Textbook in PDF format

This book results from my walks across the landscape of Physics, and was produced in nearly complete isolation, during the difficult pandemic years of 2020–2021. In previous years I had however visited many countries, and profited from long stays in different institutions, where I worked on a variety of problems, chosen by a mixture of chance and necessity. From this wandering around Physics and around the World, something stayed in my mind and eventually reached the pages of the present book.
Basic photon states
Field quantisation
Coherence
Photon–atom interactions
Boundary effects
Quantum fluids of light
Laser
Bose–Einstein condensates
Collective atomic emission
Light vortices
Superfluid light
Quantum vacuum
Basic QED concepts
Particle pair creation
Nonlinear vacuum
The axions
Appendix A. Elementary quantum
Appendix B. Lagrangians
Appendix C. Photon kinetic equation
Appendix D. Curved spacetime