What is Graviton: Definition and 158 Discussions

In theories of quantum gravity, the graviton is the hypothetical quantum of gravity, an elementary particle that mediates the force of gravity. There is no complete quantum field theory of gravitons due to an outstanding mathematical problem with renormalization in general relativity. In string theory, believed to be a consistent theory of quantum gravity, the graviton is a massless state of a fundamental string.
If it exists, the graviton is expected to be massless because the gravitational force is very long range and appears to propagate at the speed of light. The graviton must be a spin-2 boson because the source of gravitation is the stress–energy tensor, a second-order tensor (compared with electromagnetism's spin-1 photon, the source of which is the four-current, a first-order tensor). Additionally, it can be shown that any massless spin-2 field would give rise to a force indistinguishable from gravitation, because a massless spin-2 field would couple to the stress–energy tensor in the same way that gravitational interactions do. This result suggests that, if a massless spin-2 particle is discovered, it must be the graviton.

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  1. K

    The exchange particle for gravity: the graviton?

    As far as I can see, the exchange particle involved in gravitational forces is the graviton. However, in the markscheme for both the original and revised EDEXCEL A-Level Physics PHY3 Topics Paper (topic C) it states that it is the photon. Which is correct, or are both correct? Why is there this...
  2. Antonio Lao

    Quantized Structure of a Graviton

    The quantum of gravity is called graviton. And using symbols for quanta of length, \psi_E and \psi_B and quanta of linear momentum, \phi_E and \phi_B, the time independent structure of graviton, G^{-} is given by G^{-} = \psi_E \times \phi_E \cdot \psi_B \times \phi_B
  3. wolram

    Is General Covariance the Key to Understanding Gravity?

    am i correct in thinking that the graviton is out of favor, along with other "things", that could explain gravity?
  4. F

    Graviton Questions: How Do Gravitons Pass Through Objects?

    Say a penny is falling to Earth from a height, Gravitons shoot up from the earth’s surface grabbing the penny and pulling it down to earth. Fair enough. Now imagine that directly above that penny is another penny, also falling to earth, the gravitons pulling at this second penny must have...
  5. D

    Why do we need the graviton?

    I'm under the impression that general relativity with it's curved space-time as a description of the gravitational force is commonly accepted in the physics-community. However there is another interpretation of the gravitational force in terms of a particle, the graviton. This seems to me as...
  6. J

    Exploring the Possibility of Graviton Existence in Loop Quantum Gravity

    Does Loop Quantum Gravity support the existence of graviton? I can't imagine how is it possible that graviton can exist if it is to agree with GR, since GR says that gravity is merely a curvature of spacetime and is isn't a force. GR => SR => time dilation & length contraction =>> how does...
  7. G

    Can Graviton Mass Be Calculated Using Universal Constants?

    "Weighing the Graviton" 9^9 (387,420,489) Combinations/Equations http://physics.nist.gov/cuu/Constants/ [UPDATED 1998 CODATA-NIST VALUES] The Primary Universal Base Unit Values 1) mass… (hc/G)^1/2 = 5.4563026(39) x 10^-8 kg 2) length… (hG/c^3)^1/2 = 4.0507625(38) x 10^-35 m 3) time…...
  8. E

    Calculating Gravitons using Spin Wave Equation and Constraints (1): Explained

    Could it be calculated that way?..for example take a gravitational classic wave DHab=0, then by proposing a plane wave solution like that Hab=AabExp(KaXb) being Aab a tensor we would have the constraint.. AabKaXb=0 or expressed in momentum..AabPaPb=0 (1) so i think it would by proposing a...
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