# Withdrawn question

I have just noticed that this question, which I have found quite exciting (and so have at least 14 other users who have voted for it) has been withdrawn by the OP. Is there any way to figure out the reason for that?

• It's now undeleted. – Todd Trimble Sep 28 '18 at 17:01
• I think all you can do is ask. The site mods have no behind-the-scenes insight here. – Todd Trimble Sep 28 '18 at 17:33
• @ToddTrimble This problem has imposed by someone to me for doing research on it. Today he told me that he did not allowed me to present the problem to others. So I deleted the question and informed him. Sorry for this mistake, but I ask the moderators to agree with my decision. – Mostafa Sep 28 '18 at 20:55
• @Mostafa Let me take a look. In general we discourage self-deletions, but there can be extenuating circumstances. Please check very carefully next time -- thanks. – Todd Trimble Sep 28 '18 at 22:02
• Okay, I've deleted it. Please know that I am loath to delete especially those questions that have already received upvoted answers. Luckily it had not been answered yet. – Todd Trimble Sep 28 '18 at 22:04
• @Mostafa In case you aren't aware of it, this problem has appeared in print before. Yuster has a paper on it and attributes it to Caro pdfs.semanticscholar.org/6f3b/… In particular Alon and Lovasz and other mathematicians from that circle have looked at this problem. It still remains open, and maybe it hasn't had much visibility, but I though of letting you know that it has a small history. – Gjergji Zaimi Sep 28 '18 at 23:46
• @GjergjiZaimi: The problem considered by Yuster (following Alon et al) is actually subtly different: he seeks a vector $v\in\mathbb F_p^n$ such that all coordinates of $Av$ are non-zero, and all coordinates of $v$ are in $\{0,1\}$. – Seva Sep 29 '18 at 10:52
• I think moderators should ask the user (hoping there is a way) for reason to delete the question before reversing that delete done by user... I think to undelete with out inquiring about the reason seems to be not a good idea.. This does not mean I think well received question can be deleted... – Praphulla Koushik Sep 29 '18 at 13:02
• @GjergjiZaimi To add to my previous comment. At the end of page 2, Yuster writes: "The first nontrivial family of graphs for which the answer to Problem 1.2 has been shown true is the family of trees." If we interpret Problem 1.2 your way, then Problem 1.2 is trivial for the trees: take a leaf away, find an appropriate vector $x\in\mathbb F_p^{n-1}$ for the resulting graph, and you will always be able to append a coordinate to it for the leaf that has been taken away to keep the property in question. – Seva Sep 29 '18 at 17:22
• @GjergjiZaimi: Quoting from an e-mail message I received from Yuster, Well, Zaimi is right that the problem 1.2 is for any vector $x$ (not just a 0-1 vector) see the definition in line 4 of Page 2. But you are right that since I quote Caro and Jacobson, then the special case where we require 0-1 is what they looked at in that paper. Also, my proof uses only 0-1 in the vector. In any case, as far as I know, even the less restrictive version (where you allow $x$ to be arbitrary) is open. – Seva Sep 30 '18 at 1:40