  Flaming phenomena represent the divergence in the strength of user dynamics
as created by user interactions in online social networks (OSNs). Although it
has been known that flaming phenomena occur when the Laplacian matrix of the
OSN has non-real eigenvalues, it was recently shown that flaming phenomena may
occur even if all the eigenvalues are real numbers. This effect appears only in
the situation that some eigenvalues are degenerate, and a special unitary
transformation is applied to the equations representing user dynamics; whether
actual OSNs satisfy this condition has not been fully discussed. In this paper,
we clarify that the user dynamics caused by the degeneration of eigenvalue 0 is
one specific example of the above condition. We also investigate the mechanism
and characteristics of flaming phenomena generated by degenerated eigenvalues.
Furthermore, we demonstrate through numerical simulations that the degeneration
of eigenvalues can cause divergence.
