Monday, May 23, 2022

Explaining Bell's Local Realism

Opinions vary widely on Bell's Theorem.

From a recent Italian paper:

In a lecture held in 1983, Richard Feynman argued that the Bell theorem “is not a theorem that anybody thinks is of any particular importance. We who use quantum mechanics have been using it all the time. It is not an important theorem. It is simply a statement of something that we know is true – a mathematical proof of it.” (quoted in Whitaker 2016b, 493): in Feynman’s view, what ‘we know is true’ is simply that quantum theory is not a classical theory. No matter what is the tenability of the Feynman charge of irrelevance about the Bell theorem, a common view of what it takes for a physical theory to be ‘classical’ is that the physical systems the theory is about can be assumed to have measurement- independent properties or, in other terms, that – in the well-specified situations that are suitable for physical investigation – these physical systems can be assumed to have pre- existing values for all relevant quantities, values that the measurement is supposed just to reveal. In this vein, ‘classicality’ is thus equated more othen than not with a loose notion of ‘realism’.
I agree with this. Bell's theorem is just a way of saying that quantum mechanics is not a classical theory, and that had been everyone's understanding since about 1930.

All of this would be non-controversial except that Bell started convincing people that what he really proved was that quantum mechanics violated local realism, whatever that is. Physicists were willing to give up classicality, not not realism.

It is all verbal trickery. Realism does not mean anything useful. Read the paper for details.

Thursday, May 19, 2022

Susskind Tackles Computers Falling into Black Holes

Physicist Leonard Susskind gave a lecture:
Black Holes and the Quantum-Extended Church-Turing Thesis | Quantum Colloquium

A few years ago three computer scientists named Adam Bouland, Bill Fefferman, and Umesh Vazirani, wrote a paper that promises to radically change the way we think about the interiors of black holes. Inspired by their paper I will explain how black holes threaten the QECTT, and how the properties of horizons rescue the thesis, and eventually make predictions for the complexity of extracting information from behind the black hole horizon. I'll try my best to explain enough about black holes to keep the lecture self contained.

Susskind explains that his last great accomplishment was to convince his colleagues that if two entangled particles fall into two black holes, then they will be connected by a wormhole. See EP = EPR for more.

Now he is excited by the physics of quantum complexity theory. It had long been thought that Turing machines are good models for computation, in that computable functions can be performed by Turing machines, and polynomial time computability corresponds to polynomial time Turing machines. He says this is now believed to be false, because a quantum computer might do something in polynomial time that a Turing machine might require longer time.

Susskind's insight is that a computer falling into a black hole might achieve a higher complexity than what would otherwise be possible. The catch is that it could never communicate its result to anyone.

Update: Susskind claimed that EP=EPR has become accepted wisdom, but Peter Shor says:

One of the problems with It from Qubit is that it’s really quite hard to tell the papers that are nonsense from the ones that aren’t. For example, Maldacena and Susskind’s ER=EPR paper is a speculative idea that has no chance of being correct (but listening to his most recent talk, Susskind hasn’t given up on it). And when you actually corner other people in the area they (or at least some of them) will admit that this paper has virtually no chance of being correct, but for some reason they aren’t willing to say this publicly.

There are undoubtedly other papers in this field which are equally improbable. But it seems to me that any field where you have to be in the cogniscenti to know which papers are the ones worth paying attention to is in deep trouble.

That gets this response:
I wonder on what grounds ER=EPR is supposed to have “no chance” of being correct. There is already the curious parallel of non-traversibility of wormholes, and non-transmission of information via entanglement alone; obtaining both of these limitations from a common origin is exactly the kind of beautiful conceptual connection one expects from a deep correct insight.
So there are two theoretical examples of non-communication, and saying they are the same is a deep insight. I say both are the same as the Easter Bunny. Is that deep also?

I wonder if anyone has published a respectable paper saying that EP=EPR is nonsense. Or if everyone is too polite to say so. Or if physicists think that because the EP=EPR paper was written by two great geniuses, failing to understand it must be a deficiency of their own brain power.

Peter Woit's response:

Probably others have the same problem I have with writing anything publicly about this. The literature is huge and complicated, so it would be a full time job to master it to the point of being sure there is no there there. I’ve been through this before with string theory claims and wasted far too much time on that.
It used to be that leading physicists would explain why the theory makes sense or is good for something.

Monday, May 16, 2022

Praising the Great Paradigm Shifters

Peter Woit declares:
If one tried to pick a single most talented and influential figure of the past 100 years in each of the fields of pure mathematics and of theoretical physics, I’d argue that you should pick Alexander Grothendieck in pure math and Edward Witten in theoretical physics.
Several comments give some good reasons for disagreeing with this assessment.

Grothendieck is almost completely unknown outside Mathematics, as his work was in the abstract foundations of algebraic geometry. As for Witten:

And he [Ed Witten] rarely came to our floor, fourth floor, but here he was, coming and knocking at my door, and then saying, “Have you heard about the revolution?”…

I said, “What revolution?” He said, “The SO(32) revolution.”

Witten convinced everyone of these string "revolutions". This one was a minor technical result in 1984. There is still no known relation to the physical world.

This "revolution" terminology stems from philosoher T. Kuhn, who based it on a study of the "Copernican revolution", where the Earth does revolutions about the Sun. He said that Copernican theory was not measurably better than Ptolemaic (Earth-centered), but was great anyway because it became accepted.

The lesson here is that if you call something a revolution and persuade your colleagues, you can be a great genius without showing any measurable advantages.

Woit credits Witten largely because he was-influential in conning everyone into studying string theory, a big dead end. Dirac, Feynman, Weinberg, and all the other theoretical physicists just advanced the state of the art, and did what others might have done later. Maybe no one would have bothered with string theory, if it were not for a few leaders like Witten.

Thursday, May 5, 2022

Multiverse in the Movies

I usually like science fiction, but it seems that the movies take the most ridiculous science ideas. A few years ago, everyone was doing time travel. Now they are all doing the multiverse. Here are some current movies.

Everything Everywhere All at Once

The plot follows a Chinese-American woman (Yeoh) being audited by the Internal Revenue Service who discovers that she must connect with parallel universe versions of herself to prevent a powerful being from causing the destruction of them all.
Spider-Man: No Way Home
When the spell goes wrong, the multiverse is broken open which allows visitors from alternate realities to enter Parker's universe.
Doctor Strange in the Multiverse of Madness
In the film, Strange and his allies travel into the multiverse to protect a young girl from Wanda Maximoff, who will stop at nothing to take back her own sons at all costs.
Find more at IMDB Multiverse in Movies.

Tuesday, May 3, 2022

Pinker says AAAS is too Leftist

You know Science is getting too politicized when academic leftist criticize the leading science organizations for being to overtly leftist. See Steve Pinker's criticism of AAAS
For precisely these reasons I cannot in good conscience agree to your request to donate money to the AAAS. The Association is currently making these hazards worse, not better.

First, it is astonishing that an association for the advancement of science does not take a scientific approach to public acceptance of scientific conclusions. ...

I will give three examples of how the AAAS appears to be going out of its way to alienate any politician or citizen who is not a strong leftist. ...

As best I can tell, awareness of the hazards of politicization of science among the officers of AAAS and the editors of Science is zero.

He is right about this. Here is the AAAS response:
Thanks for your note. We’re sorry to lose you as a donor, but I disagree with your analysis. We will continue to cover the evidence for and impact of systemic racism. Thanks for your support of AAAS in the past.
In other words, the leftist shift is accelerating.

Update: Scientific publications are already lining up to attack a court opinion:

A leaked draft of a Supreme Court opinion suggests the nation’s highest court is poised to overturn Roe v. Wade, the landmark ruling that guarantees the right to an abortion. The opinion was first reported by Politico. ....

The study found that women denied the procedure were more likely to experience negative health impacts—including worse mental health—than women who received one. The former were also more likely to face worse financial outcomes, including poor credit, debt and bankruptcy. (The study did not include pregnant people who did not identify as women.)

Note that it has to apologize for citing a study of pregnant women that did not include pregnant men.

The leaked opinion is filled with historical and legal fact-finding. It is interesting that all these academic scholars have not found fault with the facts or reasoning. They just disagree with the law being determined by elected representatives.