What commands should I use to type the following operators
and 
?
[Tex/LaTex] How to write Mathematical expectation and Probability in the following form
math-modesymbols
Related Solutions
\DeclareMathOperator{\foo}{foo} and \DeclareMathOperator*{\hocolim}{hocolim} for sub- and superscripts in the limits position.
This requires
\usepackage{amsmath}
which is recommended for math documents anyway.
Minimal example:
\documentclass{article}
\usepackage{amsmath}
\DeclareMathOperator{\foo}{foo}
\DeclareMathOperator*{\hocolim}{hocolim}
\begin{document}
Example of $\foo(x)$ and $\foo x$.
Example of $\hocolim_{x\in X} f(x)$ and displayed
\begin{equation*}
\hocolim_{x\in X} f(x)
\end{equation*}
\end{document}
The following will work nicely:
\documentclass{article}
\usepackage{amsmath}
\usepackage{mathtools}
\DeclareMathOperator{\Hessian}{Hess}
\begin{document}
\begin{align}
(\Hessian f)_{ij} &\equiv \frac{\partial^{2} f}{\partial x_{i} \partial x_{j} } \\
\Hessian\left( \frac{x^{2}}{y} \right) &=
\begin{bmatrix}
\frac{2}{y} & - \frac{2x}{y^{2}} \\
-\frac{2x}{y^{2}} & \frac{2x^{2}}{y^{3}}
\end{bmatrix}
\end{align}
\end{document}
Best Answer
This looks just like a sans serif font to me. So I would do the following.
\displaylimitsis just used in order to get the first image of your referred homepage. I would leave it away.d\omegawould look better as\mathrm{d}\omegain my eyes. Matter of taste.