1 3 Ju n 20 09 Bifurcation of gap solitons in periodic potentials with a sign - varying nonlinearity coefficient
نویسنده
چکیده
We address the Gross–Pitaevskii (GP) equation with a periodic linear potential and a periodic sign-varying nonlinearity coefficient. Contrary to the claims in the previous works of Abdullaev et al. [PRE 77, 016604 (2008)] and Smerzi & Trombettoni [PRA 68, 023613 (2003)], we show that the intersite cubic nonlinear terms in the discrete nonlinear Schrödinger (DNLS) equation appear beyond the applicability of assumptions of the tight-binding approximation. Instead of these terms, for an even linear potential and an odd nonlinearity coefficient, the DNLS equation and other reduced equations for the semi-infinite gap have the quintic nonlinear term, which correctly describes bifurcation of gap solitons.
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