Carl Mummert

Marshall University

science.marshall.edu/mummertc

Age: 36

I work in mathematical logic. My main areas of interest are arithmetic, reverse mathematics, computability, and proof theory.
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awarded elementary-set-theory
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comment Requests for Reopen & Undeletion Votes, etc. (volume 01/2015 - ) [current version]
@Git Gud: I don't think the reputation is the issue - it's just a few points. I do think that, as a general principle, a request to re-open a deleted question by someone who answered the question comes across as less objective than a request by someone who has not previously interacted with a question.
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comment Requests for Reopen & Undeletion Votes, etc. (volume 01/2015 - ) [current version]
@Git Gud: questions like that have been unacceptable for some time - that is why the "no context" closure reason (used on that question) was added in the first place!
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comment Why close old questions with accepted answers using the "no context" reason?
The key to the stagnancy issue is to ignore the claims by SE.com that this site is primarily an archive. A few questions may be useful as an archive, but it seems clear from experience that the main benefit of this site (math.SE) is to provide answers to the OP of each question. Not only are old questions not re-exposed, the search feature is nearly useless for mathematics. @Bill Dubuque
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comment Requests for Reopen & Undeletion Votes, etc. (volume 01/2015 - ) [current version]
@Git Gud: if we don't know how the question can be made acceptable, short of deleting the text and rewriting it from scratch, I don't see a strong argument to undelete the question?
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comment Requests for Reopen & Undeletion Votes, etc. (volume 01/2015 - ) [current version]
To Najib Idrissi: the question was already edited by Famous Blue Raincoat. But it is not normal practice on this site to significantly change a question - that is up to the OP. Which is why it is relevant (@Git Gud) that the OP has long departed this site.
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comment Requests for Reopen & Undeletion Votes, etc. (volume 01/2015 - ) [current version]
To include the full story, we should mention that you answered the question, and the OP has been absent since the end of 2013. Also, the question was closed the day it was asked, so it seems inaccurate to refer to changing standards - it seems like a question that had sat closed for more than a year, and finally people got around to cleaning it up.
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comment Is my interpretation of the definition of free variable correct?
@DanielV: in the formula "$x = x$", $x$ is certainly a free variable. I am not sure what you mean that there is no such thing.
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answered Is my interpretation of the definition of free variable correct?
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comment Is my interpretation of the definition of free variable correct?
@DanielV: in the context of first-order logic, $\pi$ is a constant, not a variable.
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awarded Student
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comment Revisiting: user can vote to delete more than once
@animuson: I know I have inadvertently added at least two :( - and I have seen several more. It seems incredible to me that the number would still be so small, especially if we look network wide.
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asked Revisiting: user can vote to delete more than once
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comment Other integral related to Ahmed's integral
Please edit your post to add additional information: (1) context: where did you encounter the integral? Why is it interesting? (2) What have you tried? Posts that merely state a problem without context are discouraged on mathematics.stackexchange.com
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comment Limit of integral with continuous function
On this site, we look for questions that do not just state a problem. Please edit the question to include more context: where did you encounter the problem? What have you tried already?
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comment Probability of first player rolling double six first
@Jyrki Lahtonen: are moderator undeletions not permanent? I was surprised, when I tested it just now, that I was able to vote to delete this again - I assume you can always undelete it again if you want. In any case, it has been undeleted for a week now, but not re-opened - so the idea that undeleting it would help the situation doesn't seem to be correct.
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comment Every subgroup of $(\mathbb {Z_n},+)$ is closed under multiplication
Getting stuck is not too hard - what did you try? I would suggest induction on $b$, and prove that $G$ is closed under multiplication by every natural number.
Feb
28
comment Show we cannot define an ordering in $(\mathbb Z, +, 0,1)$
The equality symbol is often taken for granted. I voted to re-open this, but it needs other people to vote on it. The theory you are looking at now is indeed Presburger arithmetic - except that you are looking at $\mathbb{Z}$ instead of $\mathbb{N}$, which changes some things. In particular, $<$ is definable in $(\mathbb{N}, 0, 1, +, =)$ but not in $(\mathbb{Z}, 0, 1, +, =)$. The following thread has the ideas - mathoverflow.net/questions/78727/…
Feb
28
revised Show we cannot define an ordering in $(\mathbb Z, +, 0,1)$
added 1 character in body; edited tags
Feb
28
comment Completeness of a set of propositional formulas
I have voted to put this on-hold because it is not about research level mathematics - this question would be a better fit on mathematics.stackexchange.com. In any event: when we have a finite set of variables and a finite set of formulas, it is trivially decidable whether the set is complete, by using truth tables. When the set of formulas may be infinite, it is not decidable whether a given set is complete, by a simple diagonalization argument.
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