" Hans Bethe and Physics in/of the 20th Century.". Fermi Lab December 12, 2012. Hans Bethe (1906-2005). 1926-28 Sommerfeld Munich 1928/29 Frankfurt/ Ewald Stuttgart 1930 Cambridge –Fermi 1931 Fermi 1932/3 T ü bingen 1933/4 Manchester/Bristol
" Hans Bethe and Physics in/of the 20th Century." Fermi Lab December 12, 2012
1926-28 Sommerfeld Munich • 1928/29 Frankfurt/ Ewald Stuttgart • 1930 Cambridge –Fermi • 1931 Fermi • 1932/3 Tübingen • 1933/4 Manchester/Bristol • 1935- Cornell
Epistemic cultures [are] those amalgams of arrangements and mechanisms — bonded through affinity, necessity, and historical coincidence – which, in a given field, make up how we know what we know. Epistemic cultures are cultures that create and warrant knowledge. •  (Knorr-Cetina 1999, 1
It was Bethe’s ability to translate his technical mastery of the microscopic world ‑‑ i.e. the world of nuclei, electrons, atoms, and molecules ‑‑ into an understanding of the macroscopic properties of materials and into the design of macroscopic devices, -- such as radar and atomic bombs,..– that rendered his services so valuable at the Radiation Lab at M.I.T., and at Los Alamos.
Assembled attendees of the 1947 Conference on Quantum Mechanics. Left to right are: Isidor I. Rabi, Linus Pauling, John van Vleck, Willis E. Lamb, Gregory Breit, Duncan MacInnes, Karl K. Darrow, George E. Uhlenbeck, Julian Schwinger, Edward Teller, Bruno Rossi, Arnold Nordsieck, John von Neumann, Hans Bethe, Robert Serber, Robert Marshak, Abraham Pais, Robert Oppenheimer, David Bohm, Richard Feynman, Victor F. Weisskopf, Herman Feshback. Not pictured is Hendrick A. Kramers.
. • Hendrick A. Kramers
6It was first suggested by Schwinger and Weisskopf that hole theory must be used to obtain convergence in this problem. • Schwinger Feynman : basic observables • QFT Renormalization Program
Acknowledgments: • Paul Ewald 1929 • von Weiszäcker 1938 • Hendrick Kramers 1947
In their joint paper Critchfield and Bethe stated that the pp reaction is not a significant contributor to solar output, and in both the abstract and the text of his 1939 paper Bethe stated unambiguously that the CNO cycle is entirely the source of the output by the sun and similar stars, and that no other nuclear process can play this role. This is not the current view.
Carl von Weiszäcker in his study of nucleosynthesis had earlier come up with the carbon cycle. His analysis had assumed that Li5 was stable and he also had made assumptions regarding where the heaviest elements were produced which Bethe did not believe. In contrast to von Weiszäcker and to Gamov, who also was primarily interested in nucleosynthesis, Bethe believed the problems of nucleosynthesis and of energy generation could and should be separated.
What had happened is that Bethe and Critchfield when considering the pp cycle had not taken into account all the possible He3reactions. The initial reaction is • The deuteron produced in the p-p reaction gets destroyed almost at once by the reaction • There are now two sets of reactions possible. The one that Bethe and Critchfield considered with Be7and Li7as intermediaries in making nuclei and the reaction • which they had overlooked.
Fowler and Lauritsen after the war indicated that the cross section for this reaction is 106 larger than the reactions that Bethe and Critchfield had considered. So even for a central temperature of the sun of 16 x 106 K ( the temperature that Bethe and Critchfield had assumed) the proton-proton reaction is as efficient as the carbon cycle.
To validate my assertion that after WW II the practice of theoretical physics became the same over much of the western world let me indicate some of the factors responsible for this homogenization. • 1.) The broad governmental support given after the war and during the Cold War to the sciences, and to physics in particular, -- in the US, in Europe and in the Soviet Union, -- was certainly one of the enabling conditions responsible for the important, transformative, advances in physics from 1945 to 1955. • 2.) The mimeograph machine and the ditto machine
3.) Summer Schools ( Michigan, Les Houches, Cargèse, Boulder, Brandeis..) • 4.) 1946. Robert Oppenheimer appointed the director of the Institute for Advanced Study in Princeton (IAS) and aprofessor of physics there. He used the institution to implement his universalist vision of science. In 1948 he began inviting a host of foreigners to the Institute. These included: Faqir Auluck, Aage Bohr, Freeman Dyson, Léon van Hove, Res Jost, Nicolaas van Kampen, Toichiro Kinoshita, Maurice Lévy, Cécile Morette, Yoichiro Nambu, Abraham Pais, Guilio Racah, Abdus Salam, Sin-Itiro Tomonaga, Hideiki Yukawa, John Ward and Chen Ning Yang.
5.) Another important development had its origin at the IAS: the formation of the modern mathematical physics community. In 1948 three young theorists -- Léon von Hove, Res Jost and Arthur Wightman -- attended the lectures on C* algebras that John von Neumann was delivering at the Institute. Van Hove and Jost were fellows at the IAS, and Wightman at the time was an instructor at Princeton University. Together with Rudolf Haag, Daniel Kastler, Arthur Jaffe, and others they went on to establish mathematical physics, as a recognized, institutionalized, sub-discipline of physics and mathematics.
\ • 1947 Lamb Shift • 1949 Effective Range Theory • 1944 Landau and Smorodinski • k cot δ(k) = -(1/a) + ½r0k2 + • 1947 Schwinger . Variational Principle. • 1949. Bethe • Parametrization of unknown knowledge.
1957 • Lee and Yang, Wu et al, Garwin, Lederman , Weinrich, Telegdi, Friedman. • Parity-non conservation. • Lille Conference • BCS. Superconductivity Sputnik
Hugenholtz Perturbation Theory of Many Fermion Systems 1-46 • Brueckner Theory of Nuclear Structure and of MBS 47-242 • Thouless Theory of Nuclear Matter 243-256 • Bloch and De Dominicis Grand Partition Function MFS 257-282 • Mottelson Nuclear Structure 283-316 • Weisskopf Properties of Nuclear Matter 317-325 • Lipkin Collective Properties of MPS 326-342 • Beliaev Bogoliubov Methods 343-400 • Bohm Theory of Collective Coordinates 401-516 • Pines Electrons, Plasmons and Phonons 517-540 • Schrieffer Theory of Superconductivity 541-578 • Leyton Exp. Superconductivity and Superfluidity 579-600 • Huang Hard Sphere Gases 601-670
The role that symmetry plays in quantum field theory was enlarged and greatly extended by BCS’s theory: it ushered in the concept of a spontaneously broken symmetry into high energy physics and quantum field theory. • Whenever a continuous symmetry is spontaneously broken there must exist excitations of the system with a frequency that vanishes in the limit of large wavelength. In elementary particle physics that means a particle of zero mass. (Goldstone, Nambu)
Uniqueness of Ground State • Stone-von Neumann Theorem (1930-1)
An effective field theory is a description of phenomena in a certain energy regime bounded by some energy less than some energy cut-off Λ and in terms of wavelengths longer than some length scale h/Λ. An effective field theory assumes that the physics in the domain in which it is valid can be given in terms of “elementary” entities out of which the composite entities that populate that domain are built. These “elementary” entities constitute the effective degrees of freedom appropriate to that scale. They depend on a more “fundamental” theory only through a small set of parameters that enter in the description of the dynamics of these entities
Hacking-Type Scientific Revolution • (i) They transform a wide range of scientific practices and they are multidisciplinary. • In a Hacking-type revolution something happens in more than • one discipline; a multiplicity of scientific disciplines are transformed. • (ii) New institutions are formed that epitomise the new directions. • (iii) They are linked with substantial social change. After a Hacking-type revolution there is a different feel to the world, there is a marked change in the texture of the world. And • (iv) because they are ‘big', there can be no complete, all-encompassing history of a Hacking-type revolution.
A Hacking revolution must have associated with it a new style of scientific reasoning. • Styles of reasoning are the constructs that specify what counts as scientificc knowledge and constitute the cognitive conditions of possibility for science (Hacking, 1992). • They are made concrete and explicit through the specification of ontological and explanatory models. • The emergence of a new style is associated with the introduction of new types of sentences, entities and explanations. • The following as examples of styles of reasoning: the taxonomic, experimental, statistical and genetic or evolutionary styles of reasoning.
The Quantum Revolution as a Hacking Type Revolution • Style of Reasoning : Hierarchization of Physical Nature • Quantum Field Theory as its Language • (K. Wilson’s interpretation of renormalization, BCS, • phase transitions) • Limitations
Local quantum field theory is the natural framework for the synthesis of quantum mechanics and special relativity. • It is is based on three foundational principles (Weinberg): • 1.) that the evolution in time of the state vector of the system is given by a unitary operator, U(t2,t1) and that the linear superposition principle for state vectors applies as in ordinary quantum mechanics; • 2.) that the formulation is Lorentz invariant; and • 3.) that the cluster decomposition principle is valid, which essentially is the requirement that experiments performed at widely separated locations will yield uncorrelated results.
Macroscopic systems, whose characteristic time T, mass M, and length L, are such that ML2/T >> h are described by classical mechanics, those for which ML2/T ≈ h are described by quantum mechanics.
All ultimate questions without exception are affected by purely political events, even though these may appear to be superficial (external). • Max Weber • Summer 1917
One of the most memorable hours of my life was the time when PSAChad its meeting with President Eisenhower after Sputnik. The Presidenthad asked us to meet with him, and we had spent one or two days among ourselves, preparing for the meeting. During the meeting, I.I. Rabi, who had been the Chairman of PSAC until that date, presented our ideas. Eisenhower was truly amazing in the speedof his understanding of oursuggestions. After eachsuggestion, he might ask for a few details, but then he quickly agreed, and asked his adjutant, Brigadier General Goodpaster, to make a note and see that our suggestionwas implemented. I have never before been present at a session where so much was decided in such a short time. Eisenhower was most impressive.
As the Director of the Theoretical Division of Los Alamos, I participated at the most senior level in the World War II Manhattan Project that produced the first atomic weapons. Now at age 88, I am one of the few remaining such senior persons alive. Looking back at the half century since that time, I feel the most intense relief that these weapons have not been used since World War II,mixed with the horrorthat tens of thousands of such weapons have been built since that time – onehundred times more than any of us at Los Alamos could ever have imagined. Today we are rightly in an era of disarmament and dismantlement of nuclear weapons. But in some countries nuclear weapons development still continues. Whether and when the various Nations of the World can agree to stop this is uncertain. But individual scientists can still influence this process by withholding their skills. Accordingly, I callon all scientists in all countries to ceaseand desist from work creating, developing, improving and manufacturing further nuclear weapons - and, for that matter, other weapons of potential mass destruction such as chemical and biological weapons.