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I have some comments/questions about the terminology used for dielectrics in physics textbooks. Linear dielectric means that components of [itex]\vec{P}[/itex] are linear

combination of the components of [itex]\vec{E}[/itex].

Homogeneous dielectric means that dielectric constant is not the function of coordinates.

Isotropic dielectric means that at any given point inside the dielectric , the dielectric constant (and hence [itex]\chi[/itex] ) is same in all directions, which ,means that all off diagonal elements in the matrix [itex]\chi[/itex] are zero.

Physics textbooks most often talk about homogeneous isotropic linear dielectric. But some times they relax some conditions but don't specify the nature of the dielectric exactly. Lot of sloppy language there.

Now I am just trying to play with these 3 words and see what I get. for example , consider,

homogeneous nonisotropic linear dielectric. So here [itex]\chi[/itex] is a tensor and

off diagonal elements are non zero. Further it is not function of coordinates.

Do such dielectrics exist ?

Next, consider nonhomogeneous isotropic linear dielectric. Here [itex]\chi[/itex] is a scalar

which is a function of coordinates and we still have linearity. Again do such materials exist ?

Finally, nonhomogeneous nonisotropic nonlinear dielectrics. I know J.D.Jackson talks about

non linear dielectrics , but I am not sure if he talks about this particular case, which is

most general. Do such materials exist ?

thanks

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# Terminology about dielectrics

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