63 | Solo -- Finding Gravity Within Quantum Mechanics
Sep 9, 2019
01:50:26
auto_awesome Snipd AI
The podcast discusses the challenges of quantum gravity and how Many-Worlds provides the best framework for understanding it. It explores the concept of wave function collapse and superposition, and the emergence of classical trajectories through decoherence. The hosts also delve into the connection between quantum gravity and the Many Worlds interpretation, and the significance of the Born Rule-like behavior in nature.
Read more
AI Summary
Highlights
AI Chapters
Episode notes
auto_awesome
Podcast summary created with Snipd AI
Quick takeaways
The emergence of the classical world from quantum mechanics relies on decoherence and locality, where interactions occur when objects are nearby.
The many worlds interpretation offers a simplified and pure approach to understanding quantum mechanics, highlighting the role of entanglement and decoherence.
Exploring how locality arises from the quantum wave function is essential in understanding the emergence of space and the classical world from quantum mechanics.
Decoherence and the specific way interactions occur when objects are nearby play a key role in determining the classical world we observe.
Deep dives
Locality and Decoherence Lead to Classical World
Locality and the process of decoherence play a crucial role in the emergence of the classical world from an abstract quantum wave function. Interactions in the universe are local in space, meaning they occur when objects are nearby. Decoherence, the process by which the wave function of a system becomes entangled with its environment, leads to the appearance of classical behavior. Specifically, the wave function decoheres in a way that the different branches of the wave function interact only with their respective environments, resulting in the observation of either an awake cat or a sleeping cat, but not both. This emergence of locality and classical behavior from the quantum wave function is central to understanding how space and the classical world we observe emerge from quantum mechanics.
Quantum Mechanics Formulations and Many Worlds Interpretation
Quantum mechanics has multiple formulations, each with distinct interpretations of what is truly happening. The many worlds interpretation, formulated by Hugh Everett, posits that the quantum wave function describes the entire state of the universe, and when a measurement is made, the universe branches into different parallel worlds. The focus of Everettian quantum mechanics is on the wave function, which is the fundamental entity, and not on classical notions like particles and fields in space. It emphasizes that quantizing gravity and finding gravity within quantum mechanics might be more fruitful than treating gravity as a separate theory. The many worlds interpretation offers a simplified and pure approach to understanding quantum mechanics, highlighting the role of entanglement and decoherence, as well as the emergent nature of classical behavior.
The Emergence of Space and Interaction Localities
The emergence of classical behavior and the existence of space are deeply connected to interactions being local in space. Quantum mechanics, in its abstract form, involves an infinite-dimensional Hilbert space with an infinite number of possible quantum states. However, considerations from black hole entropy suggest that the number of degrees of freedom in the observable universe is finite. This discrepancy between quantum field theory, which assumes infinite-dimensional Hilbert space, and gravity, which cannot be fully described by quantum field theory, raises questions about the fundamental nature of space and the emergence of locality. Exploring how locality arises from the quantum wave function and why interactions are local in space is a central challenge in understanding the emergence of space and the classical world from quantum mechanics.
Quantum Mechanics, Observations, and Entanglement
Quantum mechanics presents challenges in understanding how observations and measurements lead to definite values while encompassing the possibility of superposition. The conventional Copenhagen interpretation suggests that the wave function collapses upon observation, resulting in a specific measurement outcome, while the many worlds interpretation implies that observed outcomes are due to entanglement between the observer and the system being observed. Decoherence plays a crucial role in the emergence of classical behavior by causing the wave function to separate into distinct branches corresponding to different measurement outcomes. Locality and the specific way in which interactions occur when objects are nearby are key factors in determining the classical world we observe.
Quantum field theory as a good approximation
Quantum field theory is seen as a good approximation, but not the final story in describing reality. Quantum gravity is viewed as a more fundamental theory that takes into account hints from black hole entropy.
Finite number of degrees of freedom in quantum gravity
The assumption is made that there are only a finite number of degrees of freedom in every region of space in quantum gravity. This suggests that quantum gravity treats space differently than quantum field theory, which takes space seriously.
Locality determines the laws of physics
The laws of physics are thought to be determined by the concept of locality, where interactions between different parts of the universe appear to be local with respect to space locations. Space is seen as a defining factor for locality.
Geometry of spacetime and entropy
Spacetime geometry is suggested to be connected to entropy. The idea is that the area of a boundary of a region of space is proportional to the entanglement entropy inside the region. This concept can be derived from an abstract quantum system and is connected to Einstein's equation of general relativity.
I suspect most loyal Mindscape listeners have been exposed to the fact that I’ve written a new book, Something Deeply Hidden: Quantum Worlds and the Emergence of Spacetime. As I release this episode on Monday 9 September 2019, the book will officially be released tomorrow, in print, e-book, and audio versions. To get in the mood, we’ve had several podcast episodes on quantum mechanics, but the “emergence of spacetime” aspect has been neglected. So today we have a solo podcast in which I explain a bit about the challenges of quantum gravity, how Many-Worlds provides the best framework for thinking about quantum gravity, and how entanglement could be the key to showing how a curved spacetime could emerge from a quantum wave function. All of this stuff is extremely speculative, but I’m excited about the central theme that we shouldn’t be trying to “quantize gravity,” but instead looking for gravity within quantum mechanics. The ideas here go pretty far, but hopefully they should be accessible to everyone.
The end of this episode includes a bonus, a short snippet from the audio book, read by yours truly. Audio excerpted courtesy Penguin Random House Audio. And here are links to some of the technical papers mentioned in the podcast.
