Inspired by possible connections between gravity and foundational question in quantum theory, we consider an approach for the adaptation of objective collapse models to a general relativistic context. We apply these ideas to a list of open problems in cosmology and quantum gravity, such as the emergence of seeds of cosmic structure, the black hole information issue, the problem of time in quantum gravity and, in a more speculative manner, to the nature of dark energy and the origin of the very special initial state of the universe. We conclude that objective collapse models offer a rather promising path to deal with all of these issues.
Inspired by possible connections between gravity and foundational question in quantum theory, we consider an approach for the adaptation of objective collapse models to a general relativistic context. We apply these ideas to a list of open problems in cosmology and quantum gravity, such as the emergence of seeds of cosmic structure, the black hole information issue, the problem of time in quantum gravity and, in a more speculative manner, to the nature of dark energy and the origin of the very special initial state of the universe. We conclude that objective collapse models offer a rather promising path to deal with all of these issues.
We study a proposal for the resolution of the black hole information puzzle within the context of modified versions of quantum theory involving spontaneous reduction of the quantum state. The theories of this kind, which were developed in order to address the so-called measurement problem in quantum theory have, in the past, been framed in a nonrelativistic setting and in that form they were previously applied to the black hole information problem. Here, and for the first time, we show in a simple toy model, a treatment of the problem within a fully relativistic setting. We also discuss the issues that the present analysis leaves as open problems to be dealt with in future refinements of the present approach.
Introduction Contemporary cosmology includes inflation as one of its central components. It corresponds to a period of accelerated expansion thought to have occurred very early in cosmic history, which takes the universe from relatively generic post Planckian era conditions to a stage where it is well described (with exponential accuracy in the number of e-folds) by a flat Robertson–Walker space-time (which describes a homogeneous and isotropic cosmology). It was initially proposed to resolve various naturalness problems: flatness, horizons, and the excess of massive relic objects, such as topological defects, that were expected to populate the universe according to grand unified theories (GUT). Nowadays, it is lauded because it predicts that the universe's mean density should be essentially identical to the critical value, a very peculiar situation which corresponds to a spatially flat universe. The existing data support this prediction. However, its biggest success is claimed to be the natural account for the emergence of the seeds of cosmic structure in terms of primordial quantum fluctuations, and the correct estimate of the corresponding microwave spectrum. This represents, thus, a situation which requires the combined application of general relativity (GR) and quantum theory, and that, moreover, is tied with observable imprints left from the early universe, in both the radiation in cosmic microwave background (CMB), and in the large scale cosmological structure we can observe today. It should not be surprising that, when dealing with attempts to apply our theories to the universe as a whole, we should come face to face with some of the most profound conceptual problems facing our current physical ideas. In fact, J. Hartle had noted long ago [28] that serious difficulties must be faced when attempting to apply quantum theory to cosmology, although the situations that were envisioned in those early works corresponded to the even more daunting problem of full quantum cosmology, and not the limited use of quantum theory to consider perturbative aspects, which is what is required in the treatment of the inflationary origin of the seeds of cosmic structure. This led him and his collaborators to consider the Consistent Histories framework, which is claimed to offer a version of quantum theory that does not rely on any fundamental notion of measurements, as the favored approach to use in such contexts. We will have a bit more to say about this shortly.
We put forward a proposal that combines objective collapse models, developed in connection with quantum-foundational questions, with the so-called Weyl curvature hypothesis, introduced by Roger Penrose as an attempt to account for the very special initial state of the universe. In particular, we explain how a curvature dependence of the collapse rate in such models, an idea already shown to help in the context of black holes and information loss, could also offer a dynamical justification for Penrose's conjecture.
General relativity and quantum mechanics rely on fundamentally incompatible conceptions of spacetime: the former treats spacetime as a smooth, dynamical entity, while the latter presupposes a fixed background on which quantum states evolve. This work introduces the Collapse Spacetime Model (CSM), a foundational framework in which spacetime itself is not fundamental but emerges from discrete ontological transition events (OTEs)—objective, irreversible acts of actualization that generate localized spacetime structure. Within CSM, quantum state reduction is reinterpreted as one particular manifestation of a more general ontological transition, rather than as an anomaly within unitary dynamics. A central refinement, the Multiplicity of Spacetime Hypothesis (MSH), proposes that physical systems construct their own partial spacetimes, with the classical spacetime continuum arising from stable intersections among these locally generated structures. Constants such as the speed of light are interpreted as invariant structural ratios of spacetime co-generation, rather than as fundamental properties of matter or signals. The model aligns conceptually with causal set theory, emergent network geometry, and collapse-based approaches, while offering a unified ontological account of spacetime emergence, time’s passage, and the relational origin of geometry. CSM reframes physical reality as a becoming universe, providing a coherent foundation for quantum gravity, cosmology, and the philosophy of time, while deliberately postponing detailed dynamical and mathematical formalization to future work.
Abstract In this work we consider a wide variety of alternatives opened when applying the continuous spontaneous localization (CSL) dynamical collapse theory to the inflationary era. The definitive resolution of many of the issues discussed here will have to await, not only for a general relativistic CSL theory, but for a fully workable theory of quantum gravity. Our concern here is to explore these issues, and to warn against premature conclusions. This exploration includes: two different approaches to deal with quantum field theory and gravitation, the identification of the collapse-generating operator and the general nature and values of the parameters of the CSL theory. All the choices connected with these issues have the potential to dramatically alter the conclusions one can draw. We also argue that the incompatibilities found in a recent paper, between the CSL parameter values and the cosmic microwave background observational data, are associated with specific choices made for the extrapolation to the cosmological context of the CSL theory (as it is known to work in non-relativistic laboratory situations) which do not represent the most natural ones.
Abstract This paper proposes a parameter-free objective reduction theory where wavefunction collapse is induced by gravitational self-energy differences between mass distributions. Unlike Continuous Spontaneous Localization (CSL) models, which rely on phenomenological parameters, the collapse rate in this model (Γ = Eg/ħ) is uniquely determined by universal constants G and ħ. Key Highlights: Dynamical Derivation of the Born Rule: The model demonstrates that the Born probability rule emerges naturally from the martingale property of the stochastic dynamics, rather than being postulated. Experimental Consistency: The theory is shown to be consistent with current laboratory constraints, including double-slit interference experiments with large molecules (mcrit ≈ 10⁻¹⁴ kg) and loophole-free Bell inequality tests. Astrophysical Stability: Analysis confirms the stability of compact objects like neutron stars and the preservation of primordial fluctuations in the Cosmic Microwave Background (CMB). Relativistic Extension: A Lorentz-covariant field-theoretic generalization is provided, using the energy-momentum tensor to source collapse noise while respecting microcausality. The results suggest a self-contained, falsifiable framework for the transition from quantum to classical spacetime without the need for adjustable parameters.