# Quintic NLS

#### Quintic NLS on ${\displaystyle R}$

• This equation may be viewed as a simpler version of [#dnls-3_on_R cubic DNLS], and is always at least as well-behaved. It has been proposed as a modifiation of the Gross-Pitaevski approximation for low-dimesional Bose liquids KolNewStrQi2000
• Scaling is sc = 0, thus this is an [#L^2-critical_NLS L^2 critical NLS].
• LWP is known for s ³ 0 CaWe1990, Ts1987.
• For s=0 the time of existence depends on the profile of the data as well as the norm.
• Below L^2 we have ill-posedness by Gallilean invariance considerations in both the focusing [KnPoVe-p] and defocusing [CtCoTa-p2] cases.
• GWP for s>4/9 in the defocussing case [Tzi-p]
• For s>1/2 this is in CoKeStTkTa-p6
• For s>2/3 this is in CoKeStTkTa-p4.
• For s > 32/33 this is implicit in Tk-p.
• For s³ 1 this follows from LWP and Hamiltonian conservation.
• One has GWP and scattering for small L2 data for any quintic non-linearity. The corresponding problem for large L2 data and defocussing nonlinearity is very interesting, but probably very difficult, perhaps only marginally easier than the corresponding problem for the [#Cubic_NLS_on_R^2 2D cubic NLS]. It would suffice to show that the solution has a bounded L6 norm in spacetime.
• Explicit blowup solutions (with large L2 norm) are known in the focussing case BirKnPoSvVe1996. The blowup rate in H1 is t-1 in these solutions. This is not the optimal blowup rate; in fact an example has been constructed where the blowup rate is |t|^{-1/2} (log log|t|)^{1/2}[Per-p]. Furthermore, one always this blowup behavior (or possibly slower, though one must still blow up by at least |t|^{-1/2}) whenever the energy is negative [MeRap-p], [MeRap-p2], and one either assumes that the mass is close to the critical mass or that xu is in L^2.
• One can modify the explicit solutions from BirKnPoSvVe1996 and in fact create solutions which blow up at any collection of specified points in spacetime BoWg1997, Nw1998.
• Remark: This equation is pseudo-conformally invariant. GWP results in Hs automatically transfer to GWP and scattering results in L2(|x|s) thanks to the pseudo-conformal transformation.
• Solitons are H1-unstable.

#### Quintic NLS on ${\displaystyle T}$

• This equation may be viewed as a simpler version of cubic DNLS, and is always at least as well-behaved.
• Scaling is sc = 0.
• LWP is known for s > 0 Bo1993.
• For s < 0 the solution map is not uniformly continuous from C^k to C^{-k} for any k [CtCoTa-p3].
• GWP is known in the defocusing case for s > 4/9 (De Silva, Pavlovic, Staffilani, Tzirakis)
• For s > 2/3 this is commented upon in [Bo-p2] and is a minor modification of [CoKeStTkTa-p].
• For s >= 1 one has GWP in the defocusing case, or in the focusing case with small L^2 norm, by Hamiltonian conservation.
• In the defocusing case one has GWP for random data whose Fourier coefficients decay like 1/|k| (times a Gaussian random variable) Bo1995c; this is roughly of the regularity of H^{1/2}. Indeed one has an invariant measure. In the focusing case the same result holds assuming the L2 norm is sufficiently small.

#### Quintic NLS on ${\displaystyle R^{2}}$

• Scaling is sc = 1/2.
• LWP is known for s ³ 1/2 CaWe1990.
• For s=1/2 the time of existence depends on the profile of the data as well as the norm.
• For s<s_c we have ill-posedness, indeed the H^s norm can get arbitrarily large arbitrarily quickly [CtCoTa-p2]. In the focusing case we have instantaneous blowup from the virial identity and scaling.
• GWP for s ³ 1 by Hamiltonian conservation.
• This has been improved to s > 1-e in CoKeStTkTa2003b. This result can of course be improved further.
• Scattering in the energy space Na1999c
• One also has GWP and scattering for small H^{1/2} data for any quintic non-linearity.

#### Quintic NLS on ${\displaystyle R^{3}}$

• Scaling is sc = 1.
• LWP is known for s ³ 1 CaWe1990.
• For s=1 the time of existence depends on the profile of the data as well as the norm.
• For s<s_c we have ill-posedness, indeed the H^s norm can get arbitrarily large arbitrarily quickly [CtCoTa-p2]. In the focusing case we have instantaneous blowup from the virial identity and scaling.
• GWP and scattering for s³1 in the defocusing case [CoKeStTkTa-p]
• For radial data this is in [Bo-p], Bo1999.
• Blowup can occur in the focussing case from Glassey's virial identity.