On Water, Steam and String Theory

TL;DR

This review explains the water-steam phase transition using the renormalization group, illustrating its applications in physics and string theory, and discusses recent results on renormalization flows in theories with gravity.

Contribution

It provides an accessible overview of the renormalization group in phase transitions and introduces novel insights into its role in theories with dynamical gravity and string theory.

Findings

Renormalization group accurately computes critical coefficients for water-steam transition.

Gravity influences critical phenomena, modifying phase diagrams and flow behaviors.

Oscillating and quantum flows emerge in theories with dynamical gravity.

Abstract

This is a colloquium-style review lecture for physicists and non-physicists, as part of the requirements for ``Habilitation'' at the university of Bern: At a pressure of 220 atm. and a temperature of 374 Celsius there is a second-order phase transition between water and steam. Understanding it requires the concept of the renormalization group. Images from computer simulations of the lattice gas model (included) are used to explain its basic ideas. It is briefly reviewed how the renormalization group is used to compute critical coefficients for the water-steam phase transition, in good agreement with experiment. Applications in particle physics and string theory are mentioned. The appendix contains a sample of the author's results on renormalization group flows in theories with dynamical gravity and their relation to perturbative string theory: gravity modifies critical coefficients and phase diagrams, in agreement with numerical calculations, and leads to curious phenomena such as oscillating flows and quantum mechanical flows.