All talks will take place in Room ELG04. Tea and coffees will be served in the foyer area outside ELG01 and lunch can be purchased in the canteen.
10:30-11:00 Welcome, tea and coffee
11:00-12:00 Hugh Jones, "A Review of PT Symmetry in Quantum Mechanics and Classical Optics."
12:00-12:30 Joseph Durnin, "Prethermalisation and Thermalisation in Perturbed Integrable Systems"
14:00-15:00 Olalla Castro-Alvaredo, "Entanglement Dynamics in the Ising Field Theory"
15:00-15:30 Rajath Radhakrishnan, "Entanglement Entropy in Topological Quantum Field Theory"
15:30-16:00 Tea and coffee
16:00-17:00 Dionysios Anninos, "Degrees of freedom in an expanding spacetime"
17:00-17:30 Manya Sahni, "On the Localization of 5D Spinning Black Hole"
List of invited speakers:
Hugh Jones (Imperial College London)
"A Review of PT Symmetry in Quantum Mechanics and Classical Optics."
The idea of PT symmetry in quantum mechanics arose initially from the observation that the spectrum of the potential V=i x^3 is purely real, even though V is not Hermitian. It was subsequently developed as a generalization of standard quantum mechanics, with PT symmetry replacing the usual requirement of Hermiticity. However, it is best regarded as a framework for effective theories, with the non-Hermiticity arising from an external source. Surprisingly the same framework can be applied to classical optics, with the role of V taken by the refractive index. This has been an extremely active field recently, with many interesting results.
Olalla Castro-Alvaredo (City, University of London)
"Entanglement Dynamics in the Ising Field Theory"
In this talk I will review recent work in collaboration with Máté Lencsés, István M. Szécsényi and Jacopo Viti regarding the time-dependence of the entanglement entropy after a mass quench in the Ising field theory. For the lattice version of this model (the Ising chain) this problem has been studied in detail in the past, however there was so far no study directly in the QFT using the methods available in this context. In this work we have employed two perturbative approaches and adapted them to deal with branch point twist fields, well-known to be related to measures of entanglement. We find that for large times, the leading feature of the entanglement entropy is that it grows linearly in time. However, we also find long-lived oscillatory corrections to this behaviour which we can fully characterize by our methods. These features are confirmed by numerical simulations.
Dionysios Anninos (King's College London)
"Degrees of freedom in an expanding spacetime"
We consider the fate of low energy degrees of freedom in a spacetime experiencing accelerating expansion. The question is explored through the examination of a toy model containing a tower of particles with increasing spin. Time permitting, we also discuss recent progress in embedding such a spacetime into an asymptotic anti-de Sitter universe.
Manya Sahni (King's College London)
"On the Localization of 5D Spinning Black Hole"
In the 70s, similarities found between black hole mechanics and thermodynamic systems, suggested that black holes have an entropy. For a classical black hole interacting with quantum particles, Bekenstein and Hawking found that the entropy is proportional to the area of a black hole. As in thermodynamcis, black holes are also classified by three macroscopic parameters, namely by their mass, charge and angular momentum. The area, and therefore the Bekenstein-Hawking entropy, is a function of these parameters. This leads to the question - can we model the entropy of a black hole as the log of the number of microstates? In order to answer this, we need the total entropy of the black hole, including quantum corrections. For an extremal black hole, quantum black hole entropy is given by the expectation value of a Wilson line inserted at the boundary. We can use SUSY localization to evaluate this exactly. There has been much work on the quantum entropy in 4d using this method. We look for the localisation manifold of N = 2;D = 5 SUGRA coupled to nV vector multiplets.
Joseph Durnin (King's College London)
"Prethermalisation and Thermalisation in Perturbed Integrable Systems"
Interacting many-body quantum systems are inherently difficult to study; the exponential increase in the size of the Hilbert space with system size means approximations must be made to obtain predictions from model Hamiltonians. An exception to this occurs for integrable systems, which may often be solved exactly. The study of such systems has been incredibly fruitful, however they have several highly atypical properties, such as the existence of an extensive number of conserved quantities, which forbids conventional thermalisation. Here I pose the question: given our relatively extensive understanding of integrable models, can we use this understanding to learn something about systems which are close to being integrable? I discuss recent progress made in this direction, including the emergence of prethermalisation at intermediate time-scales as a precursor to thermalisation.
Rajath Radhakrishnan (Queen Mary University of London)
"Entanglement Entropy in Topological Quantum Field Theory"
Unlike a general quantum field theory, a topological quantum field theory (TQFT) enjoys a mathematically precise definition. It is an important arena in which calculations can be done explicitly to learn more about QFTs in general. Moreover, a 3D TQFT can be described using a purely algebraic object called a Modular Tensor Category (MTC). An MTC is a rigid structure which enables us to find interesting maps between physically distinct TQFTs. In this talk, I will discuss how entanglement entropy of links in different TQFTs are related to each other. These reveal interesting relationships between a coarse-grained version of link invariants in different TQFTs.