Kdjykuj

When I try to remove the outer brackets in the following diagram, by removing the first occurrence of begin{pmatrix} and the last occurrence of end{pmatrix} I get the error misplaced alignment tab character &. I cannot see which tab character is causing the problem and why it is causing the problem. How can I remove the outer parentheses without incurring this problem, and preserving all other properties as is, except for perhaps making the gap between rows slightly smaller. I have used \ \ below, but this gap is too big, whilst \ is too small.

documentclass[11pt]{beamer}

usepackage{pgfpages,amsmath,amssymb,mathtools,color, graphicx, amsfonts, braket}

usepackage{subfig}

usetheme{Madrid} 

usepackage{empheq}

usepackage{multicol}

usepackage{gb4e}



begin{document}



begin{frame}



[begin{pmatrix}begin{matrix} begin{array}{c|c}

multicolumn{2}{c}{cfrac{ t  }{ e to e to t  }}

end{array} \ \ text{John} \ \ cfrac{ operatorname{[;]} }{ saw } end{matrix} &

begin{pmatrix}

begin{array}{c|c}

multicolumn{2}{c}{cfrac{ t  }{ e to e to t  }}

end{array}     & begin{array}{c|c}

multicolumn{2}{c}{cfrac{ t  }{ e to e to t  }}

end{array}  \  \ 

text{saw}         & text{Mary}\ \

cfrac{ operatorname{[;]} }{ a } & cfrac{ operatorname{[;]} }{ b }

end{pmatrix}

end{pmatrix}

]





end{frame}



end{document}

Change pmatrix (which automatically add a pair of brackets) to matrix:

documentclass[11pt]{beamer}

usepackage{pgfpages,amsmath,amssymb,mathtools,color, graphicx, amsfonts, braket}

usepackage{subfig}

usetheme{Madrid} 

usepackage{empheq}

usepackage{multicol}

usepackage{gb4e}



begin{document}



begin{frame}



[begin{matrix}begin{matrix} begin{array}{c|c}

multicolumn{2}{c}{cfrac{ t  }{ e to e to t  }}

end{array} \ \ text{John} \ \ cfrac{ operatorname{[;]} }{ saw } end{matrix} &

begin{pmatrix}

begin{array}{c|c}

multicolumn{2}{c}{cfrac{ t  }{ e to e to t  }}

end{array}     & begin{array}{c|c}

multicolumn{2}{c}{cfrac{ t  }{ e to e to t  }}

end{array}  \  \ 

text{saw}         & text{Mary}\ \

cfrac{ operatorname{[;]} }{ a } & cfrac{ operatorname{[;]} }{ b }

end{pmatrix}

end{matrix}

]





end{frame}



end{document}

Avoid using double \s. You always have \:

documentclass[11pt]{beamer}

usepackage{pgfpages,amsmath,amssymb,mathtools,color, graphicx, amsfonts, braket}

usepackage{subfig}

usetheme{Madrid} 

usepackage{empheq}

usepackage{multicol}

usepackage{gb4e}



begin{document}



begin{frame}



[begin{matrix}begin{matrix} begin{array}{c|c}

multicolumn{2}{c}{cfrac{ t  }{ e to e to t  }}

end{array} \[2ex] text{John} \ cfrac{ operatorname{[;]} }{ saw } end{matrix} &

begin{pmatrix}

begin{array}{c|c}

multicolumn{2}{c}{cfrac{ t  }{ e to e to t  }}

end{array}     & begin{array}{c|c}

multicolumn{2}{c}{cfrac{ t  }{ e to e to t  }}

end{array}  \[2ex] 

text{saw}         & text{Mary}\

cfrac{ operatorname{[;]} }{ a } & cfrac{ operatorname{[;]} }{ b }

end{pmatrix}

end{matrix}

]





end{frame}



end{document}