Link: https://macquarie.zoom.us/j/89267161769

Abstract: In linearized gravity, defining a local energy–momentum tensor for the gravitational field via variation of the action with respect to the metric is generally problematic. This difficulty arises from the principle of equivalence, which allows one to choose a local reference frame along any timelike curve in which the gravitational field vanishes, implying that any local gravitational energy density must also vanish there. Despite this limitation, certain local tensors can still characterize the strength of the gravitational field. In this talk, I will focus on the Bel–Robinson tensor, a four-index tensor that possesses many properties analogous to those of an energy–momentum tensor. Working in a de Sitter background spacetime, I will first demonstrate explicitly the non-negativity of the Bel–Robinson tensor when contracted with timelike vectors. I will then quantize the linearized gravitational perturbations and derive a quantum energy inequality, providing a lower bound on the timelike-averaged Bel–Robinson quantity along a timelike geodesic. Finally, I will discuss the bound in the Bunch–Davies vacuum of de Sitter spacetime.

Bio:  Dr. Eleni-Alexandra Kontou is a lecturer in theoretical physics at King's College London. She was awarded a PhD in Physics from Tufts University in 2015. After successfully applying for a Horizon 2020 EU grant she was a Marie Skłodowska-Curie research fellow at the Department of Mathematics at the University of York from 2017 to 2019.  From 2020 until 2022 she was a postdoctoral researcher at the University of Amsterdam. She has also worked as a visiting Assistant Professor at Bard College and the College of the Holy Cross. Her research interests cover a variety of topics in quantum field theory in curved spacetime, mathematical physics, and cosmology but most of her work focuses on energy conditions, quantum inequalities, and their applications.