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

21 Dec 2016, 08:45 → 23 Dec 2016, 13:00 Europe/Rome

Aula C, second floor (University of Perugia, Dipartimento di Fisica e Geologia)

Andrea (ULB Brussels) Campoleoni (Université Libre de Bruxelles), Andrea Marini (PG), Daniele (Durham U.) Dorigoni (Durham U.), Davide (LPTHE Paris) Cassani, Francisco Peña Benitez (Università di Perugia), Gianluca Grignani (PG), LOCAL ORGANIZERS:, Marta Orselli, Michele (Bologna U. & ICTP) Cicoli (Bologna U. & ICTP), Stefano (Durham U.) Cremonesi (Durham U.), Valentina (Iceland U.) Giangreco Puletti (Iceland U.)

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.
The meeting is traditionally scheduled just before the Christmas break to facilitate the participation of Italian postdocs and PhD students working abroad who can take the chance of their travel back home for Christmas to meet young colleagues and exchange 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.

Wednesday, 21 December

08:45 → 09:00 Opening

Speakers: Prof. Gianluca Grignani (PG), Valentina Giangreco Puletti

09:00 → 11:00 Defects in conformal and supersymmetric field theories

In a quantum or statistical field theory, the action of operators on the vacuum describes how a physical system is affected by a probe. Often, the probes are extended objects: the word-line of a heavy particle, a boundary or an interface, etc. We describe some general features of extended probes, in highly symmetric QFTs. We first focus on conformal field theories. We discuss properties of the Operator Product Expansion in the presence of defects and give examples of topological and non topological conformal defects. We then move to the case of supersymmetric theories, in which we can construct defects with two-dimensional (or higher) support. We explain how certain kinds of extended probes are able to detect the phases of the theory. Finally, we describe the relevance of defects in constructing a large class of superconformal N=2 theories in four dimensions, and how one can use properties of topological defects in two dimensions to compute the expectation value of line operators in these theories.

Speakers: Marco Meineri (EPFL Lausanne), Simone Giacomelli ((ICTP Trieste))

0 Abstract_Giacomelli&Meineri.pdf

11:00 → 11:30 Coffee-break

11:30 → 12:30 Defects in conformal and supersymmetric field theories - Discussion session

Speakers: Marco Meineri (EPFL Lausanne), Simone Giacomelli (ICTP Trieste), Stefano Cremonesi (Durham)

12:30 → 14:30 Lunch

14:30 → 16:30 Soft terms in string compactifications

Supersymmetry is a generic prediction of string theory. Given that it is not an exact symmetry of nature, in order to connect string compactifications to particle physics, we must understand how supersymmetry is broken. This issue is intimately related to the moduli stabilisation problem in string theory, as the latter determines the vacuum structure of the theory. Interestingly, SUSY-breaking in string theory is typically soft, which means that the supersymmetric cancellation of quadratic divergences in the Higgs mass endures. Such breaking is then parameterised by soft terms, which roughly determine the masses of superpartners. If SUSY-breaking generates soft-terms at energy scales accessible to particle accelerators (as expected if low-energy SUSY is the correct way of addressing the hierarchy problem) then, remarkably, they would directly relate properties of the string compactification to experiments. We will begin by reviewing the motivation and description of soft SUSY-breaking in the MSSM and supergravity, commenting on current constraints from the LHC. We will then describe the main mechanisms for moduli stabilisation, SUSY-breaking and mediation in string theory. Putting these tools together we will illustrate, within the Heterotic and Type IIB theories, interesting possibilities for the soft-terms in string compactifications. A particular focus will be on the interplay with cosmology, which has been best studied in Type IIB models. The presence of moduli in these compactifications leads to a modification of the standard Big Bang Theory, in which the reheating of the universe is driven by the decay of the lightest modulus. In particular, we will show that such non-standard cosmological history of the universe plays a crucial role in constraining SUSY-breaking in string models. Interestingly, it turns out that, once all the cosmological constraints are taken into account, it is actually rather difficult to get low-energy SUSY from string theory. Finally, we will briefly review the cosmological scenarios which could arise from such string compactifications.

Speakers: Francesco Muia (Oxford), Susha Parameswaran (Liverpool)

Abstract and references Abstract_Muia&Parameswaran.pdf

16:30 → 17:00 Coffee-break

17:00 → 18:00 Soft terms in string compactifications - Discussion session

Speakers: Francesco Muia (Oxford), Michele Cicoli (BO), Susha Parameswaran (Liverpool)

Thursday, 22 December

09:00 → 11:00 Black hole mergers and gravitational waves

The broad scope of these lectures is to introduce the basic elements which are necessary to understand the GW signals from a BH binary merger recently-observed by LIGO, and to provide the basis of some state-of-the-art applications in this rapidly-growing field. Content i) A GW physics primer. ii) Introduction to the post-Newtonian formalism. The case of circular inspiral. iii) Black-hole perturbations and quasinormal modes (QNMs) iv) GWs from a radial plunge of a test particle into a black hole: QNM ringing v) Black-hole spectroscopy: tests of gravity and of near-horizon physics vi) Numerical Relativity and Effective-One-Body (EOB) approach

Speakers: Paolo Pani (Rome Sapienza), Sebastiano Bernuzzi (P)

Abstract and references Abstract and references

11:00 → 11:30 Coffee-break

11:30 → 12:30 Black hole mergers and gravitational waves - Discussion session

Speakers: Daniele Dorigoni (Durham), Paolo Pani (Rome Sapienza), Sebastiano Bernuzzi (P)

12:30 → 14:30 Lunch

14:30 → 16:30 Topological states of matter and non-supersymmetric dualities

In the first part of the lecture, we will briefly introduce topological phases of matter and their main properties by employing effective quantum field theories, such as Chern-Simons and relativistic fermion theories. In particular, we will review the role of the Dirac theory in these quantum phases by focusing on the fractional quantum Hall effect with filling factor 1/2 (FQHE-1/2), where an emergent particle-hole symmetry plays a prominent role. The second part of the lecture deals with dualities and their possible application to topological states of matter. Specifically, we will review recent papers where, starting from a relativistic form of flux attachment designed to transmute the statistics of particles, a web of new dualities can be derived. This includes the usual particle-vortex duality for bosons as well as the recently discovered counterpart for fermions in the FQHE-1/2 and on the surface states of three-dimensional topological insulators.

Speakers: Andrea Amoretti (Wuerzburg), Giandomenico Palumbo (Utrecht)

Abstract and references Abstract_Amoretti&Palumbo.pdf

16:30 → 17:00 Coffee-break

17:00 → 18:00 Topological states of matter and non-supersymmetric dualities - Discussion session

Speakers: Andrea Amoretti (Wuerzburg), Dr Andrea Campoleoni (Université Libre de Bruxelles), Giandomenico Palumbo (Utrecht)

20:00 → 23:00 Conference Dinner

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Friday, 23 December

09:00 → 11:00 Exact results for superconformal field theories

One of the most widely used approaches to study interacting quantum field theories is perturbation theory, where physical quantities are expressed as a series expansion in some small parameter. Despite its many successes, the perturbative approach cannot be used to study important physical phenomena like confinement and chiral symmetry breaking in QCD for which non-perturbative and strong-coupling effects play a key role. While these are still largely open problems, in the last few years the field has witnessed tremendous progress in understanding the non-perturbative and strongly coupled behaviors of many interesting quantum field theories, especially in the supersymmetric context where we can now compute several observables of interest, such as partition functions and correlation functions, exactly in the coupling constant. In these lectures we will present some of these recent developments, focusing in particular on four dimensional N=2 supersymmetric field theories. After introducing the theories of interest, we will discuss how these are related to integrable systems and how this correspondence can be used to compute their partition function around a generic strong-coupling point. In the case where these theories also enjoy conformal symmetry, the partition function encodes detailed information about correlation functions of chiral operators. We will describe how the 3-point functions of chiral primaries can be computed exactly using techniques from localization and the tt* equations.

Speakers: Antonio Sciarappa (KIAS Seoul), Marco Baggio (KUL Leuven)

Abstract and references Baggio-Sciarappa.pdf

11:00 → 11:30 Coffee-break

11:30 → 12:30 Exact results for superconformal field theories - Discussion session

Speakers: Antonio Sciarappa (KIAS Seoul), Davide Cassani (LPTHE Jussieu), Marco Baggio (KUL Leuven)