1/f noise and quantum criticality

One of those nice if obvious-after-the-fact results -- quantum critical correlations are preserved under the addition of 1/f noise. It's obvious after the fact because (a) 1/f noise has power law correlations in time, so it's "critical" in some sense; (b) more precisely, the 1/f noise term appears in the Keldysh action in precisely the same way as the "equilibrium" noise term -- from the FDT -- that drives the superconductor-insulator transition in a Josephson junction.

Quantum critical states and phase transitions in the presence of non-equilibrium noise
E. della Torre et al., Nature Physics doi:10.1038/nphys1754 [also arXiv:0908.0868]

"If you cannot be kind, at least have the decency to be vague"

I'm glad blogger finally got around to doing something about the comment spam. On the other hand, a small fraction of it will be missed.

I intend to revive this blog because I'm spending the semester in Santa Barbara, and would like to avoid spamming the population of Urbana with papers that I think are interesting.

On that note -- there actually are physicists called "D'Eath" and "Payne" who published a series of papers together.

Numbering equations 1a, 1b etc in TeX

This is how it's done:

One nice trick is if you want equations with lettered sublabels - 1a, 1b, etc. First you must include the amsmath package, and the enclose the relevant equations in the 'subequations' environment like this:

\documentclass{article}
\usepackage{amsmath}
\begin{document}
...
\begin{subequations}
\begin{eqnarray}
x
&=& y^2 \\
&=& (a-b)^2 \nonumber \\
&=&
c
\end{eqnarray}
\end{subequations}
...
\end{document}

where the \nonumber command suppresses numbering of that line. You can use any number of ordinary equations or equation arrays inside the subequations environment.