I'm studying hyperbolic conservation laws. I went through LeVeque's book [1], chapters 7 and 8. It gives a very good description of shock and rarefaction waves construction for non-linear systems. However I'm not being able to relate it with Riemann invariants. I'm referring Smoller's book [2] for the same.
I know that in case of a shock wave, along the $k$th eigenvector (integral curve) all the components of $u$ remain constant except the $k$th component (strictly hyperbolic systems).
And now the Riemann invariant $w$ is given by $$\nabla_u w \cdot r_k = 0$$ (Does it mean that the Gradient of $w$ with respect to $u$ along the k-eigenvector of the system is zero?)
Are the two things above related in some way? If I'm completely wrong, I would be very glad if you could recommend some references to start with.
[1] Randall J. LeVeque, Numerical Methods for Conservation Laws, Birkhäuser, 1992. doi:10.1007/978-3-0348-8629-1
[2] Joel Smoller, Shock Waves and Reaction—Diffusion Equations, Springer, 1994. doi:10.1007/978-1-4612-0873-0