and I a for space-time and (the usual) space-only RWRE on Z^ d. By Jensen's inequality, I
a≤ I q. In the space-time case, when d≥ 3+ 1, I q and I a are known to be equal on an open
set containing the typical velocity ξ o. When d= 1+ 1, we prove that I q and I a are equal only
at ξ o. Similarly, when d= 2+ 1, we show that I a< I q on a punctured neighborhood of ξ o. In
the space-only case, we provide a class of non-nestling walks on Z^ d with d= 2 or 3, and …