Unformatted text preview: MicroUniverse Summary MicroUniverse Summary The bricks of matter Universal Forces Quantum Mechanics A Probabilistic MicroWorld Entangled States/Phenomena The Standard Model The MTheory The Bricks of Matter The Bricks of Matter The structure of an atom – electron, proton and neutron Hundreds of relatives Antiparticles Most of the elementary particles and antiparticles are built out of quarks The electron and its relatives (leptons) do not contain quarks Universal Forces Universal Forces In macroworld the gravitational and electromagnetic are the universal forces In microworld two nuclear universal forces are added: All forces are described as an “exchange of carriers” process (Feynman diagrams) The weak force is responsible for the disintegration of particles The strong force is the force that chains quarks together (also called color force) The nuclear force between protons and neutrons is a weaker relative of the color force A Probabilistic MicroWorld A Probabilistic MicroWorld Heisenberg’s Uncertainty Principle: one cannot specify the position of a particle which moves with a welldefined energy. Dirac’s Uncertainty Principle: it is impossible to determine the energy of a particle at an exact moment in time. Consequence: particle probability waves, best demonstrated by the double slit experiment. Consequence: creation of virtual particles used to carry universal forces Entangled States/Phenomena Entangled States/Phenomena In an atom the electrons “sense” each other. A correct description of each electron must include the ensemble of electrons In microworld various phenomena occur in parallel with a certain probability. The correct description of each phenomenon must include the other parallel phenomena. An experiment (by an external observer) focuses on a specific state/phenomenon, but to obtain the same result theoretically one must consider the entanglement with the other states/phenomena. Alternative histories Alternative histories In 1940s Richard Feynman gave another interpretation of quantum mechanics – the alternative histories. In the Double Slit experiment one can say that the electrons follow with a certain probability every possible classical trajectory and interferences appear when these trajectories intersect each other. MacroWorld Determinism MacroWorld Determinism External observers destroy the entanglement of states/phenomena. In the macroworld no states /phenomena can be totally isolated from external cosmic particles and therefore we cannot see any entanglement. However, at the Universal scale we might be able to assume that no external observers exist and therefore the “many worlds” interpretation of quantum mechanics makes sense. The Standard Model The Standard Model Bricks: 24 = 6 quarks of 3 colors + 6 leptons Antibricks: 24 Universal forces / carriers:
gravitation / gravitons electromagnetism / photons weak nuclear / weakons strong nuclear / gluons Limitations of the Standard Model Superstrings Superstrings Particles are superstrings resonances The basic idea is that particles correspond to resonances (i.e. distinct frequencies of vibration of superstrings) They are 1020 times smaller than a proton, or 1036 cm. Superstrings are extremely small Complicated motions No infinities if calculated in 10 dimensions. M Theory M Theory Recently there were 5 competing 10dimensional superstrings theories Edward Witten proved the 5 theories to be equivalent and related to an 11dimensional MTheory Superstring cosmology assumes that our 4 dimensional spacetime corresponds to a 4 dimensional brane vibrating in 5 dimensions. Contemporary experiments performed with the most powerful supercolliders will try to produce the additional particles predicted by the Mtheory The Mtheory has not only superstrings, but also 2,3.. etc dimensional branes (multidimensional vibrations). ...
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