The 20th Nordic String Meeting, Helsinki

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Program

Time	Thursday, Oct 27	Friday, Oct 28
09.00	D. Martelli	S. Ross
09.30	D. Martelli	S. Ross
10.00	D. Martelli	S. Ross
10.30	D. Martelli	S. Ross
11.00	Coffee	Coffee
11.30	K. Zarembo	K. Zarembo
12.00	K. Zarembo	K. Zarembo
12.30	Lunch & Free time for discussions	Lunch & Free time for discussions
13.00
13.30
14.00
14.30
15.00	N. Obers	U. Lindström
15.30	M. Zabzine	L. Freyhult
16.00	Coffee	Coffee
16.30	A. Bredthauer	S. Nakamura
17.00	M. Larfors	N. Pidokrajt
17.30		N. Drukker
18.00		End
...
19.00	Conference dinner

Speakers:
Bredthauer, Andreas: First-order supersymmetric sigma models and target space geometry
We study the conditions under which N=(1,1) generalized sigma models support an extension to N=(2,2). The enhanced supersymmetry is related to the target space complex geometry. Concentrating on a simple situation, related to Poisson sigma models, we develop a language that may help us analyze more complicated models in the future. In particular, we uncover a geometrical framework which contains generalized complex geometry as a special case.

Drukker, Nadav: Loop operators in conformal field theories

Freyhult, Lisa: Deformations in AdS/CFT: Integrable spin chains with U(1)^3 symmetry (pdf)
The most general three-state spin chain with U(1)^3 symmetry and nearest neighbour interaction is considered. The model contains as a special case the spin chain describing the holomorphic three scalar sector of the three parameter complex deformation of N=4 SYM, dual to type IIB string theory in the generalized Lunin-Maldacena backgrounds discovered by Frolov. We formulate the coordinate space Bethe ansatz, calculate the S-matrix and determine for which choices of parameters the S-matrix fulfills the Yang-Baxter equations. We find in total four classes of integrable models. In particular, each already known model of the above type is nothing but one in a family of such models.

Larfors, Magdalena: 4D black holes and holomorphic factorization of the 0A matrix model
The 0A matrix model at self-dual radius is related to the topological string on the conifold. We see that the free energy of the matrix model equals the sum of the topological and anti-topological string amplitudes. This factorization of the string amplitudes is matched by a holomorphic factorization of the 0A matrix model. Since the topological string is related to 4D black holes, a very interesting application of the matrix model is thus to compute certain properties of the black holes.

Lindström, Ulf: Sigma models with special holonomy
A study of (1,1) supersymmetric two-dimensional non-linear sigma models with boundary on special holonomy target spaces is presented. In particular, the consistency of the boundary conditions under the various symmetries is studied. Models both with and without torsion are discussed.
e-Print Archive: hep-th/0507035

Martelli, Dario: Recent results in AdS/CFT (ps)

Nakamura, Shin: SRT Map: a New Bridge between Topological and Bosonic Non-critical Strings
Recently, a topologically twisted SL(2)_n/U(1) model with n>1 (or n=1) has been conjectured to be equivalent to a non-minimal bosonic strings with c<1 (or c=1). We show that a certain class of N-point correlation functions in the twisted theory can be directly translated to those of the bosonic theory for arbitrary N by using Stoyanovsky-Ribault-Teschner map.

Obers, Niels: Instabilities of Near-Extremal Smeared Branes and the Correlated Stability Conjecture (pdf)
The classical and local thermodynamic stability of non- and near-extremal D-branes smeared on a transverse circle is considered. These two types of stability are related via the correlated stability conjecture, for which a proof is given for this specific class of branes. The boost/U-duality map from neutral black strings to smeared branes is used to explicitly construct the unstable Gregory-Laflamme modes of these branes. Various issues concerning the near-extremal branes, T-duality and the dual gauge theories will be discussed as well.

Pidokrajt, Narit: Geometry of Higher-Dimensional Black Hole Thermodynamics (pdf)
We investigate thermodynamic curvatures of the Kerr and Reissner-Nordström (RN) black holes in spacetime dimensions higher than four. These black holes possess thermodynamic geometries similar to those in four dimensional spacetime. The thermodynamic geometries are the Ruppeiner geometry and the conformally related Weinhold geometry. The Ruppeiner geometry for d=5 Kerr black hole there is no extremality but the Ruppeiner curvature diverges where one suspects that the black hole becomes unstable. The Weinhold geometry of the Kerr black hole in arbitrary dimension is a flat geometry. For RN black hole the Ruppeiner geometry is flat in all spacetime dimensions, whereas its Weinhold geometry is curved. In d \geq 5 the Kerr black hole can possess more than one angular momentum. Finally we discuss the Ruppeiner geometry for the Kerr black hole in d=5 with double angular momenta.

Ross, Simon: Smooth geometries and their CFT duals (pdf)

Zabzine, Maxim: On topological M-theory
I will describe the construction of topological membrane on G2-manifolds. The theory is localized on associative manifolds. I will discuss the reduction of the theory to topological A-model on Calabi-Yau manifold.

Zarembo, Konstantin: Integrability and Bethe ansatz in AdS/CFT correspondence (ppt/part 1) (pp/part 2)

Conference dinner at Ravintola Fokka:

There will be a choice between a vegetarian/nonvegetarian menu. Thursday morning we will circulate a list, where we ask you to indicate your choice, and inform us of any food allergies.