This book is an English translation from a Hungarian book designed for graduate and postgraduate students about the use of variational principles in theoretical physics. Unlike many academic textbooks, it dashes across several lecture disciplines taught in physics courses. It emphasizes and demonstrates the use of the variational technique and philosophy behind the basic laws in mechanics, relativity theory, electromagnetism, and quantum mechanics. The book is meant for advanced students and young researchers in theoretical physics but, also, more experienced researchers can benefit from its reading.

Autorentext

Tamás Biró received a master's degree in Physics and Biophysics and a Ph.D. from Eötvös Loránd University in Budapest. He first worked on theoretical heavy-ion physics and strange quark production in quark-gluon plasma at KFKI Research Institute for Particle and Nuclear Physics in Budapest. He then continued as a researcher at the Niels Bohr Institute in Copenhagen, at the GSI Centre for Heavy Ion Research in Darmstadt, and at the Institute for Theoretical Physics at the University of Giessen. From 2013 to 2019, he served as Vice Director of the Institute for Particle and Nuclear Physics at the Wigner Research Centre for Physics in Budapest.

He proposed the color rope model for describing the early phase of ultra-relativistic heavy-ion collisions in 1983, participated in studies of chaotic dynamics in strongly interacting non-abelian gauge fields from 1991 to 2004, and then developed a framework for the statistical physics of complex systems and non-extensive thermodynamics.

Currently, he leads the Nanoplasmonic Laser Inertial Fusion Experiment, NAPLIFE, at the Wigner RCP (2020-2025). He has collaborated with colleagues at Duke University in North Carolina, USA, at Bergen University in Norway, at the Universities of Cape Town and Johannesburg, South Africa, at the Central China Normal University in Wuhan, China, at the Yukawa Institute in Kyoto, Japan, at the UBB Cluj in Romania, and at TU Wien in Austria. He edited Acta Physica Hungarica and served as Editor-in-Chief of EPJ A (Hadrons and Nuclei).