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Martin Sleziak
Martin Sleziak
5:54 AM
1
Q: Reordering entries of integer symmetric matrix via linear combinations into a symmetric matrix with all its eigenvalues positive with det condition

HvjurthukSuppose we have a symmetric matrix $M\in\operatorname{Sym}{M}_{n}(\mathbb{Z})$ having some negative eigenvalues. Are there algorithms filling the entries of a (possibly) bigger symmetric matrix $M'\in\operatorname{Sym}{M}_{m}(\mathbb{Z})$ whose entries $M'_{i,j}$ are obtained with the same formul...

computational-number-theory integer-matrices reordering-of-entries division-of-determinants selection-of-eigenvalues
In the past, there were a few questions introducing four or five new tags.
 
 
3 hours later…
Martin Sleziak
Martin Sleziak
9:02 AM
@LSpice If you wish, you can test this for yourself. The question "Are there locally compact groups which have no compact open subgroups and no discrete infinite cyclic subgroups?" contains a link to this post: Discrete cyclic subgroup.
But at the moment, no linked questions are shown in the sidebar.
If you add a comment with a link to the post, the list of linked questions will be displayed. If you remove the comment a few minutes later, the list of linked questions will remain there (even after the removal of the comment).
Basically the proces I tried to explain here: Retroactively add linked questions. (I tried to give relatively detailed explanation in the footnote.)
Typically I used to write something like: This is a temporary comment - in order to update the list of linked questions: [Discrete cyclic subgroup.](https://mathoverflow.net/q/30092#34005).
> This is a temporary comment - in order to update the list of linked questions: Discrete cyclic subgroup..
 
 
4 hours later…
LSpice
LSpice
1:30 PM
@MartinSleziak Sorry, what would I be testing?
 
Martin Sleziak
Martin Sleziak
1:50 PM
Hi, @LSpice - see the message I've replied to.
Jul 31 at 12:35, by LSpice
@MartinSleziak Good question! I don't know. But also conversely, will a question disappear from the linked questions link, once it appears, if the comment or body text that linked to it is removed? Anyway, one way or the other, it's linked!
You have asked whether the question remains in the list of the linked questions after the comment is removed.
So if you want to check whether it indeed works the way I mentioned here and in the linked post on meta.
Jul 31 at 17:47, by Martin Sleziak
@LSpice Maybe I should clarify. If a question is linked only in a comment - it will not stay among the linked question. But in cases like this, it is linked in the question, too - so after removal of the comment, the question stays in the list.
5 hours ago, by Martin Sleziak
Basically the proces I tried to explain here: Retroactively add linked questions. (I tried to give relatively detailed explanation in the footnote.)
 
LSpice
LSpice
2:13 PM
@MartinSleziak Ah, sorry, I didn't realise that little up-left arrow was an indicator of a reply. I have tried it, and it seems to work as you say.
 
Martin Sleziak
Martin Sleziak
2:28 PM
@LSpice I'm glad to hear that.
Since we talked about this, I decided to ask whether you want to make an "experiment" to check this.
 

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