Shape Dynamics and The Universe: Foundations and Implications

TL;DR

Shape dynamics offers a background-independent, relational approach to classical universe dynamics, emphasizing observable intrinsic degrees of freedom and addressing foundational philosophical questions.

Contribution

This paper provides a comprehensive review of shape dynamics, including its historical development, foundational principles, formulation, and cosmological applications.

Findings

Shape dynamics aligns with Mach's principles and Leibnizian philosophy.

It offers new insights into the problem of the arrow of time.

The theory has promising applications in cosmology.

Abstract

Shape dynamics is an alternative background-independent approach to classical dynamics that implements Leibnizian philosophy and Mach's Principles. It is a formulation of the dynamics of the universe in terms of the intrinsic and relational degrees of freedom which are objectively observable and not properties defined with respect to an external frame of reference. Shape dynamics is not a very old field of study. Although it was already gradually coming alive out of Julian Barbour's early works on Mach's Principle back in the 1980s, it was invigorated by a series of rigorous works in the last decade. This work is an exhaustive review of the historical and conceptual underpinning of the theory that extends to Leibniz and Newton's philosophy, and the currently established formulation of the theory, together with some of the major results of its cosmological applications. The structure of this work consists of two parts: In the first one we cover the foundations and the formulation of the theory (both the field and particle ontology), and in the second one we study its applications and reflect on the resolution of the problem of the arrow of time. We end our journey by contemplating some recent ideas and prospects for further developing the theory.