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String Theory Journal Club
    Mondays, 12pm, Frohlich library

    The PhD student journal club meets once a week to discuss topics of interest in String Theory. Topics roughly alternate between review articles and new papers. Note that every participant is expected to have read the paper of the week before the meeting.

    Fall 2012 Schedule

    Date - Speaker - Topic - References

  • 8th October - Paul Dempster, An introduction to the a-theorem, 1107.3987

  • 15th October - William Walters, Matter from geometry, hep-th/9606086

  • 22nd October - Hasan Sonmez, The free fermionic construction, 1208.2145, notes

  • 29th October - Siraj Khan, Branes in string theory, hep-th/9802067, notes.

  • 5th November - Panos Athanasopoulos, Introduction to toroidal compactifications of heterotic strings, Phys. Rev. D, notes

  • 12th November - David Errington, Strong Cosmic Censorship in polarised Gowdy Spacetimes, Paper (pdf), notes

  • 19th and 26th November - Paul Dempster, Symmetry breaking in string compactifications, Nucl. Phys. B, notes

  • 3rd December - Owen Vaughan, The r-map, c-map and black hole solutions.

    • Spring 2013 Schedule

  • 28th January - Panos Athanasopoulos, Introduction to Gepner's ideas, Gepner's notes, Nucl. Phys. B, my notes

  • 4th February - Owen Vaughan, Special geometry of N = 2 supergravity and black hole solutions, notes

  • 11th February - Siraj Khan, D3 branes in flat space and the Maldacena limit, hep-th/9711200

  • 18th February - William Walters, Introduction to Dynkin diagrams, Physics Reports, notes

  • 25th February - Owen Vaughan, Lie algebras and coset spaces, notes

  • 4th March - Paul Dempster, The Higgs mechanism: a geometrical perspective, notes

  • 11th March - Viraf Mehta, Gauge coupling unification in two classes of SO(10) models.

  • 8th April - Paul Dempster, The doubled formulation of string theory, 1303.6727

  • 15th April - William Walters, Aspects of F-theory GUTs.

  • 22nd April - Panos Athanasopoulos, Complementarity and firewalls, 1207.3123, handwritten notes

  • 29th April - Paul Dempster, Yet another introduction to AdS/CFT: aspects of the dictionary.

  • 13th May - Panos Athanasopoulos, Introduction to toroidal orbifolds, handwritten notes

  • 20th and 28th May - David Errington, Introduction to Calabi-Yau manifolds, notes

  • 3rd June - Marc-Olivier Renou, Dirichlet's theorem on arithmetic progressions.

    • Summer 2013 Schedule

  • 8th July - Marc-Olivier Renou, Theoretical computer science: calculability, Turing machines and the first Gödel theorem.

  • 15th July - Joshua Davies, Introduction to quantum information theory, handwritten notes

    • Fall 2012 Abstracts

  • An introduction to the a-theorem : Consider a d-dimensional CFT in the UV which flows, via the Renormalization Group (RG) flux, to a CFT in the IR. We can think of this as a dynamical system in the space of d-dimensional Quantum Field Theories, where the CFTs act as fixed points. For d=2 it was shown by Zamolodchikov (1986) that such a flow is irreversible, which heavily constrains the possible dynamics of the RG flux. Here we will discuss the state of the art in d=4, specifically focusing on the 2011 proof by Komargodski and Schwimmer of the so-called "a-theorem", originally conjectured by Cardy (1988). The main bulk of the talk will focus on Sections 2, 4, and Appendix B of the reference.

  • Matter from geometry : The paper describes how to obtain charged matter from the deformation of singularities. This is in contrast to what I spoke about in the strings seminar, where we were enhancing the singularity type. I would recommend reading up to and including Section 4.3, as the deformation of E-type singularities covered at the end is particularly messy and confusing.

  • The free fermionic construction : We will look briefly into the basics of free fermionic construction and show how we start model building in certain gauge groups. Furthermore, we will focus on the SU(6)xSU(2) GUT model.

  • Branes in string theory : Section II of reference only. We'll introduce the concept of D-branes as surfaces in perturbative string theory on which open strings can end, and move towards their importance as non-perturbative objects which play a central role in string and M-theory dualities.

  • Introduction to toroidal compactifications of heterotic strings: We will use the reference as an excuse to introduce a few basic ideas and notations in toroidal compactifications of the heterotic string. The paper is rather technical so don't worry too much about the specific calculations as long as you get the main idea. In fact, make sure you read the notes BEFORE reading the paper.

  • Strong Cosmic Censorship in polarised Gowdy Spacetimes: An introduction to polarised Gowdy spacetimes and the idea behind the cosmic censorship hypothesis as well as an overview of how to prove SCC for these spacetimes.

  • Symmetry breaking in string compactifications: The mid 80s saw a marked leap in the hopes people held for string theory. The work of Green and Schwarz (1984) which ushered in the first superstring revolution hinted at the possibility that one could use string theory to obtain realistic phenomenology. We will discuss one of the first attempts at this, by Candelas, Horowitz, Strominger and Witten (1985). One of the main ideas, which is elucidated in Witten (1985), is to perform compactifications with Wilson loops, which breaks the gauge group of the original theory. We will review this material, as outlined in the notes. NB. Notes updated as of 26/11/2012.

  • The r-map, c-map and black hole solutions: I will give a brief overview of my PhD thesis.

    • Spring 2013 Abstracts


  • Introduction to Gepner's ideas: I will present some important aspects of Gepner's work on the heterotic string. For this talk I will follow my notes which are in turn heavily based on Gepner's lecture notes. The relevant paper in Nucl Phys B also contains all the information but it is much more technical.

  • Special geometry of N = 2 supergravity and black hole solutions: Notes now online.

  • D3 branes in flat space and the Maldacena limit: The low-energy (massless state limit) of IIB theory of D3-branes in 10d flat space can be obtained in a convenient manner by taking the 'Maldacena limit'. (1) We find as a result that we get the conformally invariant N=4 d=10 SU(N) Super Yang Mills and a bulk SUGRA. (2) We can also take the Maldacena limit whilst considering the 'near horizon' and 'far' limits of the geometry which gives rise to IIB on AdS5xS5 and a bulk SUGRA. Since both cases, (1) and (2), correspond to the low energy limits of the same theory, it is not surprising that a conjecture is made of the AdS/CFT duality of the Yang Mills and the AdS5xS5 parts, a duality supported by much evidence.

  • Introduction to Dynkin diagrams: I will show how one can use Dynkin diagrams to easily find subgroups of higher gauge groups, and also derive representations. Section 4 onwards of the reference is the most useful, but I'll start from scratch.

  • Lie algebras and coset spaces: We will discuss how various Lie algebras are related by complex extension, focussing on SU(n) and SU(p,q). We will then discuss coset spaces, and prove that SU(2)/U(1) = S^2 and SU(1,1)/U(1) = H^2. The main reference is Chapter 6 of Gilmore "Lie groups, Lie algebras, and some of their applications."

  • The Higgs mechanism: a geometrical perspective: We'll look at a number of the mathematical structures arising in the Higgs mechanism, which are often brushed aside in the canonical QFT treatments but become important when thinking about more novel symmetry-breaking scenaria. We'll finish by looking at the example of separating stacks of parallel D3-branes. Notes updated as of 4/3/2013.

  • Gauge coupling unification in two classes of SO(10) models: We explore two classes of SO(10)xU(1) models: one with an E_6 embedding and one without. We investigate gauge coupling unification in both classes by specifying a model in each class. We motivate the symmetry breaking patterns and field content and show that only one class allows for gauge coupling unification within phenomenologically viable bounds.

  • The doubled formulation of string theory: The double field theory (DFT) of Siegel (1993), generalised geometry of Hitchin, and the duality-symmetric string theory of Duff (1990) and Tseytlin (1990) are all, in some way, related to the idea of making manifest some of the hidden symmetries present in string theory. In this introductory talk, we'll concentrate on T-duality in the NS-NS sector of the Type II superstring. This is enhanced to a manifest O(d,d) symmetry by "doubling" the coordinates of the target space. We'll look at some of the basic tools and techniques that crop up in this formalism in preparation for the String Meeting talk the week after.

  • Aspects of F-theory GUTs: I will give a brief overview of my thesis.

  • Complementarity and firewalls: The paper by Polchinski et al last July initiated a huge debate after claiming that in order to uphold the principle of complementarity observers falling in to a black hole must hit a firewall (and therefore "burn"=thermalize). I will review the basic steps of the argument and explain possible ways out of it, as outlined in some newer papers.

  • Yet another introduction to AdS/CFT: aspects of the dictionary: In order to prepare us for a summer of topics with tenuous links to gauge-gravity duality, I'll go through some of the basic aspects of the so-called "AdS/CFT dictionary". As preparatory reading it'd be a good idea to remind yourselves of some of the basic motivation, etc. for the duality. Notes to appear.

  • Introduction to toroidal orbifolds: We will introduce the basic concepts of toroidal orbifolds, mainly following Chapter 10 of "Basic Concepts of String Theory" by Blumenhagen, Lust and Theisen.

  • Introduction to Calabi-Yau manifolds: I will provide an introduction to Calabi-Yau manifolds. This will necessitate a discussion of complex manifolds, cohomology and Chern classes. To end with, I will discuss one of the best known examples of a Calabi-Yau three-fold: the quintic in CP^4.

  • Dirichlet's theorem on arithmetic progressions: Full abstract.

    • Summer 2013 Abstracts


  • Introduction to quantum information theory: I will give a brief introduction to some concepts in Quantum Information Theory. Handwritten notes are available.

    • Resources on preparing a talk

  • Robert Geroch's "Suggestions For Giving Talks": gr-qc/9703019

  • David Tong's "How to Make Sure Your Talk Doesn't Suck": PDF