The Nobel in Physics was awarded today. Half of the prize went to Yochiro Nambu "for the discovery of the mechanism of spontaneous broken symmetry in subatomic physics" and the other half to Makoto Kobayashi and Toshihide Maskawa "for the discovery of the origin of the broken symmetry which predicts the existence of at least three families of quarks in nature."

This prize represents a bit of backfill as this was theoretical work that took place in the 60's and 70's. It set the stage for much of the work in the 80's that has already been recognized by Nobel prizes such as Weinberg-Salaam's electroweak theory, Rubbia's discovery of the W bosons, Richter & Ting for discovering charmed quarks, and Lederman for the bottom quark.

As the Nobel press release notes about Nambu's work "Spontaneous broken symmetry conceals nature’s order under an apparently jumbled surface. It has proved to be extremely useful, and Nambu’s theories permeate the Standard Model of elementary particle physics."

Kobayashi and Maskawa's work also underlies the standard model. The "Kobayashi-Maskawa mixing matrix" describes the coupling between different quark flavors. As such, a lot of experimental work goes into measuring the KM matrix elements. Their work established the current standard model structure of three generations of quarks and predicted the existence of charm, top and bottom before they were discovered.

Symmetry breaking impacts areas such as CP violation which, as we know, is one of reasons for the matter-antimatter imbalance in the universe. The press release notes "A hitherto unexplained broken symmetry of the same kind lies behind the very origin of the cosmos in the Big Bang some 14 billion years ago. If equal amounts of matter and antimatter were created, they ought to have annihilated each other. But this did not happen, there was a tiny deviation of one extra particle of matter for every 10 billion antimatter particles. It is this broken symmetry that seems to have caused our cosmos to survive."

So, all in all, better late than never. A well deserved prize.

ETA: For those with some technical background, check out the scientific background paper from the Nobel site.

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