Teoretisk Fysik

Home , Albert Fert, Frederick Reines, Herbert Kroemer, Igor Tamm, Masatoshi Koshiba, Riccardo Giacconi

1 Teoretisk fysik

Institutionen för fysik Helsingfors Universitet 12.11. 2008 Paul Hoyer

530013 Presentation av de fysikaliska vetenskaperna (3 sp, 1 sv)

Kursbeskrivning: I kursen presenteras de fysikaliska vetenskaperna med sina huvudämnen astronomi, fysik, geofysik, meteorologi samt teoretisk fysik. Den allmänna studiegången presenteras samt en inblick i arbetsmarkanden för utexaminerade fysiker ges.

Kursens centrala innehåll: Kursen innehåller en presentation av de fysikaliska vetenskapernas huvudämnes uppbyggnad samt centrala forskningsobjekt. Presentationen ges av institutionens lärare samt av utomstående forskare och fysiker i industrin.

Centrala färdigheter: Att kunna tillgodogöra sig en muntlig presentation sam föra en diskussion om det presenterade temat.

Kommentarer: På kursen kan man även behandla speciella ämnesområden, såsom: speciella forskningsområden inom fysiken samt specifika önskemål inom studierna. 2 Bakgrund

Den fortgående specialiseringen inom naturvetenskaperna ledde till att teoretisk fysik utvecklades till ett eget delområde av fysiken Professurer i teoretisk fysik år 1900: 8 i Tyskland, 2 i USA,1 i Holland, 0 i Storbritannien Professorer i teoretisk fysik år 2008: Talrika! Även forskningsinstitut för teoretisk fysik (Nordita @ Stockholm, Kavli @ Santa Barbara,...)

Teoretisk fysik är egentligen en metod (jfr. experimentell och numerisk fysik) som täcker alla områden av fysiken:

Kondenserad materie Optik Kärnfysik Högenergifysik,... 3 Kring nyttan av teoretisk fysik

Rutherford 1910: “How can a fellow sit down at a table and calculate something that would take me, me, six months to measure in the laboratory?”

1928: Dirac realized that his equation in fact describes two spin-1/2 particles with opposite charge. He first thought the two were the electron and the proton, but it was then pointed out to him by Igor Tamm and Robert Oppenheimer that they must have the same mass, and the new particle became the anti-electron, the positron. It was discovered by Carl Anderson in 1932 (Nobel Prize 1936):

Cloud chamber photograph by C.D. Anderson of the first positron ever identified. A 6 mm lead plate separates the upper half of the chamber from the lower half. The positron must have come from below since the upper track is bent more strongly in the magnetic field indicating a lower energy

Rutherford 1933: “ It seems to me that in some way it is regrettable that we had a theory of the positive electron before the beginning of the experiments... I would have liked it better if the theory had arrived after the experimental facts had been established.” 4 The QED experience 5 In his report to the 12th Solvay Congress (Brussels, 1961) on “The Present Status of Quantum Electrodynamics” (QED), Feynman called for more insight and physical intuition in QED calculations:

“It seems that very little physical intuition has yet been developed in this subject. In nearly every case we are reduced to computing exactly a coefficient of some specific term. We have no way to get a general idea of the result to be expected. To make my view clearer, consider, for example, the anomalous electron moment, (g–2)/2 = α/2π – 0.328α2/π2 . We have no physical picture by which we can easily see that the correction is roughly α/2π , in fact, we do not even know why the sign is positive (other than by computing it). In another field we would not be content with the calculation of the second order term to three significant figures without enough understanding to get a rational estimate of the order of magnitude of the third. We have been computing terms like a blind man exploring a new room, but soon we must develop some concept of this room as a whole, and to have some idea of what is contained in it. As a specific challenge, is there any method of computing the anomalous moment of the electron which, on first rough approximation, gives a fair approximation to the α term and a crude one to α2 ; and when improved, increases the accuracy of the α2 term, yielding a rough estimate of α3 and beyond?” 6

gµ/2 = 1.0 011 659 214 (8)(3) e /2mµ 7

Teori och experiment är nära förbundna: I det längre loppet är fysiker inte intresserade av teorier som inte kan verifieras genom mätningar.

Teori drivs av experiment: Elektromagnetism (Maxwell), speciell relativitetsteori (Einstein), Kvantmekanik (Planck, Einstein, Bohr,...)... och vice versa: Allmän relativitetsteori (Einstein), antimaterie (Dirac), ...

Framgångarna med att förutsäga och förklara experimentella data har givit teoretisk fysik hög status: Många nobelpris ges till teoretiska fysiker The Nobel Prize in Physics 2008

"for the discovery of the "for the discovery of the origin of the broken symmetry mechanism of which predicts the existence of at least three families of spontaneous broken quarks in nature" symmetry in subatomic physics"

Photo: Universtity of Chicago Photo: KEK Photo: Kyoto University

Yoichiro Nambu Makoto Kobayashi Toshihide Maskawa

1/2 of the prize 1/4 of the prize 1/4 of the prize

USA Japan Japan

Enrico Fermi Institute, University High Energy Accelerator Research Kyoto Sangyo University; Yukawa of Chicago Organization (KEK) Institute for Theoretical Physics Chicago, IL, USA Tsukuba, Japan (YITP), Kyoto University Kyoto, Japan

b. 1921 b. 1944 b. 1940 (in Tokyo, Japan)

Titles, data and places given above refer to the time of the award.

http://nobelprize.org/cgi-bin/print?from=%2Fnobel_prizes%... 10/22/08 10:26 AM All Nobel Laureates in Physics

The Nobel Prize in Physics has been awarded to 183 individuals since 1901. (John Bardeen was awarded the prize in both 1956 and 1972.) Click on a name to go to the Laureate's page.

9 JumpNobel down Prizesto: | 1980 in | 1960 theoretical | 1940 | 1920 physics,| 1901 | 1989 – 2008

2008 - Yoichiro Nambu, Makoto Kobayashi, Toshihide Maskawa 2007 - Albert Fert, Peter Grünberg 2006 - John C. Mather, George F. Smoot 2005 - Roy J. Glauber, John L. Hall, Theodor W. Hänsch 2004 - David J. Gross, H. David Politzer, Frank Wilczek 2003 - Alexei A. Abrikosov, Vitaly L. Ginzburg, Anthony J. Leggett 2002 - Raymond Davis Jr., Masatoshi Koshiba, Riccardo Giacconi 2001 - Eric A. Cornell, Wolfgang Ketterle, Carl E. Wieman 2000 - Zhores I. Alferov, Herbert Kroemer, Jack S. Kilby 1999 - Gerardus 't Hooft, Martinus J.G. Veltman 1998 - Robert B. Laughlin, Horst L. Störmer, Daniel C. Tsui 1997 - Steven Chu, Claude Cohen-Tannoudji, William D. Phillips 1996 - David M. Lee, Douglas D. Osheroff, Robert C. Richardson 1995 - Martin L. Perl, Frederick Reines 1994 - Bertram N. Brockhouse, Clifford G. Shull 1993 - Russell A. Hulse, Joseph H. Taylor Jr. 1992 - Georges Charpak 1991 - Pierre-Gilles de Gennes 1990 - Jerome I. Friedman, Henry W. Kendall, Richard E. Taylor 1989 - Norman F. Ramsey, Hans G. Dehmelt, Wolfgang Paul 1988 - Leon M. Lederman, Melvin Schwartz, Jack Steinberger 1987 - J. Georg Bednorz, K. Alex Müller 1986 - Ernst Ruska, Gerd Binnig, Heinrich Rohrer 1985 - Klaus von Klitzing 1984 - Carlo Rubbia, Simon van der Meer 1983 - Subramanyan Chandrasekhar, William A. Fowler 1982 - Kenneth G. Wilson 1981 - Nicolaas Bloembergen, Arthur L. Schawlow, Kai M. Siegbahn 1980 - James Cronin, Val Fitch 1979 - Sheldon Glashow, Abdus Salam, Steven Weinberg 1978 - Pyotr Kapitsa, Arno Penzias, Robert Woodrow Wilson 1977 - Philip W. Anderson, Sir Nevill F. Mott, John H. van Vleck 1976 - Burton Richter, Samuel C.C. Ting 1975 - Aage N. Bohr, Ben R. Mottelson, James Rainwater 1974 - Martin Ryle, Antony Hewish 1973 - Leo Esaki, Ivar Giaever, Brian D. Josephson 1972 - John Bardeen, Leon N. Cooper, Robert Schrieffer 1971 - Dennis Gabor 1970 - Hannes Alfvén, Louis Néel 1969 - Murray Gell-Mann 1968 - Luis Alvarez 1967 - Hans Bethe 1966 - Alfred Kastler 1965 - Sin-Itiro Tomonaga, Julian Schwinger, Richard P. Feynman 1964 - Charles H. Townes, Nicolay G. Basov, Aleksandr M. Prokhorov 1963 - Eugene Wigner, Maria Goeppert-Mayer, J. Hans D. Jensen 1962 - Lev Landau 1961 - Robert Hofstadter, Rudolf Mössbauer 1960 - Donald A. Glaser 1959 - Emilio Segrè, Owen Chamberlain 1958 - Pavel A. Cherenkov, Il´ja M. Frank, Igor Y. Tamm 1957 - Chen Ning Yang, Tsung-Dao Lee 1956 - William B. Shockley, John Bardeen, Walter H. Brattain 1955 - Willis E. Lamb, Polykarp Kusch 1954 - Max Born, Walther Bothe 1953 - Frits Zernike 1952 - Felix Bloch, E. M. Purcell 1951 - John Cockcroft, Ernest T.S. Walton 1950 - Cecil Powell 1949 - Hideki Yukawa 1948 - Patrick M.S. Blackett 1947 - Edward V. Appleton 1946 - Percy W. Bridgman 1945 - Wolfgang Pauli 1944 - Isidor Isaac Rabi 1943 - Otto Stern

http://nobelprize.org/cgi-bin/print?from=%2Fnobel_prizes%... 10/22/08 10:37 AM http://www.phys.uu.nl/~thooft/theorist.html#aqmechanics 10

HOW to BECOME a GOOD THEORETICAL PHYSICIST

by Gerard 't Hooft

This is a web site (still under construction) for young students - and anyone else - who are (like me) thrilled by the challenges posed by real science, and who are - like me - determined to use their brains to discover new things about the physical world that we are living in. In short, it is for all those who decided to study theoretical physics, in their own time.

It so often happens that I receive mail - well-intended but totally useless - by amateur physicists who believe to have solved the world. They believe this, only because they understand totally nothing about the real way problems are solved in Modern Physics. If you really want to contribute to our theoretical understanding of physical laws - and it is an exciting experience if you succeed! - there are many things you need to know. First of all, be serious about it. All necessary science courses are taught at Universities, so, naturally, the first thing you should do is have yourself admitted at a University and absorb everything you can. But what if you are still young, at School, and before being admitted at a University, you have to endure the childish anecdotes that they call science there? What if you are older, and you are not at all looking forward to join those noisy crowds of young students ? Gerard 't Hooft (cont.) 11

Theoretical Physics is like a sky scraper. It has solid foundations in elementary mathematics and notions of classical (pre-20th century) physics. Don't think that pre-20th century physics is "irrelevant" since now we have so much more. In those days, the solid foundations were laid of the knowledge that we enjoy now. Don't try to construct your sky scraper without first reconstructing these foundations yourself.

The first few floors of our skyscraper consist of advanced mathematical formalisms that turn the Classical Physics theories into beauties of their own. They are needed if you want to go higher than that. So, next come many of the other subjects listed below. Finally, if you are mad enough that you want to solve those tremendously perplexing problems of reconciling gravitational physics with the quantum world, you end up studying general relativity, superstring theory, M- theory, Calabi-Yau compactification and so on. That's presently the top of the sky scraper. There are other peaks such as Bose-Einstein condensation, fractional Hall effect, and more. Also good for Nobel Prizes, as the past years have shown. Gerard 't Hooft (cont.) 12 LIST OF SUBJECTS, IN LOGICAL ORDER

It should be possible, these days, to collect # Languages all knowledge you need from the internet. # Primary Mathematics Problem then is, there is so much junk on the # Classical Mechanics internet. Is it possible to weed out those very # Optics rare pages that may really be of use? I know # Statistical Mechanics and exactly what should be taught to the Thermodynamics beginning student. The names and topics of # Electronics the absolutely necessary lecture courses are # Electromagnetism easy to list, and this is what I have done # Quantum Mechanics below. # Atoms and Molecules # Solid State Physics # Nuclear Physics # Plasma Physics Note that this site NOT meant to be very # Advanced Mathematics pedagogical. I avoid texts with lots of colorful # Special Relativity but distracting pictures from authors who try # Advanced Quantum Mechanics hard to be funny. Also, the subjects included # Phenomenology are somewhat focused towards my own # General Relativity interests. # Quantum Field Theory # Superstring Theory http://www.pbs.org/wgbh/nova/elegant/view-glashow.html 13

Viewpoints on String Theory

NOVA: In the '60s and '70s when there were tremendous breakthroughs in particle physics, how would you describe the relationship between theory and experiment?

Glashow: I was at the University of California in Berkeley from Sheldon Glashow roughly 1963 to 1966 as a professor, and I remember clearly that the Arthur G.B. Metcalf experimenters and the theorists were in very close contact. Luis Professor of Physics at Alvarez, who was a very distinguished and brilliant experimental Boston University and physicist, would hold a meeting at his home on a more or less weekly winner of the 1979 Nobel Prize in Physics basis to which he would invite his experimental group and a few of the local theorists, myself included. It was a very wonderful experience. Each week or every couple of weeks we would hear about the latest discoveries—there would always be one or two—and we were trying to help the experimenters interpret their data just as they were posing questions to us about what these strange effects they saw in the laboratory were. It was a very intimate relationship. NOVA - Glashow (cont.) 14

This intimacy continued and it continues today certainly at my university. But oddly there has been a new development, in which a new class of physicists is doing physics, undeniably physics, but physics of a sort that does not relate to anything experimental. This new class is interested in experiment from a cultural but not a scientific point of view, because they have focused on questions that experiment cannot address.

So this is a change. It's something that began to develop in the '80s, grew in the '90s, and today attracts many of the best and brightest physicists. It's called superstring theory and it is, so far as I can see, totally divorced from experiment or observation. If not totally divorced, pretty well divorced. They will deny that, these string theorists. They will say, "We predicted the existence of gravity." Well, I knew a lot about gravity before there were any string theorists, so I don't take that as a prediction. 15 http://vega.org.uk/video/subseries/8 Richard Feynman

The Douglas Robb Memorial Lectures

Home Programmes Science Lectures Richard Feynman

Chosen by the New Scientist - best on-line videos 2007. A set of four priceless archival video recordings from the University of Auckland (New Zealand) of the outstanding Nobel prize-winning physicist Richard Feynman - arguably the greatest science lecturer ever. Although the recording is of modest technical quality the exceptional personal style and unique delivery shine through.

Richard Feynman Video - The Douglas Robb Memorial Lectures - Part 1: Photons - Corpuscles of Light A gentle lead-in to the subject, Feynman starts by discussing photons and their properties.

Richard Feynman Video - The Douglas Robb Memorial Lectures - Part 2: Fits of Reflection and Transmission - Quantum Behaviour What are reflection and transmission, and how do they work?

Richard Feynman Video - The Douglas Robb Memorial Lectures - Part 3: Electrons and their Interactions. Feynman diagrams and the intricacies of particle interaction.

Richard Feynman Video - The Douglas Robb Memorial Lectures - Part 4: New Queries What does it mean, and where is it all leading?

Feynman gives us not just a lesson in basic physics but also a deep insight into the scientific mind of a 20th century genius analyzing the approach of the 17th century genius Newton.

For the young scientist, brought up in this age of hi-tech PC / Power Point-based presentations, we also get an object lesson in how to give a lecture with nothing other than a piece of chalk and a blackboard. Furthermore we are shown how to respond with wit and panache to the technical mishaps that are part-and-parcel of the lecturer's life.

If you are unable to access the streaming video or would like a copy of the lectures, they are available from the University of Auckland, contact [email protected], or The Tuva Trader.

Links To Other Information:

Auckland University Physics Department

Order Video These lectures are available on DVD

Feynman The official Richard Feynman website

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