A causal signal is any signal that is zero before time 0 (see §5.3).
Only moving particles have momentum, so if we ignore the p² bit on the grounds that is zero, we get back to the rest mass equation E=m.
We consider differentiated and non-differentiated satellites with both free (that is no horizontal stresses) and rigid (that is zero velocity) boundary conditions at the body surface.
This contrasts with the case of unbounded provers, where Goldreich and Krawczyk (ICALP '90, SICOMP '96) exhibited a protocol that is zero knowledge under the GMR definition, but for which the sequential composition of 2 copies is not zero knowledge.
I take i, I delete the first row, I delete the first column, I get this two-by-two determinant here and I get zero times zero, that is zero, minus zero times one.
They point out that it is easier to explain a cosmological constant with an extremely large value or one that is zero than to understand how it could be close to zero, as in the models for the missing energy.
