Effective mass of Dirac electron increased by electrostatic potential?

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SUMMARY

The discussion centers on the effective mass of a Dirac electron influenced by an electrostatic potential in the context of the Higgs vacuum field. The simplified Dirac equation, incorporating the electrostatic potential A_0 = φ, leads to the conclusion that the state ψ_L + ψ_R can be interpreted as having an effective mass of gv + eφ. The presence of an electrostatic field does indeed increase the electron's mass beyond that induced by the Higgs vacuum field alone. The nonrelativistic limit of the Dirac equation and the Foldy-Wouthuysen representation are essential for further understanding this phenomenon.

PREREQUISITES
  • Understanding of the Dirac equation and its implications in quantum mechanics.
  • Familiarity with the concepts of Higgs vacuum field and electrostatic potentials.
  • Knowledge of Weyl or Chiral basis representations in quantum field theory.
  • Basic grasp of particle physics, particularly the behavior of fermions.
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  • Research the Foldy-Wouthuysen representation for insights into the nonrelativistic limit of the Dirac equation.
  • Explore the implications of the Higgs mechanism on particle mass in quantum field theory.
  • Study the effects of electrostatic potentials on fermionic states in quantum mechanics.
  • Examine the relationship between energy and mass in relativistic quantum mechanics.
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Physicists, particularly those specializing in quantum mechanics and particle physics, as well as students and researchers interested in the effects of electromagnetic fields on particle mass.

johne1618
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The Dirac electron in the Higgs vacuum field v and an electromagnetic field with vector potential A_\mu is described by the following equation:

i \gamma^\mu \partial_\mu \psi = g v \psi + e \gamma_\mu A^\mu \psi

where g is the coupling constant to the Higgs field and e is the coupling constant to the electromagnetic field.

Let us assume that we are in the rest frame of the electron so that:

\partial_x=\partial_y=\partial_z=0

Let us also assume that there is only an electrostatic potential A_0=\phi so that:

A_x = A_y = A_z = 0

So the simplified Dirac equation is now:

i \gamma^0 \partial_t \psi = g v \psi + e \gamma_0 \phi \psi

Let us choose the Weyl or Chiral basis so that:

\gamma^0 = \begin{pmatrix} 0 & I \\ I & 0 \end{pmatrix}

where I is the 2\times2 unit matrix.

In this representation:

\psi=\begin{pmatrix} \psi_L \\ \psi_R \end{pmatrix}

where \psi_L and \psi_R are left-handed and right-handed two-component Weyl spinors.

Subtituting into the simplified Dirac equation above we get:

i \begin{pmatrix} 0 & I \\ I & 0 \end{pmatrix} \begin{pmatrix} \partial \psi_L / \partial t \\ \partial \psi_R / \partial t \end{pmatrix} = g v \begin{pmatrix} \psi_L \\ \psi_R \end{pmatrix} + e \phi \begin{pmatrix} 0 & I \\ I & 0 \end{pmatrix} \begin{pmatrix} \psi_L \\ \psi_R \end{pmatrix}

This equation separates into two equations of two-component Weyl spinors:

i \partial \psi_R / \partial t = g v \psi_L + e \phi \psi_R

i \partial \psi_L / \partial t = g v \psi_R + e \phi \psi_L

Now let us add these two equations together to obtain:

i \frac{\partial}{\partial t} (\psi_L + \psi_R) = (g v + e \phi)(\psi_L + \psi_R)

My question is this:

Does the state \psi_L + \psi_R describe an electron with an effective mass given by gv + e \phi?

Does the presence of an electrostatic field increase the electron's mass over and above the mass induced by the Higgs vacuum field alone?
 
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johne1618, Mass is more than just "energy at rest". To define what the mass is, you need to see how the energy changes when the object is slowly moving (as in p2/2m.) The nonrelativistic limit of the Dirac equation is a thoroughly studied topic. I suggest you google for material on the Foldy Wouthuysen representation.
 
Prof Susskind has kindly answered my question in an attachment. Adding a constant potential is equivalent to an overall phase shift and has no effect on the electron's equation of motion.

The file is attached to a reply to my similar thread in the Particle Physics Forum.

https://www.physicsforums.com/showthread.php?t=562314
 
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