“…This theory has been extensively applied to elliptic and parabolic problems in the context of finite element approximation, as evidenced by various studies [27,6,12,4,3,7,13,14,18,19,20,28,17]. However, the a posteriori analysis of hyperbolic problems, whether using the finite element method or the spectral element method, remains relatively unexplored in the literature [5,10,11,16,24,25,15,1,2].…”