a first English translation of Einstein's 1931 SAW paper and the discovery of an error in Einstein's calculation of the matter density of the universe. 30 pages, 2 figure

Ultracold, radiative charge transfer in hybrid Yb ion - Rb atom traps

Ultracold hybrid ion-atom traps offer the possibility of microscopic manipulation of quantum coherences in the gas using the ion as a probe. However, inelastic processes, particularly charge transfer can be a significant process of ion loss and has been measured experimentally for the Yb$^{+}$ ion immersed in a Rb vapour. We use first-principles quantum chemistry codes to obtain the potential energy curves and dipole moments for the lowest-lying energy states of this complex. Calculations for the radiative decay processes cross sections and rate coefficients are presented for the total decay processes. Comparing the semi-classical Langevin approximation with the quantum approach, we find it provides a very good estimate of the background at higher energies. The results demonstrate that radiative decay mechanisms are important over the energy and temperature region considered. In fact, the Langevin process of ion-atom collisions dominates cold ion-atom collisions. For spin dependent processes \cite{kohl13} the anisotropic magnetic dipole-dipole interaction and the second-order spin-orbit coupling can play important roles, inducing couplingbetween the spin and the orbital motion. They measured the spin-relaxing collision rate to be approximately 5 orders of magnitude higher than the charge-exchange collision rate \cite{kohl13}. Regarding the measured radiative charge transfer collision rate, we find that our calculation is in very good agreement with experiment and with previous calculations. Nonetheless, we find no broad resonances features that might underly a strong isotope effect. In conclusion, we find, in agreement with previous theory that the isotope anomaly observed in experiment remains an open question.Comment: 7 figures, 1 table accepted for publication in J. Phys. B: At. Mol. Opt. Phys. arXiv admin note: text overlap with arXiv:1107.114

Spin-polarized tunneling through randomly transparent magnetic junctions: Reentrant magnetoresistance approaching the Julliere limit

Electron conductance in planar magnetic tunnel junctions with long-range barrier disorder is studied within Glauber-eikonal approximation enabling exact disorder ensemble averaging by means of the Holtsmark-Markov method. This allows us to address a hitherto unexplored regime of the tunneling magnetoresistance effect characterized by the crossover from momentum-conserving to random tunneling as a function of the defect concentration. We demonstrate that such a crossover results in a reentrant magnetoresistance: It goes through a pronounced minimum before reaching disorder- and geometry-independent Julliere's value at high defect concentrations.Comment: 7 pages, 5 figures, derivation of Eq. (39) added, errors in Ref. 7 correcte

First in family students – what they say about being at university

This article is open access under a Creative Commons Attribution Licence (CC-BY).Exploring what students say in semi-structured, open-ended interviews provides a rich and personal understanding of their encounters with the university. The opportunity to discuss the experiences of First in Family (FiF) students as they progress through their degree or reach its end allows us to gain insight into their reasons for attending university, their determination to stay and what they believe helped them succeed. This paper discusses the three main themes related to the FiF student experience we uncovered as a result of a detailed literature review and through our interviews. These themes are, their ‘journey’ into and through higher education; their position as ‘student’ which includes the demographic aspects as well as their own concepts of themselves as students; and, the ‘networks’ they have used and developed to succeed at university. The students’ insights may be used to encourage and help future FiF students to complete their studies

Beyond the economics, benefit and cost of higher education: First in family student perspectives

This article is open access under a Creative Commons Attribution Licence (CC-BY).Internationally, higher education is considered key to individual and societal economic success. Using a narrative inquiry approach, this paper broadens our understanding of the benefit and cost of participating in higher education (HE) beyond employment opportunities and tuition fees. The qualitative study on which this paper is based explores the lived experience of eighteen First in Family (FiF) students to create a collection of narrative accounts. On the basis of this evidence, we argue that the benefit of HE extends to encompass the strengthening of FiF students’ sense of competencies and confidence, contributes towards broadening of social experiences, and transforms perspectives. Furthermore, associated non-monetary costs of HE includes the requirement to balance competing life demands and the adoption of poor health behaviours. The study highlights the importance of both monetary and non-monetary factors when assessing overall return on investment of HE