Re: Why can't we beat 2nd Thermo with low f-ratio?

I believe the question you raise is explained by the etendue invariant
theorem discussed most thoroughly in non-imaging optical text books.
The theorem can be stated in optical terminology as: "The density of
rays in phase space is invariant through the optical system". For your
contention to be true, this theorem would have to be shown to be false.
The proof of this theorem is carried out in the appendix A of Non
Imaging Optics by Winston, Minano, and Benitez. The proof has been
accomplished several ways, including using an analogy from Hamiltonian
Mechanics. The proof given in the non imaging text is based directly
on optical details and thus doesn't need the second law of
thermodynamics to explain it. The LT2 doesn't "conspire" to restrict
the phenomenon you speak of.

Perhaps the complex math involved in these proofs has made it simpler
to draw analogies such as the one regarding LT2's limit to explain it
in terms people are more familiar with rather than rigorous proofs.

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