Semiclassical Physics explores the fascinating and deep connection between classical motion and quantum fluctuations. The book conveys a way of describing quantum effects in a physical system using the periodic orbit theory of Gutzwiller, which focuses on the classical dynamics of the system. The authors seek to demonstrate its usefulness for understanding quantum fluctuations in interacting many-body systems, exhibiting the close link of the shorter classical periodic orbits with the partly resolved shell fluctuations. The extended Thomas-Fermi model is developed in detail and shown...