Total gas+radiation momentum

B_out is the cumulative outward momentum flux; J_external is the impulse supplied by externally fixed matter. Gas/radiation internal exchange is not subtracted from their total.

M1 RK1

Normalization: initial total gas+radiation energy / physical c = 1.7068923037254753e+24.

P = integral(rho v + F_lab/c²) dV; gas energy includes internal and kinetic energy, not rest-mass energy.

Raw change includes physical boundary impulses and external fixed-matter forces.

Normalization by E0/c can amplify floating-point roundoff relative to initial bulk momentum. Here |P0|/(E0/c) = 93803.5; this ratio describes the change of scale, not an error bound.

Physical-c M1 should balance recorded boundary and external impulses to numerical accuracy.

FLD

Normalization: initial total gas+radiation energy / physical c = 1.7068923037254753e+24.

P = integral(rho v + F_lab/c²) dV; gas energy includes internal and kinetic energy, not rest-mass energy.

Raw change includes physical boundary impulses and external fixed-matter forces.

Normalization by E0/c can amplify floating-point roundoff relative to initial bulk momentum. Here |P0|/(E0/c) = 93803.5; this ratio describes the change of scale, not an error bound.

FLD flux is derived. Physical total momentum is a diagnostic, not an exactly conserved evolved FLD invariant.

Full gas and radiation boundary impulse is not recorded; zero placeholders were not used.

Complete boundary and external fixed-matter impulse records are unavailable.