I am getting these strange eigenvalues of this simple looking 4-dimensional matrix:
mymatrix = {{1 - a, -((I Conjugate[b])/Sqrt[2]), b/Sqrt[
2], -((I a)/2)}, {(I b)/Sqrt[2], a/2, 0, 0}, {Conjugate[b]/Sqrt[
2], 0, a/2, 0}, {(I a)/2, 0, 0, 0}};
Eigenvalues[mymatrix]
(**{a/2, Root[
a^3 + (4 a - 6 a^2 - 8 b Conjugate[b]) #1 + (-8 + 4 a) #1^2 +
8 #1^3 &, 1],
Root[a^3 + (4 a - 6 a^2 - 8 b Conjugate[b]) #1 + (-8 + 4 a) #1^2 +
8 #1^3 &, 2],
Root[a^3 + (4 a - 6 a^2 - 8 b Conjugate[b]) #1 + (-8 + 4 a) #1^2 +
8 #1^3 &, 3]})
What to do with this Root[] stuff?
Root
in the documentation? $\endgroup$