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    • CommentRowNumber1.
    • CommentAuthorHarry Gindi
    • CommentTimeMay 23rd 2010

    There are a lot of instances on the lab of stackrel’d pairs of arrows, which look pretty silly;:

    We can produce double arrows simply by typing

    A\rightrightarrowsB and NZN\leftleftarrows Z

    To produce larger numbers of arrows, I believe that you’re forced to use xypic.

    • CommentRowNumber2.
    • CommentAuthorTobyBartels
    • CommentTimeMay 23rd 2010

    To produce larger numbers of arrows, I believe that you’re forced to use xypic.

    Or \stackrel again (even though it doesn’t look right), since we don’t have Xy. But you’re right, using \stackrel for only two arrows is a poor choice.

    • CommentRowNumber3.
    • CommentAuthorMike Shulman
    • CommentTimeMay 23rd 2010

    While we’re on the subject, I find that \rightrightarrows on the ’lab doesn’t put enough space around them to look good, so I sometimes write \;\rightrightarrows\; instead. I’m not sure if this is an issue only with my fonts or what.

    • CommentRowNumber4.
    • CommentAuthorTobyBartels
    • CommentTimeMay 23rd 2010
    • (edited May 23rd 2010)

    It’s an issue with the browser’s treatment of MathML, not the fonts as such. Somebody (us, the browser, or a MathML standard, I don’t know which) tells browsers to put space around ‘\rightarrow’ (even here where it’s not appropriate) but not around ‘\rightrightarrows’. (TeX handles this with a much better system, if you ask me.)

    Actually, I think that I’m getting some extra space around both of these on the left only. That may be from the font.

    • CommentRowNumber5.
    • CommentAuthorTodd_Trimble
    • CommentTimeMay 23rd 2010

    By the way, I’m the perpetrator of a lot of those stackrels. My knowledge of latex is quite primitive and I’m always happy to learn something new.

    • CommentRowNumber6.
    • CommentAuthorUrs
    • CommentTimeMay 24th 2010
    • (edited May 24th 2010)

    I am also guilt of plenty of \stackrels. But is there a command that would stack symbols but keep both same size and vertzically aligned neutrally? Such as \atop in LaTeX?

    • CommentRowNumber7.
    • CommentAuthorAndrew Stacey
    • CommentTimeMay 24th 2010

    Try … \atop. You need to use braces to delimit it abcda {b \atop c} d. Same again in display:

    abcd a {b \atop c} d

    Even if there’s nothing either side, you still need the braces (it seems): bc{b \atop c}.

    • CommentRowNumber8.
    • CommentAuthorUrs
    • CommentTimeMay 24th 2010
    • (edited May 24th 2010)

    Ah. I guess I should have thought of that…

    Let’s see…

    Sh(C)LPSh(C) Sh(C) { \overset{L}{\leftarrow} \atop \hookrightarrow} PSh(C)

    … ah, no, this doesn’t come out the way it should. Hm.

    • CommentRowNumber9.
    • CommentAuthorHarry Gindi
    • CommentTimeMay 24th 2010

    It looks right to me.

    • CommentRowNumber10.
    • CommentAuthorUrs
    • CommentTimeMay 24th 2010

    I see, maybe it’s just my system: I see the two arrows vertically aligned above and below the maximal and minimal vertical extension, respectively, of Sh(C)Sh(C) and PSh(C)PSh(C). Hence: too high and too low. Is it different for you?

    • CommentRowNumber11.
    • CommentAuthorHarry Gindi
    • CommentTimeMay 24th 2010

    The top arrow is slightly below the top of the P, and the bottom arrow is a little bit too low, but that’s not surprising considering that you used the hooked right arrow. Do you have the STIX fonts installed?

    • CommentRowNumber12.
    • CommentAuthorMike Shulman
    • CommentTimeMay 24th 2010

    It looks mostly okay to me, although the arrows are spaced a bit further apart vertically than would be ideal. They actually look a bit better in the image display than in the MathML.

    • CommentRowNumber13.
    • CommentAuthorAndrew Stacey
    • CommentTimeMay 24th 2010

    Really ought to be trying these in the Sandbox since there’s no absolute guarantee that what we see here will be the same as that in the nLab (though if there are significant differences, let me know)

    Sh(C)LPSh(C) Sh(C){{L \atop \leftarrow} \atop \hookrightarrow} PSh(C) Sh(C)LPSh(C) Sh(C){\textstyle{{L \atop \leftarrow} \atop \hookrightarrow}} PSh(C)
    • CommentRowNumber14.
    • CommentAuthorTobyBartels
    • CommentTimeMay 26th 2010

    Right now I’m using Firefox 3.6 on Windows 7. I see it the same way as Urs. I see Andrew’s this way as well (too much space) in the first one, but the second one looks nice.

    • CommentRowNumber15.
    • CommentAuthorHarry Gindi
    • CommentTimeMay 26th 2010
    • (edited May 26th 2010)

    They appear the same using the font STIXSize5. I suppose that this is due to you guys having your math font set to STIXGeneral rather than STIXSize5. STIXGeneral is currently very buggy for me (in firefox and opera), but STIXSize5 displays everything perfectly.

    The final fonts were supposed to come out yesterday, but they were delayed to the 28th.