Category Archives: Quantum Mechanics

Why Sabine Hossenfelder is Just Wrong

Posted on November 11, 2024 by woit

Sabine Hossenfelder’s latest video argues There’s no reason for nature to be pretty (5:00) Working on a theory of everything is a mistake because we don’t understand quantum mechanics (8:00). These are just wrong: nature is both pretty and described … Continue reading →

Posted in Quantum Mechanics | 20 Comments

The Mystery of Spin

Posted on November 22, 2022 by woit

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

Posted on August 6, 2022 by woit

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

Posted on July 12, 2021 by woit

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 →

Posted in Quantum Mechanics, Quantum Theory: The Book, Uncategorized | 11 Comments

Fall Quantum Mechanics Class

Posted on September 7, 2020 by woit

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

Posted on August 6, 2020 by woit

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

Posted on September 17, 2019 by woit

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 →

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An Apology

Posted on September 15, 2019 by woit

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 →

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Regarding Papers about Fundamental Theories

Posted on September 9, 2019 by woit

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

Posted on September 7, 2019 by woit

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