XI AVOGADRO MEETING <br> on Strings, Supergravity and Gauge Theories

16 Dec 2015, 08:45 → 18 Dec 2015, 13:00 Europe/Rome

1 (Floor -1) (University of Bologna, Department of Physics and Astronomy)

Andrea (ULB Brussels) Campoleoni, Daniele (DESY Hamburg) Dorigoni, Davide (LPTHE Paris) Cassani, Michele (Bologna U. & ICTP) - Local organizer Cicoli (Università di Bologna & ICTP), Stefano (King's College London) Cremonesi, Valentina (Iceland U.) Giangreco Puletti

The Avogadro Meetings started in 2005 as an occasion for young Italian theoretical physicists to share their ideas and results in an informal atmosphere. The meeting is named after the University of Piemonte Orientale that hosted its first three editions.
It is usually scheduled just before the Christmas break to simplify the participation of Italian postdocs and PhD students working abroad who can take the occasion of their travel back home for Christmas to meet their young colleagues and exchange their ideas.
In order to stress the pedagogical aim of the meeting, preference is given to extended presentations on general themes rather than to conventional seminars on specific works, possibly organised and illustrated by more than one speaker and followed by a long discussion session.
Consistently with the original spirit of the event, the invited speakers are usually Italian. However participation is open to anybody and non-Italians are more than welcome to join. For this reason the seminars are presented in English.

Group picture in front of old Physics Department:

Slides IMG_0369.JPG

Wednesday, 16 December

1 Opening

2 Branes and supersymmetry breaking

The lectures will give a pedagogical introduction to various aspects of anti-brane supersymmetry breaking in string theory. The first part is based on the holographic standpoint meant both as an application to study QFT at strong coupling and as a mean of investigation of bulk physics from a dual perspective. Symmetry and supersymmetry breaking patterns are encoded in the Ward identity structure of a QFT. Holographic models realize such a structure at strong coupling through a precise holographic renormalization program. This setting is suitable to describe neatly supersymmetry breaking at strong coupling and the appearance of the goldstino in a wide and general context. The application of these techniques to cascading gauge theories offers a powerful way to study anti-branes placed in conifold bulk geometries and characterize their supersymmetry breaking. In the second part we will discuss the dynamics of anti-branes in flux compactifications, their decay channels and the quest for long-lived metastable vacua in string theory. We will cover the following topics: • The backreaction of anti-branes in warped throats • Infrared dynamics and vacuum stability • Applications: de Sitter uplift and black hole microphysics.

Speakers: Daniele Musso (ICTP, Trieste), Stefano Massai (LMU, Munich)

Abstract and References Abstract_Massai&Musso.pdf

11:00 Coffee-break

3 Branes and supersymmetry breaking - Discussion session

Speakers: Daniele Musso (ICTP, Trieste), Stefano Massai (LMU, Munich)

12:30 Lunch

4 Axions in cosmology

• Lorenzo Ubaldi I first introduce the axion as a solution to the strong CP problem, and then explain how such a light boson would be produced via the misalignment mechanism in the early universe and contribute to the energy density of cold dark matter. String theoretic or supersymmetric frameworks further predict the existence of moduli, that can decay into relativistic axions. The latter would contribute to the cosmological relativistic degrees of freedom, the so-called dark radiation. I discuss briefly the bounds on this scenario from cosmic microwave background measurements. • Francisco Pedro In this talk I will discuss some aspects of axions in the early universe, with particular emphasis on the various models of inflationary cosmology based on axionic fields. I will discuss natural inflation, aligned inflation in its various guises, N-flation and monodromy models. Throughout the talk I will make the connection between the field theoretic mechanisms for axion inflation and their embedding into string compactifications. I will review the Weak Gravity Conjecture and its potential impact on axion inflation in string theory.

Speakers: Francisco Pedro (IFT, Madrid), Lorenzo Ubaldi (Tel Aviv University)

Abstract and References Abstract_Pedro&Ubaldi.pdf

16:30 Coffee-break

5 Axions in Cosmology - Discussion session

Speakers: Francisco Pedro (IFT, Madrid), Lorenzo Ubaldi (Tel Aviv University)

Thursday, 17 December

6 Scattering amplitudes and soft theorems

This lecture is thought to provide a pedagogical introduction to the subject of scattering amplitudes, with focus on the recent developments about soft theorems. The lecture will be structured in two parts, the first of which will concern fundamental concepts such as unitarity and analyticity, as well as the singularity structure of the amplitudes and their physical importance. As far as the second part is concerned, we will review the so-called "soft theorems", their origin and the renewed interest in their structure. The relation with asymptotic symmetries will be highlighted, the attempt being to emphasize what is known and what is new. More in detail, in the first part we will touch the following topics: • Generalities: Definition and the Lorentz little group; • Analyticity, unitarity and locality; • BCFW method and the singularity structure of perturbative field theories; • Soft limits. As far as the second part is concerned: • Statement and history of soft theorems; historical importance: QCD, double scalars as probes of N = 8 moduli space. Sketch of a derivation. • Relation of soft theorems to asymptotic symmetries of the theory; definition of BMS symmetry for gravitational scattering and its relevance. • Soft theorems as Ward identities, soft bosons as Goldstone bosons.

Speakers: Matteo Rosso (Humboldt Universitaet, Berlin), Paolo Benincasa (IFT, Madrid)

Abstract and References Abstract_Benincasa&Rosso.pdf

11:00 Coffee-break

7 Scattering amplitudes and soft theorems - Discussion session

Speakers: Matteo Rosso (Humboldt Universitaet, Berlin), Paolo Benincasa (IFT, Madrid)

12:30 Lunch

8 Gauged Supergravity: formalism & applications

The embedding tensor formulation of (half-)maximal gauged supergravities in various dimensions plays a crucial role in understanding string dualities within the context of string compactifications. We will start by first giving an overview of the aforementioned formalism in 4D. Later, we will continue by discussing the embedding tensor/fluxes and Domain Wall/brane dictionaries for compactifications of type II string and M-theory. Among its many applications, gauged Supergravity provides a framework for the construction of black holes in Anti de Sitter (AdS) spacetime. These will be the focus of the second part of the seminar. We will review Supersymmetric solutions in 4 and 5 dimensions, with particular emphasis on the 1/4 BPS black holes in 4D that have triggered new investigations in recent years. We will illustrate the relations between the ungauged and gauged Supergravity solutions that emerged from the latest studies. Finally, the M-theory origin of AdS black holes and their role for holography will be discussed.

Speakers: Alessandra Gnecchi (KU Leuven), Giuseppe Dibitetto (Uppsala University)

Abstract and References Abstract_Dibitetto&Gnecchi.pdf

16:30 Coffee-break

9 Gauged Supergravity: formalism & applications - Discussion session

Speakers: Alessandra Gnecchi (KU Leuven), Giuseppe Dibitetto (Uppsala University)

20:00 Social dinner

Friday, 18 December

10 Aspects of 6D theories: geometric engineering and holography

6D theories are in between the most elusive and interesting supersymmetric systems whose existence is predicted by string theory. The main aim of the first part of these lectures is to convince the audience that this is the case, and to review their geometric engineering in M-theory and F-theory, with emphasis on the recent results obtained by means of the latter. In the second part of the lectures, we will focus on the brane constructions in type IIA, involving NS5, D6, and D8 branes. We will then link holographically these brane configurations to the AdS_7 gravity dual solutions of massive IIA supergravity.

Speakers: Fabio Apruzzi (UNC, Chapel Hill), Michele Del Zotto (Harvard University)

Abstract and References Abstract_Apruzzi&DelZotto.pdf

11:00 Coffee-break

11 Aspects of 6D theories: geometric engineering and holography - Discussion session

Speakers: Fabio Apruzzi (UNC, Chapel Hill), Michele Del Zotto (Harvard University)

12 Closure and Christmas greetings