Teoretisk fysik. Institutionen för fysik Helsingfors Universitet Paul Hoyer - PDF

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Teoretisk fysik 1 Institutionen för fysik Helsingfors Universitet Paul Hoyer Presentation av de fysikaliska vetenskaperna (3 sp, 1 sv) Kursbeskrivning: I kursen presenteras de fysikaliska

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Teoretisk fysik 1 Institutionen för fysik Helsingfors Universitet Paul Hoyer 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. Bakgrund 2 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 Stockholm, Santa Barbara,...) Teoretisk fysik är egentligen en metod (jfr. experimentell och numerisk fysik) som täcker alla områden av fysiken: Kondenserad materie Optik Kärnfysik Högenergifysik,... Kring nyttan av teoretisk fysik 3 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. The QED experience 4 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 0.328α 2 /π 2. 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 α 2 ; and when improved, increases the accuracy of the α 2 term, yielding a rough estimate of α 3 and beyond? g µ /2 = (8)(3) e /2m µ 6 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 for the discovery of the mechanism of spontaneous broken symmetry in subatomic physics for the discovery of the origin of the broken symmetry which predicts the existence of at least three families of quarks in nature 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 Nobel Prizes in theoretical physics, Yoichiro Nambu, Makoto Kobayashi, Toshihide Maskawa Albert Fert, Peter Grünberg John C. Mather, George F. Smoot Roy J. Glauber, John L. Hall, Theodor W. Hänsch David J. Gross, H. David Politzer, Frank Wilczek Alexei A. Abrikosov, Vitaly L. Ginzburg, Anthony J. Leggett Raymond Davis Jr., Masatoshi Koshiba, Riccardo Giacconi Eric A. Cornell, Wolfgang Ketterle, Carl E. Wieman Zhores I. Alferov, Herbert Kroemer, Jack S. Kilby Gerardus 't Hooft, Martinus J.G. Veltman Robert B. Laughlin, Horst L. Störmer, Daniel C. Tsui Steven Chu, Claude Cohen-Tannoudji, William D. Phillips David M. Lee, Douglas D. Osheroff, Robert C. Richardson Martin L. Perl, Frederick Reines Bertram N. Brockhouse, Clifford G. Shull Russell A. Hulse, Joseph H. Taylor Jr Georges Charpak Pierre-Gilles de Gennes Jerome I. Friedman, Henry W. Kendall, Richard E. Taylor Norman F. Ramsey, Hans G. Dehmelt, Wolfgang Paul 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.) It should be possible, these days, to collect all knowledge you need from the internet. Problem then is, there is so much junk on the internet. Is it possible to weed out those very rare pages that may really be of use? I know exactly what should be taught to the beginning student. The names and topics of the absolutely necessary lecture courses are easy to list, and this is what I have done below. Note that this site NOT meant to be very pedagogical. I avoid texts with lots of colorful but distracting pictures from authors who try hard to be funny. Also, the subjects included are somewhat focused towards my own interests. LIST OF SUBJECTS, IN LOGICAL ORDER 12 # Languages # Primary Mathematics # Classical Mechanics # Optics # Statistical Mechanics and Thermodynamics # Electronics # Electromagnetism # Quantum Mechanics # Atoms and Molecules # Solid State Physics # Nuclear Physics # Plasma Physics # Advanced Mathematics # Special Relativity # Advanced Quantum Mechanics # Phenomenology # General Relativity # Quantum Field Theory # Superstring Theory 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 roughly 1963 to 1966 as a professor, and I remember clearly that the experimenters and the theorists were in very close contact. Luis Alvarez, who was a very distinguished and brilliant experimental physicist, would hold a meeting at his home on a more or less weekly 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. Sheldon Glashow Arthur G.B. Metcalf Professor of Physics at Boston University and winner of the 1979 Nobel Prize in Physics 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. Richard Feynman 15 The Douglas Robb Memorial Lectures Home Programmes Science Lectures Richard Feynman Chosen by the New Scientist - best on-line videos 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? Videos Search advanced Upload 16 THE PLEASURE OF FINDING THINGS OUT (part 1 of 5) From: melah65 Added: June 10, 2007 (more info) Subscribe Why do we do science? Beyond altruistic and self-agg... URL Embed object width= 425 height= 344 param name= m More From: melah65 Related Videos THE PLEASURE OF FINDING THINGS OUT (part 2 of 5) 10:05 From: melah65 Views: 35,643 feynman lecture 01:02 From: wangjie123 Views: 83,756 Rate: Richard Feynman 373 ratings Views: 80,057 Share Favorite Playlists Flag Send Video MySpace Facebook more share options Richard Feynman explains the feeling of confusion 00:43 From: pablompa Views: 43,221 THE PLEASURE OF FINDING THINGS OUT (part 3 of 5) 10:01 From: melah65 Views: 28,097 BBC interview with Feynman (uncertainty) 00:53 From: nebnoid Views: 35,550 Commentary Statistics & Data Promoted Videos Video Responses: 0 Text Comments: 121 Video Responses (0) Post a Video Response The Late Late Show - Fe... New Scientis t Hallowee New York City's Village. Want To Be In A Bollywo. THEORETICAL PHYSICS D epartment of Physics Faculty of Science 17 P. O. B o x 6 4 ( G u s t a f H ä l l s t r ö m i n k a t u 2 ) F I U N I V E R S I T Y O F H E L S I N K I F I N L A N D Suomeksi På svenska In English Theoretical Physics LOCATION AND CONNECTIONS INFONI: Current Old numbers CONTACT INFORMATION: Department of Physics P.O. Box 64 (Gustaf Hällströmin katu 2) FIN University of Helsinki FINLAND Phone: +358-(0) Fax: +358-(0) (to secretary Mrs. Liisa Koivisto): Theoretical Physics is a field of study separate from Physics. The compulsory lectures on mechanics, electrodynamics, quantum physics and statistical physics, required for the Bachelor or Master degrees, teach the basics about the laws of physics. Learning the skills needed for analytic and numerical computations is emphasized. Special courses in particle physics, cosmology, general relativity, mathematical physics and solid state physics are also offered on a regular basis. The current research fields in theoretical physics are particle physics, cosmology, space physics, materials physics, and nanoscience. Professors 18 19 20 21
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