We introduce a simple variational principle for coherent material vortices in twodimensional turbulence. Vortex boundaries are sought as closed stationary curves of the averaged Lagrangian strain. Solutions to this problem turn out to be mathematically equivalent to photon spheres around black holes in cosmology. The fluidic photon spheres satisfy explicit differential equations whose outermost...

Evidence of coherent synchrotron radiation has been reported recently at the electron storage rings of several light source facilities. The main features of the observations are (i) a radiation wavelength short compared to the nominal bunch length, and (ii) a coherent signal showing recurrent bursts of duration much shorter than the radiation damping time, but with spacing equal to a substantia...

Oceanic flows have the property to self-organize into large scale coherent structures such as rings (robust vortices) and jets. The concomitant turbulent nature of such flows, and their self-organization property, gives a strong incentive for a statistical mechanics approach. Here we apply equilibrium statistical mechanics theory to a simple ocean model, in order to answer basic questions: What...

we introduce the notion ofstrongly $alpha$-reversible rings which is a strong version of$alpha$-reversible rings, and investigate its properties. we firstgive an example to show that strongly reversible rings need not bestrongly $alpha$-reversible. we next argue about the strong$alpha$-reversibility of some kinds of extensions. a number ofproperties of this version are established. it is shown ...