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# Category Archives: Quantum Mechanics

## Fall Quantum Mechanics Class

I’ll be teaching a course on quantum mechanics this year here at Columbia, from a point of view aimed somewhat at mathematicians, emphasizing the role of Lie groups and their representations. For more details, the course webpage is here. The … Continue reading

Posted in Quantum Mechanics
19 Comments

## (Imaginary) Time Asymmetry

When people write down a list of axioms for quantum mechanics, they typically neglect to include a crucial one: positivity (or more generally, boundedness below) of the energy. This is equivalent to saying that something very different happens when you … Continue reading

Posted in Quantum Mechanics
22 Comments

## Metaphorical Worlds Interpretation

Chad Orzel has a piece at Forbes which I like a lot, where he argues that the “Many Worlds” of the MWI interpretation should be taken metaphorically, and thus the MWI really should be the “Metaphorical Worlds Interpretation”. I urge … Continue reading

Posted in Quantum Mechanics
Comments Off on Metaphorical Worlds Interpretation

## An Apology

I’m afraid I made a serious mistake in this previous posting discussing Sean Carroll’s new book. Since the book was relatively reasonable, while the jacket and promotional material that came with it were nonsense, I assumed that Carroll was just … Continue reading

Posted in Quantum Mechanics
Comments Off on An Apology

## Regarding Papers about Fundamental Theories

Discussion in the comment section of the previous blog entry led me to do a little bit of historical research this morning, and I thought I’d write up the results here. First of all, for some interesting comments from people … Continue reading

Posted in Quantum Mechanics
26 Comments

## Quantum Supremacy II

About the only thing that has transcended the bitter partisan divisions between Democrats and Republicans in the US during recent years has been quantum mechanics, with the enactment late last year of the National Quantum Initiative Act (the NQI was … Continue reading

Posted in Quantum Mechanics
26 Comments

## What’s the difference between Copenhagen and Everett?

I’ve just finished reading Sean Carroll’s forthcoming new book, will write something about it in the next few weeks. Reading the book and thinking about it did clarify various issues for me, and I thought it might be a good … Continue reading

Posted in Quantum Mechanics
27 Comments

## Not So Spooky Action at a Distance

I’ve recently read another new popular book about quantum mechanics, Quantum Strangeness by George Greenstein. Before getting to saying something about the book, I need to get something off my chest: what’s all this nonsense about Bell’s theorem and supposed … Continue reading

Posted in Book Reviews, Quantum Mechanics
62 Comments

## Is Quantum Mechanics a Probabilistic Theory?

There is a simple question about quantum theory that has been increasingly bothering me. I keep hoping that my reading about interpretational issues will turn up a discussion of this point, but that hasn’t happened. I’m hoping someone expert in … Continue reading

Posted in Quantum Mechanics
74 Comments

## What is Real?

There’s a new popular book out this week about the interpretation of quantum mechanics, Adam Becker’s What is Real?: The Unfinished Quest for the Meaning of Quantum Physics. Ever since my high school days, the topic of quantum mechanics and … Continue reading

Posted in Book Reviews, Quantum Mechanics
74 Comments