Equation position changing

Question

Kindly have a look at the LaTeX code below:

\documentclass[10pt,a4paper,xcolor=dvipsnames,xcolor=table]{beamer}
\pdfpageattr{/Group <</S /Transparency /I true /CS /DeviceRGB>>}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                  PACKAGES
\usepackage{mathrsfs,amsmath,amsfonts,amssymb,makeidx}

\begin{document}
\begin{frame}
  \[QQ=RR\]\pause
    \begin{itemize}
    \item Retarded
    \item \only<2>{Exp1}
      $A=B$\\
      \only<2>{$B=C$}\pause
    \item $C=D$\\
      \only<3>{
    where {
      \begin{align}
        P&=Q \nonumber\\
        Q &=0&\nonumber
      \end{align}
    }
      }
      \pause
    \item Exp2 
      \[W=U\]
  \end{itemize}
\end{frame}
\end{document}

The problem is, as I alter the materials, as expected, LaTeX fits it what it thinks is best withing the page. So, the equations keep jumping up and down (look at eqn 1).

What I want is to keep the position of those equation within the page fixed. New materials will come and go at the bottom, but will not alter the position of displayed equations.

Is this possible?

Answer 1

Section 9.5 of the beamer manual on "Dynamically Changing Text or Images" discusses this problem, which is not just due to equations. You can use the overlay environment to control this behaviour. Its main downside, is that you have to specify the height of the area to be used; putting that height to \textheight, means the material will not be centered in the usual way on the frame.

\documentclass[10pt,a4paper,xcolor=dvipsnames,xcolor=table]{beamer}
\pdfpageattr{/Group <</S /Transparency /I true /CS /DeviceRGB>>}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                  PACKAGES
\usepackage{mathrsfs,amsmath,amsfonts,amssymb,makeidx}

\begin{document}
\begin{frame}
  \begin{overlayarea}{\textwidth}{6cm}
    \[QQ=RR\]\pause
    \begin{itemize}
    \item Retarded
    \item \only<2>{Exp1}
      $A=B$\\
      \only<2>{$B=C$}\pause
    \item $C=D$\\
      \only<3>{ where {
      \begin{align}
        P&=Q \nonumber\\
        Q &=0&\nonumber
      \end{align}
      } } \pause
    \item Exp2
      \[W=U\]
    \end{itemize}
  \end{overlayarea}
\end{frame}
\end{document}

Answer 2

You can use

\begin{frame}[t]

then the equation stays at the same place.