# Physics Theory Seminar

Division of Theoretical Physics at the Department of Physics organizes a series of theory seminars. Physics theory seminars are open.

Time: Monday 14:15 - 15:00

Location: Realfagbygget E5-103

Coordinator: Jan Myrheim

## Theory seminars for the autumn 2015

### September 10

Jens Braun, Technische Universität Darmstadt

«Generation of structure under extreme conditions»

# September 10

Jens Braun, Technische Universität Darmstadt

«Generation of structure under extreme conditions»

**Thursday **September 10. at 14:15 in E5-103

#### Abstract

### Generation of structure under extreme conditions

The theory of the strong interaction describes the appearance of the fundamental building blocks of matter in the early Universe. This state of matter is currently probed in relativistic heavy-ion collision experiments, where we encounter temperatures much larger than those of any other experiment. As a complement, experiments with fermionic atoms in the nano-Kelvin regime provide a remarkably clean and versatile environment to test our understanding of a broad range of phenomena: from superconductivity and the formation of condensates to the generation of bound states in strongly coupled systems.

What do these systems have in common? As I will explain in this talk, studies of ultracold atomic gases and the theory of the strong interaction are actually similar in many ways, yet a consistent first-principles description of the experimental data remains challenging. I will present an overview of some of the most intriguing open questions on the phase diagrams of the theory of the strong interaction and ultracold gases, and discuss how an exchange of techniques between these fields is helping us to understand collective phenomena and phase transitions in strongly coupled matter in general.

### October 12

David Weir, University of Stavanger (UiS)

«Gravitational waves from a thermal first-order phase transition: numerical simulations»

# October 12

David Weir, University of Stavanger (UiS)

«Gravitational waves from a thermal first-order phase transition: numerical simulations»

#### Abstract

### Gravitational waves from a thermal first-order phase transition: numerical simulations

With the LHC placing constraints on extensions of the Standard Model of particle physics, and the first generation of space-based gravitational wave detectors under development, it is an exciting time to consider the detectable consequences of phase transitions in the early universe. Motivated by this, we present large-scale numerical simulations of the gravitational radiation produced by a first order phase transition in the early universe. The resulting gravitational wave power spectrum has a power-law form between scales set by the average bubble separation and the bubble wall width. However, the general form of the power spectrum is different from that predicted by the widely-applied envelope approximation, and the gravitational wave energy density is at least two orders of magnitude larger.

### October 19

Eirik Eik Svanes, The Lagrange Institute (ILP), Paris

«Heterotic string compactifications: Old and New»

# October 19

Eirik Eik Svanes, The Lagrange Institute (ILP), Paris

«Heterotic string compactifications: Old and New»

#### Abstract

### Heterotic string compactifications: Old and New

I will give a short introduction to string compactifications, moduli and string phenomenology in the context of the heterotic string. The heterotic string is particularly favorable for particle phenomenology compared to its type II cousins, due to the presence of a gauge group which fits the Standard Model. Some problems are however harder to address in the heterotic string, the moduli problem in particular. Although Calabi-Yau compactifications are mostly under control, a full understanding of the heterotic moduli space is still lacking. I will discuss recent developments in this direction.

I will cover the basics of complex manifolds and moduli in the talk.

#### For a more rigorous introduction to these topics, see for example:

Nakahara "Geometry, Topology and Physics", Chapters 5-11

Xenia de la Ossa, Notes on Calabi-Yau compactifications and Moduli: Calabi–Yau Manifolds and Mirror Symmetry [pdf]

String Theory Textbooks: Polchinski, Green Schwarz and Witten, Ibanez and Uranga, Becker Becker Schwarz, etc.

## Contact

Jan Myrheim, Coordinator

Email: jan.myrheim@ntnu.no

## Open lectures and seminars

Physics Friday Colloquia

Friday 14:15

Physics Theory Seminar

Monday 15:15

Biophysics lunchtime seminar

Tuesday 12:15