# Negative Energy and the Focussing of Light Rays

### APA

Wall, A. (2016). Negative Energy and the Focussing of Light Rays. Perimeter Institute. https://pirsa.org/16030112

### MLA

Wall, Aron. Negative Energy and the Focussing of Light Rays. Perimeter Institute, Mar. 09, 2016, https://pirsa.org/16030112

### BibTex

@misc{ pirsa_PIRSA:16030112, doi = {10.48660/16030112}, url = {https://pirsa.org/16030112}, author = {Wall, Aron}, keywords = {Other}, language = {en}, title = {Negative Energy and the Focussing of Light Rays}, publisher = {Perimeter Institute}, year = {2016}, month = {mar}, note = {PIRSA:16030112 see, \url{https://pirsa.org}} }

Aron Wall University of Cambridge

## Abstract

In any quantum field theory, the energy flux at a point of spacetime can be negative. This would produce a repulsive gravitational field causing nearby light rays to defocus. This in turn threatens to produce a variety of exotic phenomena including traversable wormholes, warp drives, time machines, and evasion of singularity theorems. I will describe a new "quantum focusing conjecture" that prevents such pathologies. In the flat spacetime limit it reduces to a novel lower bound on the energy density, which can be proven for several classes of field theories.