Math Colloquium

### Speaker: Alessandra Cagnazzo

Title: Anomalous dimension in 2d non-linear sigma models.

Location: TG-227, (tæknistofan, Tæknigarður 2nd floor)

Time: Friday, May 20 at 13:20.

### Abstract:

2d non-linear sigma models are widely used in high and low energy physics. In my talk I will present how to compute the one-loop anomalous dimension for fields in some cases in which the background is a coset space. I will review the formula for the case in which the background is a symmetric coset (that admits a \(Z_2\) automorphism) and present the new result for \(Z_4\)-cosets. The last result is applicable to the string described by the pure spinor formalism on \(\mathrm{AdS}_5\times S^5\) and it is relevant for AdS/CFT.

Applications are invited for a PhD position in theoretical high-energy physics at the University of Iceland with a starting date in Fall 2016. The position is funded by a grant from the Icelandic Research Fund.

The successful candidate will work in the area of quantum field theory and string theory with emphasis on gauge theory/gravity duality and holographic models for strongly coupled field theories. A master degree, or equivalent, in theoretical physics is required.

The application deadline is May 6, however applications will continue to be accepted until the position is filled.

Applications should be submitted electronically to

https://academicjobsonline.org/ajo/jobs/7202

and should include a CV, transcripts from undergraduate and master studies, a short description of research interests, and names and e-mail addresses of two referees, who have agreed to provide recommendation letters.

For further information please contact:

Ass. Prof. Valentina Giangreco Puletti (e-mail: vgmp[at]hi.is) or

Prof. Lárus Thorlacius (e-mail: lth[at]hi.is)

Faculty of Physical Sciences

University of Iceland

Math Colloquium

### Speaker: François David

Title: Planar maps, circle patterns and 2D gravity

Location: V-157, VRII.

Time: Friday, March 11 at 13:20.

### Abstract:

I present a model of random planar triangulations (planar maps) based on circle patterns and discuss its properties. It exemplifies the relations between discrete random geometries in the plane, conformally invariant point processes and two dimensional quantum gravity (Liouville theory and topological gravity).

Math Colloquium

### Speaker: Matin Mojaza

Title: Soft dilatons: In gravity and from conformal field theory

Location: V-148, VRII.

Time: Friday, February 19 at 11:00.

### Abstract:

In this talk I will discuss the soft factorizing properties of two seemingly different particles, which are in the literature both referred to as dilatons; i.e. the dilaton in theories of gravity appearing e.g. in string theory and supergravity as the scalar partner of the graviton, and the dilaton appearing as the Nambu-Goldstone boson in theories of spontaneously broken conformal symmetry.

I will in particular show that tree level, on-shell gauge invariance can be used to fully determine the leading, sub-leading, and sub-sub-leading behaviors of soft gravitons as well as soft “gravity dilatons”, and that Ward-identies of conformal symmetry fully determine the leading, sub-leading, and sub-sub-leading behaviors of soft Nambu-Goldstone dilatons.

I will finally discuss the relation between the soft behavior of gravity dilatons and Nambu-Goldstone dilatons.

Math Colloquium

### Speaker: Eric Laenen

Title: The Eikonal Approximation

Location: V-156, VRII.

Time: Wednesday, October 28, at 15:00-16:00.

### Abstract:

In LHC processes, when low-energy gluons are radiated, the so-called eikonal approximation may be used. In this talk I review its origin, how it works, and show some insights that emerge from it. I then discuss recent results in going beyond it: the next-to-eikonal approximation, as well as unitary and causality aspects.

Math Colloquium

### Speaker: Suresh Nampuri

Title: Mock modular forms and black hole counting

Location: V-156, VRII.

Time: Wednesday, October 21, at 15:00-16:00.

Math Colloquium

### Speaker: David Tong

Title: The Supersymmetric Quantum Hall Effect

Location: Naustið, Endurmenntun.

Time: Tuesday, August 25, at 15:00-16:00.

### Abstract:

I’ll describe the solution to a supersymmetric, but non-relativistic, gauge theory in d=2+1 dimensions. The ground states are given by the Laughlin wavefunctions describing the fractional quantum Hall effect. The model reveals explicit connections between different approaches to quantum Hall phenomenology.

Math Colloquium

### Speaker: Oleg Evnin

Title: Non-linear perturbations of AdS space-time

Location: VR-II, 147

Time: Tuesday, June 30, at 15:00-16:00.

### Abstract:

Recent, mostly numerical investigations have revealed a complex interplay of stability and instability in the dynamics of classical AdS perturbations. I’ll review some attempts to develop an analytic understanding of these fascinating phenomena, based on methods of non-linear dynamical perturbation theory.

Math Colloquium

### Speaker: Ville Keränen, University of Oxford

Title: Thermalization in the AdS/CFT duality

Location: **V-155, VR-II**

Time: **Monday**, May 18, at 15:00-16:00.

### Abstract:

The AdS/CFT duality relates the dynamics of certain strongly interacting quantum field theories to the dynamics of certain gravitational theories in spacetimes with one higher dimension. Thus, it provides an interesting tool in which one can approach unsolved questions in either side by rephrasing them in the dual theory. One hope is to learn about the long standing problem of non-equilibrium dynamics in strongly interacting quantum field theories using the gravitational description. I will describe some work towards this goal. More precisely, by studying a few relatively simple examples, I will describe how the process of thermalization in the strongly coupled quantum field theory is captured in the gravitational description.

Math Colloquium

### Speaker: David Lowe

Title: Cosmology from conformal field theory

Location: **VR-156**

Time: **Tuesday**, March 31., at 15:00-16:00.

### Abstract:

Our universe appears to be entering a de Sitter phase, where expansion becomes dark energy dominated. In this limit, the isometries of the spacetime are the same as the conformal group. There exists an integral transform that maps spacetime observables to holographic observables respecting the conformal symmetry. By studying the properties of this holographic conformal field theory, we deduce long wavelength instabilities appear after a large number of e-folds of expansion.