How do I get less thick matrix lines?

Question

Currently for my column vectors they look like this:

I want them to look like this:

Right now I'm using the lgroup/rgroup symbols to get them the right curliness, but I can't get them to be the right "boldness", my current code follows.

\left\lgroup\begin{matrix} 1 \\2 \end{matrix}\right\rgroup+\lambda\left\lgroup\begin{matrix} -1 \\3 \end{matrix}\right\rgroup

I looked at this response Make a character thinner on this website and they've used Tikz to make a new definition of a "thinbrace". Can someone help me do this with the lgroup and rgroup symbols?

For reference here are all my user packages

\usepackage{amsmath}    
\usepackage{amssymb}
\usepackage{esvect}
\usepackage{nicematrix}
\usepackage{anyfontsize}
\usepackage[inline]{asymptote} 
\usepackage{changepage} 
\usepackage{color}      
\usepackage{enumitem}   
\usepackage{fancyhdr}  
\usepackage{framed}    
\usepackage{geometry}   
\usepackage{graphicx}  
\usepackage{helvet}    
\usepackage{marginnote} 
\usepackage{newtxtext}
\usepackage[upint]{newtxmath} 
\usepackage{multicol}   
\usepackage{multirow}   
\usepackage{pgffor}    
\usepackage{setspace}  
\usepackage{tikz}       
\usepackage{totalcount} 
\usepackage{accents}  

Answer 1

I have found that \lgroup and \rgroup has bad weight in classical 7bit Computer Modern math font, but the weight is correct when Unicode font LatinModern-Math is used. Try this:

\useOpTeX
Lgroup/rgroup from 7-bit CM math fonts:
$$\left\lgroup\matrix{1\cr3}\right\rgroup,
  \left(\matrix{1\cr3}\right)$$
\fontfam[lm] 
Lgroup/rgroup from LatinModern-Math, Unicode font:
$$\left\lgroup\matrix{1\cr3}\right\rgroup,
  \left(\matrix{1\cr3}\right)$$
\bye

My advice is: Use Unicode fonts.

Answer 2

I've ever encountered such question too (see the link). In my opinion, it's not a good idea to use the tikz package to solve the question. I found an elegant way to change the large brace and parenthesis only, that is to invoke such largesymbols from the other font file which is already existed in the TeX system. The codes are as follows:

\documentclass{article}
\usepackage{amsmath}    
\usepackage{amssymb}
\usepackage{esvect}
\usepackage{nicematrix}
\usepackage{anyfontsize}
\usepackage[inline]{asymptote} 
\usepackage{changepage} 
\usepackage{color}      
\usepackage{enumitem}   
\usepackage{fancyhdr}  
\usepackage{framed}    
\usepackage{geometry}   
\usepackage{graphicx}  
\usepackage{helvet}    
\usepackage{marginnote} 
\usepackage{newtxtext}
\usepackage[upint]{newtxmath} 
\usepackage{multicol}   
\usepackage{multirow}   
\usepackage{pgffor}    
\usepackage{setspace}  
\usepackage{tikz}       
\usepackage{totalcount} 
\usepackage{accents}
\makeatletter
\DeclareSymbolFont{mylargesymbols}{OMX}{ccex}{m}{n}%
%change the thickness of large left and right braces 
\DeclareMathDelimiter{\lbrace}{\mathopen}{symbols}{"66}{mylargesymbols}{"08}
\DeclareMathDelimiter{\rbrace}{\mathclose}{symbols}{"67}{mylargesymbols}{"09}
%change the thickness of large left and right parenthesis
\DeclareMathDelimiter{(}{\mathopen}{operators}{"28}{mylargesymbols}{"00}
\DeclareMathDelimiter{)}{\mathclose}{operators}{"29}{mylargesymbols}{"01}
%change the thickness of large left and right brakets
\DeclareMathDelimiter{[}{\mathopen}{operators}{"5B}{mylargesymbols}{"02}
\DeclareMathDelimiter{]}{\mathclose}{operators}{"5D}{mylargesymbols}{"03}
%change the thickness of large above and under braces
\DeclareMathSymbol{\braceld}{\mathord}{mylargesymbols}{"7A}
\DeclareMathSymbol{\bracerd}{\mathord}{mylargesymbols}{"7B}
\DeclareMathSymbol{\bracelu}{\mathord}{mylargesymbols}{"7C}
\DeclareMathSymbol{\braceru}{\mathord}{mylargesymbols}{"7D}
%change the thickness of large left and right groups
\DeclareMathDelimiter{\lgroup}{\mathopen}{mylargesymbols}{"3A}{largesymbols}{"3A}
\DeclareMathDelimiter{\rgroup}{\mathclose}{mylargesymbols}{"3B}{largesymbols}{"3B}
%change the thickness of large left and right braceverts
\DeclareMathDelimiter{\bracevert}{\mathord}{mylargesymbols}{"3E}{largesymbols}{"3E}
\makeatother
\begin{document}
\huge
[\left\lgroup\begin{matrix} 1 \2 \end{matrix}\right\rgroup+\lambda\left\lgroup\begin{matrix} -1 \3 \end{matrix}\right\rgroup]
We have
    [
    f(x)=
    \begin{cases}
    2x^{2018}+9&x<2018;\
    3x+2018&x\geq 2018.
    \end{cases}
    ]
    And we also have
    [
    \left(\left{
    \begin{array}{cc}
     x   &m  \
     y   &n  \
     x   &m  \
     y   &n
    \end{array}
    \right}\right)
    ]
    and 
    [k\leq \langle \underbrace{a,\cdots,a,b,\cdots,b}_{a+b~\text{many}}\rangle.]
    We don't change the thickness of any other large symbols, for example
    [\sum^x_yx+y=\prod_y^x xy.]
\end{document}

And the output is as follows.

You can also use the other large symbol font codes instead of ccex as you wish, for example, the line weight produced by llcmex is smaller than that produced by ccex.

---

By the way, please give a minimal working sample next time when you ask a question.

Answer 3

MWE:

\documentclass{report}
\usepackage{amsmath,amssymb}
\begin{document}
\begin{equation}
    \begin{pmatrix}
        1 \ 2 
    \end{pmatrix}
    + \lambda 
    \begin{pmatrix}
        -1 \ 3
    \end{pmatrix}
\end{equation}
\end{document}