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.
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.
Well sure if each new person could make their own universe. But that is much stronger assumption than just new universes being possible.