Papers and talks 

An up-to-date list of my papers can be found on SPIRES, or if necessary on Google Scholar (not maintained).

My PhD thesis can be found here.

Research interests:

The past few years, I have spent a lot of time thinking about Hamiltonian truncation. This is a numerical method used to study quantum field theories. The goal is to compute certain observables (say, critical exponents at a strongly coupled critical point) with percent-level precision. This is done by isolating N ~ several thousand states in the infinite Hilbert space, computing stuff in this approximate Hilbert space, and then increasing N as much as possible, using only a reasonable amount of computing power. (For non-physicists, this sounds perhaps similar to principal component analysis, where one restricts very high-dimensional data to N axes.)

I have also worked on bootstrap methods in quantum field theory. Here the idea is that in some theories, a priori unknown input data {x_i} satisfies:

• inequalities of the form f({x_i}) >= 0, which arise from the fact that probabilities must always be positive;

• equalities, which reflect the fact that some physical quantities X can be expressed in different but ultimately equivalent ways: for example X = F({x_i}) = G({x_i}) where F and G are two different functions.

The name of the game is to develop analytical or numerical technology to exploit these two facts together, and to prove theorems about the unknown data {x_i}. In practice, such data can be a critical exponent, the mass of an interacting particle, or a coupling that appears in a scattering amplitude.

Talks given in 2021/2022

An outreach talk for BSc students visiting our department.

Hamiltonian Truncation in AdS:

• at a CERN workshop on nonperturbative physics (video recording, example code on GitHub)

• ICTP Trieste, high energy theory seminar (PDF)

• Les Diablerets research station - SwissMAP Advances on Quantum Gravity workshop

Conformal bootstrap approach to inflationary cosmology:

• cosmo/string seminar at CEICO, Czech Academy of Sciences, Prague (PDF)

• journal club at Scuola Normale Superiore, Pisa

• King's College, London, cosmo/strings seminar (PDF)

• Cambridge University, cosmology lunch talk

• Bootstrap Collaboration - Zoom seminar (YouTube recording)

Bounding perturbative fixed points:

• Rencontres théoriciennes - Paris joint string theory seminar (PDF, YouTube recording) 

2019/2020

[cont.]

• Tel Aviv University - high energy theory group meeting

• Università degli Studi di Milano-Bicocca - string theory seminar

• INFN Torino

• Oxford University, Dalitz Seminar in Fundamental Physics

• GeNeZiSS meeting
 @ Bern University

Sphere partition functions and Hamiltonian truncation:

• Bootstrap conference @ Perimeter Institute, Canada (video recording)

• University of Michigan, Ann Arbor (slides)

• Princeton University - High Energy Theory seminar

2018

[cont.]

• EPFL, Lausanne

• Kavli IPMU, Kashiwa (Japan)

• Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing

• Asia-Pacific Center for Theoretical Physics, Pohang (South Korea)

Harmonic analysis and the conformal bootstrap:

• Weizmann Institute, Tel Aviv

• University of Amsterdam string seminar

2017

[cont.]

• University of Milano-Bicocca

• CERN, string theory seminar (PDF)

• Texas A&M University

• Boston University

2016

• APCTP, Pohang (South Korea) - Frontiers of Particle Physics workshop; invited review talk on conformal bootstrap (PDF)

Logarithmic CFTs in d dimensions:

• Korean Institute for Advanced Study (KIAS), Seoul (PDF)

• University of Michigan, Ann Arbor -  Brown Bag seminar

• CERN, String Theory journal club

• Yale University, Particle Theory seminar

• Perimeter Institute, Quantum Fields and Strings seminar

2015 and earlier

Hamiltonian truncation - an alternative to lattice Monte Carlo?

• University of Cambridge/DAMTP - high energy phenomenology seminar

• ICTP, Trieste (PDF)

• Perimeter Institute - Quantum Fields and Strings seminar

• Humboldt University/DESY - Joint Lattice seminar

• Back to the Bootstrap 4 conference, Porto

Conformal block technology

• EPSHEP conference, Stockholm (PDF)

• Back to the Bootstrap 3 conference, Geneva

Before my PhD I did some work on the triviality of phi^4 theory (NPB publication here), using so-called worm algorithms. I don't have slides, but you can view a representation of this algorithm below.

An ancient (2009) public outreach article of mine on nanotechnology can be found here (in Dutch; published in the magazine NW&T).