Thomas Heinzl | Plymouth University (original) (raw)

Papers by Thomas Heinzl

The European Physical Journal C

By combining an adiabatic approach based on a ‘locally monochromatic’ approximation with a local ... more By combining an adiabatic approach based on a ‘locally monochromatic’ approximation with a local Hilbert transform, it is demonstrated how vacuum birefringence in the strong field regime can be calculated using a rate approach suitable for Monte Carlo simulation codes. Results for the flipping of the photon’s polarisation (helicity) are benchmarked with evaluation of exact expressions in a circularly (linearly) polarised plane wave of finite extent. For the circularly polarised case, the Heisenberg–Euler approach predicts a null result; an approximation similar to the ‘locally constant’ form is presented, which recovers the correct low-energy scaling. Example probabilities are given for typical experimental parameters.

International journal of modern physics., 2012

This contribution presents an overview of fundamental QED processes in the presence of an externa... more This contribution presents an overview of fundamental QED processes in the presence of an external field produced by an ultra-intense laser. The discussion focusses on the basic intensity effects on vacuum polarisation and the prospects for their observation. Some historical remarks are added where appropriate.

Nucleation and Atmospheric Aerosols, 1999

We show that the method of “discretized light-cone quantization” (DLCQ) is in conflict with the p... more We show that the method of “discretized light-cone quantization” (DLCQ) is in conflict with the principle of microcausality.

Journal of High Energy Physics, Dec 4, 2002

We perform a lattice analysis of the Faddeev-Niemi effective action conjectured to describe the l... more We perform a lattice analysis of the Faddeev-Niemi effective action conjectured to describe the low-energy sector of SU (2) Yang-Mills theory. To this end we generate an ensemble of unit vector fields ('color spins') n from the Wilson action. The ensemble does not show long-range order but exhibits a mass gap of the order of 1 GeV. From the distribution of color spins we reconstruct approximate effective actions by means of exact lattice Schwinger-Dyson and Ward identities ('inverse Monte Carlo'). We show that the generated ensemble cannot be recovered from a Faddeev-Niemi action, modified in a minimal way by adding an explicit symmetry-breaking term to avoid the appearance of Goldstone modes.

Bulletin of the American Physical Society, Oct 31, 2016

Lecture Notes in Physics, 2001

These lecture notes review the foundations and some applications of lightcone quantization. First... more These lecture notes review the foundations and some applications of lightcone quantization. First I explain how to choose a time in special relativity. Inclusion of Poincaré invariance naturally leads to Dirac's forms of relativistic dynamics. Among these, the front form, being the basis for light-cone quantization, is my main focus. I explain a few of its peculiar features such as boost and Galilei invariance or separation of relative and center-of-mass motion. Combining light-cone dynamics and field quantization results in light-cone quantum field theory. As the latter represents a first-order system, quantization is somewhat nonstandard. I address this issue using Schwinger's quantum action principle, the method of Faddeev and Jackiw, and the functional Schrödinger picture. A finite-volume formulation, discretized light-cone quantization, is analysed in detail. I point out some problems with causality, which are absent in infinite volume. Finally, the triviality of the light-cone vacuum is established. Coming to applications, I introduce the notion of light-cone wave functions as the solutions of the light-cone Schrödinger equation. I discuss some examples, among them nonrelativistic Coulomb systems and model field theories in two dimensions. Vacuum properties (like chiral condensates) are reconstructed from the particle spectrum obtained by solving the light-cone Schrödinger equation. In a last application, I make contact with phenomenology by calculating the pion wave function within the Nambu and Jona-Lasinio model. I am thus able to predict a number of observables like the pion charge and core radius, the r.m.s. transverse momentum, the pion structure function and the pion distribution amplitude. The latter turns out to be the asymptotic one.

We discuss pair creation in a strong laser background. Using lightfront field theory, we show tha... more We discuss pair creation in a strong laser background. Using lightfront field theory, we show that all the physics is contained in the lightfront momentum transfer from the laser, and probe, to the produced pair. The dependence of this momentum transfer on the geometry of the laser leads to resonance and diffraction effects in pair production spectra. The lightfront approach naturally explains the interpretation of laser-stimulated pair production as a multi-photon process creating pairs of an effective mass.

Springer eBooks, 2002

arXiv (Cornell University), Jul 1, 2013

We discuss classical and quantum corrections to Thomson scattering between an electron and a lase... more We discuss classical and quantum corrections to Thomson scattering between an electron and a laser. For radiation reaction, nonlinear, and quantum effects we identify characteristic dimensionless parameters in terms of which we determine the leading order correction terms.

arXiv (Cornell University), Jun 25, 2003

We derive effective actions for SU (2) Polyakov loops using inverse Monte Carlo techniques. In a ... more We derive effective actions for SU (2) Polyakov loops using inverse Monte Carlo techniques. In a first approach, we determine the effective couplings by requiring that the effective ensemble reproduces the single-site distribution of the Polyakov loops. The latter is flat below the critical temperature implying that the (untraced) Polyakov loop is distributed uniformly over its target space, the SU (2) group manifold. This allows for an analytic determination of the Binder cumulant and the distribution of the meanfield, which turns out to be approximately Gaussian. In a second approach, we employ novel lattice Schwinger-Dyson equations which reflect the SU (2) × SU (2) invariance of the functional Haar measure. Expanding the effective action in terms of SU (2) group characters makes the numerics sufficiently stable so that we are able to extract a total number of 14 couplings. The resulting action is short-ranged and reproduces the Yang-Mills correlators very well.

arXiv (Cornell University), Apr 3, 1996

arXiv (Cornell University), Oct 17, 2003

The vacuum problem of light-cone quantum field theory is reanalysed from a functional-integral po... more The vacuum problem of light-cone quantum field theory is reanalysed from a functional-integral point of view.

arXiv (Cornell University), Sep 19, 2008

We give a brief overview of the most important QED effects that can be studied in the presence of... more We give a brief overview of the most important QED effects that can be studied in the presence of extreme fields such as those expected at the Vulcan laser upgraded to a power of 10 Petawatts.

arXiv (Cornell University), Dec 17, 2002

It is shown how to calculate simple vacuum diagrams in light-cone quantum field theory. As an app... more It is shown how to calculate simple vacuum diagrams in light-cone quantum field theory. As an application, I consider the one-loop effective potential of φ 4 theory. The standard result is recovered both with and without the inclusion of zero modes having longitudinal momentum k + = 0.

arXiv (Cornell University), Dec 21, 1998

We review the foundations as well as a number of important applications of light-cone dynamics. B... more We review the foundations as well as a number of important applications of light-cone dynamics. Beginning with the peculiarities of relativistic particle dynamics we discuss the choice of a time parameter as the gauge fixing within reparametrization invariant dynamical systems. Including Poincaré invariance, we are naturally led to Dirac's forms of relativistic dynamics. Among these, the front form is our main focus as it is the basis for light-cone dynamics. We explain the peculiar features of the light-cone formulation such as boost and Galilei invariance or separation of relative and center-of-mass motion. Combining light-cone dynamics and field quantization leads to the introduction of light-cone quantum field theory. We show how the positivity of the kinematical longitudinal momentum implies the triviality of the light-cone vacuum. We point out that its special features make the light-cone formulation a unique framework to deal with bound states as few-body systems based on quantum field theory. In a first application, we analyze spontaneous symmetry breaking for scalar field theory in 1+1 dimensions. The importance of modes with vanishing longitudinal momentum is elucidated. For fermionic field theories, we suggest to reconstruct vacuum properties, like chiral condensates, from the particle spectrum. The latter can be obtained by solving the light-cone Schrödinger equation as we explicitly demonstrate for the 't Hooft and Schwinger models. Finally, we make contact with phenomenology by calculating the pion wave function within the Nambu and Jona-Lasinio model. We are thus able to predict a number of observables like the pion charge and core radius, the r.m.s. transverse momentum and the pion distribution amplitude. The latter turns out being not very different from the asymptotic one.

arXiv (Cornell University), Aug 26, 1999

We demonstrate that front form quantisation with periodicity in a compact light-like direction ("... more We demonstrate that front form quantisation with periodicity in a compact light-like direction ("discretized light-cone quantisation") violates microcausality.

The Plymouth Student Scientist, 2015

We briefly discuss some peculiarities of undergraduate research in mathematics and present two ex... more We briefly discuss some peculiarities of undergraduate research in mathematics and present two examples from our educational practice

Cornell University - arXiv, Mar 2, 2022

This is a write-up of a short tutorial talk on high-intensity QED, videopresented at the 2021 ann... more This is a write-up of a short tutorial talk on high-intensity QED, videopresented at the 2021 annual Christmas meeting of the Central Laser Facility at Rutherford-Appleton Lab, UK. The first half consists of a largely historical introduction to (quantum) electrodynamics focussing on a few key concepts. This well-established theory is then compared to its strong-field generalisation when a high-intensity laser is present. Some supplementary material and a fair amount of references have been added.

Europhysics News, 2020

The vacuum of quantum electrodynamics (QED) can be viewed as a medium akin to a dielectric which ... more The vacuum of quantum electrodynamics (QED) can be viewed as a medium akin to a dielectric which can be polarised by external fields. If these are sufficiently strong, the response of the vacuum becomes nonlinear and involves phenomena such as lightby- light scattering (‘nonlinear optics’) and, in extremis, ‘dielectric breakdown’, i.e. real pair production, if a critical field strength is exceeded. The LUXE experiment aims to realise near-critical fields through collisions of photons stemming from an ultra-intense optical laser with high energy electrons or photons provided by the European XFEL linear accelerator. This set-up provides a golden opportunity to enter the uncharted territory of strong-field quantum electrodynamics in the non-perturbative regime.