Abstract

In 1867, just two years after laying the foundations of electromagnetism, J. Clerk Maxwell presented a fundamental paper on kinetic gas theory, in which he described the evolution of the gas in terms of certain ‘moments’ of its velocity distribution function. This inspired Ludwig Boltzmann to formulate his famous kinetic equation, from which followed the H-theorem and the connection with entropy. On the occasion of the 150th anniversary of publication of Maxwell's paper, we review the Maxwell–Boltzmann formalism and discuss how its generality and adaptability enable it to play a key role in describing the behaviour of a variety of systems of current interest, in both gaseous and condensed matter, and in modern-day physics and technologies which Maxwell and Boltzmann could not possibly have foreseen. In particular, we illustrate the relevance and applicability of Maxwell's formalism to the dynamic field of plasma-wakefield acceleration.

Highlights

  • Clerk Maxwell is regarded as one of the most influential physicists of all time [1,2,3], and his work continues to underpin many areas of modern-day scientific research and technological development. He is best known for his equations of electromagnetism [4], but is recognised for seminal contributions in other areas of physics, including statistical mechanics and kinetic theory

  • The most significant contribution to the field came in a paper presented to the Royal Society of London 150 years ago [6], in which he linked the microscopic world of atoms with macroscopically measurable properties, through velocity averages or ‘moments’ of a nonequilibrium velocity distribution function f (r, v, t)

  • Its applicability ranges from traditional gas transport theory to present-day cutting-edge research on ultra-relativistic electron beams in plasma-wakefield accelerators

Read more

Summary

Maxwell’s moment equations

Clerk Maxwell (pictured in figure 1) is regarded as one of the most influential physicists of all time [1,2,3], and his work continues to underpin many areas of modern-day scientific research and technological development He is best known for his equations of electromagnetism [4], but is recognised for seminal contributions in other areas of physics, including statistical mechanics and kinetic theory. The most significant contribution to the field came in a paper presented to the Royal Society of London 150 years ago [6], in which he linked the microscopic world of atoms with macroscopically measurable properties, through velocity averages or ‘moments’ of a nonequilibrium velocity distribution function f (r, v, t) In this paper, he developed ‘moment equations’, sometimes referred to as ‘equations of change’, describing the evolution of the properties of a mixture of two monatomic gases, accounting explicitly for the influence of collisions between atoms. It is only in the equilibrium limit that Maxwell discusses an explicit form of the distribution function

Maxwell versus Boltzmann
The enduring influence of Maxwell’s ‘equations of matter’
Coupling Maxwell’s equations of electromagnetism and matter
About this article
Velocity averages and distribution function
Moment equations
The collision term
Relativistic electrons in a plasma medium
The equilibrium distribution function
Maxwell model of interaction
Boltzmann’s equation
Solution of Boltzmann’s equation
Relativistic kinetic equation
Beam emittance in plasma-based accelerators
Moment approach
Result from moment approach and comparison to PIC simulations
Concluding remarks
Maxwell’s collision term
Transport coefficients
Findings
Beyond Maxwell’s collision model

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.