why the prod command do not display bold character like in the picture below

enter image description here

here the code and my output

\usepackage {minitoc} 
\usepackage[authory ar,comma,longnamesfirst,sectionbib]{natbib}
\usepackage[colorlinks=true,linkcolor=black, citecolor=blue, urlcolor=blue]{hyperref}

P^{\circ M,j}_{t+s\textbar{t}}(k)\equiv 
\displaystyle{\prod_{i=1}^{s}} \Pi^{\theta}_{m,t+s-i} 
\bar{\Pi}^{s(1-\theta)}_{m} P^{\circ{M,j}}(k) 

my output

enter image description here

  • Please provide full minimal examples that we can just copy and test without having to add stuff. A lot of those packages surely have nothing to do with this issue. What exactly are you trying to do, I do not quite understand the code. \textbar should probably be \bar etc – daleif Dec 27 '16 at 10:08
  • why the \prod command do not display the product symbol in bold ?? – haithem Dec 27 '16 at 10:11
  • Where are you asking it to display it in bold? Isn't the different just that you are not using the same fonts? – daleif Dec 27 '16 at 10:20
  • Please, format your code so that it becomes readable (not on a single line). – egreg Dec 27 '16 at 10:32
  • 1
    @daleif - Weirdly, \textbar{t} is equivalent to \mid t. Don't ask... – Mico Dec 27 '16 at 13:12

Use the following package \usepackage{bm} and code with \bm with required symbol like below:

P^{\circ M,j}_{t+s\textbar{t}}(k)\equiv \displaystyle{{\bm\prod}_{i=1}^{s}} \Pi^{\theta}_{m,t+s-i} \bar{\Pi}^{s(1-\theta)}_{m} P^{\circ{M,j}}(k) \]
  • \textbar isn't appropriate in math mode; use \mid instead. Separately, the \displaystyle directive is both unnecessary and applied incorrectly: it's a switch, i.e., it doesn't take an argument. – Mico Dec 27 '16 at 14:39

You could also always try \mathbb{\Pi}, thats what I usually use. Requires \usepackage{amssymb}.

  • 1
    Your suggested approach is going to create no end of confusion between the \Pi symbols already present in the equation and the (bold) product symbol. – Mico Dec 27 '16 at 13:34

In order to reproduce the screenshot with the objectionable-looking product symbol, it appears to be essential to load the txfonts font package:

enter image description here

P^{\circ M,j}_{t+s\mid t}(k) \equiv \prod_{i=1}^{s} \Pi^{\theta}_{m,t+s-i} 
\bar{\Pi}^{s(1-\theta)}_{m} P^{\circ{M,j}}(k) 

If txfonts is not loaded, the following look is generated:

enter image description here

Note that the \prod symbol is not rendered in bold in either screenshot. It's just naturally "darker" when using Computer Modern fonts.

Incidentally, you shouldn't use \textbar in math mode; use \mid instead.

If you must use Times Roman text and math fonts in your document but simply can't stand the look of the \prod symbol that's generated by either the \txfonts or the \newtxmath font packages, consider using either the mathptmx or the mtpro2 packages. (Aside: the full mtpro2 package isn't free of charge; however, its "lite" subset, which is all that's needed for the example code at hand, is indeed free.)

  • thanks a lot,it works now , your comments are always useful. – haithem Dec 27 '16 at 14:33

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