Mathematics Subject Classification. Primary: 35Q55; Secondary: 35B40. Key words and phrases. Schrödinger equation with higher order dispersion, scattering problem. 219 220 JEAN-CLAUDE SAUT AND JUN-ICHI SEGATAIn this paper, we study the asymptotic behavior in time of solutions to (1.2).The Cauchy problem for the homogeneous fourth order nonlinear Schrödinger type equationhas been studied by many authors, most of the results holding also when lower dispersive terms are added. By using the Strichartz estimates in [3] one shows that the Cauchy problem is locally well-posed in the energy space H 2 (R d ) for the energy subcritical case (i.e., 1 < p < 1 + 8/(d − 4) when d ≥ 5 and 1 < p < ∞ when d ≤ 4) and in L 2 (R d ) for the mass subcritical case (1 < p < 1 + 8/d). We also refer to Bouchel [6] who studies the Cauchy problem and furthermore gives non-existence, existence and qualitative properties results of solitary wave solutions for (1.1). See also [12] for results on the Cauchy problem for slightly more general situations.There are several results concerning the scattering and blow-up of solutions for (1.3). For the defocusing case λ < 0, the global well-posedness and scattering for (1.3) with the energy-critical nonlinearity (i.e., (1.3) with d 5, and p = 1 + 8/(d − 4)) was studied by Pausader [32] for radially symmetric initial data by combining the concentration-compactness argument by Kenig-Merle [25] and Morawetz-type estimate. Later, Miao, Xu and Zhao [28] proved a similar result for (1.3) in the energy-critical and higher dimensional case d 9 without radial assumption on initial data. In [33], Pausader has shown the global well-posedness and scattering of (1.3) with cubic nonlinearity for the case 5 d 8. Pausader and Xia [34] proved the global well-posedness and scattering for (1.3) with mass supercritical nonlinearity (i.e., (1.3) with p > 1 + 8/d) for low dimensions 1 d 4 by using a virial-type estimate instead of the Morawetz-type estimates.For the focusing case λ > 0, Pausader [31] and Miao, Xu and Zhao [27] independently showed the global well-posedness and scattering for (1.3) with the energycritical nonlinearity for radially symmetric initial data withḢ 2 and energy norms below that of the ground state. When the initial data is sufficiently small, Hayashi, Mendez-Navarro and Naumkin [14] proved the global existence and the scattering for (1.3) with d = 1 and p > 5 by using the factorization technique developed by the authors [16]. In [14] they also shown the small data global existence and the decay estimates for (1.3) with d = 1 and p > 4 under the assumption that the initial data is odd. In the subsequent paper [15], they proved that when d = 1, p = 5 and λ < 0, a solution to (1.3) has dissipative structure and gains additional logarithmic decay. Aoki, Hayashi and Naumkin [2] showed the global existence and scattering of (1.3) with d = 1, 2 and p > 1 + 4/d. We refer also to the series of paper by Hayashi and Naumkin [18,19,21] and work by Hirayama and Okamoto [22] for interesting phenomena on the...