Vortices, Instantons and Branes

The purpose of this paper is to describe a relationship between the moduli space of vortices and the moduli space of instantons. We study charge k vortices in U(N) Yang-Mills-Higgs theories and show that the moduli space is isomorphic to a special Lagrangian submanifold of the moduli space of k instantons in non-commutative U(N) Yang-Mills theories. This submanifold is the fixed point set of a U(1) action on the instanton moduli space which rotates the instantons in a plane. To derive this relationship, we present a D-brane construction in which the dynamics of vortices is described by the Higgs branch of a U(k) gauge theory with 4 supercharges which is a truncation of the familiar ADHM gauge theory. We further describe a moduli space construction for semi-local vortices, lumps in the CP(N) and Grassmannian sigma-models, and vortices on the non-commutative plane. We argue that this relationship between vortices and instantons underlies many of the quantitative similarities shared by quantum field theories in two and four dimensions.Comment: 32 Pages, 4 Figure

Moulting reduces freeze susceptibility in the Antarctic mite Alaskozetes antarcticus (Michael)

The effect of moulting on the cold hardiness of the oribatid mite Alaskozetes antarcticus (Michael) is investigated. Non moulting animals show clear seasonal patterns of cold hardiness with high supercooling points (SCPs) at the peak of summer and an increasing proportion of low SCPs with declining environmental temperatures. By contrast, both field-fresh and laboratory acclimated (5 °C) mites in the moult state are consistently found to have low SCPs regardless of environmental temperature

Supercooling point frequency distributions in Collembola are affected by moulting

1. Many arthropods depress the freezing point of their body fluids (supercool) to avoid freezing at subzero temperatures. This is normally a seasonal response and is achieved by the production of specific biomolecules including cryoprotectants, a cessation in feeding, and the removal or masking of ice-nucleating material from their bodies. 2. In springtails, the mid-gut is shed during moulting which results in the complete evacuation of the gut and a concomitant reduction in the supercooling point (SCP). We determined whether this non-adaptive explanation could account for the variability observed in the SCP of summer-acclimatized springtails. 3. Moult preparation resulted in a highly significant reduction in the SCP. Feeding after moulting restored the SCP to previous high levels. 4. Significant differences in SCP between springtails sampled from vegetation and the soil surface, on different days, and at different sites on the same day were also documented, demonstrating that not all variation in SCP is environmentally induced. 5. Investigations of the responses of the SCP to environmental variation in springtails and other arthropods should take into account the effects of moulting before solely adaptive conclusions are drawn