Single and Many Particle Correlation Functions and Uniform Phase Bases for Strongly Correlated Systems

The need for suitable many or infinite fermion correlation functions to describe some low dimensional strongly correlated systems is discussed. This is linked to the need for a correlated basis, in which the ground state may be postive definite, and in which single particle correlations may suffice. A particular trial basis is proposed, and applied to a certain quasi-1D model. The model is a strip of the 2D square lattice wrapped around a cylinder, and is related to the ladder geometries, but with periodic instead of open boundary conditions along the edges. Analysis involves a novel mean-field approach and exact diagonalisation. The model has a paramagnetic region and a Nagaoka ferromagnetic region. The proposed basis is well suited to the model, and single particle correlations in it have power law decay for the paramagnet, where the charge motion is qualitatively hard core bosonic. The mean field also leads to a BCS-type model with single particle long range order.Comment: 23 pages, in plain tex, 12 Postscript figures included. Accepted for publication in J.Physics : Condensed Matte

Effects of the roller feed ratio on wrinkling failure in conventional spinning of a cylindrical cup

In this study, wrinkling failure in conventional spinning of a cylindrical cup has been investigated by using both finite element (FE) analysis and experimental methods. FE simulation models of a spinning experiment have been developed using the explicit finite element solution method provided by the software Abaqus. The severity of wrinkles is quantified by calculating the standard deviation of the radial coordinates of element nodes on the edge of the workpiece obtained from the FE models. The results show that the severity of wrinkles tends to increase when increasing the roller feed ratio. A forming limit study for wrinkling has been carried out and shows that there is a feed ratio limit beyond which the wrinkling failure will take place. Provided that the feed ratio is kept below this limit, the wrinkling failure can be prevented. It is believed that high compressive tangential stresses in the local forming zone are the causes of the wrinkling failure. Furthermore, the computational performance of the solid and shell elements in simulating the spinning process are examined and the tool forces obtained from wrinkling and wrinkle-free models are compared. Finally, the effects of the feed ratio on variations of the wall thickness of the spun cylindrical cup are investigated. </jats:p

Effect of pairing correlations on nuclear low-energy structure: BCS and general Bogoliubov transformation

Low-lying nuclear states of Sm isotopes are studied in the framework of a collective Hamiltonian based on covariant energy density functional theory. Pairing correlation are treated by both BCS and Bogoliubov methods. It is found that the pairing correlations deduced from relativistic Hartree-Bogoliubov (RHB) calculations are generally stronger than those by relativistic mean-field plus BCS (RMF+BCS) with same pairing force. By simply renormalizing the pairing strength, the diagonal part of the pairing field is changed in such a way that the essential effects of the off-diagonal parts of the pairing field neglected in the RMF+BCS calculations can be recovered, and consequently the low-energy structure is in a good agreement with the predictions of the RHB model.Comment: 5 figures, 5 page

Count Me In: The dimensions of social inclusion through culture and sport

This study was set up to examine claims made for the ability of cultural projects to promote social inclusion (cultural projects are here taken to include those incorporating sport, the arts, media, heritage and outdoor adventure). This was to be achieved primarily by collecting evidence from a sample of 14 projects selected from some 200 that had volunteered their services. The report to the government’s Social Exclusion Unit (SEU) from the Policy Action Team (PAT10) (1999)2 noted the potential. In his foreword, Chris Smith (then Secretary of State for the Department for Culture Media and Sport (DCMS)) wrote: “… art and sport can not only make a valuable contribution to delivering key outcomes of lower long term unemployment, less crime, better health and better qualifications, but can also help to develop the individual pride, community spirit and capacity for responsibility that enable communities to run regeneration programmes themselves”. Similar statements have followed from other politicians, particularly in the recent Commons debate on sport and social exclusion (22/11/01), and again in the public health debate (13/12/01). However, the PAT 10 report also came to the same conclusion as previous commentators (e.g. Glyptis, 19893; Allison & Coalter, 19964; Long & Sanderson, 19985) that there is little ‘hard’ evidence of the social benefits that accrue

Count Me In: The Dimensions of social inclusion through Culture, Media & Sport (Executive Summary)

This study was set up to examine claims made for the ability of cultural projects to promote social inclusion (cultural projects are here taken to include those incorporating sport, the arts, media, heritage and outdoor adventure). This was to be achieved primarily by collecting evidence from a sample of 14 projects selected from some 200 that had volunteered their services. The report to the government’s Social Exclusion Unit (SEU) from the Policy Action Team (PAT10) (1999) noted the potential. In his foreword, Chris Smith (then Secretary of State for the Department for Culture Media and Sport (DCMS)) wrote: “… art and sport can not only make a valuable contribution to delivering key outcomes of lower long term unemployment, less crime, better health and better qualifications, but can also help to develop the individual pride, community spirit and capacity for responsibility that enable communities to run regeneration programmes themselves”. Similar statements have followed from other politicians, particularly in the recent Commons debate on sport and social exclusion (22/11/01), and again in the public health debate (13/12/01). However, the PAT 10 report also came to the same conclusion as previous commentators (e.g. Glyptis, 19893; Allison & Coalter, 19964; Long & Sanderson, 1998) that there is little ‘hard’ evidence of the social benefits that accrue

Anomalous scaling of conductivity in integrable fermion systems

We analyze the high-temperature conductivity in one-dimensional integrable models of interacting fermions: the t-V model (anisotropic Heisenberg spin chain) and the Hubbard model, at half-filling in the regime corresponding to insulating ground state. A microcanonical Lanczos method study for finite size systems reveals anomalously large finite-size effects at low frequencies while a frequency-moment analysis indicates a finite d.c. conductivity. This phenomenon also appears in a prototype integrable quantum system of impenetrable particles, representing a strong-coupling limit of both models. In the thermodynamic limit, the two results could converge to a finite d.c. conductivity rather than an ideal conductor or insulator scenario.Comment: 6 pages, 3 figures. Submitted to PR