## Physics items

Here are some interesting physics links I stumbled upon in the last few days.

The first is an interview of Murray Gell-Mann who is of course famous for proposing the quark model in the sixties. He is talking about Sheldon Glashow, one of the fathers of the standard model of particle physics, and his opinions about string theory.

Sheldon Glashow seems to be pretty critical about string theory:

http://www.pbs.org/wgbh/nova/elegant/view-glashow.html

One of Glashow’s points revolves around the testability of string theory, or at least that it doesn’t make any definite predictions about energy ranges that are potentially accessible in the near future.

Gell-Mann responds by saying that Glashow himself is participating in exactly the same kind of science, by proposing (together with Howard Georgi) a model for a Grand Unified Theory (GUT) where all three forces of the standard model become unified. The relevant energy scale for that is $10^{15}$ GeV; compare this to the energies the LHC can probe, $10^{4}$ GeV. (You can read about GUTs and more in this wonderful article by Natalie Wolchover: https://www.quantamagazine.org/no-proton-decay-means-grand-unification-must-wait-20161215/ )

This, however, is an interesting point since incidentally Glashow & Georgi’s SU(5) model is already falsified since it predicted the proton lifetime to be within a certain range that is by now experimentally excluded. So whatever one thinks about string theory, this doesn’t seem to be a good argument for being either for or against it.

Another interesting article is about the nature of the neutrino:

https://www.sciencenews.org/article/quest-identify-nature-neutrinos-alter-ego-heating

People have long been wondering whether the neutrino is its own antiparticle and a lot of experiments are running or under way to test that via trying to observe neutrinoless double beta decay. If neutrinos are indeed their own antiparticles, this seems to explain a host of open problems in high energy physics, e.g. why there is way more matter than antimatter. Read about it in that article!