COVID 19 epidemiology and virus dynamics : nonlinear physics and mathematical modeling This book addresses the COVID 19 pandemic from a quantitative perspective based on mathematical models and methods largely used in nonlinear physics. It aims to study COVID 19 epidemics in countries and SARS CoV 2 infections in individuals from the nonlinear physics perspective and to model explicitly COVID 19 data observed in countries and virus load data observed in COVID 19 patients. The first part of this book provides a short technical introduction into amplitude spaces given by eigenvalues eigenvectors and amplitudes.In the second part of the book mathematical models of epidemiology are introduced such as the SIR and SEIR models and applied to describe COVID 19 epidemics in various countries around the world. In the third part of the book virus dynamics models are considered and applied to infections in COVID 19 patients. This book is written for researchers modellers and graduate students in physics and medicine epidemiology and virology biology applied mathematics and computer sciences. This book identifies the relevant mechanisms behind past COVID 19 outbreaks and in doing so can help efforts to stop future COVID 19 outbreaks and other epidemic outbreaks. Likewise this book points out the physics underlying SARS CoV 2 infections in patients and in doing so supports a physics perspective to address human immune reactions to SARS CoV 2 infections and similar virus infections.