How can I get bold Greek letters with mathptmx?

Question

I'm currently using these packages in my document:

\usepackage{mathptmx}
\usepackage[margin=1.2in]{geometry}
\usepackage{fancyhdr}
\usepackage{amsmath, amsthm, amssymb, amsbsy}
\usepackage{graphicx}
\usepackage{hyperref}
\usepackage{enumerate}
\usepackage{enumitem}
\usepackage[utf8]{inputenc}
\usepackage[danish]{babel}
\usepackage[T1]{fontenc}
\usepackage{caption}
\usepackage{subcaption}

But when I try to use:

\boldsymbol{\sigma}

As and example, well, nothing happens. It's not bold. I've also tried \mathbf and such. But nothing happens.

I don't know if it is because I'm using the "Times New Roman"-like package ?

Can anyone help me out?

Answer 1

As a last resort, over-printing (or under-printing) as a method to simulate boldness (or fake bold) is an option using the contour package. It may come in handy when there is no bold version of a font/symbol available:

\documentclass{article}
\usepackage{mathptmx}% http://ctan.org/pkg/mathptmx
\usepackage{array,contour}% http://ctan.org/pkg/{array,contour}
\begin{document}
\begin{tabular}{rl@{\quad}>{\contourlength{0.01em}}l}
\verb|\sigma|: & $\sigma$ & $\sigma$ \\
\verb|\contour[1]{red}{$\sigma$}|: & \contour[1]{red}{$\sigma$} & \contour[1]{red}{$\sigma$} \\
\verb|\contour[10]{black}{$\sigma$}|: & \contour[10]{black}{$\sigma$} & \contour[10]{black}{$\sigma$} \\
\verb|\contour{black}{$\sigma$}|: & \contour{black}{$\sigma$} & \contour{black}{$\sigma$} \\
\verb|\contour*{black}{$\sigma$}|: & \contour*{black}{$\sigma$} & \contour*{black}{$\sigma$}
\end{tabular}
\end{document}

The default interface is \contour[<number>]{<color>}{<stuff>} that prints <number> copies of <stuff> under <stuff> using colour <color>. The default is 16 repetitions if none are specified, while the starred-version \contour* prints 32. \contourlength{<len>} sets the radius of the under-printing. The two column above are default (0.03em) and 0.01em.

To make the under-printing more obvious/clear, here's a close-up view of the above contours at the default setting:

And, for \contourlength{0.01em}:

Answer 2

With newtx you can get bold math symbols; the text font is very similar to what you'd get with mathptmx and the math fonts are surely much better.

\documentclass{article}
\usepackage{newtxtext,newtxmath}
\usepackage{bm}

\begin{document}
$\Sigma\sigma$

$\bm{\Sigma}\bm{\sigma}$

$\sum\bm{\sum}\displaystyle\sum\bm{\sum}$
\end{document}

Note that \boldsymbol provided by the amsbsy package is to be considered obsolete as \bm is much better.

Answer 3

I have amsfonts loaded:

An ex­tended set of fonts for use in math­e­mat­ics, in­clud­ing: 
ex­tra math­e­mat­i­cal sym­bols; black­board bold let­ters (up­per­case only); frak­tur let­ters; 
sub­script sizes of bold math italic and **bold Greek let­ters**; 
sub­script sizes of large sym­bols such as sum and prod­uct; 
added sizes of the Com­puter Modern small caps font; 
cyril­lic fonts (from the Univer­sity of Wash­ing­ton); Euler math­e­mat­i­cal fonts. 

Even though you say it didn't work, it is working fine on my end.

 \begin{equation} \mbox{\boldmath$\sigma$} =\frac{\mathbf{j}}{\mathbf{E}}, \label{eq:3.1} \end{equation}

produced:

as you can see I just added real quick to a document I am working on.

Here is a regular sigma next to it.