# Angelika Fertig

Perimeter Institute for Theoretical Physics

Areas of research:

### Research Interests

I am interested in bouncing cosmologies in which the big bang is replaced by a bounce from an earlier, contracting phase to the expanding universe we observe. I want to understand if it is possible to describe such a bounce in the semi-classical limit of quantum gravity, i.e. without having a full fundamental theory that combines the smallest scales (quantum physics) with the highest energies (general relativity).
I work on a new approach to quantize relativistic physics with a path integral over worldlines. An initial wave function over spacetime is propagated and the resulting spacetime amplitude gives the relative probability to find the particle in one spacetime region rather than another. We extend weak values, the outcome of weak measurements first introduced by Aharonov et al, to relativistic worldliness. We can thus describe the quantum particle between two state selections. The framework can be applied to study the Schwinger effect, that is pair creation in an electric field, and also to pair production in de Sitter space.
Moreover, I am interested in the action-at-a-distance formulation by Feynman and Wheeler, based on work by Tetrode and Fokker. Their time-reversal invariant theory describes the motion of elementary particles and their interactions on each other without employing the notion of fields. We would like to extend the Wheeler-Feynman absorber theory of electromagnetism to an action-at-a-distance reformulation of Yang-Mills, and eventually to an action-at-a-distance reformulation of gravity, also building on the work of Hoyle and Narlikar.

### Positions Held

### Recent Publications

- Angelika Fertig, Jean-Luc Lehners, Enno Mallwitz, Edward Wilson-Ewing, "Converting entropy to curvature perturbations after a cosmic bounce", JCAP 1610 (2016) no.10, 005, arXiv: 1607.05663.
- Angelika Fertig, Jean-Luc Lehners, Enno Mallwitz, "Conflation: a new type of accelerated expansion", JCAP 1608 (2016) no.08, 073, arXiv: 1507.04742.
- Angelika Fertig, Jean-Luc Lehners, "The Non-Minimal Ekpyrotic Trispectrum", JCAP 1601 (2016) no.01, 026, arXiv: 1510.03439.
- Angelika Fertig, Jean-Luc Lehners, Enno Mallwitz, "Ekpyrotic Perturbations With Small Non-Gaussian Corrections", Phys.Rev. D89 (2014) no.10, 103537, arXiv: 1310.8133.
- PhD Thesis: Alternatives to Inflation - non-minimal ekpyrosis and conflation, Humboldt University, Berlin. 2016. 157 pp.

### Seminars

- Seminar: Quantum Tunneling with a Lorentzian Path Integral, Albert-Einstein-Institute, Potsdam.
- Group Meeting Talk: Quantum Tunneling with a Lorentzian Path Integral, Achim Kempf's group, University of Waterloo.
- Conference Talk: Quantum Tunneling with a Lorentzian Path Integral, Women in Physics Canada Conference at the University of Waterloo.
- Conference Talk: Quantum Tunneling with a Lorentzian Path Integral, Theory Canada 12 Conference at York University, Toronto.
- PIRSA:19010016, PSI 2018/2019 - Cosmology Review - Lecture 15, 2019-01-25, PSI 2018/2019 - Cosmology Review (Xu)
- PIRSA:19010015, PSI 2018/2019 - Cosmology Review - Lecture 14, 2019-01-24, PSI 2018/2019 - Cosmology Review (Xu)
- Real time path integral for quantum tunnelling and pair creation I, 2017-11-13, The Path Integral for Gravity workshop
- Quantum Tunneling with a Lorentzian Path Integral, 2017-07-06, Cosmology Group Meeting
- PIRSA:17060101, Discussion Session 2, 2017-06-26, Bounce Scenarios in Cosmology
- PIRSA:16090041, Converting entropy to curvature perturbations after a cosmic bounce , 2016-09-06, Cosmology & Gravitation
- PIRSA:15120027, Alternatives to Inflation - Non-Minimal Ekpyrosis & Conflation , 2015-12-15, Cosmology & Gravitation