Jorge Pullin is an Argentine-American theoretical and experimental physicist. He is a professor at Louisiana State University and a member of the LIGO team.

In this Interdialogue I spoke to Pullin about his pioneering role in the development of Loop Quantum Gravity and about foundational questions related to the nature of time and space. We also spoke about his more recent focus on Gravitational Wave and Multi-Messenger Astronomy, of which he wrote a book called “Sounds of the Cosmos.”

We explored background independence and the discrete nature of space and time in LQG, and the emergence of spacetime from spin foam. We also spoke about the Montevideo interpretation of quantum mechanics that he developed with his longtime collaborator Rodolofo Gambini, the black hole information paradox, and much more. 

The conversation then shifts towards the exciting gravitational wave observations made by LIGO of neutron star and black hole collisions, and how this has opened up a new era of multi-messenger astronomy, where electromagnetic, neutrino, cosmic ray and gravitational wave observatories can all work together to study objects and events in the Cosmos. We finish by speaking about how this new era of astronomy and experimental astrophysics will help to solve fundamental questions in cosmology, such as the Hubble Tension.

Chapters

00:00 :00 Introduction

00:05:25 – The nature of time, the measurement problem, fundamental decoherence and the Montevideo interpretation of quantum mechanics

00:13:03 – The black hole information paradox, spherical symmetry, singularities, Planck stars and other research on Loop Quantum Gravity

00:22:05 – Loop Quantum Gravity vs. String Theory

00:28:20 – Discrete vs. continuous nature of spacetime, and the intersection between foundational LQG and Complex Systems Science

00:30:49 – Details of Loop Quantum Gravity: intersecting loops, spin networks, spin foam, and the emergence and nature of spacetime

00:38:59 – Loop Quantum Cosmology, and the frontiers and limitations of Loop Quantum Gravity research

00:47:12 – Revisiting the nature of time as fundamental and discrete, and the potential emergence of gravity and other physical laws

00:51:55 – A personal journey through gravitational physics: from theoretical quantum gravity to experimental gravitational wave astronomy

00:57:24 – Gravitational waves, LIGO detections, the cosmic origins of gold, and the birth of multi-messenger astronomy

01:09:22 – “The Sounds of the Cosmos” book publication, the history and future of gravitational wave physics, and foundational questions in Cosmology