我在使用乳胶海报时遇到了一个奇怪的问题，我想给背景上色，但海报顶部总有一条白色条纹，不会上色。
\documentclass[final,20pt]{beamer}
\usepackage[utf8]{inputenc}
\usepackage{tikz}
\usepackage{tcolorbox}
%\definecolor{background}{rgb}{0.1, 0.1, 0.1}
\setlength{\paperwidth}{46.8in}
\setlength{\paperheight}{33.1in}
\usepackage{geometry}
\geometry{paperwidth=46.8in,paperheight=33.1in,margin=2cm}
\setbeamertemplate{navigation symbols}{}
\setbeamertemplate{headline}{}
\begin{document}
\setbeamercolor{background canvas}{bg=blue}
\font\titlefont=cmr12 at 70pt
\font\authorfont=cmr12 at 50pt
\font\intitutefont=cmr12 at 50pt
\title{\titlefont The Bubble Chamber} % Poster title
\author{\authorfont CT} % Author(s)
\date{}
\begin{frame}
% Title section
\begin{columns}
\vspace{5cm}
\begin{column}{0.3\linewidth}
\end{column}
\begin{column}{0.3\linewidth}
\maketitle
\vskip1cm
\centering
\vskip1cm
\end{column}
\begin{column}{0.3\linewidth}
\end{column}
\end{columns}
\hrule
\vspace{3cm}
% Page is split into 1-2-1 arrangement for first half
\begin{columns}[t,totalwidth=\linewidth]
\begin{column}{0.24\linewidth}
\vspace{0.7cm}
\begin{tcolorbox}[colback=white,colframe=blue,boxrule=5pt,title=\centering \Huge Production Process ]
The bubble chamber was exposed to a beam of $K^-$ mesons which are slowed by ionising the gas in the chamber, creating bubbles until they are close to stationary at which point the $K^-$ will interact with a neighbouring proton.
This process occurs through the strong interaction wherein the proton and kaon exchange a quark and some gluons:
\end{tcolorbox}
\begin{tcolorbox}[colback=white,colframe=blue,boxrule=5pt,title=\centering \Huge $\Sigma$ Identification]
Visually this is presented in the bubble chamber as a kaon track stopping and two other tracks emerging from it with a $180^{\circ}$ angle between them as shown in Fig 1.
Events where the angle between the tracks $\neq 180^{\circ}$ indicates that the particles are not stationary in the lab frame when the interaction, violating one of the requirements for the use of the mass formula.
\end{tcolorbox}
\end{column}
\begin{column}{0.49\linewidth}
\begin{columns}[t,totalwidth=0.49\linewidth]
\begin{column}{0.49\linewidth}
\begin{tcolorbox}[colback=white,colframe=blue,boxrule=5pt,title=\centering \Huge Decay Process ]
The decay of the hyperon then occurs via the weak interaction, a W boson is produced by the Hyperon which pair produces a quark antiquark pair:
However there is the possibility of a semileptonic decay mode, replacing the $q\bar{q}$ pair with a lepton and neutrino:
\begin{align}
\Lambda \to p + e^- + \bar{\nu}_e
\end{align}
Which could be seen in the bubble chamber as an single electron line and proton line emerging instead of a pair of lines corresponding to a proton and pion.
However this process is \textbf{forbidden} by isospin/hypercharge baryon model, thus study of it allows us to test that description of these particles.
\end{tcolorbox}
\end{column}
\begin{column}{0.49\linewidth}
\end{column}
\end{columns}
\vspace{1cm}
\begin{tcolorbox}[colback=white,colframe=red,boxrule=5pt,title=\centering \Huge $\Sigma$ Mass Formula ]
The mass of the sigma baryon is calculated through the application of energy and momentum conservation:
\begin{gather}
p_{\pi} = p_{\Sigma} \hspace{1cm} \textrm{Momentum Conservation} \\
m_0 c^2 = \sqrt{m_{\Sigma}^2 c^4 + p_{\Sigma}^2 c^2} + \sqrt{m_{\pi}^2 c^4 + p_{\pi}^2 c^2} \hspace{1cm} \textrm{Energy Conservation}
\end{gather}
When these two are combined a singe formula for the mass of the Sigma baryon is obtained:
\begin{equation}
m_{\Sigma} = \frac{1}{c^2} \left[\left( m_0c^2 - \sqrt{m_{\pi}^2c^4+p_{\pi}^2c^2} \right)^2 - p_{\pi}^2c^2 \right]^{1/2} \hspace{0.7cm} m_0 = m_p + m_K
\end{equation}
\end{tcolorbox}
\end{column}
\begin{column}{0.24\linewidth}
\begin{tcolorbox}[colback=blue,coltext=white]
\centering
\Huge Production Process
\end{tcolorbox}
Some text here.
\end{column}
\end{columns}
\end{frame}
\end{document}
以下是一张屏幕截图，您可以看到问题所在：
我尝试过一些操作，比如在所有内容下方放置一个 vspace 以强制将内容置于页面顶部，但白框仍然存在。
任何帮助都将不胜感激。我还没见过任何人遇到过这个问题，所以我现在真的不知道该怎么办。
答案1
问题是由您margin=2cm在几何选项中的设置引起的。这不仅设置了水平边距，还设置了顶部和底部的边距，这会干扰投影仪自身对顶部边距的设置。
最简单的解决方案是仅在几何设置中设置水平边距，并让 beamer 使用顶部边距执行自己的操作：
\documentclass{beamer}
\usepackage{geometry}
\geometry{paperwidth=46.8in,paperheight=33.1in,hmargin=2cm}
\setbeamertemplate{navigation symbols}{}
\setbeamertemplate{headline}{}
\setbeamercolor{background canvas}{bg=blue}
\begin{document}
\begin{frame}
test
\end{frame}
\end{document}