I have a question about my Physics Stack Exchange post: Shankar Quantum Mechanics: Proof Inverse Of Operators


I don't get why my question was flagged as homework plus a down-vote. It is not meant as homework. Also, that line beneath the imgur link was my (poorly?) proof, In the footnote: they said: see for the concepts at the end of Theorem A.1.1. There, the proof was also one line. So what I did was simply switched the symbols and asking if its a valid proof.

Kind regards


2 Answers 2


Just a hunch (I can't do any better than that, I don't know the topic nor did I vote to close), but I think the reason may be that your question looks like a "Check my work" kind of question.

I say that because the only part of the question that tries to explain/justify your work or where you are stuck just says "Would this be correct ..." and gives an equation. That sounds a lot like "check my work" or "derive this for me".

I cannot offer any real explanation for how to improve it because it's not my subject area.

The downvote may/may not be related. I would downvote it because you link to a png of fairly long explanation that is both external to the site and a long read. It would be much better to summarize what you are using from that text in the question directly so it is concise and self-contained. Feel free to link to the full text still, but the person who wants to answer shouldn't need to go somewhere else to read and extract what you are using.


Beyond your protest would you please care to explain how this is NOT a homework question? It certainly seems like a legitimate homework question that an instructor would ask.

I see your question and I immediately suspect it is taken from an assignment: you took your question out of a textbook, included a page of the textbook as an image to which you refer, you ask the community to check your work, and you provide minimal context to your question (you did not define $\mathbb{V}^n$ or even $n$).

What part of the discussion in Shankar makes you doubt your solution? Can you find similar examples in other texts, or counterexamples elsewhere for which this simple proof of yours would not work. This would show prior research and also show that you are interested in something beyond just "check my work please".


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