Causality as a guiding principle for physics beyond General Relativity

TL;DR

This thesis explores how causality can serve as a foundational principle in developing quantum gravity theories, emphasizing emergent spacetime structures inspired by condensed matter physics without relying on specific models.

Contribution

It provides a conceptual roadmap for emergent quantum gravity approaches, highlighting the role of causality and background structures without committing to particular theories.

Findings

Causality can guide the development of emergent gravity theories.

Emergent spacetime may arise without fundamental horizons or singularities.

Background structures influence the formulation of emergent quantum gravity.

Abstract

This thesis is situated within the context of quantum gravity, broadly understood as any effort to explore the interplay between gravitation and the quantum realm, without necessarily requiring the quantization of the gravitational field itself. We focus on emergent theories, particularly those in which the causal structure and geometric concepts underlying the gravitational field in General Relativity are not fundamental but instead arise from more basic underlying degrees of freedom. Our attention is directed toward emergent approaches inspired by condensed matter physics. Rather than developing a full-fledged emergent theory and analyzing its detailed consequences, this work offers a concise roadmap of analyses and reflections relevant to emergent frameworks, without committing to any specific model. The thesis is divided into two parts, reflecting the distinct tools and analyses employed in each. The first addresses fundamental and conceptual aspects of emergent theories, focusing on the role of background structures, both regarding their implications for the theory and their constructive relevance. The second assumes the absence of singularities and horizons, a feature often expected in emergent frameworks, though the analyses remain agnostic and independent of specific theoretical commitments.