  The standard formulation of parton physics involves light-cone correlations
of quark and gluon fields in a hadron, which leads to a widespread impression
that it can only be studied through real-time Hamiltonian dynamics or
light-front quantization, which are challenged by non-perturbative computations
with a pertinent regulator for light-cone/rapidity divergences (or zero modes).
As such, standard lattice QCD studies have been limited to indirect parton
observables such as first few moments and short-distance correlations, which do
not provide the $x$-distributions without solving the model-dependent inverse
problem. Here I describe an alternative formulation of partons in terms of
equal-time (or Euclidean) correlators, which allows to compute
precision-controlled $x$-distribution through lattice QCD simulations. This
approach is in accord with Weinberg's pioneering idea of effective field theory
as well as Wilson's renormalization group, in which the large hadron momentum
serves as a natural cut-off for light-cone/rapidity divergences and can
ultimately be eliminated through a method like the ``perfect action'' program
in lattice QCD.
