Maybe I'm missing something, please correct me if I'm wrong.
In the event of an empty mempool (and with a 0 btc subsidy), for a miner to obtain a profit would be necesary to wait until enough new fee paying transactions enter into the mempool, otherwise keep mining at a loss.
Isn't this the same as saying
"In order for a transaction to be added to the blockchain, a sufficient fee must be provided"
In the event of an empty mempool (and with a 0 btc subsidy), for a miner to obtain a profit would be necesary to wait until enough new fee paying transactions enter into the mempool, otherwise keep mining at a loss.
Isn't this the same as saying
"In order for a transaction to be added to the blockchain, a sufficient fee must be provided"
It's a matter of whether we're talking about the fee per transactions, or the total fees that a miner can claim when he builds a block. In the case where R->0, you could post a TX with a generous fee1 but it still won't make sense for a miner to attempt to mine a block just for you. You'd need to wait until others have broadcast similarly fee paying transactions, in order to push the block size into the "profitable" zone in Mengerian's graph:
1There would be some fee that you could pay to get your TX mined, but it would be vastly more costly than waiting for other fee-paying transactions to begin re-filling the miners' mempools.