They claim in Physical Review Letters 1 that the ghostly particles called neutrinos, which come in three different flavours, can inter-convert between the three in a thoroughly irregular way that the researchers call 'neutrino anarchy'.
Neutrinos are amongst the most mysterious of 'fundamental particles', the building blocks of matter.
They were first predicted in 1931 to explain some puzzling features of radioactive decay. Three years later, the Italian physicist Enrico Fermi gave them their name, meaning the 'little neutral one'. Neutrinos were predicted to be electrically neutral and extremely light, perhaps even having no mass at all. They would therefore barely interact with other kinds of matter at all, and it was not until 1959 that they were observed for the first time. Neutrinos are generated in the nuclear reactions that power the Sun, and so the Sun is a kind of neutrino factory.