Thursday , October 17 2019
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*Something Deeply Hidden: Quantum Worlds and the Emergence of Spacetime*

Summary:
That is the new, interesting, and engaging book by Sean Carroll.  Some of it is exposition, the rest argues for a version of Many Worlds Theory, but with a finite number of universes.  Here is one excerpt: String theory, loop quantum gravity, and other ideas share a common pattern: they start with a set of classical variables, then quantize.  From the perspective we’ve been following in this book, that’s a little backward.  Nature is quantum from the start, described by a wave function evolving according to an appropriate version of the Schroedinger equation.  Things like “space” and “fields” and “particles” are useful ways of talking about that wave function in a appropriate classical limit.  We don’t want to start with space and fields and quantize them; we want to extract them from an

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That is the new, interesting, and engaging book by Sean Carroll.  Some of it is exposition, the rest argues for a version of Many Worlds Theory, but with a finite number of universes.  Here is one excerpt:

String theory, loop quantum gravity, and other ideas share a common pattern: they start with a set of classical variables, then quantize.  From the perspective we’ve been following in this book, that’s a little backward.  Nature is quantum from the start, described by a wave function evolving according to an appropriate version of the Schroedinger equation.  Things like “space” and “fields” and “particles” are useful ways of talking about that wave function in a appropriate classical limit.  We don’t want to start with space and fields and quantize them; we want to extract them from an intrinsically quantum wave function.

I very much liked the discussion on pp.300-301 on how a finite number of quantum degrees of freedom implies a finite-dimensional Hilbert space for the system as a whole, that in turn constraining the number of worlds in an Everett-like model.  If only I understood it properly…

You can buy the book here.

The post *Something Deeply Hidden: Quantum Worlds and the Emergence of Spacetime* appeared first on Marginal REVOLUTION.

Tyler Cowen
Tyler Cowen is an American economist, academic, and writer. He occupies the Holbert C. Harris Chair of economics as a professor at George Mason University and is co-author, with Alex Tabarrok, of the popular economics blog Marginal Revolution. Cowen and Tabarrok have also ventured into online education by starting Marginal Revolution University. He currently writes the "Economic Scene" column for the New York Times, and he also writes for such publications as The New Republic, the Wall Street Journal, Forbes, Newsweek, and the Wilson Quarterly.

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