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Zenith Grant Awardee

Sara Imari Walker

Arizona State University


Chiara Marletto; University of Oxford

Project Title

Accommodating observers in fundamental physics with causal mechanics

Project Summary

Among the most perplexing problems in modern physics is reconciling our experience of reality with our most fundamental physical theories. Nowhere is this more evident than with observers – physical systems that actively utilize information to affect the world. This behavior seems at odds with the current best physical explanations, because they are all cast as predictions of a single trajectory for the whole universe, specified by an initial state and fixed dynamical laws. To the end of unifying observers' causal power with fundamental physics, we propose a new theoretical framework, called Causal Mechanics. By taking information as a fundamental aspect of physical reality, via the new conceptual tools of the recently proposed Constructor Theory of Information, many of the perplexing dilemmas associated with unifying physics and observers, are resolved. We test Causal Mechanics in cellular automata models, examining how to reconcile information with causal power, as necessary for observers to be active participants in the unfolding of the universe, and local, reversible laws as characterize our universe. Our results therefore have potential to shed light on one of oldest and most perplexing problems of human existence, cast within fundamental physics – can we matter to the world?

Technical Abstract

The characteristic properties of observers appear incompatible at a foundational level with our traditional approaches to fundamental physics, which explain everything in terms of predictions given initial conditions and immutable laws of motion. This is because observers involve concepts such as information, information with causal power, and the capacity to affect the environment by using such information, which are only ambiguously defined in our current approaches. Here we propose a new theoretical framework, causal mechanics, to investigate in what way key properties of observers associated with their use of information can in fact be compatible with underlying simple, reversible and local laws. To that end, we shall deploy the tools of the newly proposed constructor theory of information, to express in exact, non-approximate, terms key properties of observers and explore their consequences in dynamical systems. To do so, we will apply the proposed principles of causal mechanics to Cellular Automata models, a widely utilized framework for exploring how complexity emerges from simple, local rules. Our results will shed new light on how the properties of information associated with observers are accommodated by laws that are simple, local and reversible, such as the laws of physics that describe our universe.

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