Witten has argued that in 2+1 dimensions local supersymmetry can ensure the vanishing of the cosmological constant without requiring the equality of bose and fermi masses. We find that this mechanism is implemented in a novel fashion in the (2+1)-dimensional supersymmetric abelian Higgs model coupled to supergravity. The vortex solitons are annihilated by half of the supersymmetry transformatio...

A commuting row contraction is a d-tuple of commuting operators T1, . . . , Td such that ∑d i=1 TiT ∗ i ≤ I. Such operators have a polynomial functional calculus which extends to a norm closed algebra of multipliers Ad on Drury-Arveson space. We characterize those row contractions which admit an extension of this map to a weak-∗ continuous functional calculus on the full multiplier algebra. In ...

Congestion control in Signaling System #7 faces new challenges as mobile communication systems and Intelligent Networks grow rapidly. New services change traffic patterns, add to signalling network load, and raise demands on shorter service completion times. To handle new demands, the congestion control mechanisms must foresee an overload situation, and respond to it so that the network can mai...

The Brusselator is a generic reaction-diffusion model for a tri-molecular chemical reaction. We consider the case when the input and output reactions are slow. In this limit, we show the existence of K-periodic, spatially bi-stable structures, mesas, and study their stability. Using singular perturbation techniques, we find a threshold for the stability of K mesas. This threshold occurs in the ...

Long after its alleged demise, phlogiston was still presented, discussed and defended by leading chemists. Even some of the leading proponents of the new chemistry admitted its 'absolute existence'. We demonstrate that what was defended under the title 'phlogiston' was no longer a particular hypothesis about combustion and respiration. Rather, it was a set of ontological and epistemological ass...

Experimental and modeling studies have accumulated strong evidence suggesting that A-currents control firing rates in invertebrate neurons. However, the direct demonstration of a similar role remains to be established in vertebrate neurons. We tested this possibility in a simulated neuron embedded with a generic model of vertebrate A-currents. Under simulated current-clamp protocols, the generi...

0. Introduction. In this note, k denotes a field of characteristic p > 0, and the letters T, X and Y are formal indeterminants. Let F: k[[T]] —• /c[[X,Y]] be a (fixed) one-dimensional formal group law [Dieudonné, Hazewinkel, Lazard, Lubin] of height h > 0. Let V denote a k[[T]] module of finite length. Suppose Ann(V) = (T). Let q = p denote the least power of p such that n < q. It follows that ...

We study the dynamics of vortex-antivortex (VA) pairs in an infinitely thin ferromagnetic film with easy-plane anisotropy. These are localized excitations with finite energy that are characterized by a topological (skyrmion) number N = 0,±1. Topologically trivial (N = 0) VA pairs undergo Kelvin motion analogous to that encountered in fluid dynamics. In contrast, topologically nontrivial (N = ±1...

This paper presents initial results on the control of mechanical systems for which group symmetries exist (i.e., the dynamics are invariant under the action of a Lie group) and are not fully annihilated by the addition of nonholonomic constraints. These types of systems are characterized by the persistence of momentum-like drift terms which are not directly controllable via the inputs to the sy...