What can we compute from the standard model?
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It is believed that lattice QCD would converge with indefinitely
refined and increasing lattice size to true QCD. If this holds,
all proton properties can be calculated in principle from sufficiently
accurate calculations in a lattice QCD+QED. QCD alone should suffice
for the mass; QED is needed for the electromagnetic form factors.
But since the confinement mechanism is not really understood,
it is difficult to tell whether this is really the case.
Scalar Phi^4 theory exists perturbatively, but the lattice
approximations seem to converge instead to a trivial theory.
This shows that some doubt is appropriate.
The standard model is very poorly understood on the level of bound
states. Only high energy scattering is well developed in theory, and
well-checked by experiment. So people do not expect surprises in the
low energy (confinement) regime, but good techniques for analyzing
the consequences of the standard model in this regime are currently
missing.