Graviton

thumb|Interactions between elementary particles in the Standard Model, including the hypothetical Graviton. In theories of quantum gravity, the graviton is the hypothetical, Massless particle massless, elementary particle that mediates the force of gravitational interaction. The unsolved mathematical problem of renormalization in general relativity might require string theory to explain the graviton. Even though gravitational waves have been detected, gravitons as the quantum components of such waves would be vastly more difficult to detect. Quotes Weinberg especially stressed the strong constraints of the S-matrix describing interaction of massless particles, which are equivalent to Gauge fixing gauge invariance requirements in the more familiar theoretical context. He showed how one could derive, for massless vector particles, both Maxwell's equations and conserved currents; that for Spin (physics) spin greater than 2, there is no interesting low frequency theory possible at all (there being no conserved static quantifies corresponding to Electric charge charge or mass) while for spin 2, the low frequency form of the interactions implies amongst other things, the equivalence principle (universality of matter-graviton vertices) for all systems including the gravitons themselves. Stanley Deser, Peter van Nieuwenhuizen, and David G. Boulware, Chapter. Uniqueness and nonrenormalizability of quantum gravitation General relativity and gravitation 1975 1–18 (quote from p. 4; pdf book text at chern.ch) I spoke about a question that I have often thought about but never been able to answer. Is it in principle possible to observe individual gravitons? A slightly different version of the question asks whether we can design a thought-experiment to test the theory of quantum gravity. The talk describes three different kinds of graviton-detectors that might answer the question positively if any of them can be demonstrated to work. The three kinds are: first, a LIGO-style detector, measuring the change in the distance between two objects caused by a low-energy graviton passing by; second, a gravito-electro detector, observing an electron or other particle kicked out of an atom by a medium-energy graviton; third, a coherent photon detector, observing the coherent mixing of electromagnetic and gravitational fields at high energies. Freeman J. Dyson, Introduction Birds and Frogs: Selected Papers of Freeman Dyson, 1990–2014 World Scientific Publishing Company 2015 9789814602877 https://books.google.com/books?id=PK5EDwAAQBAJ&pg=PA12 1–12 (376 pages; quote from p. 12) Any correct theory must include Einstein’s general-relativistic theory of gravitation as an approximation, and we know that when quantum mechanics is brought in as well, the gravitational force must be carried by a quantum, which we call the graviton, and many properties can be readily deduced from Einstein's theory. (For example, it is electrically neutral, it travels with the speed of light like the photon, and it has two units of a certain quantity called “Quantum spin spin.”) Murray Gell-Mann, offprint of Chapter. Is the Whole Universe Composed of Superstrings? Festi-Vak Festschrift for Val Telegdi North-Holland Amsterdam 1988 119–140 https://inspirehep.net/files/f519d0b80e3061b7b3f702de80d2a5e0 (talk given at the Michelson-Morley Centennial Symposium, October 1987; offprint pages 1–20; quote from p. 12) External links Category:Quantum mechanics