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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.


1d
comment Has New Horizons' visit to Pluto taught us anything deeper than mere… facts?
Yes. For a start, Pluto and Charon apparently have internal sources of heating. For the moons of the outer Solar system their internal heat source was assumed to be tidal heating, but this can't be the case here. Depending on what's causing it, it might mean that the outer moons' internal heat is not just tidal heating after all. (Disclaimer: I'm no expert and this is all heresay from the popular press.)
Jul
21
comment What is the entropy of a mixed state in classical physics?
I'm not really sure what you mean by talking about "pure states" and "mixed states" in a classical system, since that terminology is from quantum mechanics. Can you elaborate on what you mean?
Jul
5
comment Is particle number a problem for formulating statistical physics in a mathematically rigorous manner?
@joshphysics you're right, that statement is too strong, it's also meaningful in the thermodynamic limit for the microcanonical ensemble. (In the limit, both ensembles agree unless you're at a phase transition.) I'll correct my answer when I'm back at a computer, if I remember.
Jun
14
comment Is there any easy process that absorbs heat?
I take it you mean "absorb heat from the environment at room temperature"? Otherwise cooking an egg (or anything else) would be an example - the coking reactions absorb heat, resulting in the pan being very slightly cooler than it would be otherwise, but still quite hot. For an easy process that absorbs heat at room temperature, you might try evaporation of water. (Or of anything else - ethanol evaporates faster, producing a more dramatic cooling effect.)
Jun
13
comment Motivation for the use of Tsallis entropy
(I suspect such an argument will not come from Tsallis himself. The paper you linked to has this text: "If we knew how to deduce [the Gibbs-Shannon entropy] from first principles for those systems ... whose microscopic dynamics ultimately leads to ergodicity, we could try to generalize along that path. But this procedure is still unknown, the [Shannon formula] being adopted, as we already mentioned, at the level of a postulate." (Emphasis added.) This is just completely wrong - the first derivation is due to Boltzmann, with finer points added by Gibbs, Shannon and Jaynes.)
Jun
13
comment Motivation for the use of Tsallis entropy
@nalewkoz thank you, your comment was helpful. I'll keep Toucehette's distinction in mind in future. From the Tsallis article I got that the motivation is not so much "we need an entropy that fails to be additive for independent systems" as "we need an entropy that is additive for systems that are correlated in some particular way." That does make more sense, but I still don't understand the motivation fully. For the Gibbs-Shannon entropy I know multiple arguments for why one should expect that particular function to be maximised, but for the Tsallis it still seems to be missing.
Jun
13
comment Help me solve a roommate argument about leaving the AC on / vs turning on two when needed
I actually don't know the physics (I'm curious about it), but my experience in very humid Japan is that turning on the AC results in a comfortable temperature in less than an hour, and turning it off results in discomfort within an hour - which suggests that leaving it on all day is more or less pointless. With heating in winter it seems different, with the time scale being several hours - I've often wondered why. (Note that Japanese apartments tend to have a light weight construction with no double glazing and little insulation.)
Jun
12
comment Surviving underwater explosions
Obviously the survivability of an explosion in water vs air is a matter of physics. Not off topic in any sense.
Jun
11
comment What happens if gravity of all objects in the universe disappears?
Don't forget that the atmosphere would suddenly want to rush out into the vacuum of space too. That might get us first of all...
Jun
8
comment Taking selfies while falling, would you be able to notice a horizon before hitting a singularity?
It's not a duplicate.
Jun
7
comment Why Thermodynamic cycles and no single process
"An isothermal process is reversible by definition because temperature is not defined in an irreversible process." - this is misleading. It's quite possible for an irreversible process to take place very slowly compared to the time scale of thermal equilibration with a heat bath. Thus even a manifestly irreversible process such as a chemical reaction can be performed under conditions so close to isothermal that they're typically regarded as such.
Jun
3
comment Conservation Laws and time-reversal symmetry
This is not a duplicate of the linked question, it is a special case of it that is not specifically discussed in the other question or its answers.
May
21
comment Why does lightning generate multiple branches?
It's a great question with a very interesting answer, which I unfortunately don't have time to write right now. However, you might find some useful information by searching for the term "dielectric breakdown", which is the general term for the breakdown of an electrical insulator. (Lightning is a specific example.)
May
16
comment Plane Mirror as the Screen in Young's experient
This question is essentially the same as "what happens if I shine a flashlight at a mirror?" - I suggest you give that a try.
May
5
comment Is possible to create water?
Every cell in your body creates water all the time. As an animal, you breathe in $\mathrm{O_2}$ and eat food that to a first approximation has the chemical formula $\mathrm{CH_2O}$ (e.g. sugar is $\mathrm{C_6H_2O}$). Your respiration is a complex series of chemical reactions that convert these into $\mathrm{CO_2}$ and $\mathrm{H_2O}$. Making water is how you live.
May
5
comment What do the recent vacuum tests mean for the believability of NASA's EM Drive?
FWIW I think this is a question that deserves to be answered here. It might be more on topic on Skeptics though. (I don't know for sure, I'm not a participant there.) There have been a lot of articles praising the new success (mostly on obscure news sites, which is a bad sign), and if someone has the knowledge to address them from a less frothy perspective they'd be doing the public a favour.
Apr
28
comment Hydrogen-boron fusion
I don't see any reason to close this. It can trivially be reworded as "would this work, and if not, why?", which is a perfectly well-defined question. Even in its current form I can't really see how the claim of "too broad" can be justified.
Apr
26
comment Is angular momentum the conjugate momentum of an angle?
The question seems pretty clear to me. (The answer is just "yes.")
Apr
13
comment Singing for physicists: How to resonate by body cavities with my voice?
Although at heart this is a physics problem, I doubt there is much in the way of practical advice that can come from considering the physics from first principles. What you need are singing lessons - I imagine there are no end of appropriate tutorial videos on YouTube.
Apr
5
comment The unreasonable effectiveness of the partition function
One might also mention that the moment generating function is essentially the Laplace transform of the probability distribution, which (if the reader is familiar with Laplace transforms) explains why information isn't lost in calculating it.