Physics

The Standard Model is a physical theory of a spectacularly successful sort. It is built on beautiful and deep mathematics, covers almost all known physical phenomena, and agrees precisely with the result of every single experiment ever done to test it. It leaves open a very small number of questions: why this specific combination of small symmetry groups and their representations? What determines the parameters of the model (18 if you ignore neutrino masses, 7 more if you include them)? What about gravity? Does it need to be extended to account for dark matter? For several decades now, there has been a very active and heavily advertised field of “Beyond Standard Model” physics, the study of extensions of the standard model that remain consistent with experimental bounds. While BSM models have played a role in guiding experimentalists towards things to look for that are not already ruled out by what is known, they have never come anywhere near fulfilling the hope that they might provide some insight into the SM itself. They provide no explanation of the unexplained aspects of the Standard Model, instead adding a great deal of additional unexplained structure. Perhaps the simplest and most widely studied example is the minimal supersymmetric extension of the SM, which not only explains none of the 25 undetermined SM parameters, but adds more than 100 additional such parameters to the list. Theorists have traditionally followed what has been described as “Albert Einstein’s dream that the laws of nature are sublimely beautiful, inevitable and self-contained”, and the SM is our closest approach so far to Einstein’s dream. If you shared this dream, the known BSM models would never have much appealed to you, since they just added complexity and extra unexplained parameters. You also would not have been at all surprised by the strong negative results about such models that are one of the two major achievements so far of the LHC (the other is the Higgs discovery). If you’re a follower of Einstein’s dream, the obvious reaction to the LHC results so far would be to rejoice in the vindication of this dream, welcome the triumph of the simplicity of the SM, and hope that further study of the Higgs sector will somehow provide a hint of a better idea about where the SM parameters come from (almost all of them are Higgs couplings). Remarkably, a very different story is being sold to the public by those who had a great deal invested in now failed BSM models. In this story, the BSM models were the ones of Einstein’s dream: they were “natural”, and their failure leaves us with the “unnatural” Standard Model. An article entitled Is Nature Unnatural? is the source of the above quote about Einstein, and it tells us that Decades of confounding experiments have physicists considering a startling possibility: The universe might not make sense… In peril is the notion of “naturalness,” Albert Einstein’s dream that the laws of nature are sublimely beautiful, inevitable and self-contained. Without it, physicists face the harsh prospect that those laws are just an arbitrary, messy outcome of random fluctuations in the fabric of space and time… “The universe is impossible,” said Nima Arkani-Hamed, 41, of the Institute for Advanced Study, during a recent talk at Columbia University [more about this talk here]. What is behind this sort of claim that down is up is abuse of the English word “naturalness”, which in this particular case has been adopted by theorists to refer a technical property better described as “not quadratically sensitive to the cut-off scale”. There’s a lot to be said (and a lot that has been said on this blog) about the precise technical issue here. It’s a real one, and likely an important hint about the true nature of the Higgs sector of the SM and where all those undetermined parameters come from. Getting

The Smithsonian has a long article about Lisa Randall here. The Wall Street Journal has a shorter article about Randall’s high school classmate Brian Greene here. Brian’s World Science Festival will start here in New York on Wednesday. I’ll probably skip the World Science Festival in favor of an event at the CUNY Graduate Center: a conference on the work of Jim Simons, in honor of his 75th birthday. The conference will start off Tuesday morning with talks by Witten and Deligne (for a recent piece about Deligne and the Weil conjectures by Ed Frenkel, see here) One of many worthwhile things funded by Simons is Simons Science News, which now carries some of the best science journalism around. There’s a new interview with David Gross, who talks about the way QFT overcame those who wanted to do away with it in the sixties. About string theory: String theory is not as revolutionary as we once hoped. Its principles are not new: They are the principles of quantum mechanics. String theory is part and parcel of quantum field theory. About the multiverse: There are frustrating theoretical problems in quantum field theory that demand solutions, but the string theory “landscape” of 10500 solutions does not make sense to me. Neither does the multiverse concept or the anthropic principle, which purport to explain why our particular universe has certain physical parameters. These models presume that we are stuck, conceptually. About the current situation “Sometimes, he says, science is just plain stuck until new data, or a revolutionary idea, busts the status quo.” The latest article at Simons is one by Natalie Wolchover, who was at the same Nima Arkani-Hamed talk I recently attended. See her take here, mine here. Will write yet again about “naturalness” and some of the content of this article in a separate posting. For the state of SUSY, and particle physics in general, check out recent talks here, especially Matt Reece’s SUSY theory overview. I think a fair description of the current state of affairs is that the only SUSY theories standing are either “fine-tuned” (removing the main argument of LHC-scale SUSY), or highly contrived (e.g. by going beyond the MSSM in various ways to escape LHC negative results). For the latest experimental results about SUSY, watch for this CMS talk on Tuesday. For the latest in speculative theorizing about HEP and cosmology, see this past week’s Planck 2013 conference.

The first direct observation of the orbital structure of an excited hydrogen atom has been made by an international team of researchers. The observation was made using a newly developed “quantum microscope”, which uses photoionization microscopy to visualize the structure directly. The team’s demonstration proves that “photoionization microscopy”, which was first proposed more than 30 years ago, can be experimentally realized and can serve as a tool to explore the subtleties of quantum mechanics.... Tushna Commissariat. (2013) 'Quantum microscope' peers into the hydrogen atom. physicsworld.com. info:/

Internal stress in a glass material is an important source of strength. Theory and experiments provide a new molecular-scale understanding of the process by which such stress develops. Published Fri May 24, 2013

Lisa C. Jeffrey In this article we describe the relation between the Chern-Simons gauge theory partition function and the partition function defined using the symplectic action functional as the Lagrangian. We show that the partition functions obtained using these two Lagrangians agree, and we identify the semiclas ... [J. Math. Phys. 54, 052304 (2013)] published Fri May 24, 2013.

Lisa C. Jeffrey We compute the semiclassical formulas for the partition functions obtained using two different Lagrangians: the Chern-Simons functional and the symplectic action functional. ... [J. Math. Phys. 54, 052305 (2013)] published Fri May 24, 2013.

A. Sakabekov and E. Auzhani In this article, we prove the analogue of the mass conservation law for one-dimensional nonlinear Boltzmann's moment system equations in third approximation and some effect of the mass conservation law. ... [J. Math. Phys. 54, 053512 (2013)] published Fri May 24, 2013.

S. Lopez-Rosa, I. V. Toranzo, P. Sanchez-Moreno, and J. S. Dehesa The internal disorder of hydrogenic Rydberg atoms as contained in their position and momentum probability densities is examined by means of the following information-theoretic spreading quantities: the radial and logarithmic expectation values, the Shannon entropy, and the Fisher information. As wel ... [J. Math. Phys. 54, 052109 (2013)] published Fri May 24, 2013.

Antiferromagnetic interaction created between potassium atoms