I personally don't understand the closure of this question: in its current form, it's a thoughtful, conceptual question that happens to be phrased in a mathematical way. If you're a person who thinks the closure/deletion was a good decision, I'd like to understand your reasoning. If, on the other hand, you're a person who agrees with me, I'd like a million upvotes. And also a pony.
I think this is a typical case where an initial close vote encouraged others, in a snowball effect. We've seen a very similar occurrence recently here. This is worrying and should be reversed.
I think much of this stems from a misguided urge to help the community, the thinking being that if a question already has close votes, it must be bad; hence anybody that can add close votes should do so, to 'get rid of the trash' faster. But the number of close votes required is set at 5 for a good reason, and this kind of thinking lowers the number to 1 or 2, making results much less reliable.
I would propose that:
- People shouldn't close questions as duplicates unless they fully understand both questions, and their answers.
- People shouldn't close questions that contain equations as 'homework' unless they know how to answer the question themselves.
- People shouldn't close QM questions as 'unclear' unless they can confidently answer clear QM questions. (The same going for GR, QFT, etc.)
Let me try to explain why I voted to close, and why I chose not to answer.
The question, as it is phrased now, seems to ask about very specific aspects of the AKLT model. However, in order to be able provide a specific answer (which does not form a full explanation of the AKLT model), the OP would have to supply sufficient information on their prior knowledge, i.e., lay out the overall scenario considered and their understanding of it to an extent which allows to answer the question in a concise way. The way the question is phrased now, this is not the case: E.g. the screenshot from the paper is far from helpful for an answer and does not really explain which part of the construction the OP understands (also to me, such screenshots to some extent seem like a low-effort sign), one would have to basically explain the whole AKLT model, which would be a disproportional effort compared to the effort which went into the question.
Now I'm not generally against writing a detailed explanation of the AKLT model, but I feel it is slightly lost effort if it is posted as an answer to a question which is seemingly concerned with details -- another poster with questions about the AKLT model will likely not see that the answer contains the full explanation of the model, rather than just assume it is an answer to a very specific question. Now given the apparent current interest in the AKLT model, I might consider writing such an answer for a question asking about the AKLT model in general. (The downside seems to me that as such, such a question -- which would basically just state "Could someone please explain the AKLT model?" might (rightfully) be badly received here.)