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I'm a post-doctoral researcher with a wide range of interests. My career is in complex systems science (or maybe cybernetics) and the origins of life, but I also have research interests in

  • the foundations of statistical mechanics and its relationship to information theory
  • Earth systems science
  • non-equilibrium thermodynamics in general

I'm also generally interested in the foundations of quantum mechanics and in black holes, though I wouldn't say I'm an expert on those things.

It's probably worth noting that despite the fact that my research is in physics-related areas, all my degrees are in other subjects. If I occasionally seem to start talking in an alien language, this is probably why.


Jan
27
comment Is there a thermodynamic limit on how efficiently you can solve a Rubik's cube?
...so if you have an inexhaustible supply of initially solved dummy cubes then you can indefinitely solve cubes by transferring their scrabledness into the dummy cubes - but with one dummy cube you can't solve more than one other cube.
Jan
27
comment Is there a thermodynamic limit on how efficiently you can solve a Rubik's cube?
@CJDennis that's a good idea, and it took me a while to see why it can't work. Let's say you've solved the cube and now you want to offload the 'waste' information about its initial state into the dummy cube. If the dummy cube is in a known state (e.g. already solved), you can just 'swap' the information in memory with the dummy cube's state, clearing the memory. But if you (the machine's designer) don't know the dummy cube's state then this doesn't work; there's $2^{65}$ bits of unknown information in memory, and another $2^{65}$ bits in the dummy cube - it can't all compress into the cube.
Jan
26
comment Lagrangian mechanics and initial conditions vs boundary conditions
More reasonable for what? They are different types of problem and each has its uses.
Jan
25
revised Bra-ket of products
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Jan
25
comment Is the work-energy theorem valid for only particles or rigid bodies as well?
@Gerard work is being done, but just not on the block. Instead it's being done on the atoms that make up your hand and the block, and it is indeed increasing their kinetic energy, which you feel as heat.
Jan
23
answered Why hasn't an exact solution to the Navier-Stokes equations been found?
Jan
23
comment Is there a thermodynamic limit on how efficiently you can solve a Rubik's cube?
@MarkEichenlaub I think your comment is right; another way to look at it is that the link you seek is exactly Landauer's principle. It says that although information need not be preserved on the macroscopic level, we can't erase macroscopic information without increasing the number of microscopic states. This is essentially because of what you say in your comment: at any given time the total state of the system can be partitioned into $\text{macrostate}\otimes\text{microstate}$, so by Liouville's theorem you can't decrease the first without increasing the second.
Jan
23
comment Is there a thermodynamic limit on how efficiently you can solve a Rubik's cube?
@MarkEichenlaub it looks like the discussion resolved the rest of your questions - is that right?
Jan
23
comment Is there a thermodynamic limit on how efficiently you can solve a Rubik's cube?
@MarkEichenlaub (replying to your first comment) this is just because the machine has to know the state of the cube in order to solve it; once that information's been copied into the machine's state, there's no way to erase it without generating heat. To see it another way, there are $\sim 2^{65}$ possible initial (macro)states of the cube+machine system, so there must be the same number of possible final states unless information has been lost. The cube always ends up in the same state, so the machine must end up in one of $\sim 2^{65}$ states, depending on the initial state of the cube.
Jan
23
comment Is there a thermodynamic limit on how efficiently you can solve a Rubik's cube?
@immibis I guess the reference would be Landauer's paper (pitt.edu/~jdnorton/lectures/Rotman_Summer_School_2013/…), though I have to admit I haven't read it. Any recent treatment of Maxwell's demon should have a good explanation of how the demon can reduce the entropy of a gas, allowing work to be done, unless it has to erase the information that it inevitably stores about the gas as it operates.
Jan
23
comment Is there a thermodynamic limit on how efficiently you can solve a Rubik's cube?
@JánLalinský this might be down to imprecision of language on my part. I meant to say "it can indefinitely reduce the thermodynamic entropy of its environment, but only through processes that involve indefinitely increasing the information entropy of its own internal state." It's not just the correlation that makes the entropy decrease, it's the fact that it can make measurements and act on them without having to generate heat. I guess the reference would be Landauer's paper, though I have to admit I haven't read the original. (See next comment for link)
Jan
22
awarded  Good Answer
Jan
21
awarded  Enlightened
Jan
21
awarded  Nice Answer
Jan
21
revised Is there a thermodynamic limit on how efficiently you can solve a Rubik's cube?
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Jan
21
revised Is there a thermodynamic limit on how efficiently you can solve a Rubik's cube?
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Jan
21
revised Is there a thermodynamic limit on how efficiently you can solve a Rubik's cube?
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Jan
21
answered Is there a thermodynamic limit on how efficiently you can solve a Rubik's cube?
Jan
21
comment What is the relativistic mass of this spinning ball?
I can see quite a bit of conceptual stuff in the second to last paragraph.
Jan
19
comment Are the large moons of Jupiter, Saturn, and Neptune still cooling and does this give and indication of their age?
This question might (or might not) be more likely to get a good answer at earth science stack exchange. (It's on topic here as well though.)