Three seminars

I've been to some interesting seminars in the last couple of days.

Yesterday I went to hear Nigel Goldenfeld give a seminar at Harvard. Prof. Goldenfeld is on the list I've been preparing of potential postdoc supervisors, though his research is a little more biologically focused than my particular interest.

He spoke about his view that the genetic code, i.e. the formula from going from the sequence of DNA bases to the proteins that need to be made, is not arbitrary. It is optimised to be as error-resistant as possible, according to a particular way of measuring this that seems reasonable. This gives us some inspiration in trying to think about the shape evolution took on the grandest scale. As he mentioned, it took a billion years or less after the formation of the earth for the architecture of the cell to develop, and since then things haven't changed very much in the scheme of things. It seems that there was a transition between modes of evolution, corresponding to the development of the linear mode of passing on genes that predominates today.

This afternoon I went to listen to Jorn Dunkel argue that the definition of entropy and temperature usually used in describing systems is not the right one. I can accept his quantitative arguments, but I think one needs to be very careful in claiming what they imply. The zeroth law gives a clear definition of temperature for some kinds of system, and I think that is not the temperature he presents (we had a bit of discussion about this at the end of the seminar). To be fair, the temperature he's complaining about isn't either, though it's very closely related (I think in the thermodynamic limit, the conventional definition is correct). There are some other properties we want temperature or entropy to obey, and I think his definition is correct regarding those in the microcanonical ensemble. But since the canonical ensemble is where we usually want to use temperature, I'm not sure how much difference it really makes.

In the slightly later afternoon, I went to hear Lyderic Bocquet talk about nanofluidics. This was perhaps the most down-to-earth talk of the three, describing the possibility of using boron nitride nanotubes to obtain energy from the salt difference between seawater and river water. Or more accurately, the talk described science that suggests such an application!

It's nice to have semester started and some talks to go to: sitting at a desk all day can get tedious.