The Mass Spectrum of a Static Adjoint Particle

The bound states of fermions in the adjoint representation are of interest in supersymmetric models. We investigate the energy spectrum of the simplest -- the gluino-gluon bound states -- on several lattices in the quenched approximation. We use a static approximation for the gluino propagator. We find continuum limits of the splitting between the few lowest states, with the energy difference between the two lowest states of $354 \pm 9$ MeV.Comment: 3 pages, Latex, to appear Lattice 97 proceding

MEASURING AN ALMOST IDEAL DEMAND SYSTEM WITH GENERALIZED FLEXIBLE LEAST SQUARES

Structural change in meat consumption has been the focus of many researchers during the last two decades. In this paper we develop a dynamic linear Almost Ideal Demand System (AIDS) model from a cost function that allows for time varying parameters. This model is consistent with inertia in the parameters of the cost and indirect utility functions. It allows for persistent preferences which may arise from cultural biases, lifestyles, peer pressure, etc. An empirical application is conducted with US meat consumption and price data using a generalized system of flexible least squares, Generalized Flexible Least Squares (GFLS). GFLS allows parameters to evolve slowly over time through incorporating of penalties in fluctuations. Estimated quarterly elasticities were subjected to additional analysis to determine how highly they were related to the Brown and Schrader Cholesterol Index and relative prices. The combined results support that the movements of elasticities over time are related to both.Demand and Price Analysis, Institutional and Behavioral Economics,

Hadronic decay of a vector meson from the lattice

We explore the decay of a vector meson to two pseudoscalar mesons on the lattice with $N_f=2$ flavours of sea quark. Although we are working with quark masses that do not allow a physical decay, we show how the transition rate can be evaluated from the amplitude for $\rho \to \pi \pi$ and from the annihilation component of $\pi \pi \to \pi \pi$. We explore the decay amplitude for two different pion momenta and find consistent results. The coupling strength we find is in agreement with experiment. We also find evidence for a shift in the $\rho$ mass caused by mixing with two pion states.Comment: 13 pages, version as accepted for Physics Letters

Real-time observation of epitaxial graphene domain reorientation.

Graphene films grown by vapour deposition tend to be polycrystalline due to the nucleation and growth of islands with different in-plane orientations. Here, using low-energy electron microscopy, we find that micron-sized graphene islands on Ir(111) rotate to a preferred orientation during thermal annealing. We observe three alignment mechanisms: the simultaneous growth of aligned domains and dissolution of rotated domains, that is, 'ripening'; domain boundary motion within islands; and continuous lattice rotation of entire domains. By measuring the relative growth velocity of domains during ripening, we estimate that the driving force for alignment is on the order of 0.1 meV per C atom and increases with rotation angle. A simple model of the orientation-dependent energy associated with the moiré corrugation of the graphene sheet due to local variations in the graphene-substrate interaction reproduces the results. This work suggests new strategies for improving the van der Waals epitaxy of 2D materials

Hadronic transitions from the lattice

I discuss strategies to determine hadronic decay couplings from lattice studies. As a check of the methods, I explore the decay of a vector meson to two pseudoscalar mesons with $N_f=2$ flavours of sea quark. Although we are working with quark masses that do not allow a physical decay, I show how the transition rate can be evaluated from the amplitude for $\rho \to \pi \pi$ and from the annihilation component of $\pi \pi \to \pi \pi$. I explore the decay amplitude for two different pion momenta and find consistent results. The coupling strength found is in agreement with experiment. I also find evidence for a shift in the $\rho$ mass caused by mixing with two pion states. I also present results for the decay of a hybrid meson, for the case of heavy valence quarks.Comment: 10 pages, 7 ps figures, proc LHP03, Cairn