equations
I try to write this code but I have a Missing { inserted error.
Can anyone help me?
\begin{gather}
\begin{split}
\mathop{\min}\limits_{P_{ng},P_l,R_n,Z_l,\theta _n \in \,\,\Omega ^{OTS}} & {\mathop {\max}\limits_{P_{nd} \in \,\,US}
\quad \overbrace {\sum\limits_{\forall n \in {\Omega ^N}} {\sum\limits_{\forall g \in {\Omega ^{G - n}}} {{C_{ng}}{P_{ng}}} } }^{{\rm{T1}}}+\\
&\overbrace {\sum\limits_{\forall n \in {\Omega ^N}} {VOLL_n} \cdot {R_n} }^{\rm{T2}}}\\
\end{split}
\end{gather}
The $ are not needed here since the align environment is in math mode. Give this a shot.
\begin{align}
\int_{-1}^{1}\int_{0}^{2}\frac{1}{2^{3/4}}(1+y)dydx &= \int_{-1}^{1}\Big[\frac{y}{2^{3/4}}+\frac{y^{2}}{2^{7/4}}\Big]_{0}^{2}dx\\
&= \int_{-1}^{1}\frac{2}{2^{3/4}}+\frac{4}{2^{7/4}}dx\\
&= \Big[\frac{2x}{2^{3/4}}+\frac{4x}{2^{7/4}}\Big]_{-1}^{1}\\
&= \frac{2}{2^{3/4}}+\frac{4}{2^{7/4}}-\Big(\frac{-2}{2^{3/4}}-\frac{4}{2^{7/4}}\Big)\\
&= 4\sqrt[4]{2}
\end{align}
If you do not want each line to be numbered, simply use align* instead of align.
Hope this helps!
Your problem arises from the misuse of \textbf in the first subscript: as @Zarko pointed out, for it to work, instead of \Gamma_\textbf{P} you could use \Gamma_{\textbf{P}}. Nevertheless this is not recommended, since textbf is a text command. In order to have bold text in math mode you'd better use:
mathbf which uses an upright bold math font, or
\usepackage{bm} and then the bm command, which gives an italic bold math font
mix and match the two.
Also, is quite pointless to have an align environment without alignments. I substituted it with a plain equation.
Example with mathbf
\documentclass{article}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{makeidx}
\usepackage{graphicx}
\usepackage{physics}
\begin{document}
\begin{equation}
\Gamma_\mathbf{P}(\mathbf{r})=-\frac{2\pi}{m}\int \frac{\dd[3]{k}}{(2\pi)^3} e^{-i\mathbf{k\cdot\mathbf{r}}}f_p(\mathbf{k})
\end{equation}
\end{document}
Example with bm
\documentclass{article}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{makeidx}
\usepackage{graphicx}
\usepackage{physics}
\usepackage{bm}
\begin{document}
\begin{equation}
\Gamma_{\bm{P}}(\bm{r})=-\frac{2\pi}{m}\int \frac{\dd[3]{k}}{(2\pi)^3} e^{-i\bm{k\cdot\bm{r}}}f_p(\bm{k})
\end{equation}
\end{document}
Best Answer
You're using too many unnecessary braces and it's easy to lose oneself in balancing them.
Here's a reduced (and improved version):
Note that
\maxand\minare already math operators taking limits; with\substackit's possible to break a long condition into several lines. Also\rmshould never be used,\mathrmis the right command. ForVOLLit's better to use\mathitbecause it's a single variable name, not the product of four quantities. The same might apply toUSandOTS, check their meaning.I'd remove all
\forall, which are generally not used in that context (but it depends on the field of research).