Effects of non-perturbatively improved dynamical fermions in UKQCD simulations

We present results for QCD with 2 degenerate flavours of quark using a non-perturbatively improved action on a lattice volume of $16^3\times32$ where the bare gauge coupling and bare dynamical quark mass have been chosen to maintain a fixed physical lattice spacing and volume (1.71 fm). By comparing measurements from these matched ensembles, including quenched ones, we find evidence of dynamical quark effects on the short distance static potential, the scalar glueball mass and the topological susceptibility. There is little evidence of effects on the light hadron spectrum over the range of quark masses studied ($m_{\pi}/m_{\rho}\geq 0.60$).Comment: Lattice 2000 (Spectrum and quark masses), 4 pages, 5 figure

A voyage to Mars: A challenge to collaboration between man and machines

A speech addressing the design of man machine systems for exploration of space beyond Earth orbit from the human factors perspective is presented. Concerns relative to the design of automated and intelligent systems for the NASA Space Exploration Initiative (SEI) missions are largely based on experiences with integrating humans and comparable systems in aviation. The history, present status, and future prospect, of human factors in machine design are discussed in relation to a manned voyage to Mars. Three different cases for design philosophy are presented. The use of simulation is discussed. Recommendations for required research are given

Critical Behaviour of the Two Dimensional Step Model

We use finite--size scaling of Lee--Yang partition function zeroes to study the critical behaviour of the two dimensional step or sgn $O(2)$ model. We present evidence that, like the closely related $XY$--model, this has a phase transition from a disordered high temperature phase to a low temperature massless phase where the model remains critical. The critical parameters (including logarithmic corrections) are compatible with those of the $XY$--model indicating that both models belong to the same universality class.Comment: 6 pages latex, 3 postscript figures, compressed and uuencoded (revised remarks on Lee_Yang theorem, version to appear in Phys Rev B

Approximate actions for dynamical fermions

Recent developments and applications of approximate actions for full lattice QCD are described. We present first results based on the stochastic estimation of the fermion determinant on $12^3\times 24$ configurations at $\beta=5.2$.Comment: 3 pages, Latex, no figures, Contribution to Lattice 97, The XV International Symposium on Lattice Field Theory, Edinburgh 22-26 July 199

Finite size effects and scaling in lattice CP(N-1)

We present model predictions for the spectrum of $CP^{N-1}$ in a periodic box and use them to interpret the strong finite size effects observed in lattice simulations at medium values of $N$. The asymptotic scaling behaviour of alternative lattice actions is discussed along with some aspects of multigrid algorithm efficiency.Comment: 6 pages of text plus 2 pages of figures, Liverpool Preprint LTH28

Conditions for building a community of practice in an advanced physics laboratory

In this paper we explore the theory of communities of practice in the context of a physics college course and in particular the classroom environment of an advanced laboratory. We introduce the idea of elements of a classroom community being able to provide students with the opportunity to have an accelerated trajectory towards being a more central participant of the community of practice of physicists. This opportunity is a result of structural features of the course and a primary instructional choice which result in the development of a learning community with several elements that encourage students to engage in more authentic practices of a physicist. A jump in accountable disciplinary knowledge is also explored as a motivation for enculturation into the community of practice of physicists. In the advanced laboratory what students are being assessed on as counting as physics is significantly different and so they need to assimilate in order to succeed.Comment: 14 pages, 1 figur

Unquenching the Schwinger Model (revised)

We study the quenched and unquenched lattice Schwinger model with Wilson fermions. The lowest non-trivial order of the systematic expansion recently proposed by Sexton and Weingarten is shown to allow good estimates of long distance physics from quenched configurations. Results for the static potential and the lowest bound state mass are presented.Comment: 4 pages, 2 figures, self-unpacking uuencoded compressed postscript Contribution to Lattice 95 [Revision: value corrected on p.3