Fixed Number and Quantum Size Effects in Nanoscale Superconductors

In recent experiments on nanoscale Al particles, whose electron number was fixed by charging effects, a ``negative gap'' was observed in particles with an odd number of electrons. This observation has called into question the use of a grand canonical ensemble in describing superconductivity in such ultrasmall particles. We have studied the effects of fixed electron number and finite size in nanoscale superconductors, by applying the canonical BCS theory for the attractive Hubbard model. The ground state energy and the energy gap are compared with the conventional and parity-projected grand canonical BCS results, and in one dimension also with the exact solutions by the Bethe ansatz. The crossover from the bulk to quantum limit is studied for various regimes of electron density and coupling strength. The effects of boundary conditions and different lattice structures are also examined. A ``negative gap'' for odd electron number emerges most naturally in the canonical scheme. For even electron number, the gap is particularly large for ``magic numbers'' of electrons for a given system size or of atoms for a fixed electron density. These features are in accordance with the exact solutions, but are essentially missed in the grand canonical results.Comment: 2 pages, 4 figures, submitted to Physica C for M2S-HTSC-VI Proceeding

Universal scaling relations for logarithmic-correction exponents

By the early 1960's advances in statistical physics had established the existence of universality classes for systems with second-order phase transitions and characterized these by critical exponents which are different to the classical ones. There followed the discovery of (now famous) scaling relations between the power-law critical exponents describing second-order criticality. These scaling relations are of fundamental importance and now form a cornerstone of statistical mechanics. In certain circumstances, such scaling behaviour is modified by multiplicative logarithmic corrections. These are also characterized by critical exponents, analogous to the standard ones. Recently scaling relations between these logarithmic exponents have been established. Here, the theories associated with these advances are presented and expanded and the status of investigations into logarithmic corrections in a variety of models is reviewed.Comment: Review prepared for the book "Order, Disorder, and Criticality. Vol. III", ed. by Yu. Holovatch and based on the Ising Lectures in Lviv. 48 pages, 1 figur

The music of organising: Exploring aesthetic ethnography

Through a discussion of Ingarden’s phenomenology, this paper proposes an aesthetic ethnographic methodology. Aesthetic ethnography enables the researcher to view organisations as if they are works of art. This involves observing the continual oscillation between order and chaos, a quality Schiller terms as the play impulse. The shifts in focus from naïve outsider (Emotional Attachment) to critical insider (Cognitive Detachment) and then to informed outsider (Integrated Synthesis) are explored, followed by a case study of a symphony orchestra undergoing governance change

Recent Progress in Intersecting D-brane Models

The aim of this article is to review some recent progress in the field of intersecting D-brane models. This includes the construction of chiral, semi-realistic flux compactifications, the systematic study of Gepner model orientifolds, the computation of various terms in the low energy effective action and the investigation of the statistics of solutions to the tadpole cancellation conditions.Comment: 13 pages, 1 figure, contribution to the proceedings of the 37. Symposium Ahrenshoop, 23-27 August 2004, Wernsdorf, Germany, v3: more refs. adde