NBIA-Oxford Colloquium on Theoretical Physics

13 Apr 2015, 08:00 → 15 Apr 2015, 18:00 Europe/Copenhagen

Slides

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Monday, 13 April

1 Welcome

Speakers: Dr Poul Henrik Damgaard (Niels Bohr Institute), Prof. Robert Feidenhansl (Niels Bohr Institute)

2 Modelling our Galaxy

Chemodynamical models will be central to efforts to interpret data from the massive stellar surveys now in hand. Cosmological simulations are not rigorous and are much too expensive to be fitted to data. I'll show that models that have analytic (extended) distribution functions provide excellent fits to the data. The models already provide the strongest constraints on the Galaxy's dark-matter distribution and they are becoming steadily more sophisticated and constraining.

Speaker: Prof. James Binney (Oxford University)

Slides Modelling_our_Galaxy.pdf

16:00 Tea/Coffee

3 The vernacular of the S-matrix

The past several years have been witness to an ongoing revolution in our understanding of (perturbative) quantum field theory. In particular, a concrete proposal now exists for how to reformulate any theory recursively---without any reference to virtual particles, gauge redundancies, or any of the other unphysical baggage that so complicates computations in the traditional formalism. In addition to greatly simplifying computations, the recursive reformulation provides an important connection between field theory and the geometry (and combinatorics) of certain subspaces of the Grassmannian---a connection that has proven extremely fruitful for both physics and mathematics in recent years. Because both sides of this connection are greatly simplified (and best understood) in the case of planar, maximally supersymmetric Yang-Mills, this will be the primary example discussed. I will provide a broad overview to these ideas, starting from basic principles of quantum mechanics.

Speaker: Dr Jacob Bourjaily (Niels Bohr Institute)

Slides bourjaily_nbia_oxford_colloquium.pdf

17:15 Reception

All participants are welcome

Tuesday, 14 April

4 QCD for the LHC

Speaker: Prof. Giulia Zanderighi (University of Oxford)

Slides NBIA-Zanderighi.pdf

5 Past present and the possible future in precision Higgs phenomenology

The discovery of a Higgs like boson in Run I of the LHC kicked off a vigorous effort to systematically develop the theoretical formalism of a model-independent approach to precision Higgs physics. The idea is to have a general theoretical framework that can interpret consistently any deviation in the properties of the Higgs without guessing the underlying theory. It has also become clear that incorporating previous precision data, primarily from LEP, is also an essential task in developing a consistent theoretical framework for a true SM effective theory. I will discuss the current state of the art in this approach and how the theoretical formalism is being developed further in anticipation of the Run II data set.

Speaker: Dr Michael Trott (Niels Bohr International Academy)

Slides Trott.pdf

11:00 Coffee/Tea

6 Beyond the Standard Model (or not) after the Higgs

To date, the LHC has not observed indications of structure beyond the Standard Model (BSM) of particle physics. Moreover the measured properties of the Brout-Englert-Higgs boson hint at an underlying simplicity of the model without such new physics. This has led to a re-evaluation of the hierarchy problem on which much of our faith in BSM physics rests. In this talk I will review these issues and their implications for BSM discovery at the LHC.

Speaker: Prof. Graham Ross (University of Oxford)

Slides GGRNBIAOxfordcolloquium.pdf

7 The hidden simplicity of scattering amplitudes (and of hydrogen)

Physical systems with unexpected, or 'hidden’, symmetries have often played a role in physics. I will argue that the symmetry responsible for the degeneracies of the hydrogen spectrum extends to a unique relativistic quantum field theory - a maximally supersymmetric (`N=4') cousin of the strong-interaction Yang-Mills theory. I will discuss how this is enabling its solution, and what this teaches us more generally about other theories

Speaker: Mr Simon Caron-Huot (Niels Bohr International Academy)

Slides CaronHuot.pdf

13:00 Lunch

8 Toward a theory of plasma dynamo: Magnetic fields and microinstabilities in a weakly collisional plasma

Speaker: Prof. Alexander Schekochihin (University of Oxford)

Slides Schekochihin.pdf

9 The turbulent dynamics of accretion disks

Accretion disks are flattened, differentially rotating gaseous structures that can be found surrounding young stars, white dwarfs, neutron starts, and black holes. Understanding the physical processes that determine the rate at which matter accretes and energy is radiated in these disks is vital for unraveling the formation, evolution, and fate of almost every type of object in the Universe. These processes are regulated by the rate at which angular momentum can be transported outwards. It is currently thought that the transport of angular momentum is mediated by magnetohydrodynamic turbulence. In this talk, I will give an overview of some of the basic ideas that have been around for the last few decades and will argue that a first-principles theory to describe magnetohydrodynamics turbulence in disks will likely have to consider the anisotropic nature of the flow at a fundamental level.

Speaker: Dr Martin Pessah (Niels Bohr International Academy)

Slides mpessah-nbia-oxford-2015.pdf

15:45 Tea/Coffee

16:00 Excursion

Walk to Nyhavn - boat trip leaving at 17:05 (http://www.havnerundfart.dk/)

18:15 Dinner

http://www.saltrestaurant.dk/

Wednesday, 15 April

10 Strontium Ruthenate: Why this material has remained interesting for 20 years and what is new now

Speaker: Prof. Steve Simon (University of Oxford)

Slides Simon.pdf

11 From Pauli's Principle to Fermionic Entanglement

The Pauli exclusion principle is a constraint on the natural occupation numbers of fermionic states. It has been suspected for decades, and only proved very recently, that there is a multitude of further constraints on these numbers, generalizing the Pauli principle. Surprisingly, these constraints are linear: they cut out a geometric object known as a polytope. This is a beautiful mathematical result, but are there systems whose physics is governed by these constraints? In order to address this question, we studied a system of a few fermions connected by springs. As we varied the spring constant, the occupation numbers moved within the polytope. The path they traced hugs very close to the boundary of the polytope, suggesting that the generalized constraints affect the system. I will mention the implications of these findings for the structure of few-fermion ground states and then discuss the relation between the geometry of the polytope and different types of fermionic entanglement.

Speaker: Dr Matthias Christandl (Niels Bohr Institute)

Slides Christandl.pdf

11:00 Coffee/Tea

12 Nonequilibrium dynamics in isolated many-particle quantum systems

Speaker: Prof. Fabian Essler (University of Oxford)

Slides Essler.pdf

13 Alchemy for the 21st century: creating topological behavior in periodically-driven systems

Recent work on topological materials has revealed a wide variety of intriguing phenomena that may arise when particles move in "non-trivial" bands. Modern advances in experimental capabilities for controlling electronic, atomic, and optical systems raise the possibility that analogous phenomena may be generated dynamically in driven systems. In this talk I will review the basic ideas behind topological band theory, and then discuss the corresponding situation for periodically driven systems. In the driven case, intriguing new types of robust topological phenomena emerge. I will explain how this occurs, and give some outlook on recent and proposed experiments on these so-called Floquet topological insulators.

Speaker: Dr Mark Rudner (Niels Bohr International Academy)

Slides Rudner.pdf

13:00 Lunch

14 Particle physics from string theory

String theory contains many of the generic features required for particle physics. Establishing the detailed connection between string theory and particle physics, however, is not straightforward and I will discuss some of the successes and problems in this area. In particular, I will describe some recent progress in constructing the standard model of particle physics from heterotic string theory.

Speaker: Prof. Andre Lukas (University of Oxford)

Slides Lukas.pdf

15 Solvable matter on 2d Causal Dynamical Triangulation?

Models with matter coupled to two dimensional CDT are hard to solve analytically, somewhat contrasting with matter coupled to dynamical triangulations which can be solved by a plethora of methods. Recently Atkin and Zohren introduced a restricted dimer model which can be solved. I’ll discuss some of its bizarre characteristics and introduce a generalisation that is also solvable and shows these to be somehow non-generic. Finally I’ll discuss whether these results are really representative in the continuum limit of a field theory coupled to 2d gravity.

Speaker: Prof. John Wheater (University of Oxford)

Slides Wheater.pdf

16 Concluding remarks

Speaker: Prof. Subir Sarkar (NBI Copenhagen and University of Oxford)

16:00 Coffee/Tea