Lost in Math?

Lost in Math? A review of ‘Lost in Math: How Beauty Leads Physics Astray’, by Sabine Hossenfelder

Jeremy Butterfield
This is a review of Hossenfelder’s book, ‘Lost in Math: How Beauty Leads Physics Astray’. The book gives a breezy exposition of the present situation in fundamental physics, and raises important questions: both about the content of the physics, and the way physics research is organized. I first state my main disagreements. Then, I mostly praise the book: I concentrate on Hossenfelder’s discussion of supersymmetry, naturalness and the multiverse.
Read more at https://arxiv.org/ftp/arxiv/papers/1902/1902.03480.pdf

After primordial inflation

D. V. Nanopoulos, K. A. Olive, M. Srednicki
We consider the history of the early universe in the locally supersymmetric model we have previously discussed. We pay particular attention to the requirement of converting the quanta of the field which drives primordial inflation (inflatons) to ordinary particles which can produce the cosmological baryon asymmetry without producing too many gravitinos. An inflaton mass of about 1013 GeV (a natural value in our model) produces a completely acceptable scenario.
Read more at https://lib-extopc.kek.jp/preprints/PDF/1983/8305/8305219.pdf

An introduction to the classical three-body problem

Lagrange’s periodic solution with three bodies at vertices of equilateral triangles. The constant ratios of separations
are functions of the mass ratios alone

Govind S. Krishnaswami, Himalaya Senapati
The classical three-body problem arose in an attempt to understand the effect of the Sun on the Moon’s Keplerian orbit around the Earth. It has attracted the attention of some of the best physicists and mathematicians and led to the discovery of chaos. We survey the three-body problem in its historical context and use it to introduce several ideas and techniques that have been developed to understand classical mechanical systems.
Read more at https://arxiv.org/pdf/1901.07289.pdf

 

John Archibald Wheeler: A Biographical Memoir

John Wheeler as a postdoc of Niels Bohr in
Copenhagen, 1934

Kip S. Thorne
John Archibald Wheeler was a theoretical physicist who worked on both down-to-earth projects and highly speculative ideas, and always emphasized the importance of experiment and observation, even when speculating wildly. His research and insights had large impacts on nuclear and particle physics, the design of nuclear weapons, general relativity and relativistic astrophysics, and quantum gravity and quantum information. But his greatest impacts were through the students, postdocs, and mature physicists whom he educated and inspired.
He was guided by what he called the principle of radical conservatism, inspired by Niels Bohr: base your research on well established physical laws (be conservative), but push them into the most extreme conceivable domains (be radical). He often pushed far beyond the boundaries of well understood physics, speculating in prescient ways that inspired future generations of physicists.
After completing his PhD with Karl Herzfeld at Johns Hopkins University (1933), Wheeler embarked on a postdoctoral year with Gregory Breit at NYU and another with Niels Bohr in Copenhagen. He then moved to a three-year assistant professorship at the University of North Carolina (1935-37), followed by a 40 year professorial career at Princeton University (1937-1976) and then ten years as a professor at the University of Texas, Austin (1976-1987). He returned to Princeton in retirement but remained actively and intensely engaged with physics right up to his death at age 96.
Read more at https://arxiv.org/ftp/arxiv/papers/1901/1901.06623.pdf

Two Notions of Naturalness

Porter Williams
My aim in this paper is twofold: (i) to distinguish two notions of naturalness employed in BSM physics and (ii) to argue that recognizing this distinction has methodological consequences. One notion of naturalness is an “autonomy of scales” requirement: it prohibits sensitive dependence of an effective field theory’s low-energy observables on precise specification of the theory’s description of cutoff-scale physics. I will argue that considerations from the general structure of effective field theory provide justification for the role this notion of naturalness has played in BSM model construction. A second, distinct notion construes naturalness as a statistical principle requiring that the values of the parameters in an effective field theory be “likely” given some appropriately chosen measure on some appropriately circumscribed space of models. I argue that these two notions are historically and conceptually related but are motivated by distinct theoretical considerations and admit of distinct kinds of solution.
Read more at https://arxiv.org/pdf/1812.08975.pdf

The black hole fifty years after: Genesis of the name

Ann Ewing’s article in 1964 where the term Black Hole is published for the first time

Carlos A. R. Herdeiro, José P. S. Lemos
Black holes are extreme spacetime deformations where even light is imprisoned. There is an extensive astrophysical evidence for the real and abundant existence of these prisons of matter and light in the Universe. Mathematically, black holes are described by solutions of the field equations of the theory of general relativity, the first of which was published in 1916 by Karl Schwarzschild.
Another highly relevant solution, representing a rotating black hole, was found by Roy Kerr in 1963. It was only much after the publication of the Schwarzschild solution, however, that the term black hole was employed to describe these objects. Who invented it?
Conventional wisdom attributes the origin of the term to the prominent North American physicist John Wheeler who first adopted it in a general audience article published in 1968. This, however, is just one side of a story that begins two hundred years before in an Indian prison colloquially known as the Black Hole of Calcutta.
Robert Dicke, also a distinguished physicist and colleague of Wheeler at Princeton University, aware of the prison’s tragedy began, around 1960, to compare gravitationally completely collapsed stars to the black hole of Calcutta. The whole account thus suggests reconsidering who indeed coined the name black hole and commends acknowledging its definitive birth to a partnership between Wheeler and Dicke.
Read more at https://arxiv.org/pdf/1811.06587.pdf

The Science and Legacy of Richard Feynman

Avinash Dhar, Apoorva D. Patel, Spenta R. Wadia
This year is the 100th birth anniversary of Richard Philips Feynman. This article commemorates his scientific contributions and lasting legacy.

… He influenced the way physicists think about physics, especially physical processes whose description requires the quantum theory. Feynman’s approach to physics was to show how the solution to a problem unravels, aided by a visual language that encapsulates complicated mathematical expressions. James Gleick put this very succinctly, “Feynman’s reinvention of quantum mechanics did not so much explain how the world was, or why it was that way, as to tell how to confront the world. It was not knowledge of or knowledge about. It was knowledge how to.” He went to the heart of the problem he was working on, built up the solutions from simple ground rules in a step by step nuts and bolts way, articulating the steps as he built up the solution, keeping in mind that science is highly constrained by the fact that it is a description of the natural world. He laid bare the strategy of the solution, and was explicit about the various difficulties that need to be surmounted, perhaps now or in the next attempt to solve the problem: “In physics the truth is rarely perfectly clear.” Feynman’s attitude to ‘fundamental physics’ is well put in the collection, ‘The Pleasure of Finding Things Out’: “People say to me, ‘Are you looking for the ultimate laws of physics?’ No, I’m not, I’m just looking to find out more about the world, and if it turns out there is a simple ultimate law which explains everything, so be it, that would be very nice to discover.” …

Read more at https://arxiv.org/pdf/1810.07409.pdf