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Beyond the Quantum

Relics from the Early Universe

Antony Valentini

Published Sep 16, 2025• 0 citations
Publisher

Abstract

Abstract ‘Relics from the Early Universe’ explains how a failure of quantum mechanics could show up in relic particles left over from the early universe. We describe the ongoing mystery of ‘dark matter’ which is being searched for by astronomers. We explain how violations of Born’s formula could have survived to the present day in certain kinds of dark matter particles, and how such violations could be detected when those particles disintegrate. The chapter ends with a discussion of how Born’s formula, applied to disintegrating dark matter, can be tested by satellites in space.

DOI
10.1093/oso/9780198853749.003.0008

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Abstract ‘Relics from the Early Universe’ explains how a failure of quantum mechanics could show up in relic particles left over from the early universe. We describe the ongoing mystery of ‘dark matter’ which is being searched for by astronomers. We explain how violations of Born’s formula could have survived to the present day in certain kinds of dark matter particles, and how such violations could be detected when those particles disintegrate. The chapter ends with a discussion of how Born’s formula, applied to disintegrating dark matter, can be tested by satellites in space.
Abstract ‘A Message from the Beginning of Time’ gives a detailed account of the search for violations of quantum mechanics in the early universe, in particular as recorded in the cosmic microwave background (CMB). We begin with an overview of cosmology, with a focus on how the early history of our universe is imprinted on the ‘CMB sky’. We explain how inflationary cosmology can be employed to test Born’s formula at very early times. We describe various anomalies which have been reported in data from the Planck and other satellites, and we discuss how these might be interpreted as signs of a failure of quantum mechanics.
In terms of the de Broglie-Bohm pilot-wave formulation of quantum theory, we develop field-theoretical models of quantum nonequilibrium systems which could exist today as relics from the very early Universe. We consider relic excited states generated by inflaton decay, as well as relic vacuum modes, for particle species that decoupled close to the Planck temperature. Simple estimates suggest that, at least in principle, quantum nonequilibrium could survive to the present day for some relic systems. The main focus of this paper is to describe the behavior of such systems in terms of field theory, with the aim of understanding how relic quantum nonequilibrium might manifest experimentally. We show by explicit calculation that simple perturbative couplings will transfer quantum nonequilibrium from one field to another (for example from the inflaton field to its decay products). We also show that fields in a state of quantum nonequilibrium will generate anomalous spectra for standard energy measurements. Possible connections to current astrophysical observations are briefly addressed.
Abstract ‘Saved by Gravity’ shows how exotic gravitational effects could enable our escape from quantum death, by creating particles that violate quantum mechanics and Born’s formula. We begin with a review of quantum gravity and of the notorious ‘problem of time’. We explain why the theory is unable to give a mathematically consistent account of quantum probability. We propose that the problem can be solved if we accept that there is no quantum death, and no Born’s formula, at the deepest level of quantum gravity. The chapter ends by showing how quantum-gravitational effects can create violations of Born’s formula, in particular for radiation from exploding primordial black holes.
[Shortened Abstract:] This thesis explores the possibility that quantum probabilities arose thermodynamically. A chief concern is the detection of primordial `quantum nonequilibrium', since this is observably distinct from textbook quantum physics. Chapters 2, 3, 4, and 5 are adaptations of references [1,2,3], and [4] respectively. Chapter 2 proposes (information) entropy conservation as a minimal requirement for a theory to feature classical-style thermodynamic relaxation. The resulting structure is dubbed `the iRelax framework'. Both classical mechanics and de Broglie-Bohm quantum theory are shown to be special cases. Indications for a possible extension or unification of de Broglie-Bohm theory are briefly highlighted. Chapter 3 examines ways in which quantum relaxation may be prevented. The method of the drift-field is introduced. A systematic treatment of nodes is given. A category of quantum states is found for which relaxation is significantly impeded, and may not complete at all. Chapters 4 and 5 consider the possibility that primordial quantum nonequilibrium may be conserved in the statistics of a species of relic cosmological particle. Necessary factors for this to be the case are discussed and illustrative scenarios are given both in terms of nonequilibrium particles created by inflaton decay, as well as relic vacuum modes for species that decoupled close to the Planck temperature. The search for so-called `smoking-gun' spectral lines created by dark matter decay or annihilation is argued to be a particularly promising setting for the detection of quantum nonequilibrium. Unintuitive spectral effects relating to the contextuality of quantum measurements are described. If such a suspected source of quantum nonequilibrium were found, its subjection to a specifically quantum mechanical test would confirm or deny the presence of the quantum nonequilibrium conclusively.
We discuss several proposals for astrophysical and cosmological tests of quantum theory. The tests are motivated by deterministic hidden-variables theories, and in particular by the view that quantum physics is merely an effective theory of an equilibrium state. The proposed tests involve searching for nonequilibrium violations of quantum theory in: primordial inflaton fluctuations imprinted on the cosmic microwave background, relic cosmological particles, Hawking radiation, photons with entangled partners inside black holes, neutrino oscillations, and particles from very distant sources.
We discuss several proposals for astrophysical and cosmological tests of quantum theory. The tests are motivated by deterministic hidden-variables theories, and in particular by the view that quantum physics is merely an effective theory of an equilibrium state. The proposed tests involve searching for nonequilibrium violations of quantum theory in: primordial inflaton fluctuations imprinted on the cosmic microwave background, relic cosmological particles, Hawking radiation, photons with entangled partners inside black holes, neutrino oscillations and particles from very distant sources.