The space is one of the lengths
\belowdisplayskip=12pt plus 3pt minus 9pt
\belowdisplayshortskip=7pt plus 3pt minus 4pt
so you can set those to whatever values you like using the above primitive syntax of \setlength
so the first tries to be 12pt but will shrink to 9pt or stretch to 21pt to help page breaking.
the equation
environment is meant for a "single" equation, which may be either one line or a "subsidiary" multi=line group such as aligned
. it will not break, even with an explicit \displaybreak
.
furthermore, nesting align
within equation
will produce an error message:
! Package amsmath Error: Erroneous nesting of equation structures;
(amsmath) trying to recover with `aligned'.
trying to use \displaybreak
in this situation will produce another error:
! Package amsmath Error: \displaybreak cannot be applied here.
error messages should be heeded.
if you remove the equation
environment and simply use align
, in the presence of the global \allowdisplaybreaks
command, the multi-line display will break at the end of a page at the normal page length. even without \allowdisplaybreaks
, an explicit \displaybreak
will force a break after the line on which the command appears.
if no numbers are wanted on any line, the environment align*
can be used. and if only a single tag is wanted for the group, with align*
it is possible to insert a manual label using the \tag{...}
command on the desired line. the value will have to be handled manually. to do that, just before the display, issue the command
\stepcounter{equation}
and for the explicit label, use \tag{\theequation}
.
Best Answer
The large space is due to the
center
environment, which adds vertical unneeded space and does nothing useful, sinceequation
center its contents by default.So, simply remove the
center
environment.MWE
Output
I would also suggest to remove the blank line before the
equation
environment, so to have the following result: