如何减少报告中章节标题后的空白？

Question

由于页数限制，我试图减少报告中章节标题前后的空白。我尝试过多种方法，但似乎都不起作用。我尝试过https://tex.stackexchange.com/a/63393/252049它可以减少章节标题前的空间，但我还没有找到任何可以减少标题后空间的方法。我也试过

\RenewDocumentCommand{\chapterbelowskip}{}{\vspace*{0pt}}

但收到错误 \chapterbelowskip 未定义

以下是 MWE：

\documentclass[11pt]{report}
\usepackage{titling}
\usepackage[utf8]{inputenc}
\usepackage{caption}
\usepackage[margin=2.5cm]{geometry}
\usepackage{graphicx}
\usepackage{amsmath}
\usepackage{adjustbox}
\usepackage{booktabs,makecell,longtable}
\usepackage[T1]{fontenc}
\usepackage[dvipsnames]{xcolor}
\graphicspath{{images/}}
\setlength{\droptitle}{-8em}
\makeatletter
\def\@makechapterhead#1{%
  %%%%\vspace*{50\p@}% %%% removed!
  {\parindent \z@ \raggedright \normalfont
    \ifnum \c@secnumdepth >\m@ne
        \huge\bfseries \@chapapp\space \thechapter
        \par\nobreak
        \vskip 20\p@
    \fi
    \interlinepenalty\@M
    \Huge \bfseries #1\par\nobreak
    \vskip 40\p@
  }}
\def\@makeschapterhead#1{%
  %%%%%\vspace*{50\p@}% %%% removed!
  {\parindent \z@ \raggedright
    \normalfont
    \interlinepenalty\@M
    \Huge \bfseries  #1\par\nobreak
    \vskip 40\p@
  }}
\makeatother
\begin{document}

\chapter{Characters}

The origin of the group determinant begins with Richard Dedekind in the late 1800's. He began to explore the idea
after studying the discriminant in a normal field [A]. He made several observations about the group determinant, but
was only able to prove some of them.

\end{document}

如果有人能帮助我，那就太好了。谢谢！