From the yellow paper; for a block to be accepted as valid, an 8 byte number, n_rand, must be found that satisfies equation 253:
My interpretation is that d is the dataset - a value cryptographically derived from the number of previous blocks. From this, the Mixhash is calculated in the
Why are the dataset and MixHash values required?
If the network were to agree to accept the
PoW function with d set to 0, wouldn't the system still be cryptographically dependent on valid state transistions, as there must be consensus on H_
n? Would the system not, therefore, still work?