Cosmological choices

Jérôme Martin, Vincent Vennin

Abstract The Continuous Spontaneous Localisation (CSL) theory in the cosmological context is subject to uncertainties related to the choice of the collapse operator. In this paper, we constrain its form based on generic arguments. We show that, if the collapse operator is even in the field variables, it is unable to induce the collapse of the wavefunction. Instead, if it is odd, we find that only linear operators are such that the outcomes are distributed according to Gaussian statistics, as required by measurements of the cosmic microwave background. We discuss implications of these results for previously proposed collapse operators. We conclude that the cosmological CSL collapse operator should be linear in the field variables.

Jérôme Martin, Vincent Vennin

Philipp A. Höhn

Despite its importance in general relativity, a quantum notion of general covariance has not yet been established in quantum gravity and cosmology, where, given the a priori absence of coordinates, it is necessary to replace classical frames with dynamical quantum reference systems. As such, quantum general covariance bears on the ability to consistently switch between the descriptions of the same physics relative to arbitrary choices of quantum reference system. Recently, a systematic approach for such switches has been developed. It links the descriptions relative to different choices of quantum reference system, identified as the correspondingly reduced quantum theories, via the reference-system-neutral Dirac quantization, in analogy to coordinate changes on a manifold. In this work, we apply this method to a simple cosmological model to demonstrate how to consistently switch between different internal time choices in quantum cosmology. We substantiate the argument that the conjunction of Dirac and reduced quantized versions of the theory defines a complete relational quantum theory that not only admits a quantum general covariance, but, we argue, also suggests a new perspective on the ‘wave function of the universe’. It assumes the role of a perspective-neutral global state, without immediate physical interpretation that, however, encodes all the descriptions of the universe relative to all possible choices of reference system at once and constitutes the crucial link between these internal perspectives. While, for simplicity, we use the Wheeler-DeWitt formulation, the method and arguments might be also adaptable to loop quantum cosmology.

Menas C. Kafatos, R. Nadeau

Philip Pearle

Christopher Paradise

This paper presents the Universal Algorithm of Existence (UAE) as a speculative information-physics framework for interpreting quantum nonlocality and cosmological light observation. Rather than treating entangled correlations as “spooky action at a distance” or delayed-choice effects as evidence of retrocausality, the paper proposes that such phenomena can be understood as context-dependent resolutions of a deeper informational substrate. Using the delayed-choice quantum eraser and cosmological light retrieval as case studies, the paper formulates UAE in a disciplined mathematical language, states its consistency requirements with standard quantum mechanics and FLRW cosmology, and positions it as an interpretive research program awaiting distinctive testable predictions.