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Let me tell you a little bit about my second book, and how it relates to my first book. 1/
#t=aboutBook" target="_blank" rel="nofollow noopener">worldscientific.com/worldscibooks/…
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Will Kinney
57.7K posts
Will Kinney
@WKCosmo
Cosmologist, physicist, dirtbag mountain biker, expat Montanan, Copernican extremist. Part of the problem.
Buffalo, NY Katılım Ocak 2017
1.8K Takip Edilen41.9K Takipçiler
@PatoTinho2 @jackalblackhole @yalinewich The manifold in GR is locally Minkowski, which is a non-Euclidean metric. When mathematicians say "Euclidean" this context, they mean R^n, which need not have a metric at all.
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@WKCosmo @jackalblackhole @yalinewich GR does have an euclidean metric, which is used to calculate all distances. Rulers are real physical things, you know.
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@WKCosmo @yalinewich Are we going to get an admission you were wrong, retraction of your incorrect claim and condescension towards a quanta writer who apparently knows the math better than you, or are you going to ignore, or continue digging?
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@jackalblackhole @azerwekh OK, if you mean "locally Euclidean" means Rn, not that it has to have a Euclidean metric, then great. I withdraw my objection.
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@henry_maxfield That's the point. The target space need only be Rn, it doesn't even have to have a metric.
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@WKCosmo Quanta don’t always get everything right but in this case they’re spot on, using almost literally the definition of a (topological or smooth) manifold. You probably have in mind a manifold equipped with a metric, which could be pseudo-Riemannian
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@jackalblackhole @yalinewich Any manifold in General Relativity. They are locally Minkowski.
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@WKCosmo @yalinewich Can you name a manifold that is not locally euclidean?
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@yalinewich Manifolds can be locally Euclidean, but they don't have to be.
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@WKCosmo Isn't it just the literal, widely accepted definition of a topological manifold? Am I missing something?
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@mbw61567742 @adammarkbrazier All rules for mapping mathematics to physical systems are "metaphysical fiat."
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@adammarkbrazier @WKCosmo Yes but the density matrix becomes a collection of different classical states with different coefficients. (With complications not needed here.) But why do those coefficients represent probabilities except by metaphysical fiat? For possible reason: arxiv.org/abs/0709.0544
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A few more thoughts on decoherence, the Born Rule, and the ingredients of a scientific theory. 1/
Will Kinney@WKCosmo
This is really nice. I have for a long time been of the opinion that Zurek's approach is really the only reasonable way forward for understanding the emergence of classicality in quantum systems. No need to muddy the question with philosophical woo once you state it correctly.
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@STEM_inTamarian Hmm, I didn't notice that! I did use the Google AI eraser to get rid of a text bubble in the original meme that I didn't use, so I guess technically I did use AI.
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I'm confused. You're claiming we haven't observed environment-induced decoherence in the laboratory, or that experimenters don't know what a detector is, or the environment? I think there are a lot of people building working quantum computers who would be quite surprised to learn this.
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@WKCosmo You are confusing the observation ("we know a detector when we see it") with a definition. If you think you know the definition for detector and environment, then please write it down.
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This is really nice. I have for a long time been of the opinion that Zurek's approach is really the only reasonable way forward for understanding the emergence of classicality in quantum systems. No need to muddy the question with philosophical woo once you state it correctly.
Deivon Drago@DeivonDrago
Well, here we go. Following up on the post below. New essay: Zureka: a way forward to solving the thorniest issues in quantum mechanics. open.substack.com/pub/deivondrag…
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@skdh We have perfectly good definitions of what we mean by system, detector, and environment that are used in thousands of labs every day. Experimental science would be completely impossible if we didn't. Zurek's pointer states just demonstrate how absurd it is to claim otherwise.
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@WKCosmo Yes, but we don't have a definition for what a detector is. That is the very problem that needs to be solved, and Zurek's formalism cannot solve it.
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@skdh Right, but you can't DERIVE the map from the theory. There is no "reason" it exists, it's a definition.
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@WKCosmo No, that's just wrong. A scientific theory is always a combination of mathematical axioms and a map from the mathematical structures to reality. Without such a map, you do not have a scientific theory, you only have a set of mathematical axioms without relation to reality.
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@skdh You can perfectly well define system and environment in a lab. There's nothing inconsistent about it.
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@WKCosmo That's the observation. The question is, where is the theory that describes it. How do you explain this observation without simply assuming what you observe. That is the task that the theory must fulfil. Zurek's theory cannot fulfil this task.
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@martinmbauer He quite clearly seems to be implying that entangled particles are connected by actual, physical Einstein-Rosen bridges. That's not something that was invented by YouTube.
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I’m not going to defend susskinds style of vague speculation. But to focus on that part is certainly a choice. I don’t think postdocs working on this topic are confused by that, not the ones I know at least. But it doesn’t help when press releases, or physicists on YouTube and elsewhere are
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How can it be both incoherent assertions and something that’s just been ruled out?
Hint: neither is true
Will Kinney@WKCosmo
I remember we had a journal club devoted to the ER=EPR paper when it came out, and when I read it, it was just a bunch of incoherent assertions, with almost no calculations. I tried to point this out, and all the other people in the room were like "No, no! This is really profound!" and I felt like I was at a cult meeting, not a physics seminar.
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@MarkusQ Yeah, good luck clawing back that indirect from the university.
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@WKCosmo Not to mention the fact that, even if you hadn't and "gave it all back", 2/3s of it would have already vanished into the pipeline that got it to you.
Not sure if there's be the same administrative overhead on the way back. 😈
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Joke's on them, they can't claw it back if I've already spent it.
nature.com/articles/d4158…
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@ParzivalsEgg Turns out that a pair of real numbers and a few algebraic rules can create remarkably rich structrure!
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Once again for those at that back: a complex number is just a pair of real numbers that obey certain algebraic rules. OF COURSE you can write QM only in terms of reals. It just makes your life really inconvenient.
Quanta Magazine@QuantaMagazine
For an “imaginary” number, 𝑖 is surprisingly handy across many scientific disciplines: It shows up in geometry, optics, signal analysis, and, controversially, in quantum mechanics. quantamagazine.org/physicists-tak…
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@skdh The physics here is that entangled states collapse into mixed states extremely rapidly due to decoherence. This is not a matter of definition, it is a real thing you see in the lab.
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@skdh All of the problems you are talking about here are problems with how we construct a correspondence between the theory and the physical system it represents. You can worry about these things, but that is a philosophical problem, not physics.
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@TSHamiltonAstro I put extras spaces after my sentences in LaTeX, then it just goes ahead and does what it wants.
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Your periodic reminder that extra space between sentences has been the standard in English language typography for hundreds of years, pre-dating the typewriter. It’s there because it makes the text easier to read.
The Not So Distant Past@MemoryLaneTime
Just a friendly reminder to my friends older than 42: You don’t have to put 2 spaces after the period anymore. That was for the typewriter era. You're free
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Will Kinney retweetledi
Mark Wise 1953-2026. Hero of theoretical particle physics, master of effective field theory, much loved teacher, mentor, and colleague, my best friend for over 40 years. An immeasurable loss.
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