documentclass[20pt]{report}
usepackage[utf8]{luainputenc}
usepackage[skip=8pt,font=footnotesize]{caption}
usepackage[a4paper, total={6.5in, 9.63in}]{geometry}
usepackage{microtype}
usepackage{amsmath}
usepackage{amsfonts}
usepackage{graphicx}
usepackage{float}
usepackage{amsthm, bm}
usepackage{caption}
usepackage{subcaption}
usepackage{mwe}
usepackage{physics}
usepackage{mdframed}
usepackage{esint}
usepackage[export]{adjustbox}
usepackage{bm}
usepackage{hyperref}
usepackage[backend=bibtex]{biblatex}
usepackage[nottoc]{tocbibind}

letdundefined
renewcommand{d}{delta}