《哥本哈根学派》PPT课件

Niels Bohr (1885-1962)The Nobel Prize in Physics 1922 for his services in the investigation of the structure of atoms and of the radiation emanating from them Niels Bohrs first epoch-making papers on the quantum theory of atomic structure were published in 1913 on Philosophical Magazine Establishment of Institute for Theoretical Physics of the University of Copenhagen 1922 Niels Bohr InstituteOn Niels Bohrs 80 birthday - October 7, 1965 - the Institute for Theoretical Physics of the University of Copenhagen will be given the name it has had unofficially for many years: The Niels Bohr Institute It is the purpose of these lines to present a short survey of the development of the Institute, so intimately connected with Bohrs life-work as a physicist. 哥本哈根学派 Copenhagen Interpretation of Quantum Mechanics The Copenhagen interpretation is the mainstream interpretation of quantum mechanics; it was worked out by Niels Bohr and Werner Heisenberg while collaborating in Copenhagen around 1927. The interpretation attempts to answer some perplexing questions which arise as a result of the wave-particle duality in quantum mechanics. Bohrs complementarity http:/www.upscale.utoronto.ca/GeneralInterest/Harrison/Complementarity/CompCopen.pdf What is Quantum Mechanics?Quantum mechanics is a theory. It is ourcurrent “standard model” for describingthe behavior of matter and energy at thesmallest scales (photons, atoms, nuclei,quarks, gluons, leptons, ).Like all theories, it consists of amathematical formalism, plus aninterpretation of that formalism.However, quantum mechanics differs from other physical theories because, while its formalism of has been accepted and used for 80 years, its interpretation remains a matter of controversy and debate. Like the opinions of the 6 blind men, there are many rival QM interpretations on the market.QuantumMechanics H eisenbergs uncertainty principle:Wave-particle duality, conjugate variables, e.g., x and p, E and t;The impossibility of simultaneous conjugate measurements Borns statistical interpretation: The meaning of the wave function y as probability: P = y y*;Quantum mechanics predicts only the average behavior of a system.Bohrs complementarity:The “wholeness” of the system and the measurement apparatus; Complementary nature of wave-particle duality: a particle OR a wave;The uncertainty principle is property of nature, not of measurement.H eisenbergs knowledge interpretation:Identification of y with knowledge of an observer;y collapse and non-locality reflect changing knowledge of observer.H eisenbergs positivism: “Dont-ask/Dont tell” about the meaning or reality behind formalism;Focus exclusively on observables and measurements. The Copenhagen Interpretation QuantumMechanics double-slit experimentThe rules of quantum mechanics tell you statistically where the particles will hit the screen, and will identify the bright bands where many particles are likely to hit and the dark bands were few particles are likely to hit. However, for a single particle, the rules of quantum mechanics cannot predict where the particle will actually be observed. What are the rules to determine where an individual particle is observed? What happens to the particle in between the time it is emitted and the time that it is observed? The particle seems to be interacting with both slits and this appears inconsistent with the behavior of a point particle, yet when the particle is observed, one sees a point particle. What causes the particle to appear to switch between statistical and non-statistical behaviors? When the particle is moving through the slits, its behavior appears to be described by a non-localized wave function which is traveling through both slits at the same time. Yet when the particle is observed it is never a diffuse non-localized wave packet, but appears to be a single point particle.The questions this experiment poses are The act of measurement causes an instantaneous collapse of the wave function. This means that the measurement process randomly picks out exactly one of the many possibilities allowed for by the states wave function, and the wave function instantaneously changes to reflect that pick.The Copenhagen interpretation answers these questions as follows:The probability statements made by quantum mechanics are irreducible in the sense that they dont just reflect our limited knowledge of some hidden variables. In classical physics, probabilities were used to describe the outcome of rolling a die, even though the process was thought to be deterministic. Probabilities were used to substitute for complete knowledge. By contrast, the Copenhagen interpretation holds that in quantum mechanics, measurement outcomes are fundamentally indeterministic. Physics is the science of outcomes of measurement processes. Speculation beyond that cannot be justified. The Copenhagen interpretation rejects questions like where was the particle before I measured its position as meaningless. Copenhagen Conference 1929 Copenhagen Conference 1930 Copenhagen Conference 1932 Many physicists have subscribed to the null interpretation of quantum mechanics summarized by Feynmans famous dictum: Shut up and calculate! 1930年代中期，研究发现了许多中子诱发的核反应。玻尔提出了原子核的液滴模型，很好地解释了重核的裂变。 玻尔 “对应原理”，即宏观与微观理论，以及不同领域相似问题之间的对应关系。对应原理指出经典理论是量子理论的极限近似,而且按照对应原理指出的方向,可以由旧理论推导出新理论。这在后来量子力学的建立发展过程中得到了充分的验证。 Copenhagen: a (Re) Play In 1941 the German physicist Werner Heisenberg made a strange clandestine trip to Copenhagen to see his Danish counterpart, Niels Bohr. Their work together on quantum mechanics and the uncertainty principle had revolutionized atomic physics. But now the world had changed and the two men were on opposite sides in a world war. Why Heisenberg went to Copenhagen and what he wanted to say to Bohr are questions that have vexed historians ever since. Scientists and historians have argued ever since about why Heisenberg went, and what the two men said. Copenhagen: a (Re) Play Copenhagen, a thought-provoking drama by Michael Frayn, retraces their journey through the mysteries of the world around us - and on into the even stranger mysteries of the world within. The play reenacts the 1941 visit of Werner Heisenberg, who was then in charge of the Nazi nuclear power program, to Niels Bohr, his mentor, and collaborator in creating quantum mechanics, complementarity, and the uncertainty principle, in German - occupied Denmark. The third long-winded character is Bohrs wife Margrethe. Copenhagen: a (Re) Play In Michael Frayns ambitious, fiercely intelligent, and daring new play Heisenberg and Bohr meet once again to discuss the intricacies of physics and to ponder the metaphysicalthe very essence of human motivation.Frayn does not pretend to solve the mystery: he just replays in many different ways (interpretations) what could have happened in that meeting. Nobody alive actually knows what was said. The same uncertainty that was proven by the two scientists to be unavoidable in physics, pervades every aspect of this play. We do know that something terrible happened between the two friends, which all but destroyed their relationship for the rest of their lives. Copenhagen: a (Re) Play Speculation about the intent of Heisenbergs call has been rife among physicists and historians ever since the visit became known. Did Heisenberg want to warn Bohr and through him the Allies that the Germans were working on an atomic bomb and if so to what end? Was it to convey the impression that he was about to succeed and that the Allies should therefore make peace with Hitler, or was it say that he had given up on an impossible task and that therefore the other side shouldnt try either? Did Heisenberg want to find out whether the Allies were actually working on an A - bomb? Or did he hope to convince Bohr to issue a joint declaration with him denouncing efforts to build a bomb and pledging not to work on it? Copenhagen: a (Re) Play The Play does not answer, but examines such questions, opening the facts to all possible interpretations. The Tony Awardwinning play that soars at the intersection of science and art, Copenhagen is just an explosive re-imagining of the mysterious wartime meeting between the two Nobel laureates to discuss the atomic bomb. The Nobel Prize in Physics 1975Aage Niels Bohr 1/3 of the prize for the discovery of the connection between collective motion and particle motion in atomic nuclei and the development of the theory of the structure of the atomic nucleus based on this connection Ben Roy Mottelson Leo James Rainwater Solvay 1927