2,661 research outputs found
On the partition sum of the NS five-brane
We study the Type IIA NS five-brane wrapped on a Calabi-Yau manifold X in a
double-scaled decoupling limit. We calculate the euclidean partition function
in the presence of a flat RR 3-form field. The classical contribution is given
by a sum over fluxes of the self-dual tensor field which reduces to a
theta-function. The quantum contributions are computed using a T-dual IIB
background where the five-branes are replaced by an ALE singularity. Using the
supergravity effective action we find that the loop corrections to the free
energy are given by B-model topological string amplitudes. This seems to
provide a direct link between the double-scaled little strings on the
five-brane worldvolume and topological strings. Both the classical and quantum
contributions to the partition function satisfy (conjugate) holomorphic anomaly
equations, which explains an observation of Witten relating topological string
theory to the quantization of three-form fields.Comment: 35 page
Blurring the picture:Introductions, invasions, extinctions - Biogeography in a global world
Global biogeography and phylogeography have gained importance as research topics in zoology, as attested by the steady increase in the number of journals devoted to this topic and the number of papers published. Yet, in a globalising world, with species reintroductions, invasions of alien species, and large-scale extinctions, unravelling the true biogeographic relationships between areas and species may become increasingly difficult. We present an introduction to the symposium ‘Biogeography: explaining and predicting species distributions in space and time’ held in Amsterdam in 2007, and the resulting papers as published in this special issue, including papers on crustaceans, birds and mammals
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