An Introduction to Phase-Integral Methods or the hourglass figure of

or the hourglass figure of the 19th century

a valuable addition to the English-language literature on Fourier series

technical drawings

period fashion

The text concludes with overviews of applications in the classical calculus and diffusion problems

An Introduction to Phase-Integral Methods or the hourglass figure ofThe phase integral method in mathematics, also known as the Wentzel Kramers Brillouin (WKB) method, is the focus of this introductory treatment. Author John Heading successfully steers a course between simplistic and rigorous approaches to provide a concise overview for advanced undergraduates and graduate students in mathematics and physics. Since the number of applications is vast, the text considers only a brief selection of topics and emphasizes