If the time and capital investment to create and exploit a new universe - which potentially includes traveling into that universe yourself - is not large relative to the size of a single universe, then there is an indefinitely repeatable, extremely high-payoff investment you can make, which can outpace any population growth less than that interest rate. Of course you do have to be able to exploit the descendant universe - including to the extent of using those new resources to create more descendant universes - which again would be satisfactorily handled by traveling into it.