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Feb
9
comment How can a product of Bra and Ket be a scalar if they are matrices?
+1 because that way of visualising matrix multiplication is way better than the much more awkward one I've been using all my life up to now.
Feb
2
comment Reference for statistical mechanics from information theoretic view
I added another Jaynes reference, which I consider one of the best - I hope you don't mind
Jan
19
comment What are alternative ways to think about transfer matrix as used in Ising model?
Oh, either's fine! I can probably work through it myself, but if you have time to put some information in the answer it might be helpful. (I just figured out that if you use the convention that stochastic matrices left-multiply probability vectors then you have to use the left Perron-Frobenius eigenvector of $T$, which is what was holding me up.)
Jan
18
comment What are alternative ways to think about transfer matrix as used in Ising model?
This is an excellent answer and taught me something I needed to know. I'd really like to know more about the general case, in which the transfer matrix might not be symmetric.
Jan
15
comment What would be the implications of a Penrose Universe?
There are some studies of cellular automata on penrose tiling lattices, which might have something of the flavor of what you're asking for. If I get a chance I'll see if I can dig up some papers.
Jan
15
comment At an instant, does a system of gravitational charges exhibit equivalent behavior to a time-reversed system of like electric charges?
@endolith in GR, yes, that's true. I suppose I assumed we were in the Newtonian approximation. In the full GR case, playing the video backwards will still result in an apparent attractive force, it's just that the reversed gravitational waves will increase the energy in the system rather than decrease it over time.
Dec
31
comment Has there been any experimental verification of Jeremy England's theory of dissipation-driven adaptation?
@CuriousOne my point about imagination was that it isn't enough. You seem to have read me as saying something positive about it instead, which isn't what I intended to say at all.
Dec
31
comment Has there been any experimental verification of Jeremy England's theory of dissipation-driven adaptation?
@CuriousOne I do not understand what point you think I'm making. Your comment makes no sense in relation to what I wrote.
Dec
31
comment Has there been any experimental verification of Jeremy England's theory of dissipation-driven adaptation?
@CuriousOne my last comment does not say what you think it says.
Dec
31
comment Has there been any experimental verification of Jeremy England's theory of dissipation-driven adaptation?
@CuriousOne there is lots of data. That data is used to constrain the geochemical conditions that existed on Earth during the origins of life. Those conditions cannot be measured directly because they were 3.8-4 billion years ago and the entire surface of the Earth has been replaced since then, but that doesn't make it "not science"! Using data to constrain unknowns is precisely what science is. In principle it is no different to calculating the temperature of the core of the Sun, which we equally cannot measure directly.
Dec
31
comment Has there been any experimental verification of Jeremy England's theory of dissipation-driven adaptation?
@CuriousOne I'm referring to the consensus opinion of my geochemist colleagues. (I am not one myself.) Basically, as I understand it it comes from the observation that most of the big redox gradients on the present Earth result from the oxidation of the atmosphere, which didn't happen until about 3GYA. It's not impossible to imagine other ways to get a big redox gradient, but it's easy to talk about what we can imagine, and much harder to talk about what was actually there. If you wanted to claim such a gradient existed then the onus would be on you to explain where it came from.
Dec
31
comment Has there been any experimental verification of Jeremy England's theory of dissipation-driven adaptation?
@CuriousOne no, of course not. Nobody knows that. A fair chunk of the research in origins of life consists of putting empirical constraints on those conditions, but actually measuring it is obviously out of the question, caps lock or not.
Dec
31
comment Has there been any experimental verification of Jeremy England's theory of dissipation-driven adaptation?
@CuriousOne actually thermodynamic efficiency is one of the major mysteries in the origins of life. The first organisms were not photosynthetic, and it is unlikely that there were strong redox gradients on the early Earth, which means that the first organisms probably had to be autotrophs who fed on quite small redox potentials. Modern bacteria that survive on such small potentials have very complicated metabolisms, because they have to be extremely efficient in order to avoid making a net loss per molecule consumed. So energy efficiency would have been a major concern for the first organisms.
Dec
31
comment Has there been any experimental verification of Jeremy England's theory of dissipation-driven adaptation?
*by this I mean they should be assessed carefully on their own terms, not that they should be ranted against. His claims are neither trivial nor shallow.
Dec
31
comment Has there been any experimental verification of Jeremy England's theory of dissipation-driven adaptation?
As someone who is (a) a full-time specialist in origins of life and (b) somewhat skpetical of England's claims*, I think this is an excellent question.
Dec
31
comment What will a glass look like in 500 years?
I'm not an expert (maybe there's someone here who is) but I believe it's debatable whether glass is really a "slow liquid" rather than a solid. But even if it is a liquid, I think it will takes a lot more than 500 years for it to flow appreciably.
Dec
22
comment Is simulating the entire universe possible?
@KyleKanos I think it's entirely clear that it's asking about whether there are physical limitations that would prevent it, not about what humans can conceive. (I've edited to change the wording.)
Dec
17
comment Is it possible that a person with myopia will see a blurry picture as normal?
@DarioP it seems you're right - I had assumed that convolution (as a mathematical operation) was non-invertible, but it seems the difficulty of doing deconvolution in practical applications actually stems from not knowing the kernel exactly. But since convolution is linear and its inverse must also be linear, that seems to imply that you can sharpen an image such that it will return to its original appearance when later blurred, as long as you know the exact kernel for the blurring convolution. This might mean my answer is technically wrong.
Dec
6
comment Is it possible to learn about an event that occurred outside of your observable universe?
@brucesmitherson that was edited into the question shortly after I answered it. It makes it a more interesting question, but I don't know the answer in that case. (Logically, the resolution has to be that the bound observer has the same cosmic horizon as us, but I don't immediately know how to show that it does. It probably has to do with the fact that you can no longer consider space flat and homogeneous on the scale of interest.)
Nov
30
comment Temperature loss of a moving object
@WhatRoughBeast it's both - first the heat conducts into the air, and then the air convects away. But you're right, "convective" is a better term here.