Curt Jaimungal and Sean Carroll offer distinct ontological interpretations of the Schrödinger wave equation, reflecting different perspectives on the fundamental nature of reality.
Curt Jaimungal: Jaimungal questions the physical existence of the wave function, suggesting that it is not a direct representation of physical reality. He argues that the wave function is a mathematical tool that simplifies the description of quantum systems but comes at the cost of losing the indivisibility and concrete physical picture of the underlying ontology. According to Jaimungal, the wave function's divisibility and mathematical convenience are achieved by abstracting away the complex, indivisible, and stochastic nature of the physical world. See Debunking the “All Possible Paths” Myth: What Feynman Really Showed
Sean Carroll: Carroll, on the other hand, defends a more radical position known as "Hilbert Space Fundamentalism" or "Mad-Dog Everettianism." He posits that the fundamental ontology of the world is entirely and exactly represented by a vector in an abstract Hilbert space, evolving according to the Schrödinger equation. In this view, the wave function is a complete and exact representation of reality, and all other physical structures, including space and fields, are emergent from this fundamental description. Carroll argues that the laws of physics are determined solely by the energy eigenspectrum of the Hamiltonian, and the structure of the observed world arises as a higher-level emergent phenomenon.
These interpretations reflect a broader debate in the philosophy of physics about the nature of the wave function and its role in describing the fundamental ontology of the universe. While Jaimungal emphasizes the practical and mathematical utility of the wave function at the expense of a clear physical ontology, Carroll advocates for a more extreme position where the wave function is the fundamental reality.
David Albert is the Frederick E. Woodbridge Professor of Philosophy at Columbia University and one of the world’s most respected philosophers of physics. He is also the director of the Philosophical Foundations of Physics program at Columbia and a faculty member of the John Bell Institute for the Foundations of Physics. This is David’s fifth (!) appearance on Robinson’s Podcast. He appeared on episode #23 with Justin Clarke-Doane on metaethics and absolute space, episode #30 on the philosophy of time, episode #67 with Tim Maudlin on the foundations of quantum theory, and episode #106 with Sean Carroll on Many-Worlds and fine-tuning. In this episode, Robinson and David discuss his new book, A Guess at the Riddle: Essays on the Physical Underpinnings of Quantum Mechanics (Harvard, 2023), and the metaphysics of quantum mechanics. If you’re interested in the foundations of physics—which you absolutely should be—then please check out the JBI, which is devoted to providing a home for research and education in this important area. Any donations are immensely helpful at this early stage in the institute’s life. Wave Function Realism
In the Robinson podcast referenced below, Sean Caroll explains why he believes, contrary to Curt Jaimungal belief expressed above, that the wave function is a fundamental representation of reality.
Quantum mechanics is a theory of wave functions in Hilbert space. Many features that we generally take for granted when we use quantum mechanics -- classical spacetime, locality, the system/environment split, collapse/branching, preferred observables, the Born rule for probabilities -- should in principle be derivable from the basic ingredients of the quantum state and the Hamiltonian. I will discuss recent progress on these problems, including consequences for emergent spacetime and quantum gravity. Sean Carroll: Extracting the universe from the wave function