This book contains chapters on a range of topics in mathematics and mathematical physics, including semigroups, algebras, operator theory and quantum mechanics, most of them have been presented at the International Conference on Semigroup, Algebras, and Operator Theory (ICSAOT-22), held at Cochin, Kerala, India, from 28–31 March 2022. It highlights the significance of semigroup theory in different areas of mathematics and delves into various themes that demonstrate the subject’s diverse nature and practical applications. One of the key features of the book is its focus on the relationship between geometric algebra and quantum mechanics. The book offers both theoretical and numerical approximation results, presenting a comprehensive overview of the subject. It covers a variety of topics, ranging from C*-algebraic models to numerical solutions for partial differential equations. The content of the book is suitable for active researchers and graduate students who are just beginning their studies in the field. It offers insights and practical applications that would be valuable to anyone interested in the mathematical foundations of physics and related fields. Overall, this book provides an excellent resource for anyone seeking to deepen their understanding of the intersections between mathematics and physics.