[Tex/LaTex] thmtools: How to prevent pagebreak between theorem and proof

page-breakingtheoremsthmtools

I am using thmtools to format a collection of theorems and their proofs.

Is there any way to prevent a pagebreak from happening between the last line of a theorem statement and the first line of the proof?

I tried inserting \nopagebreak, like this

\end{thorem}
\nopagebreak[4]
\begin{proof}

…but it failed to suppress the pagebreak.

The first line of the first proof on any one page should be preceded by at least two lines from the theorem statement. (The proof always follows immediately after the statement; there never is intervening text not belonging to either environment).

FWIW: I searched for multiple variants of "pagebreak", "page break", "nopagebreak" in the thmtools docs, but got no hits.

Thanks!

Best Answer

Given that the theorem and proof environments are quite separate, it's indeed a bit tricky to forbid categorically all pagebreaks between them. All I can suggest is that you load the package needspace and insert the command

\Needspace{3\baselineskip}

close to the end of the statement of the theorem/corollary/whatever; note the uppercase N at the start of the macro. According to the manual of the needspace package, the command "\Needspace{} is less efficient [than \needspace{}] but reserves the requested space exactly. It should only be used between paragraphs." Given that you're basically facing this situation, you may want to give it a try.

You'll probably have to practice a bit to determine the best placement of this command and the number of baseline skips you require in order to always get at least two lines of the proof statement to show up on the same page as the associated theorem.

Related Solutions

[Tex/LaTex] amsthm: how to reduce the vertical spacing between theorem and proof

One possibility would be to redefine the proof anvironment as defined in amsthm.sty (the definition uses \topsep6\p@\@plus6\p@\relax, so you could make some changes there). Another approach would be to use the front-end thmtools to define a new theorem-like structure behaving like the standard proof environment, but using the spaceabove key to control the vertical space above it. The following example illustrates this second approach and shows the different spacing for the new prf environment and the standard proof environment:

\documentclass{article} 
\usepackage{amsthm} 
\usepackage{thmtools}

\declaretheorem{theorem} 
\declaretheoremstyle[%
  spaceabove=-6pt,%
  spacebelow=6pt,%
  headfont=\normalfont\itshape,%
  postheadspace=1em,%
  qed=\qedsymbol%
]{mystyle} 
\declaretheorem[name={Proof},style=mystyle,unnumbered,
]{prf}

\begin{document} 

\begin{theorem} 
A really important result.
\end{theorem}
\begin{prf} 
And its proof with less space above.
\end{prf} 
\begin{theorem} 
A really important result.
\end{theorem}
\begin{proof} 
And its proof with too much space above.
\end{proof} 

\end{document}

enter image description here

[Tex/LaTex] thmtools declaration for theorem and proof.

You're declaring twice the style mystyle, once for Proof and second for Theorem. Only the last one is remmembered. You must change one of style names and apply the change is corresponding \declaretheorem definition.

\documentclass{report}

\usepackage{amsfonts, amssymb, amsthm}
\usepackage{mathtools}
\usepackage{undertilde}
\usepackage[utf8]{inputenc}
\usepackage[english]{babel}
\usepackage{hyperref}

\usepackage{thmtools}
\declaretheoremstyle[
    spaceabove=-6pt, 
    spacebelow=6pt, 
    headfont=\normalfont\bfseries, 
    bodyfont = \normalfont,
    postheadspace=1em, 
    qed=$\blacksquare$, 
    headpunct={:}]{myproofstyle} %<---- change this name
\declaretheorem[name={Proof}, style=myproofstyle, unnumbered]{Proof}

\declaretheoremstyle[
    spaceabove=6pt, 
    spacebelow=6pt, 
    headfont=\normalfont\bfseries,
    notefont=\mdseries\bfseries, 
    notebraces={(}{)}, 
    bodyfont=\normalfont\itshape,
    postheadspace=1em,
    headpunct={:}]{mystyle}
\declaretheorem[name={Theorem}, style=mystyle,numberwithin=section]{thm}

\begin{document}

\begin{thm}
Body of my first theorem
\end{thm}

\begin{Proof}
This proves my first theorem
\end{Proof}

\end{document}

enter image description here

Best Answer

Related Solutions

[Tex/LaTex] amsthm: how to reduce the vertical spacing between theorem and proof

[Tex/LaTex] thmtools declaration for theorem and proof.

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