I've noticed that one question was recently tagged filter. (It is the only question having this tag at the moment.) I was thinking about a few related tags, which might perhaps be useful; but I wanted to ask about the opinion of other users before creating any of these tags. (I might be biased, ...

This is only marginally related to the topic from the original post, but I thought it is worth pointing out that the challenge-problem tag was created recently. At the moment in contains only one question. The tag-wiki is empty at the moment. The tag-excerpt is: For the question that is int...

In a sense every question on the site is a contest - at least that is how the rewards work, to try to motivate users to produce the best answer. There is general encouragement to work together with others (through comments and edits) and subsequent answers which are essentially the same as previo...

I've always wanted math competitions on MSE ever since I've joined. These could be either user-held or officially held, whichever seems better. User-held competitions would run as follows. A user starts a competition with a specified level, with original problems that he/she writes. People sign...

Here (in the context of Abstract Elementary Classes) on the page 43 at the bottom,-6th line, what does it technically mean $$\leq_{\frak K_\lambda}-\text{increasing continuous}$$ ? I think that this should be a condition on limit ordinals, but in his text, Shelah uses $\alpha$ for both, limit an...