x BlueRobot said:
... is there a equation to calculate Strong Interaction or express it mathematically?
Yes, there are explicit but rather formal and highly complex expressions for the "Coulomb interaction" of the QCD Hamiltonian (plus other interaction terms) depending on the gauge fixing scheme. One brief overview can be found here:
http://physik.uni-graz.at/oberwoelz2012/talks/oberwoelz2012_reinhardt.pdf - slide #9.
##H_\text{C} = - \frac{1}{2} \int J^{-1}\rho J\;(D\partial)^{-1}\,\partial^{2}\,(D\partial)^{-1}\;\rho##
J is the Jacobian determinant (Fadeev-Popov determinant)
ρ is the color charge density carried by quarks and (!) gluons
(D∂)
-1 is the Coulomb kernel in the adjoint rep.
Note that in QED the covariant derivative D is replaced by ∂, simply b/c photons do not carry charge and therefore the covariant derivative is trivial in the adjoint rep. (not in the fundamental rep.). Due to the same reason J is trivial. So in QED the integral reduces to the well-known Coulomb force between electric charge densities.
In QCD ρ as well as both operators J and the Coulomb kernel (D∂)
-1 depend on the gauge fields A.
Reinhardt (and collaborators) as well as other groups analyzed the IR properties of QCD in great detail. You will find several papers on arxiv.