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phoenix.com technology news: on september 2, zhang chaoyang officially released the third volume of zhang chaoyang's physics class and held a book signing. he introduced that "quantum mechanics has been involved in the first volume, which describes the formation and development of basic quantum mechanics. the third volume is a higher-level calculation of the entire quantum mechanics." speaking of the three years of live broadcasting of physics classes, zhang chaoyang believes that it is important to follow the "10,000-hour theory". "when you decide to do something, the most important thing is to persist. if you persist for a long time to a certain extent, quantitative changes will lead to qualitative changes."

at the event, zhang chaoyang, founder, chairman and ceo of sohu and a doctor of physics, explored the "milestone" topic of quantum mechanics, the specific heat of solids. among them, the chapter "phonons and specific heat of solids" in the third volume of the new book is a "milestone" topic in quantum mechanics. subsequently, zhang chaoyang carried out detailed derivations and calculations around this topic in the book, and analyzed the behavior of the specific heat of solids at the low temperature limit.

solids are composed of neatly arranged atoms or molecules. when heated, they absorb heat and vibrate. solids use this vibration to store energy. einstein compared lattice vibrations to oscillators, explaining for the first time why the specific heat at low temperatures approaches zero and absolute zero cannot be reached. but debye discovered that einstein's model was flawed at low temperatures and revised the dispersion relation of vibrational energy levels. zhang chaoyang explained debye's improvements through the energy level diagram on the blackboard: the gaps between sound wave energy levels are not fixed constants, and the energy level gaps corresponding to low-frequency sound waves are also low, which allows solids to convert thermal energy into internal energy more efficiently at low temperatures, thereby increasing specific heat.

(zhang chaoyang used a unique method to demonstrate that the energy level spacing of the oscillator with different k is different)

at the scene, a student asked about the popular internet meme "when in doubt, use quantum mechanics". zhang chaoyang explained that this sentence reflects the wide application of quantum mechanics. for example, many problems on earth, material properties, the behavior of liquid helium, and even some high-tech exploration projects are related to quantum mechanics. he cited the recent news that boeing's mission was delayed due to a liquid helium leak as an example. the boosters of the space shuttle need to be cooled with liquid helium, thanks to the fact that helium can remain liquid at low temperatures and normal pressures, and helium does not solidify at low temperatures, which involves the principles of quantum mechanics.

the third volume of "zhang chaoyang's physics class" focuses on quantum mechanics, from the unknown atomic nucleus to the unreachable white dwarf, from the structural details of atoms and molecules to the macroscopic laws of the transformation of material states, from the classic case of double pendulums to the cutting-edge technology of nuclear magnetic resonance, spanning multiple disciplines such as solid state physics, structural chemistry, and astronomy.

it is understood that the new book released this time is divided into 13 chapters, and the content is compiled from the 129th to 184th sohu video physics live course. zhang chaoyang introduced that the book starts with interesting questions and provides different tour routes of the ancient city of physics, which can be used as a supplementary reading material besides the textbooks of university science and engineering majors.

compared with the first two volumes, the third volume of zhang chaoyang's physics class uses more mathematical tools, including partial differential equations, matrix diagonalization, and variational calculus, to demonstrate the integration of mathematics and physics. in addition, this volume is no longer limited to explaining a few concepts and particles, but presents the appearance of quantum mechanics from all aspects, from the connection between the macro and micro, the unsolved mysteries of quantum mechanics to the application of modern technology.