# Order Plus Number ~ Geometry: A Lorentzian Approach to Quantum Gravity

### APA

Surya, S. (2017). Order Plus Number ~ Geometry: A Lorentzian Approach to Quantum Gravity. Perimeter Institute. https://pirsa.org/17100065

### MLA

Surya, Sumati. Order Plus Number ~ Geometry: A Lorentzian Approach to Quantum Gravity. Perimeter Institute, Oct. 18, 2017, https://pirsa.org/17100065

### BibTex

@misc{ pirsa_PIRSA:17100065, doi = {10.48660/17100065}, url = {https://pirsa.org/17100065}, author = {Surya, Sumati}, keywords = {Other}, language = {en}, title = {Order Plus Number ~ Geometry: A Lorentzian Approach to Quantum Gravity}, publisher = {Perimeter Institute}, year = {2017}, month = {oct}, note = {PIRSA:17100065 see, \url{https://pirsa.org}} }

Sumati Surya Raman Research Institute

## Abstract

I will give an overview of the causal set approach to quantum gravity, and what makes this "fork in the road" distinct from other approaches. Motivated by deep theorems in Lorentzian geometry, causal set theory (CST) posits that the underlying fabric of spacetime is atomistic and encoded in a locally finite partially ordered set. In the continuum approximation, the partial order corresponds to the causal structure, and the cardinality to the conformal factor. Together, these give the approximate continuum geometry. Lorentz invariance emerges as a consequence, but brings with it a certain "non-locality”, which distinguishes CST from other approaches in an essential way. It also makes the reconstruction of spacetime geometry from the causal set particularly challenging. I will describe some of the progress we have made in this geometric reconstruction program. I will then describe a particular formulation of CST dynamics inspired by the continuum path integral and discuss what we have learnt so far and where it is taking us.