How do we mathematically prove that the set of all possible excited determinants forms a complete basis for expanding the wavefunction (as in full configuration interaction)?

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    $\begingroup$ I think this is an interesting question, but it would benefit from your thoughts on the problem or what you have tried to arrive at a solution. @HBHSU $\endgroup$ – Tyberius Jun 4 '19 at 3:41
  • $\begingroup$ I have no idea how to prove that FCI is exact, but I am curious and cannot find the answer in my books or online. $\endgroup$ – HBHSU Jun 4 '19 at 17:40
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    $\begingroup$ A proof is given in section 2.2 of Szabo and Ostlund's Modern Quantum Chemistry. if you can't easily obtain a copy, I can summarize their argument here when I get a chance. @HBHSU $\endgroup$ – Tyberius Jun 4 '19 at 17:47
  • $\begingroup$ Ok, I see, Section 2.2.7. Thanks! $\endgroup$ – HBHSU Jun 4 '19 at 18:06