减小标题和作者的大小

Question

下面是 tex 文件的代码。我想做以下更改：

1. 如何改变作者和标题的大小？

2. 您会看到标题和第一页顶部之间有间隙。我想知道如何缩小这个间隙？

谢谢！

\documentclass[12pt]{amsart}
\usepackage[utf8]{inputenc}
\usepackage[usenames,dvipsnames]{xcolor}
\usepackage[draft]{pgf}
\usepackage{listings}
\usepackage{float}
\usepackage{caption}
\usepackage{pgfplots}
\pgfplotsset{compat=1.15}
\usepackage{mathrsfs}
\usetikzlibrary{arrows}
%\pagestyle{empty}

\usepackage[margin=1.2in, centering]{geometry}
\geometry{letterpaper}   
\usepackage{amsmath,amssymb,latexsym,mathtools}
\usepackage{dsfont}
\usepackage{nccmath}

\usepackage{amsthm}
\usepackage{amssymb}
\newtheorem{thm}{Theorem}[section]
\newtheorem{lem}[thm]{Lemma}
\newtheorem{cor}[thm]{Corollary}
\newtheorem{prop}[thm]{Proposition}
\newtheorem{conj}[thm]{Conjecture}
\newtheorem{exer}{exercise}[subsection]
\numberwithin{equation}{section}

\theoremstyle{definition}
\newtheorem{ques}{Question}
\newtheorem{defn}[thm]{Definition}
\newtheorem{ex}[thm]{Example}
\newtheorem{problem}[thm]{Problem}
\newtheorem*{remark}{Remark}
\newtheorem{nota}{Notation}
\newtheorem*{acknowledgement}{Acknowledgements}

\usepackage{graphicx}
\DeclareGraphicsExtensions{.pdf,.png,.jpg}
\usepackage{subfig}

%\usepackage[usenames,dvipsnames]{color}
%\usepackage{chngcntr}
\counterwithin*{equation}{section}

\usepackage{hyperref}
\hypersetup{linktocpage}

\begin{document}

\definecolor{qqttcc}{rgb}{0.,0.2,0.8}
    \title{ABC}
    \author{John Doe}
    
    \date{\today}

    \keywords{}
    \maketitle


I like math!


\bibliographystyle{plain}

\end{document}