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# Hello Azimuth!

I've always found self-introductions a bit awkward, but let's see. I'm 27 and hold a postdoc position at the MPI for Gravitational Physics (Germany). I did my PhD on "spinfoam quantum gravity", under the co-supervision of Rovelli and Rivasseau. Fascinating, yes, but a bit like John, I tend to get more interested in the real stuff these days: how you can design matter to make it behave the way you want it to, how cities scale, etc. I too share the desire to think usefully.

My first contribution to Azimuth will be a guest post on the "fluctuation theorem" of non-equilibrium statistical mechanics. This is an important recent result in physics, with lots of applications—everybody agrees on that. But my view is that it is much more than that! I see it pretty much on the same footing as the central limit theorem: a fundamental mathematical fact, with applications in essentially all branches of science. Stochastic dynamics is so central to the discussions going on here on Azimuth, I'm thinking this "fluctuation theorem" may be of interest also (and perhaps especially) to the non-physicists. Check the post next week if you're interested.

Oh, I almost forgot: I'm very much impressed by John's (and his co-contributors') commitment to share his ideas openly and freely, for so long. Impressed, and grateful.

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1.

There is a fair bit of work on fluctuation-dissipation theory in climate science, which I happen to be reading about right now. There was some hope that it would help to estimate climate feedbacks from observations of the natural variability in the climate system, but it seems that you need far too long of a time series for that approach to be directly useful. However, people keep working on extensions and generalizations, and perhaps it will pay off in the end.

Comment Source:There is a fair bit of work on fluctuation-dissipation theory in climate science, which I happen to be reading about right now. There was some hope that it would help to estimate climate feedbacks from observations of the natural variability in the climate system, but it seems that you need far too long of a time series for that approach to be directly useful. However, people keep working on extensions and generalizations, and perhaps it will pay off in the end.
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2.

Welcome! I'm looking forward to your blog post.

Comment Source:Welcome! I'm looking forward to your blog post.
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3.

Welcome Matteo!

Comment Source:Welcome Matteo!
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Nathan wrote:

There is a fair bit of work on fluctuation-dissipation theory in climate science, which I happen to be reading about right now.

Are there one or two articles you'd especially recommend? (More would be less good for me right now.) You know my personality so you know what I'd like.

Comment Source:Nathan wrote: > There is a fair bit of work on fluctuation-dissipation theory in climate science, which I happen to be reading about right now. Are there one or two articles you'd especially recommend? (More would be less good for me right now.) You know my personality so you know what I'd like.
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5.

I'll give a few more than two, but with a diversity of perspectives so you can choose where to start. I don't know any review articles from a mathematical perspective, which might be the best place for you. The seminal climate science reference is Leith (1975) which focuses on recovering the forced response of the climate system from unforced variability. One of the best known modern application papers is Gritsun and Branstator (2007), which applies this to a "perfect model" experiment with a climate model to see how well you can recover full 3D dynamics. A more math-physics oriented paper going beyond pure FDT is Lucarini and Sarno (2011) (also on arXiv).

Comment Source:I'll give a few more than two, but with a diversity of perspectives so you can choose where to start. I don't know any review articles from a mathematical perspective, which might be the best place for you. The seminal climate science reference is [Leith (1975)](http://journals.ametsoc.org/doi/abs/10.1175/1520-0469%281975%29032%3C2022%3ACRAFD%3E2.0.CO%3B2) which focuses on recovering the forced response of the climate system from unforced variability. One of the best known modern application papers is [Gritsun and Branstator (2007)](http://journals.ametsoc.org/doi/abs/10.1175/JAS3943.1), which applies this to a "perfect model" experiment with a climate model to see how well you can recover full 3D dynamics. A more math-physics oriented paper going beyond pure FDT is [Lucarini and Sarno (2011)](http://www.nonlin-processes-geophys.net/18/7/2011/npg-18-7-2011.html) (also on [arXiv](http://arxiv.org/abs/1008.0340)).
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Thanks! I'm really curious how related, or not, these are to the ideas Matteo Smerlak was discussing. I'll check them out.

Comment Source:Thanks! I'm really curious how related, or not, these are to the ideas Matteo Smerlak was discussing. I'll check them out.
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I don't see any obvious relation between the fluctuation theorem Matteo is talking about, and the fluctuation-dissipation theorem I'm talking about. (When I originally posted I didn't know what theorem he was referring to.) But who knows ...

Comment Source:I don't see any obvious relation between the [fluctuation theorem](http://en.wikipedia.org/wiki/Fluctuation_theorem) Matteo is talking about, and the [fluctuation-dissipation theorem](http://en.wikipedia.org/wiki/Fluctuation-dissipation_theorem) I'm talking about. (When I originally posted I didn't know what theorem he was referring to.) But who knows ...
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8.
"My first contribution to Azimuth will be a guest post on the “fluctuation theorem” of non-equilibrium statistical mechanics. This is an important recent result in physics, with lots of applications—everybody agrees on that."

Wow, that sounds interesting. I suppose you're referring to the Jarzynski equality? I really only have a vague idea what exactly it says, but my colleaques here are going to study it experimentally. Anyway I've been wondering if there is any connection with Stratonovich's generalizations of the F-D theorem (as described in his book ISBN 0-387-55216-2)?
Comment Source:"My first contribution to Azimuth will be a guest post on the “fluctuation theorem” of non-equilibrium statistical mechanics. This is an important recent result in physics, with lots of applications—everybody agrees on that." Wow, that sounds interesting. I suppose you're referring to the Jarzynski equality? I really only have a vague idea what exactly it says, but my colleaques here are going to study it experimentally. Anyway I've been wondering if there is any connection with Stratonovich's generalizations of the F-D theorem (as described in his book ISBN 0-387-55216-2)?
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9.

Sounds like good stuff!

Comment Source:Sounds like good stuff!