Theoretical High Energy Particle Physics Group

HEP-GR Colloquium Series

Place: Meeting Room 5
Time: Wednesdays, 2:15pm
Organisers: Dr Aleksey Cherman and Dr Pau Figueras

Please stay for tea, coffee and biscuits in the Central Core!

Michaelmas 2011

12-Oct-2011: Ricci flow and its applications to Numerical General Relativity

Pau Figueras (DAMTP, Cambridge)


Abstract: "In this talk I will present an overview of a new method, borrowed from Ricci flow, to numerically construct static and stationary black hole spacetimes with or without a cosmological constant. This method is based on the harmonic formulation of the Einstein equations and it is the state of the art in static/stationary Numerical Relativity. I will illustrate how it works with two (interrelated) examples: the numerical construction of the gravitational dual of N=4 super Yang-Mills on the background of the Schwarzschild black hole and the construction of braneworld black holes. Finally I will summarise and I will outline some future directions for research."

19-Oct-2011: Gauge-gravity duality beyond thermal equilibrium

Andrei Starinets (University of Oxford)

Abstract: "String theory technique known as gauge/gravity duality relates transport properties of strongly coupled model plasmas (their viscosities, thermal conductivities, diffusion constants) to quasinormal spectra of black holes in dual curved higher dimensional spacetimes. By computing transport coefficients for these theoretical models, one gets qualitative insights into physics of strongly coupled hot and dense nuclear matter created in heavy ion collision experiments at RHIC and LHC as well as physics of cold dense matter. We shall review (at a relatively non-technical level) the current status and perspectives of these nonperturbative methods."

26-Oct-2011: Some generalised geometries from M theory

Malcolm Perry (DAMTP, Cambridge)

Abstract: TBA

02-Nov-2011: Manifestations of monopole physics in spin ice materials

Claudio Castelnovo (Royal Holloway, University of London)

Abstract: Spin ice materials such as Dy2Ti2O7 and Ho2Ti2O7 provide a rare instance of emergent gauge symmetry and fractionalisation in three dimensions. Their elementary excitations carry a fraction of the magnetic moment of the microscopic spin degrees of freedom, and they can be thought of as magnetic monopoles. This talk aims at introducing spin ice models and materials and reviewing their unusual properties. In particular, the peculiar nature of the excitations is discussed, together with (some of the) signatures that have been so far identified in the equilibrium and response properties of spin ice materials. These include unusual neutron scattering structure factors, dynamical arrest and long lived non-equilibrium metastable states, as well as a response to external magnetic fields that promotes spin ice as a magnetic analogue of an electrolyte. The formulation of the low-temperature phase in terms of an emergent gauge field permits an unusual degree of analytical progress in the modelling of these materials.

09-Nov-2011: NONE

Mihalis Dafermos (DPMMS, Cambridge)

Abstract: Taking as a starting point a number of statements that are often repeated in the literature, I will discuss recent advances in our mathematical understanding of general relativity which may be of relevance to topical themes in theoretical physics.

16-Nov-2011: The search for dark matter

Anne Green (University of Nottingham)

Abstract: Diverse astrophysical and cosmological observations indicate that most of the matter in the Universe is cold, dark and non-baryonic. Weakly Interactive Massive Particles (WIMPs) are generically a good dark matter candidate and particle physics provides us with a well-motivated WIMP candidate in the form of the lightest supersymmetric particle. WIMPs can be detected indirectly (via the products of their annihilation) or directly (via elastic scattering in underground detectors). They can also be produced at particle colliders like the LHC. After an introduction to dark matter and WIMPs I will discuss the principles, current status and future prospects of WIMP detection experiments.

23-Nov-2011: Locally covariant QFT and the problem of formulating the same physics in all spacetimes

Chris Fewster (University of York)

Abstract: Axiomatic approaches to QFT have traditionally been confined to flat (or maximally symmetric) spacetimes, or to the analysis of particular model theories. To go beyond this, it is necessary to understand in general what it means for a theory to represent the same underlying physics in different spacetimes, without assuming the existence of a Lagrangian description. Brunetti, Fredenhagen and Verch (BFV) have proposed a framework for locally covariant QFT, using category theory, that generalizes the axiomatic approach to general curved spacetimes. In this talk, I will review the BFV framework and examine the extent to which it succeeds in formulating the same physics in all spacetimes. The talk is based on recent papers written with Rainer Verch.

30-Nov-2011: String glasses

Frederik Denef (University of Leuven)

Abstract: According to traditional beliefs, physics at subatomic scales is intrinsically simple, and complexity only emerges in the macroscopic or living world. Recent theoretical and experimental developments suggest this may be wrong. Indeed, microscopic complexity has been essential in theoretical accounts of the origin of matter and its interactions, the entropy of black holes, and the nature of dark energy. I will review some of these developments in the context of string theory and cosmology, and will discuss how ideas developed to understand the physics of glasses and other complex systems can be applied in this setting. Conversely, holographic dualities may provide new insights into the nature of such systems.

Lent 2012

18-Jan-2012: The rise, fall, and rebirth of string models of the strong interactions

Jeff Harvey (U. Chicago)

Abstract: String theory was originally developed as a theory of the strong interactions. This approach largely disappeared due to the discovery of asymptotic freedom and the development of QCD , and string theory later came to be viewed as an approach to quantum gravity and unification. Recent developments growing out of the AdS/CFT correspondence have revived the connection between string theory and the strong interactions. I will describe elements of this history and discuss recent progress in using string theory to model the strong interactions.

25-Jan-2012: Spatial pattern formation in polariton condensates

Natasha Berloff (DAMTP, Cambridge)

1-Feb-2012: The search for gravity waves in the CMB

Carlo Contaldi (Imperial U.)

Abstract: TBA

8-Feb-2012: The status of the search for the Higgs boson

Andy Parker (Cambridge U.)

Abstract: TBA

22-Feb-2012: Probing the dark universe with CMB lensing

Anthony Challinor (Institute of Astronomy, Cambridge U.)

Abstract: TBA

29-Feb-2012: cancelled

7-March-2012: The fine-scale structure of dark matter halos

Simon White (Max Planck)

Abstract: A wide range of astronomical observations indicate that cosmic structure formation is driven by the gravitational effects of dark matter. This contributes about 80 percent of the total cosmic mass budget and interacts extremely weakly with light and with all known forms of matter. It is most plausibly a new kind of elementary particle, yet to be detected directly or indirectly on Earth. At the time of recombination, 400,000 years after the Big Bang, the Universe was almost uniform, its only structure being weak linear fluctuations with statistical properties that can be inferred directly from observations of the cosmic microwave background. At this time dark matter particles had small thermal velocities and their distribution deviated from uniformity only through a gaussian field of density fluctuations with associated motions. Later evolution was driven purely by gravity and so obeyed the collisionless Boltzmann equation. This has immediate consequences for the present distribution of dark matter, even in extremely nonlinear regions such as the part of the Galaxy where the Sun resides. I will show how this structure can be followed in full generality in high-resolution N-body simulations by integrating the Geodesic Deviation Equation in tandem with the equations of motion, enhancing the effective resolution by more than 10 orders of magnitude and permitting a detailed treatment of annihilation radiation from dark matter caustics. I will also discuss how the predicted distribution at the Sun's position impacts the expectations for terrestrial experiments seeking to detect the dark matter directly, in particular, the possibility of extremely narrow line signals that may be visible in axion detectors.