[texhax] strange behavior of amsmath

Reinhard Kotucha reinhard.kotucha at web.de
Thu Dec 12 00:43:08 CET 2013

I would expect that the fleqn option of amsmath has only an impact on
horizontal glue.

Curiously, if the fleqn option is active, there is extra vertical glue
below the first formula of each paragraph and below the first formula
following ordinary text.

Here is a minimal example:

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You get correct vertical spacing if you comment out the line
containing "[fleqn]".  The relevant part of the amsmath source code
looks quite innocent.  I can reproduce the problem with TeX Live 2003
too, the oldest TL release I've currently installed.

The vertical bar in the test file is an argument of \smash, hence
both, its height and depth is zero.  Its sole purpose is to make the
extra glue more visible.

Please also note that "some text" in the test file doesn't start a new

Where does the extra vertical space come from?  I doubt that it's


Reinhard Kotucha                                      Phone: +49-511-3373112
Marschnerstr. 25
D-30167 Hannover                              mailto:reinhard.kotucha at web.de
Microsoft isn't the answer. Microsoft is the question, and the answer is NO.

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