在枚举环境中的项目中开始新行，而不会产生不必要的垂直间距

Question

我有以下代码

\documentclass[12pt,a4paper,openany]{book}
 \usepackage{enumitem}
 \usepackage{mathtools}
 \DeclareMathOperator{\im}{Im}
 \DeclareMathOperator{\id}{Id\,}
 \newcommand{\summand}{\subseteq^{\oplus}}
 \newcommand{\End}{\textup{End}}
 \newcommand{\Hom}{\textup{Hom}}
 \begin{document}
  \chapter{Preliminaries and Basic Results}
   \section{Basic Notions and Definitions}
    \begin{enumerate [font=\bfseries,
      label=\thesection.\arabic*,
      wide,
      labelindent=0pt]
    \item For right $R$-modules $M_R$ and $N_R$, we use 
     $\Hom(M_R,N_R)$ or $\Hom(M,N)$ to denote the set of all $R$- 
     homomorphisms from $M_R$ to $N_R$. Likewise, $\End(M_R)$ or 
     $\End(M)$ denotes the endomorphism ring of an $R$-module 
     $M$. We denote the identity of $\End(M)$ by $\id_M$. For an 
     $R$-homomorphism $f\in \Hom(M,N)$, $\im f$ and $\ker f$ 
     denote the image and the kernel of $f$, respectively. For a 
     submodule $V$ of $M$, $f|_V$ means the restriction of $f$ to 
     $V$. Also, ``homomorphism'' is used for ``$R$- 
     homomorphism''. When the context is clear, the subscript $R$ 
     may be omitted. We write $N\subseteq M$ if $N$ is a 
     submodule of $M$, and $N \summand M$ if $N$ is a (direct) 
     summand of $M$.  \\
     \hspace*{0.5cm} A monomorphism $f:M\to N$ is said to 
     \textit{split} if there exists $f\in \Hom(N,M)$ such that 
     $gf=\id_M$. This is equivalent to saying that $\im f 
     \summand N$.  
    \end{enumerate} 
   \end{document}

我添加了\hspace*{0.5cm}缩进，因为默认情况下没有缩进。另外，删除\\并留出空行并在下一行上书写对我来说并不适合，因为这会产生不需要的小垂直空间。

如何摆脱\hspace*{0.5cm}并克服这个压痕问题？

编辑：我添加了 MWE。