I Understanding Spin-2 Bosons & Graviton Theory of Gravity

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The discussion centers on the nature of spin-2 bosons, particularly gravitons, and their relationship to gravity as described by General Relativity (GR). It highlights that gravitons, as spin-2 particles, are associated with tensor fields, distinguishing them from spin-1 bosons like photons and gluons, which are vector fields, and spin-0 bosons like the Higgs. The conversation also addresses the current limitations of graviton theories in fully reproducing GR, noting that they may only approximate Newtonian gravity. Participants express confusion over the mathematical descriptions and implications of these theories, emphasizing the need for clearer explanations. Ultimately, the thread underscores the complexity of integrating quantum mechanics with gravitational theory.
  • #31
The electromagnetic field is an antisymmetric rank two tensor field therefore (not but) it is a vector field. Just count the number of components. Antisymmetric means its diagonal is zero. There remains one triangular block which has 3 + 2 + 1 = 6 independent components. These are the electric field and magnetic field vector.
Gravity is a symmetric rank two tensor, it's diagonal is not zero. It therefore has 6 (upper triangular block) + 4 (diagonal) = 10 independent components (the metric tensor). A spin n field has (n(
The solutions to Einstein's equations are NOT waves in general (no pun) since these are non-linear equations. But if you neglect nonlinear terms you can obtain wave-like solutions, those were detected recently. Nonlinear in this context means the graviton creates and is subject to gravitational attraction. That makes gravity similar to a non-Abelian gauge interaction such as QCD. In contrast EM is an Abelian gauge theory because the photon has no charge and therefore cannot interact with the electrons that produced it.
 
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  • #32
Of course, photons interact with electrons. That's how we detect them all the time.

Also your counting is misleading since both the photon and the graviton are massless fields and thus they have only two physical polarization states (except for scalar fields which have of course only 1).
 
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