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This question relates directly to issues that are often discussed in the philosophy of mathematics. According to one of the standard accounts of structuralism, what mathematical objects are at bottom are the structural roles that they play within a mathematical system. One might define the equivalence relation whereby element $a$ in structure $A$ is ...


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You can find several suitable queries in data explorer or create your own query. (Even for users who do not know much about SQL, it's not that difficult to look up basic info on the database schema and then try to modify the existing queries.) Some queries for finding comments by User1 on posts by User2: Comments left by a user on your posts taken from ...


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infinite chess (6th place) ZFC independence (4th place) continuum hypothesis solution (1st place) definable numbers (4th place) premium white chalk (1st place) common false beliefs (4th place) Turing undecidable (4th place) compact hausdorff topology (3rd place) Borel set even cardinalities universal partial order rigid relation Leibnizian model (2nd) ...


8

As Lucia linked in the comments above, the question you're looking for is available at How $a+b$ can grow when $a!b! \mid n!$. That user, and some related ones, were deleting for abusing the voting system.


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This is doable with the existing search. Tags are indicated by square brackets, and a - sign indicates that the term which follows should not be present in the search results. Searching for "topology -[ag.algebraic-geometry]" (without the quotes) finds all questions containing the word "topology" and lacking the tag ag.algebraic-geometry. Incidentally, to ...


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The built-in search only searches in posts (questions and answers), so you will not find comments using that. One method which is reasonable is using Google with restricting to this site. For example: proportionality site:mathoverflow.net. This searches both in posts and in comments. Another reasonable possibility is to use data explorer. You can create ...


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You can find various search modifiers in the help center. Or simply by clicking on "Advanced Search Tips" after you search for something. Specifically, to find posts by a specific user you can user user:userid. And to find your own posts you can use user:mine or user:me. Notice that if you go to some user's profile page, the search query user:userid is ...


6

I am the creator of Approach0 (https://approach0.xyz), a math-aware search engine. Approach0 is currently only indexing Math StackExchange data, however, I am considering to add MathOverflow to Approach0. I think this is a good opportunity for posting a survey here. Please give Approach0 a try and tell me to which degree do you think it can be helpful to ...


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It is kind of easy to add suggestions how to search post fact, after Todd Trimble already found that the question is this one: Random rings linked into one component?. Still, I'm tempted to add a little bit of advice about searching of your own posts using the internal search engine. There is a operator user:userid which restrict the search to posts of a ...


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Here is how I do it. I click on my own little user icon at the top of the page and this puts my own userid into the search field where I can then add keywords I want to search for.


3

Try this perhaps, and linearity of expectation will be the second answer (at 70 votes currently).


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It seems that uniquation searches both on MathOverflow and Mathematics Stackexchange (and also other sites). Among example queries, there is search for $F_{n+1}=F_n+F_{n-1}$. You can see that among the results there are posts from Math.SE and posts from MathOverflow. As I am not familiar with this search engine, I am making this post CW - feel free to edit ...


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As far as I know, in situations like this - when you deleted the post yourself, all you have to do is to check the tab with delete votes in your profile. If you do not have too deleted your posts too often, you'll see only a few posts there, so this might be a reasonable way to find the one you're interested in. This tab contains both self-deletions and ...


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The search minimal hausdorff gives a top hit.


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After performing a search, select "newest" tab (or in the reverse order) - this will work. Thats what you'll get if you'll search in this way for questions tagged with filters and then (or before) select the "newest" tab.


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As far as searching deleted questions is concerned, the site only enables you somewhat limited ability to search for your own deleted posts. I think it is quite well summarized in the answer here: Can I somewhere see my own deleted questions? I will also add that highly upvoted questions with highly upvoted answers are deleted very rarely if at all. (At ...


2

Could this be the question you mean? It's not exactly about $i$ versus $-i$, but it mentions it as a motivating example. "Co-ordinate-free" mathematics for general structures? Even if it isn't, don't miss the reference there to Shapiro - Identity, indiscernability, and ante rem structuralism: The tale of $i$ and $-i$.


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The discussion following Mike Shulman's 2013 post From Set Theory to Type Theory was useful to me to see what to say about this situation type-theoretically while writing section 3.4.3 of my book Modal Homotopy Type Theory. Mike distinguishes between the introduction of the type of complex numbers as a particular type and as an abstract type. As a particular ...


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This isn't exactly about the feature you asked for, but let me leave here a brief comment. (Hopefully, some of the information here might be useful.) One possibility to get list of all your answers (or questions) in a more compact form then here on the site is to use SEDE. (With the caveat that the data in SEDE are only updated once a week, so you won't ...


1

A few years ago we developed the search engine SearchOnMath, in order to search for mathematical formulas. Recently our tool has indexed both: Mathematics and MathOverflow. Currently, SearchOnMath is the mathematical search engine with the largest number of indexed sites (including Wikipedia, Wolfram MathWorld, among others ...). The following video ...


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Here are some further test cases. Some of them return nothing of interest from MSE. This may be because there really isn't anything relevant there. The Eilenberg-MacLane space $K(\mathbb{Z},3)$: link The ring spectrum $MO\langle 8\rangle$, entered with angle brackets or less than/greater than signs. The classifying space $BGL_n(R)$: link (The first result ...


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