Murray Gell-Mann - Cosmology, astrophysics and particle physics (159/200) скачать в хорошем качестве

Murray Gell-Mann - Cosmology, astrophysics and particle physics (159/200)

To listen to more of Murray Gell-Mann’s stories, go to the playlist:    • Murray Gell-Mann (Scientist)   New York-born physicist Murray Gell-Mann (1929-2019) was a theoretical physicist. His considerable contributions to physics include the theory of quantum chromodynamics. He was awarded the 1969 Nobel Prize in Physics for his work on the theory of elementary particles. [Listener: Geoffrey West; date recorded: 1997] TRANSCRIPT: It's unfortunate that the cultures of cosmology and astrophysics, on the one hand, and elementary particle physics on the other, are so different. It's made it difficult for people to work simultaneously, theorists to work simultaneously on both… in both domains. The reason Stephen Hawking was able to discover the Hawking radiation was that he was one of the few cosmologists who knew a little bit about particle physics. Nowadays of course there's more inter-penetration, but still it's not adequate. I think it's very important that there be much more inter-penetration and that people really work simultaneously on superstring or M-theory, whatever you want to call it, in elementary particle theory and on cosmology, at the same time and with interlocking agendas. [Q] But the potential barrier between those two is now become probably even bigger because of the tremendous technicalities that are involved in superstring theory or M-theory. It's much more difficult for people to cross... Well, maybe it's those people then who have to learn… be concerned with cosmology. Some of them are of course… [GW] Yes, it may be the other way... Some of them are concerned with cosmology, but they need to be, I think they need to be more concerned with cosmology. Many of them still have an implicit belief that they can get away in their research by considering the universe to be approximately flat and gravitation as sort of a… gravitational curvature as a kind of perturbation, and that may not be right. But or course, cosmology is undergoing a lot of rapid change now with the observational evidence seeming to indicate that the universe has lots of… will… will go to infinity with lots of juice left over, and more over with a non-zero cosmological constant. [GW] Yes, do you want to talk about that a little bit, what your reaction is to that..? Well, maybe. There's no reason not to have a cosmological constant. In fact the challenge in a theory with broken supersymmetry has always been to find a way to break the supersymmetry spontaneously without generating a huge cosmological constant. The big problem is how to make it zero. Well, a semi-plausible argument was developed with the aid of virtual baby universes or virtual black holes and an approach sometimes called third quantization where the value of the cosmological constant came out to be one over the normalization of a probability distribution, and it was an un-normalizable distribution, so you got one over infinity which would be zero. The argument never looked really clean but it was a possible indication of how the thing might come about. Well now if the sighted observations are correct, one is looking for a cosmological constant that's just of the same… that gives a… a stress image momentum tensor of the same order of magnitude as the matter density. And that means in natural units, a value of something like 10to the minus 119th, possibly the largest fudge factor in the history of science. The search for theoretical understanding of such a value then is quite exciting; if it turns out we really need it. Now maybe the argument that gave zero, or some form of an argument like that could be revived but with a cut-off, I mean a natural cut-off, at the real matter density, that would somehow allow the… the cosmological constant to be slightly non-zero. I don't know. I really don't know enough about these things to make a serious educated guess.