323 | Jacob Barandes on Indivisible Stochastic Quantum Mechanics

Episode Summary

Executive Summary: Sean Carroll and Jacob Barandes debate quantum foundations and Barandes’ new “indivisible stochastic quantum mechanics,” which replaces the wave function with point-like entities following non-Markovian stochastic laws. The discussion contrasts this view with Bohmian mechanics and Everett/many-worlds, emphasizing empirical adequacy, decoherence, Bell’s theorem, and the philosophical costs of each framework.

Main Topics: Why quantum mechanics still feels unresolved (Priority: 5/5): Carroll frames quantum mechanics as extraordinarily successful empirically yet conceptually unsettled, motivating continued work on foundations and alternative ontologies. Historical development of quantum theory (Priority: 4/5): Barandes traces the shift from Planck, Heisenberg, Schrödinger, Born, Dirac, and von Neumann toward the modern Hilbert-space formalism, highlighting the abandonment of classical pictures and the rise of measurement axioms. Bohmian mechanics and Everettian many-worlds (Priority: 5/5): The conversation contrasts Bohm’s pilot-wave theory and Everett’s branching universal wave function, including decoherence, probability, and the difficulty of extending Bohm to relativistic QFT or justifying Everett’s probability derivations. Indivisible stochastic quantum mechanics (Priority: 5/5): Barandes presents his proposal: no fundamental wave function, only classical-like configurations (e.g., particles) evolving stochastically under non-Markovian, indivisible laws that reproduce quantum predictions. Division events, decoherence, and measurement (Priority: 5/5): A central mechanism in Barandes’ theory is the “division event,” analogous to decoherence, where systems reveal configuration information and the dynamics becomes divisible at effective branch points. Conceptual and metaphysical implications (Priority: 3/5): The discussion extends to causation, probability, emergence, and whether probabilistic gravity or non-Markovian structures might inform quantum gravity and future foundational work.

Key Arguments: Quantum mechanics’ predictive success does not settle its ontology; multiple incompatible realist frameworks remain viable in principle. Bohmian mechanics is elegant for simple nonrelativistic systems but becomes unwieldy or unclear in relativistic quantum field theory and modern physics applications. Everett/many-worlds avoids collapse but requires substantial extra assumptions, especially in decision-theoretic derivations of the Born rule, raising concerns about circularity and metaphysical burden. Barandes’ proposal keeps classical ontology-like ingredients (particles/fields) but replaces standard Markovian dynamics with indivisible, non-Markovian stochastic laws. The theory reproduces standard quantum predictions without a fundamental wave function; the wave function remains a useful mathematical tool, not ontology. Decoherence is reinterpreted as the emergence of “division events,” where conditional probabilities reset and effective divisibility appears. Bell’s theorem is not a problem for the model, because the theory is local in space but non-Markovian in time, providing a temporal analogue to hidden-variable structure. The approach aims to preserve empirical adequacy while avoiding the stone-soup accumulation of ad hoc assumptions that worries Barandes in Everettian and Bohmian derivations. Open questions in gravity may relate to non-Markovianity; a probabilistic generalization of general relativity could be an intermediate step toward quantum gravity.

Data Points: Quantum theory historical milestone: 1900 - Planck’s quantum hypothesis is presented as the beginning of quantum theory. Heisenberg matrix mechanics paper: 1925 - Heisenberg’s paper marks the shift away from classical ontology. Schrödinger wave mechanics and modern formalization: 1926-1932 - Schrödinger’s equations, Dirac’s book (1930), and von Neumann’s foundations (1932) unify the modern formalism. Kolmogorov’s probability axiomatization: 1933 - Mentioned as coming after the main quantum formalism was already established. Everett dissertation length: 137 pages - Barandes notes Everett’s unpublished long-form dissertation is 137 pages. Wallace probability derivation length: 83 pages - Barandes cites Wallace’s much longer Born-rule derivation as part of his concern about added assumptions. Deutsch probability derivation length: 15 pages - Used to illustrate the increasing complexity of Everettian probability arguments. Dust decoherence timescale: ~10^-40 seconds - An example of extremely rapid decoherence for a dust particle in the cosmic environment. Quantum prediction accuracy: many decimal places / more than 10 - Carroll and Barandes discuss the precision of standard quantum-theory predictions, including the electron g-factor. Fine-structure constant reference: 137 - Barandes links Everett’s dissertation page count and his course number to the inverse fine-structure constant.

Pivotal Quotes: "the theory overdetermined the interpretation" — Jacob Barandes: His summary of his worry that quantum theory may be too rich and intricate for a single satisfactory interpretation. "the stone soup problem" — Jacob Barandes: His metaphor for Everettian derivations that seem to require many extra assumptions added one by one. "you can show that what looks like decoherence in the standard quantum formalism looks in this picture with just classical probabilities. It looks like a division event" — Jacob Barandes: His description of how his theory maps decoherence onto division events.

Implications: The conversation suggests quantum foundations may still have room for genuinely new frameworks. If Barandes’ model holds up, it could reshape how physicists think about measurement, ontology, and even probabilistic gravity, while offering a new research program beyond wave functions and branching worlds.