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# Category Archives: Quantum Mechanics

## The Mystery of Spin

Scientific American has a new article today about the supposedly mysterious fact that electrons have “spin” even though they aren’t classical spinning material objects. The article doesn’t link to it, but it appears that it is discussing this paper by … Continue reading

Posted in Quantum Mechanics
45 Comments

## Symmetry and Physics

It’s getting late, but I can’t help myself. Reading too many wrong things about symmetry and physics on Twitter has forced me to do this. And, John Baez says I don’t explain things. So, here’s what the relationship between symmetry … Continue reading

Posted in Quantum Mechanics
32 Comments

## The Problem of Quantization

I’ve been watching Witten’s ongoing talks about geometric Langlands mentioned here, and wanted to recommend to everyone, mathematician or physicist, the first of them, on The Problem of Quantization (pdf here, video here, the question session is very worthwhile). For … Continue reading

## 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 Favorite Old Posts, 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

## Something Deeply Hidden

Sean Carroll’s new (available in stores early September) book, Something Deeply Hidden, is a quite good introduction to issues in the understanding of quantum mechanics, unfortunately wrapped in a book cover and promotional campaign of utter nonsense. Most people won’t … Continue reading

Posted in Book Reviews, Multiverse Mania, Quantum Mechanics
76 Comments