There are, however, certain examples in which the interpretation listed above fails. These are exact vacuum solutions of the Einstein field equations with cylindrical symmetry. For instance, a static (infinitely long) cylinder can produce a gravitational field which has not only the expected "Coulomb"-like Weyl component Ψ Ψ 2 , but also non-vanishing "transverse wave"-components Ψ Ψ 0 and Ψ Ψ 4 . Furthermore, purely outgoing Einstein-Rosen waves have a non-zero "incoming transverse wave"-component Ψ Ψ 0 .