The conference schedule is provided in the following table, with abstracts further below.

Thursday, May 25th 2017 | |||
---|---|---|---|

Time | Name | Title | Institute |

9:00 | Registration and Welcome | ||

9:30 | Henrik Johansson | Constructing Gravity Theories from Gauge Theories | Uppsala University |

10:15 | Yuhma Asano | Transverse Five-branes in Matrix model | DIAS |

10:35 | Francisco Jose Garcia Abad | On Complexity of Holographic Flavours | Trinity College Dublin |

10:55 | Coffee | ||

11:25 | Silke Weinfurtner | Observation of superradiance in a vortex flow | University of Nottingham |

12:10 | Abraham Harte | Metric-independence of electromagnetic fields | Dublin City University |

12:30 | Peter Taylor | New and improved mode-sum prescription for regularizing the quantum stress-energy tensor | Dublin City University |

12:50 | Lunch | ||

13:50 | Mark Howard | The Cost of Tolerating Faults in a Quantum Circuit | University of Sheffield |

14:35 | Ko Sanders | Entanglement entropy in algebraic QFT | Dublin City University |

14:55 | Michael Tuite | Vertex operator algebras on Riemann surfaces | NUI Galway |

15:15 | Marianne Leitner | CFTs on higher genus Riemann surfaces by sewing and by differential equations of Gauss-Manin type | DIAS |

15:35 | Coffee | ||

16:00 | David O'Regan | Diffeogeometric compensation for basis set evolution in quantum atomistic simulations | Trinity College Dublin |

16:15 | Mauro Ferreira | Quantum Mechanics of 2D materials: Commensurability effect and impurity invisibility | Trinity College Dublin |

16:30 | Emma Sokell | Signature of Two-Electron Interference in Angular Resolved Double Photoionisation of Magnesium | University College Dublin |

16.45 | O'Raifeartaigh Lecture | ||

Fabian Essler | Quantum Master Equations and Integrability | Oxford University | |

17:45 | Reception | ||

18:30 | Public Lecture | ||

Enrico Barausse | The sound of the Universe: detecting gravitational waves in space with LISA | Institut d'astrophysique de Paris | |

20:00 | Dinner |

Friday, May 26th 2017 | |||
---|---|---|---|

Time | Name | Title | Institute |

9:15 | Lars Fritz | Interaction and disorder effects in tilted Weyl cones | Utrecht University |

10:00 | Andrew Mitchell | Condensed matter at the nanoscale: from dots to molecules | University College Dublin |

10:20 | Mikael Fremling | Trial wave functions for a Composite Fermi liquid on a torus | Maynooth University |

10:40 | John Goold | Towards the thermodynamics of boundary driven interacting disordered quantum systems | The Abdus Salam Centre for Theoretical Physics (Trieste) |

11:00 | Coffee | ||

11:30 | James Drummond | Quantum Gravity from Conformal Field Theory | University of Southampton |

12:15 | Francesco Moriello | Non-polylogarithmic Feynman integrals | Trinity College Dublin |

12:30 | Argia Rubeo | Cutoff effects in gradient flow observables | Trinity College Dublin |

12:45 | Giovanni Marco Pruna | Recent theoretical developments in the study of charged lepton flavour violation | Paul Scherrer Institut |

13:15 | Lunch | ||

14:15 | Cormac O'Raifeartaigh | The Einstein World: A Centennial Review | Waterford Institute of Technology |

14:35 | Thomas Sotiriou | Strong gravity as a probe for fundamental physics: the 4 challenges | University of Nottingham |

15:20 | Barry Wardell | Black holes in highly eccentric orbits | University College Dublin |

15:40 | Brian Dolan | Black holes: entropy and enthalpy | Maynooth University |

16:00 | Finish |

## Full list of talks

**Abraham Harte** (Dublin City University)

*Metric-independence of electromagnetic fields*

Almost all measurements of relativistic gravity rely in one way or another upon the behavior of light in curved spacetimes. Gravitational lensing has for example been developed into a routine observational tool, a fact which might lead one to conclude that much of a spacetime's geometry is encoded in some way in electromagnetic fields. I will explain that this is actually false: A single electromagnetic field is actually compatible with an enormous variety of spacetime metrics. Identifying these ambiguities unifies a number of existing results in the literature, allows new solutions to be derived, and also old ones to be better understood. Another consequence is an easy demonstration that electromagnetic and gravitational waves propagating in the same direction cannot interact.

**Andrew Mitchell** (University College Dublin)

*Condensed matter at the nanoscale: from dots to molecules*

**Argia Rubeo** (Trinity College Dublin)

*Cutoff effects in gradient flow observables*

The gradient flow provides a new class of renormalized observables which can be measured with high precision in lattice simulations. In principle this allows for many interesting applications to renormalization and improvement problems. In practice, however, such applications are made difficult by the rather large cutoff effects found in many gradient flow observables. We perform a perturtavive study and we confirm that O(a^2) Symanzik improvement is achieved at tree-level; with a non-perturbative measurement we study how to minimize these effects.

**Barry Wardell** (University College Dublin)

*Black holes in highly eccentric orbits*

If a small black hole orbits a large black hole, the leading-order radiation-reaction effect can be interpreted as a self-force acting on the particle, with a corresponding self-acceleration of the particle away from a geodesic. Such "extreme–mass-ratio inspiral" systems are likely to be important gravitational-wave sources for future space-based gravitational wave detectors. Here we consider the case where the binary is in a bound eccentric orbit and present numerical results for a number of test cases with orbital eccentricities as high as 0.98. In some cases we find large oscillations in the self-force on the outgoing leg of the orbit shortly after periastron passage. These appear to be caused by the passage of the orbit through the strong-field region close to the larger black hole, and can be understood in terms of quasinormal-mode ringing.

**Brian Dolan** (Maynooth University)

*Black holes: entropy and enthalpy *

**Cormac O'Raifeartaigh** (Waterford Institute of Technology)

*The Einstein World: A Centennial Review *

In February 1917, Einstein applied the general theory of relativity - his new theory of gravity, space and time - to the universe as a whole. The resulting model of the cosmos, known as Einstein’s Static Universe or the Einstein World, marked a key milestone in modern cosmology. This seminar will present a brief overview of the Einstein World, with an emphasis on the insights offered into Einstein’s thoughts on relativity, astronomy and cosmology. Particular attention is paid to little-known aspects of the model such as Einstein’s failure to test his model against observation, his failure to consider the stability of his model and a mathematical oversight in his interpretation of the role of the cosmological constant. We will discuss Einstein’s reaction to non-static models of the universe and consider whether the Einstein World represented his “greatest blunder”.

**David O'Regan** (Trinity College Dublin)

*Diffeogeometric compensation for basis set evolution in quantum atomistic simulations*

Many basis sets for electronic structure calculations evolve with varying external parameters, such as moving atoms in dynamic simulations, giving rise to extra derivative terms in the dynamical equations. Here we revisit these derivatives in the context of differential geometry, thereby obtaining a more transparent formalisation, and a geometrical perspective for better understanding the resulting equations. The effect of the evolution of the basis set within the spanned Hilbert space separates explicitly from the effect of the turning of the space itself when moving in parameter space, as the tangent space turns when moving in a curved space. New insights are obtained using familiar concepts in that context such as the Riemann curvature. The differential geometry is not strictly that for curved spaces as in general relativity, a more adequate mathematical framework being provided by fibre bundles. The language used here, however, will be restricted to tensors and basic quantum mechanics. The local gauge implied by a smoothly varying basis set readily connects with Berry's formalism for geometric phases. Generalised expressions for the Berry connection and curvature are obtained for a parameter-dependent occupied Hilbert space spanned by non-orthogonal Wannier functions. The formalism is applicable to basis sets made of atomic-like orbitals and also more adaptative moving basis functions (such as in methods using Wannier functions as intermediate or support bases), but should also apply to other situations in which non-orthogonal functions or related projectors should arise. The formalism is applied to the time-dependent quantum evolution of electrons for moving atoms. The geometric insights provided here allow us to propose new finite-differences time integrators, and also better understand those already proposed.

**Emma Sokell** (University College Dublin)

*Signature of Two-Electron Interference in Angular Resolved Double Photoionisation of Magnesium*

The double photoionisation of Magnesium has been studied experimentally and theoretically in a kinematic arrangement where the two, simultaneously emitted photoelectrons equally share the excess energy. The observation of a symmetrised grade amplitude, which strongly deviates from a Gaussian shape, is explained by a two-electron interference predicted theoretically, but never before observed experimentally.

**Enrico Barausse** (Institut d'astrophysique de Paris)

*The sound of the Universe: detecting gravitational waves in space with LISA*

The recent discovery of gravitational waves by LIGO was a stunning validation of Einstein's General Theory of Relativity. The European Space Agency LISA mission is a set of space-borne gravitational detectors separated by millions of kilometers that will directly observe the stretching and squeezing of spacetime. In this public lecture, the science behind the mission, the technological challenges, and the impact of the results on our understanding of the universe will be discussed.

**Fabian Essler** (Oxford University)

*Quantum Master Equations and Integrability*

**Francesco Moriello** (Trinity College Dublin)

*Non-polylogarithmic Feynman integrals*

In recent years much progress has been made in the analytic computation of Feynman integrals. This is mostly due to a better understanding of multiple polylogarithms, a class of iterated integrals that can be used to express Feynman integrals in many phenomenologically relevant situations. As we increase the number of loops and/or scales a more general class of (elliptic) iterated integrals arises, that is by now much less understood. I will discuss how the so called differential equations method can be used to find analytic representations suitable for phenomenology when such a generalised class of functions appear.

**Francisco Jose Garcia Abad** (Trinity College Dublin)

*On Complexity of Holographic Flavours*

I will introduce the notion of quantum computational complexity and a recently proposed recipe to compute this quantity through holography. Quantum complexity must satisfy a bound on it's growth rate. I will then present the results of my work on how the introduction of flavour matter into the QFT Lagrangian modifies the result, focusing in understanding if this bound is still respected or not.

**Giovanni Marco Pruna** (Paul Scherrer Institut)

*Recent theoretical developments in the study of charged lepton flavour violation*

This talk reviews recent theoretical developments in the study of charged lepton flavour violation. The first part illustrates the status of precise next-to-leading order quantum electrodynamics calculations for the background of charged lepton flavour-violating processes, with a focus on the muonic "rare" and "radiative" decays. The second part describes the recent progress in the effective field theory interpretation of charged lepton-flavour violating observables in connection with different energy scales.

**Henrik Johansson** (Uppsala University)

*Constructing Gravity Theories from Gauge Theories*

I will discuss how gravity scattering amplitudes of many different gravitational theories can be obtained from various gauge theories through a double-copy procedure. While the basic idea goes back to the old relation between open and closed strings, modern understanding show that the notion of gravity being the double copy of two gauge theories is a general concept. I will present new striking examples of gravity theories being double copies, and identify the corresponding underlying gauge theories. In particular, a new construction for conformal gravity will be introduced.

**John Goold** (The Abdus Salam Centre for Theoretical Physics, Trieste)

*Towards the thermodynamics of boundary driven interacting disordered quantum systems*

I will present some recent results on the thermodynamics of boundary driven disordered interacting systems. I will focus primarily on the conducting phase of systems which display many-body localization transition. In particular, I will focus on the non equilibrium steady states which are generated on geometries which contains diagonal disorder.

**James Drummond** (Southampton University)

*Quantum Gravity from Conformal Field Theory*

I will discuss the problem of constructing perturbative loop corrections to AdS supergravity amplitudes. By using the consistency of the operator product expansion of N=4 super Yang-Mills theory and known tree-level gravity results we are able to bootstrap loop corrections by imposing a consistent spectrum of double trace operators.

**Ko Sanders** (Dublin City University)

*Entanglement entropy in algebraic QFT*

Entanglement is an important experimental resource in quantum physics, and entanglement entropy is a measure for the amount of entanglement (which may be infinite). Based on joint work with Stefan Hollands, I will describe entanglement and entanglement entropy in the context of algebraic quantum field theory (QFT), using a Lorentzian setting and allowing curved spacetimes. I will describe some general methods to obtain upper bounds on the entanglement entropy. This complements the existing literature, which mostly deals with quantum mechanical systems or Euclidean/path integral approaches to QFT.

**Lars Fritz** (Utrecht University)

*Interaction and disorder effects in tilted Weyl cones*

**Marianne Leitner** (DIAS)

*CFTs on higher genus Riemann surfaces by sewing and by differential equations of Gauss-Manin type*

CFTs are naturally defined on Riemann surfaces. The rational ones can be solved using methods from algebraic geometry. One particular feature is the covariance of the partition function under the mapping class group. In genus g=1, one can apply the standard theory of modular forms, which can be linked to ODEs of hypergeometric type. One way to extend the theory to higher genus is by sewing tori, but in practice g>2 seems currently out of reach. In contrast, our algebraic description allows to deal with all genera at once. The talk will explain the two approaches and their relation. This is joint work with Werner Nahm.

**Mark Howard** (University of Sheffield)

*The Cost of Tolerating Faults in a Quantum Circuit*

The basic principle of error correction is that we can store and retrieve information in a way that allows us to tolerate some faults; the price of achieving this is that we introduce redundancy e.g., a message "0" gets redundantly encoded as "000". To perform a quantum computation with imperfect hardware we must use a quantum error correcting code to encode -- and therefore protect -- a state of many quantum bits. Computation is a dynamic process, however, and we need to manipulate the encoded quantum information by performing logic gates and measurements. Doing this in a way that doesn't introduce errors is a much more difficult task than the basic store-and-retrieve paradigm. This is the central topic of quantum fault-tolerance. I will review some of the main ideas and then present recent joint work with Earl Campbell along these lines.

**Mauro Ferreira** (School of Physics - Trinity College Dublin)

*Quantum Mechanics of 2D materials: Commensurability effect and impurity invisibility*

The key signature of any symmetry-breaking perturbation that arises due to the presence of impurities and/or defects in materials is the appearance of spatial fluctuations in quantities like the local density of states (LDOS) and the carrier density, both of which oscillate away from the location of the perturbation. However, in many 2D materials these oscillations are hidden by their commensurability with the lattice parameter of the host. Surprisingly, the absence of such oscillations can have a dramatic effect in a number of electronic properties of these materials, as will be shown in this talk.

**Michael Tuite** (NUI Galway)

*Vertex operator algebras on Riemann surfaces*

**Mikael Fremling** (Maynooth University)

*Trial wave functions for a Composite Fermi liquid on a torus*

We study the two-dimensional electron gas in a magnetic field at filling fraction ν = 1/2 . At this filling the system is in a gapless state which can be interpreted as a Fermi liquid of composite fermions. We construct trial wave functions for the system on a torus, based on this idea, and numerically compare these to exact wavwe functions for small systems found by exact diagonalization. We find that the trial wave functions give an excellent description of the ground state of the system, as well as its charged excitations, in all momentum sectors. We analyse the dispersion of the composite fermions and the Berry phase associated with dragging a single fermion wave function around the Fermi surface and comment on the implications of our results for the current debate on whether composite fermions are Dirac fermions.

**Peter Taylor** (DCU)

*New and improved mode-sum prescription for regularizing the quantum stress-energy tensor*

In the semi-classical Einstein equations, the source term is the expectation value of the stress-energy tensor of quantum fields in a given state. It is well-known that this quantity is formally divergent and requires regularization. The first practical regularization scheme was devised by Candelas and Howard in a seminal paper in 1984. Despite serious drawbacks, the Candelas-Howard method has remained more or less the standard approach for computing regularized quantities in quantum field theory in curved spacetime. We present a new approach to this problem motivated by mode-sum schemes used in the self-force community. Our regularization prescription is extremely efficient and enjoys many advantages over the Candelas-Howard approach. Moreover, unlike the Candelas-Howard scheme, our approach is mostly agnostic to number of dimensions which we exploit to compute, for the first time, vacuum polarization in higher-dimensional black hole spacetimes.

**Silke Weinfurtner** (University of Nottingham)

*Observation of superradiance in a vortex flow*

Wave scattering phenomena are ubiquitous to almost all Sciences, from Biology to Physics. When an incident wave scatters off of an obstacle, it is partially reflected and partially transmitted. Since the scatterer absorbs part of the incident energy, the reflected wave carries less energy than the incident one. However, if the obstacle is rotating, this process can be reversed and waves can be amplified, extracting energy from the scatterer. Even though this phenomenon, known as superradiance, has been thoroughly analysed in several theoretical scenarios (from eletromagnetic radiation scattering on a rotating cylinder to gravitational waves incident upon a rotating black hole), it has never been observed. Here we describe in detail the first laboratory detection of superradiance. We observed that plane waves propagating on the surface of water are amplified after being scattered by a draining vortex. The maximum amplification measured in the experiment was 20%, obtained for 3.70 Hz waves, in a 6.25 cm deep fluid. Our results are consistent with superradiant scattering caused by rapid rotation. In particular, a draining fluid can transfer part of its rotational energy to incident low-frequency waves. Our experimental findings will shed new light on Black Hole Physics, since shallow water waves scattering on a draining fluid constitute an analogue of a black hole. We believe, especially in view of the recent observations of gravitational waves, that our results will motivate further research (both theoretical and experimental) on the observation of superradiance of gravitational waves.

**Thomas Sotiriou** (University of Nottingham)

*Strong gravity as a probe for fundamental physics: the 4 challenges*

Gravitational waves, combined with other astronomical observations, will provide an exciting new insight into the nature of strongly gravitation systems, such as black holes and compact stars. This should then lead to novel constraints on the deviations from general relativity and more generally on fundamental physics. I will summarise what I believe are the 4 more serious challenges one faces when attempting to use strong gravity as a probe to fundamental physics.

**Yuhma Asano** (DIAS)

*Transverse Five-branes in Matrix model*

Understanding transverse M5-branes in matrix models has been a difficult problem. Although it is known that the BMN matrix model contains transverse M5-branes as its vacua, explicit construction of its geometry had been unclear. We calculated an eigenvalue distribution in the limit associated with the five-branes, and showed that the distribution forms S^5 geometry with the correct radius.