“…However, these results are either of a perturbative nature (Grillakis et al, 1987;Strauss, 1989;Rose & Weinstein, 1988;Weinstein, 1986) and deal the solutions near the bifurcation point or they deal with a weaker notion of orbital stability (Cazenave & Lions (1982), Cazenave (2003), Hajaiej & Stuart (2004)). In a major contribution to the understanding of orbital stability, conditions were established in Grillakis et al (1987) giving a rigorous setting for the Vakhitov-Kolokolov (V-K) criterion (1973) (Kivshar & Sukhorukov, 2001). In our context, the V-K criterion states that u λ (x)e −iλτ is orbital stable if…”