devnagari_maths.tex

\documentclass{amsart}

\usepackage{
  amscd,
  amsfonts,
  amsmath,
  amssymb,
  amsbsy,
  amsthm
}

% devnagari characters for extra letters
\usepackage{polyglossia}
\newfontfamily\sanskrit[Script=Devanagari]{Lohit Devanagari}
\newcommand{\Aa}{\textnormal{   \footnotesize \sanskrit अ }}
\newcommand{\Ee}{\textnormal{   \footnotesize \sanskrit इ }}
\newcommand{\Uu}{\textnormal{   \footnotesize \sanskrit ऊ }}
\newcommand{\Ree}{\textnormal{  \footnotesize \sanskrit ऋ }}
\newcommand{\Ey}{\textnormal{   \footnotesize \sanskrit ए }}
\newcommand{\Ba}{\textnormal{   \footnotesize \sanskrit ब}}
\newcommand{\Bha}{\textnormal{  \footnotesize \sanskrit भ}}
\newcommand{\Ca}{\textnormal{   \footnotesize \sanskrit च}}
\newcommand{\Cha}{\textnormal{  \footnotesize \sanskrit छ}}
\newcommand{\Da}{\textnormal{   \footnotesize \sanskrit ड}}
\newcommand{\Dda}{\textnormal{  \footnotesize \sanskrit द}}
\newcommand{\Dha}{\textnormal{  \footnotesize \sanskrit ध}}
\newcommand{\Ddha}{\textnormal{ \footnotesize \sanskrit ढ}}
\newcommand{\Dna}{\textnormal{  \footnotesize \sanskrit ण}}
\newcommand{\Ga}{\textnormal{   \footnotesize \sanskrit ग}}
\newcommand{\Gha}{\textnormal{  \footnotesize \sanskrit घ}}
\newcommand{\Ha}{\textnormal{   \footnotesize \sanskrit ह}}
\newcommand{\Ja}{\textnormal{   \footnotesize \sanskrit ज}}
\newcommand{\Jha}{\textnormal{  \footnotesize \sanskrit झ}}
\newcommand{\Ka}{\textnormal{   \footnotesize \sanskrit क}}
\newcommand{\Kha}{\textnormal{  \footnotesize \sanskrit ख}}
\newcommand{\Ksha}{\textnormal{ \footnotesize \sanskrit ष}}
\newcommand{\La}{\textnormal{   \footnotesize \sanskrit ल}}
\newcommand{\Ma}{\textnormal{   \footnotesize \sanskrit म}}
\newcommand{\Yna}{\textnormal{  \footnotesize \sanskrit ञ}}
\newcommand{\Na}{\textnormal{   \footnotesize \sanskrit न}}
\newcommand{\Nga}{\textnormal{  \footnotesize \sanskrit ङ}}
\newcommand{\Pa}{\textnormal{   \footnotesize \sanskrit प}}
\newcommand{\Pha}{\textnormal{  \footnotesize \sanskrit फ}}
\newcommand{\Ra}{\textnormal{   \footnotesize \sanskrit र}}
\newcommand{\Sa}{\textnormal{   \footnotesize \sanskrit स}}
\newcommand{\Sha}{\textnormal{  \footnotesize \sanskrit श}}
\newcommand{\Ta}{\textnormal{   \footnotesize \sanskrit ट}}
\newcommand{\Tta}{\textnormal{  \footnotesize \sanskrit त}}
\newcommand{\Tha}{\textnormal{  \footnotesize \sanskrit थ}}
\newcommand{\Ttha}{\textnormal{ \footnotesize \sanskrit ठ}}
\newcommand{\Va}{\textnormal{   \footnotesize \sanskrit व}}
\newcommand{\Ya}{\textnormal{   \footnotesize \sanskrit य}}

\title{$\alpha$ move over, \Aa is here}

\begin{document}
\maketitle

Here is some devnagari in text: \Bha \Kha \Yna

\textbf{devnagari instead of greek letters}

\begin{align*}
y_{it} &= \Aa + \Ba d_{it} + \Tha x_{it} + \Ga_i + \Ta_t + \Ey_{it} \\
d_{it} &= \Ree + \Pha z_{it} + \Ga_i + \Ta_t + \Ee_{it} \\
\end{align*}

\end{document}