Triangle Seminars
Monday, 30 Jan 2006
A new large N phase transition in two dimensional Yang-Mills theories
Sergio Arianos
(Turin University)
Abstract:
We review some correspondences between YM2 and the theory of random walks. In this spirit, we then consider YM2 in a non conventional large N limit, in which the coupling constant A is not fixed ('t Hooft scaling) but scales with a factor logN. In this regime the effective number of d.o.f. of the
model is proportional to N to the power k, with k(A) less than 2, rather than to N squared. Moreover, a transition corresponding to the cutoff transition in random walks occurs when k equal to zero. This transition may be thought of as a step further in the spirit of the Douglas-Kazakov transition.
We review some correspondences between YM2 and the theory of random walks. In this spirit, we then consider YM2 in a non conventional large N limit, in which the coupling constant A is not fixed ('t Hooft scaling) but scales with a factor logN. In this regime the effective number of d.o.f. of the
model is proportional to N to the power k, with k(A) less than 2, rather than to N squared. Moreover, a transition corresponding to the cutoff transition in random walks occurs when k equal to zero. This transition may be thought of as a step further in the spirit of the Douglas-Kazakov transition.
Posted by: brunel
Twisted and generalized K3 surfaces
Daniel Huybrechts
(Bonn)
Tuesday, 31 Jan 2006
Supersymmetry and (generalised) Geometry
Dan Waldram
(Imperial)
Wednesday, 1 Feb 2006
Black Hole Partition Functions and Duality
Thomas Mohaupt
(Liverpool)
Brane world effective actions for D-branes with fluxes
📍 London
Rodolfo Russo
(Queen Mary)
Abstract:
I will discuss how to use string techniques to systematically
derive brane world effective actions for models with magnetized (or
equivalently intersecting) D-branes. In particular, I derive the
dependence on all NS-NS moduli of the kinetic terms of the chiral
matter in a generic non-supersymmetric brane configurations with
non-commuting open string fluxes. Near a N=1 supersymmetric point the
effective action contains D and F term breaking terms which can be
explicitly computed with string diagrams.
I will discuss how to use string techniques to systematically
derive brane world effective actions for models with magnetized (or
equivalently intersecting) D-branes. In particular, I derive the
dependence on all NS-NS moduli of the kinetic terms of the chiral
matter in a generic non-supersymmetric brane configurations with
non-commuting open string fluxes. Near a N=1 supersymmetric point the
effective action contains D and F term breaking terms which can be
explicitly computed with string diagrams.
Posted by: KCL
Thursday, 2 Feb 2006
Area geometry and string backgrounds
Mattias Wohlfarth
(IFTP Hamburg)
Abstract:
Based on the observation that classical strings only couple to area, we study the generalized geometry of manifolds equipped with an area measure but not a metric length measure. This in particular includes geometries combined from a metric and a two-form. We discuss the equation of stationary surfaces on these backgrounds which leads to the identification of differential geometric structures appropriate for area geometry. This work is expected to be of relevance for the study of the gravitational sector of
strings and branes.
Based on the observation that classical strings only couple to area, we study the generalized geometry of manifolds equipped with an area measure but not a metric length measure. This in particular includes geometries combined from a metric and a two-form. We discuss the equation of stationary surfaces on these backgrounds which leads to the identification of differential geometric structures appropriate for area geometry. This work is expected to be of relevance for the study of the gravitational sector of
strings and branes.
Posted by: IC