On the afternoon of January 13, the Beijing Institute of Nanoenergy and Systems of the Chinese Academy of Sciences released two major scientific research progress, saying that Wang Zhonglin, director and chief scientist of the Beijing Institute of Nanoenergy and Systems of the Chinese Academy of Sciences and a foreign academician of the Chinese Academy of Sciences, has successfully expanded Maxwell's equations after several years of research and experimental verification.
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On January 17, the headline of "Intellectuals" published the "Hot Discussion | Academician Wang Zhonglin "Expanding Maxwell's Equations", what does the academic community think? " article. In response to the main questions mentioned in the article, on the same day, we also received an exclusive reply from Academician Wang Zhonglin. The original text of the Intellectual publishes his written response below.
Experts question one:
The electrodynamics of moving media is the problem that Einstein wanted to solve 117 years ago, and thinking and researching on this problem led to one of the greatest discoveries in the history of physics, the birth of special relativity. But this problem has been completely solved by Einstein, and the electrodynamics of moving media has long been written into textbooks.
Wang Zhonglin responded:
The theory of relativity is a great theory. And our proposed extended Maxwell equations do not contradict special relativity. Special relativity describes the different observations brought about by the simultaneous observation of an electromagnetic phenomenon occurring in the A reference frame and two different people in the B reference frame in motion, that is, two observers of one electromagnetic phenomenon. In this case, the expression of Maxwell's equations in both coordinate systems is unchanged. However , the extended Maxwell equations describe the results of two different and possibly related electromagnetic phenomena occurring in the A reference frame and the B reference frame in motion being observed by the same person in the A reference frame , i.e. two associated electromagnetic phenomena by one observer , and assume that the speed of the medium is much smaller than the speed of light. Figure 7 in the original text makes this distinction very clear. Landau and Lifshitz's book discusses the situation under special relativity, while we discuss the latter. On page 4 of our article, the earlier paragraph of Formula (14a), we clarified the boundary conditions and assumptions, and for moving objects far below the speed of light, the Galileo transformation can be processed with the equation system. At this point, it is possible that the processed system of equations does not have covariantity, but does not affect the specific object we are going to study and its application in engineering, because we are not strictly discussing field theory. [1]
[1] Zhong Lin Wang “ On the expanded Maxwell’s equations for moving charged media system – general theory, mathematical solutions and applications in TENG”， Materials Today; https://doi.org/10.1016/j.mattod.2021.10.027
Expert Question Two:
His equation simply divides the electrical displacement vector into two parts, and the time partial differential becomes a full micro-quotient, just a natural result of putting the reference frame on the moving fluid element, which does not need to be proved, and there is no theoretical contribution.
Over the past decade, we have been vigorously developing the use of frictional power effects to convert mechanical work into electrical work, that is, friction nanogenerators (TENG). Our original idea was to establish a quantitative calculation of the output power of THE TENG through the study of the displacement current. Later, inspired by the literature, we began to explore the electrodynamics of dynamic media. The maxwell equations given in the current textbooks are suitable for static media, and this assumption is generally not mentioned, so a large number of students think that maxwell equations are absolutely true under any conditions. The purpose of this article is to use this system of equations to study problems in dynamic media, and to give the corresponding mathematical solutions, hoping to develop new detection techniques or more accurate detection methods in application and engineering. Of course, our theory assumes that the speed of the medium is moving much lower than the speed of light. This is no problem in engineering applications.
In the section of Mr. Landau's Section on Continuum Mechanics - Electrodynamics of Moving Dielectrics, "The motion of a medium leads to the interaction of electric and magnetic fields" is studied. As described in the book, "§63 starts with the formula for field transformations when converting from one reference frame to another", and "the problem in dielectrics is much more complex... The speed usually involved in the motion of macroscopic objects is much smaller than the speed of light. However, it is much simpler to obtain the corresponding approximate transformation formula according to the relativistic formula that is correct in speed. ”...... It can be clearly seen that the derivation in the book is based on the deformation treatment under the theory of relativity, which is a strict treatment.
However, we are doing non-relativistic treatments much lower than the speed of light according to the specific study object. The results of the Galileo and Lorentz transforms at low speeds are similar, and the article cares more about the application and practicality of the system of equations, for example, different solutions are given later in the article. If the relativistic treatment is performed, a considerable amount of physical quantities is required, the equations will be very complex, and the calculation results may be similar to the results obtained in the article. Also: The article cites several articles by Minkowski, Hertz, Gluckman, Rozov, Tai, Costen, and others, see references 16-26 in the article.
Experts question three:
The paper itself has problems in derivation. Specifically, starting from Wang Wen's comic propaganda map, equations 1 and 4 on the left side of the figure can be obtained from the corresponding equations of motion of the Abel Yang-Mills, and the coupling to the material field (including charged particles and dielectrics) is in these two equations. Equations 2 and 3 are identities, not derived from the Yang-Mills equation, but topological constraints that any gauge theory, including non-Abel Yang-Mills theory, is required to satisfy, called the Bianchi identity. To modify equations 2 and 3, one can only be a topological object, which in electromagnetic theory is a magnetic monopole and its flow. Academician Wang's expansion is obviously not a magnetic monopole.
Our discussion is a non-relativistic treatment that does not involve the problem of magnetic single stages.
Experts question four:
Why is such an important job not published in a physics magazine? Instead of choosing a related journal in materials science?
Over the past decade, we have been working intensively to study the output characteristics and power of triboelectric nanogenerators using displacement currents. We have been doing research in this area since 2016, and the work has been published in journals related to applied physics and materials [2-4]. The purpose of our writing this article is to systematically introduce the extended Maxwell equation system and its physical concepts, hoping to use this equation system to study problems in dynamic media, and to give the corresponding mathematical solutions. Our aim is not to develop relevant field theories, but to develop new detection techniques or more precise detection methods in application and engineering. We also hope that through these works, we will arouse everyone's interest in this regard and explore new applications.
[2] Z.L. Wang and A.C. Wang “On the origin of contact electrification“ (Review), Materials Today, 30 (2019) 34-51; https://doi.org/10.1016/j.mattod.2019.05.016 [3] Z.L. Wang “From conctact electrication to triboelectric nanogenerators“ (Review), Report on Progress in Physics, 84 (2021) 096502; https://doi.org/10.1088/1361-6633/ac0a50
[4] Jiajia Shao, Morten Willatzen*, and Zhong Lin Wang* “Theoretical modelling of triboelectric nanogenerators (TENGs)” （Review）, J. Applied Physics, 128 (2020) 111101; https://doi.org/10.1063/5.0020961
Plate editor| Lucas
![Wang Zhonglin, director of the Beijing Institute of Nanoenergy and Systems of the Chinese Academy of Sciences, expanded Maxwell's equations[fig]](data:image/gif;base64,R0lGODlhAQABAIAAAP///wAAACwAAAAAAQABAAACAkQBADs=)