CPT Student Seminars

Student seminars are usually held on Monday afternoons, 5-6pm, in OC218 (the IPPP seminar room). Tea, coffee and biscuits are (sometimes) provided by the IPPP.

Feel free to invite a friend or collaborator from another institution to give a talk if they're in town.

Organisers: Jonathan Davis (IPPP) and Rafael Maldonado (Maths)


11 June 2012: Black holes and scalar fields
Sarah Chadburn (Durham, 3rd year Maths)
Does the well-known idea that "black holes have no hair" cause any problems for cosmological models that include a scalar field?

"Quintessence" is a model in which a scalar field acts as dark energy, causing the observed accelerated expansion of the universe. If there is a scalar field in the universe, it must coexist with the black holes that are already known to exist. I will talk about the question I am currently trying to answer: how a black hole would fit into a quintessence cosmology, and how the system as a whole might behave.
14 May 2012: Instantons on D4 branes
James Allen (Durham, 3rd year Maths)
Instantons are minimum energy solutions in Yang-Mills. They've been studied for decades, but my interest has been motivated by some recent developments in the connection between string theory and M-theory. But don't worry, this talk will have very little string theory in it. I'll focus on the interesting properties of instantons and how we can use some very nice mathematics and arguments to get a much better understanding of the dynamics of this sector of Yang-Mills. For the non-mathematicians it should still be easily understandable, and hopefully even interesting!
30 April 2012: Dimer models: The ultimate shortcut
Daniele Galloni (Durham, 1st year IPPP)
Dimer models have a natural simplicity, in which ordinarily complicated operations take on a very simple form. Additionally, they have the ability of linking supersymmetric quiver gauge theories with string theory through recognition of moduli spaces, making elegant use of the Seiberg-Witten curve. In this way, dimer models can check conjectured dualities as well as develop the understanding of very different areas of physics. This talk will introduce the areas linked through dimers and show how dimers encode the information on a tiling of a torus.
19 March 2012: Phase Transition and Anisotropic Deformations of Neutron Star Matter
Susan Nelmes (Durham, 3rd year Maths)
The Skyrme model is known to be a low energy, effective field theory for QCD and when coupled to a gravitational field provides an ideal semi-classical model to describe neutron stars. In this talk we explore how a Skyrme crystal solution composed of a lattice of alpha particles can be used to construct minimal energy neutron star configurations, in particular by allowing the crystal to be strained anisotropically.
12 March 2012: Higgs plus multi-gluon helicity amplitudes
Xuan Chen (Durham, 2nd year IPPP)
In this talk I will give a short review about the development of gluon fusion to Higgs plus parton amplitudes. First I would like to introduce the phenomenology status of different Higgs production channels. The complex Higgs field model would be introduced afterwards. Then I would like to talk about the technique of calculating tree and one-loop level channels. The modern method such as the helicity formalism, CSW rules and generalised unitary method will be presented. Additionally, I will introduce some example calculations, to help us understand the advantages of these methods.
5 March 2012: Periodic Monopoles
Rafael Maldonado (Durham, 2nd year Maths)
I will first discuss dimensional reduction of the self-dual Yang-Mills equations and how they are linked by the Nahm transform. With the scene set, I'll look at how the Nahm transform applies to the periodic monopole and compare the solutions obtained with those of other solitonic systems.
27 February 2012: Meson Condensation in Gauge/Gravity Duality: Finite Size Effect
Pichet Vanichchapongjaroen (Durham, 2nd year Maths)
In this talk I will introduce AdS/CFT correspondence with flavour, and then describe its application on meson condensation in the finite-sized strongly coupled QCD-like system at finite temperature and finite isospin chemical potential.
20 February 2012: Effective Theories. Sum Rules. Lambda_b to Lambda Form Factors
Matthew Yip (Durham, 3rd year IPPP)
I'll attempt to give brief introductions to effective theories in the context of Flavour Physics, and more specifically HQET (heavy quark effective theory) and SCET (soft collinear effective theory); also to the non-perturbative technique QCD sum rules; ending with the recently-published paper "Form Factors for Lambda_b to Lambda Transitions in SCET" by Thorsten Feldmann and myself (arXiv:1111.1844).
13 February 2012: A soliton menagerie in AdS
Simon Gentle (Durham, 3rd year Maths)
Anti-de Sitter space is a weird and wonderful place. In this talk I will introduce the rich variety of charged scalar solitons to be found in global AdS4, then show how these match up smoothly with another AdS favourite --- hairy black holes. Pursuing this connection leads to a host of exotic solutions and, most importantly, some pretty pictures.
30 January 2012: Supersymmetry breaking and the nature of *.inos
Daniel Busbridge (Durham, 2nd year IPPP)
The accessible mass spectra at the low scale in SUSY models with Majorana gaugino masses is severely restricted by the form of the RG equations. In particular, if it is assumed that the observable spectrum is due to the evolution of some theory defined at the high scale, then a 'forbidden zone' of low scale mass configurations arises. Interestingly, it may be possible to access such configurations if instead, the gauginos are allowed to acquire a Dirac mass.

In this talk I will spend some time motivating supersymmetry and how to build a model in a manifestly supersymmetric way (this will be familiar ground for some of the audience I am sure!). Continuous R-symmetries and their implications upon the gaugino sector will then be discussed. I will then briefly motivate the Minimal R-symmetric Supersymmetric Standard Model (MRSSM), where all fermions, including the gauginos and Higgsinos, are Dirac particles, and outline how the extra fields required by the MRSSM could be interpreted as relics from a sector of extended supersymmetry. Finally, I will touch on how such a theory would be completed with a Messenger sector.
23 January 2012: Magnetic monopoles with large charge
Derek Harland (Durham, postdoc Maths)
BPS magnetic monopoles are topological solitons that naturally occur in gauge theories. They have been the subject of intensive study for the last 30 years. Somewhat surprisingly, no one had given much thought to what monopoles with large charge look like until very recently. It has been conjectured that large-charge monopoles resemble hollow "bags", with the magnetic charge residing on the surface of the bag. I will present some new evidence supporting this conjecture, based on mathematical transform invented by Nahm.
16 January 2012: Scattering Amplitudes in N=4 SYM
Tim Goddard (Durham, 2nd year Maths)
The subject of scattering amplitudes in N=4 SYM is primarily an exploration into structure. A quick look at the mass content will convince you that this is the "wrong theory", so why study it? What are the advantages over other theories? Haven't I rather wasted the last 8 months? It is these questions which I shall be endeavouring to answer.
5 December 2011: Aspects of Holographic Superconductivity
Luke Barclay (Durham, 5th year Maths)
Having recently submitted my thesis on holographic superconductivity I thought that I might give a gentle overview of what it contained.

I will begin with a simple introduction to holographic superconductivity before presenting some of my findings on superconductors in Gauss-Bonnet gravity. I will then discuss some more recent work that involved finding Lifshitz-black hole solutions from string theory as a step towards developing a top down Lifshitz holographic superconductor.
28 November 2011: The Mixmaster Universe - It's Complicated
Angharad Kenway (Durham, 5th year Maths)
The Mixmaster Universe is a metric with an extremely complicated evolution and a singularity. In this talk I will discuss the work I have done to model the Mixmaster Universe in order to study its geodesics. I will discuss how we can use geodesics which bounce off the singularity to study the singularity via holography and whether or not we can find such geodesics in the Mixmaster Universe.
21 November 2011: The fate of sneutrinos in Cold Dark Matter models
Jonathan da Silva (Savoie/Annecy)
The aim of this talk is to present the supersymmetric partner of the right-handed (RH) neutrino as candidate to dark matter, considering astrophysical and collider constraints. For it, I will first present some motivations for dark matter and supersymmetry and the possibility to link both subjects. Then, I will speak about supersymmetric candidates to dark matter, especially the example of sneutrino in different scenarios. Finally I will emphasize the case of the RH sneutrino in U(1) extensions of the minimal supersymmetric standard model, studied in arXiv:1110.2414.
14 November 2011: From D-branes to Galaxies
Danielle Wills (Durham, 1st year Maths)
The general aim of this talk will be to establish how the "seeds of cosmic structure" may arise from string theory models of cosmology. I will give an introduction to cosmology with a focus on cosmic inflation and gravitational particle production, and then discuss the vector curvaton scenario. Following this, I will outline how these concepts may be embedded in string theory, considering open string inflation models in Type IIB theory where inflation is driven by the motion of D3-branes. I will end with a brief discussion of the D-brane vector curvaton.
7 November 2011: Aspects of Low Energy Physics
Chris Wallace (Durham, 2nd year IPPP)
I'll begin with a brief introduction and motivation for the low energy paradigm. I will then detail three areas of research that illustrate the philosophy of low energy physics, hopefully demonstrating that the fundamental structure and content of the Universe can be explored without a collider. In particular, I will talk about:
1) Lorentz and CPT violation in the Standard Model Extension
2) Tunnelling of the 3rd Kind
3) The Hidden Sector.
31 October 2011: M-Theory and Matrix Models
Gurdeep Sehmbi (Durham, 4th year Maths)
I will give an introduction to branes and M-theory followed by a recent development involving matrix models, quantum Nambu geometry and M5-branes. The paper can be found here.
24 October 2011: Hunting for Dark Matter
Jon Davis (Durham, 2nd year IPPP)
Unless I come up with a good pun, the title will be "Hunting for Dark Matter" - focusing on how, to my knowledge, Earth-based direct detection experiments aim to discover and identify the Dark Matter in our galaxy.
17 October 2011: CFT dual of the AdS Dirichlet problem: Fluid/Gravity on cut-off surfaces
Daniel Brattan (Durham, 4th year Maths)
We study the gravitational Dirichlet problem in AdS spacetimes with a view to understanding the boundary CFT interpretation. We define the problem as bulk Einstein's equations with Dirichlet boundary conditions on fixed timelike cut-off hypersurface. Using the fluid/gravity correspondence, we argue that one can determine non-linear solutions to this problem in the long wavelength regime. On the boundary we find a conformal fluid with Dirichlet constitutive relations, viz., the fluid propagates on a 'dynamical' background metric which depends on the local fluid velocities and temperature. This boundary fluid can be re-expressed as an emergent hypersurface fluid which is non-conformal but has the same value of the shear viscosity as the boundary fluid. The hypersurface dynamics arises as a collective effect, wherein effects of the background are transmuted into the fluid degrees of freedom. Furthermore, we demonstrate that this collective fluid is forced to be non-relativistic below a critical cut-off radius in AdS to avoid acausal sound propagation with respect to the hypersurface metric. We further go on to show how one can use this set-up to embed the recent constructions of flat spacetime duals to non-relativistic fluid dynamics into the AdS/CFT correspondence, arguing that a version of the membrane paradigm arises naturally when the boundary fluid lives on a background Galilean manifold.

Links to previous years' seminars: 2010/11, 2009/10, 2008/09, 2004/05.

Back to the CPT seminar list.


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