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Question: finding the dispersion relation

Question:finding the dispersion relation

WA573 80 Maple 18
homework pde pdsolve differential-equations
October 28 2022
1

How to find the dispersion relation (3) in Maple? I try it by equating the coefficients of cos(kx + wt) and its derivative to zero, but couldn't find it.

> 

restart
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with(LinearAlgebra):
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alias(E = E(x, t), P = P(x, t), N = N(x, t), Q = Q(x, t));

E, P, N, Q

 (1)
> 

d := Matrix([[c*(diff(E, t))+diff(E, x), alpha*P, 0, 0], [N[0]*E, diff(P, t), -sigma[2]*Q[0]*N/N[0], sigma[2]*omega[0]*Q], [0, sigma[1]*sigma[2]*Q[0]*P/N[0], diff(N, t), 0], [0, -omega[0]*P, 0, diff(Q, t)]]) = 0

d := (Matrix(4, 4, {(1, 1) = c*(diff(E(x, t), t))+diff(E(x, t), x), (1, 2) = alpha*P(x, t), (1, 3) = 0, (1, 4) = 0, (2, 1) = N(x, t)[0]*E(x, t), (2, 2) = diff(P(x, t), t), (2, 3) = -sigma[2]*Q(x, t)[0]*N(x, t)/N(x, t)[0], (2, 4) = sigma[2]*omega[0]*Q(x, t), (3, 1) = 0, (3, 2) = sigma[1]*sigma[2]*Q(x, t)[0]*P(x, t)/N(x, t)[0], (3, 3) = diff(N(x, t), t), (3, 4) = 0, (4, 1) = 0, (4, 2) = -omega[0]*P(x, t), (4, 3) = 0, (4, 4) = diff(Q(x, t), t)})) = 0

 (2)
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re := -c*omega^3-kappa*omega^2+(c*omega[0]*(N[0]^2*sigma[2]+Q[0]^2*sigma[1])/N[0]^2-alpha*N[0])*omega+kappa*omega[0]*(N[0]^2*sigma[2]+Q[0]^2*sigma[1])/N[0]^2 = 0;

-c*omega^3-kappa*omega^2+(c*omega[0]*(Q[0]^2*sigma[1]+N[0]^2*sigma[2])/N[0]^2-alpha*N[0])*omega+kappa*omega[0]*(Q[0]^2*sigma[1]+N[0]^2*sigma[2])/N[0]^2 = 0

 (3)
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``

``

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