SU(2) reduction in N=4 supersymmetric mechanics

We perform an su(2) Hamiltonian reduction of the general su(2)-invariant action for a self-coupled (4,4,0) supermultiplet. As a result, we elegantly recover the N=4 supersymmetric mechanics with spin degrees of freedom which was recently constructed in arXiv:0812.4276. This observation underscores the exceptional role played by the ``root'' supermultiplet in N=4 supersymmetric mechanics.Comment: 1+3 page

Linear, bounded, functional pretty-printing

We present two implementations of Oppen's pretty-printing algorithm in Haskell that meet the efficiency of Oppen's imperative solution but have a simpler, clear structure. We start with an implementation that uses lazy evaluation to simulate two co-operating processes. Then we present an implementation that uses higher-order functions for delimited continuations to simulate co-routines with explicit scheduling

Local heat flux and energy loss in a 2D vibrated granular gas

We performed event-driven simulations of a two-dimensional granular gas between two vibrating walls and directly measured the local heat flux and energy dissipation rate in the stationary state. Describing the local heat flux as a function of the coordinate x in the direction perpendicular to the driving walls, we use a generalization of Fourier's law, q_x(x) = kappa d_x T(x) + mu d_x rho(x), to relate the local heat flux to the local gradients of the temperature and density. This ansatz accounts for the fact that density gradients also generate heat flux, not only temperature gradients. The transport coefficients kappa and mu are assumed to be independent of x, and we check the validity of this assumption in the simulations. Both kappa and mu are determined for different system parameters, in particular, for a wide range of coefficients of restitution. We also compare our numerical results to existing hydrodynamic theories. Agreement is found for kappa for very small inelasticities only. Beyond this region, kappa and mu exhibit a striking non-monotonic behavior.Comment: 8 pages, 5 figure

Supermembrane limit of Yang-Mills theory

We consider Yang-Mills theory with $N{=}1$ super translation group in eleven auxiliary dimensions as the structure group. The gauge theory is defined on a direct product manifold $\Sigma_3\times S^1$, where $\Sigma_3$ is a three-dimensional Lorentzian manifold and $S^1$ is a circle. We show that in the infrared limit, when the metric on $S^1$ is scaled down, the Yang-Mills action supplemented by a Wess-Zumino-type term reduces to the action of an M2-brane.Comment: 1+6 page

Critical exponents of the driven elastic string in a disordered medium

We analyze the harmonic elastic string driven through a continuous random potential above the depinning threshold. The velocity exponent beta = 0.33(2) is calculated. We observe a crossover in the roughness exponent zeta from the critical value 1.26 to the asymptotic (large force) value of 0.5. We calculate directly the velocity correlation function and the corresponding correlation length exponent nu = 1.29(5), which obeys the scaling relation nu = 1/(2-zeta), and agrees with the finite-size-scaling exponent of fluctuations in the critical force. The velocity correlation function is non-universal at short distances.Comment: 4 pages, 3 figures. corrected references and typo

Chern-Simons flows on Aloff-Wallach spaces and Spin(7)-instantons

Due to their explicit construction, Aloff-Wallach spaces are prominent in flux compactifications. They carry G_2-structures and admit the G_2-instanton equations, which are natural BPS equations for Yang-Mills instantons on seven-manifolds and extremize a Chern-Simons-type functional. We consider the Chern-Simons flow between different G_2-instantons on Aloff-Wallach spaces, which is equivalent to Spin(7)-instantons on a cylinder over them. For a general SU(3)-equivariant gauge connection, the generalized instanton equations turn into gradient-flow equations on C^3 x R^2, with a particular cubic superpotential. For the simplest member of the Aloff-Wallach family (with 3-Sasakian structure) we present an explicit instanton solution of tanh-like shape.Comment: 1+17 pages, 1 figur

Alien Registration- Myhr, Olaf S. (New Sweden, Aroostook County)

https://digitalmaine.com/alien_docs/34402/thumbnail.jp

Lattice calculation of medium effects at short and long distances

We investigate medium effects in QCD like chromoelectric screening and quasi-particle mass generation by calculating the heavy quark potential as well as the temporal quark and gluon Coulomb gauge propagators in quenched approximation.Comment: To appear in proceedings of Quark Matter 2001, 4 pages LaTeX, uses espcrc1.st