thierrykauf
Science Advisor
Gold Member
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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.
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.