BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Talks.cam//talks.cam.ac.uk//
X-WR-CALNAME:Talks.cam
BEGIN:VEVENT
SUMMARY:On the onset of modulation instability in JONSWAP sea states - Agi
 s Athanassoulis (University of Dundee)
DTSTART:20221209T140000Z
DTEND:20221209T143000Z
UID:TALK183833@talks.cam.ac.uk
DESCRIPTION:It has long been known that plane wave solutions of the cubic 
 NLS are linearly unstable. This fact is widely known as modulation instabi
 lity (MI)\, and sometimes referred to as Benjamin-Feir instability in the 
 context of water waves. While instances of MI have been recreated in wave 
 tanks\, the relevance of plane wave solutions in realistic ocean waves is 
 seen as debatable. In this talk we will present recent results about the A
 lber equation\, which predict a stable and unstable regime for sea states 
 of known power spectra\, with the classical MI as the limit in the case of
  asymptotically narrow spectra. Crucially\, in contrast to plane wave solu
 tions\, realistic sea states may be stable or unstable\, i.e. a bifurcatio
 n exists with no counterpart in the classical theory of MI. In the unstabl
 e case\, there are clear analogies with the MI\, hence this regime can be 
 called generalised MI. The stable regime\, where the vast majority of real
 istic spectra belong\, is mathematically extremely similar to Landau dampi
 ng. Finally\, a new numerical investigation of the bifurcation from Landau
  damping to generalised MI in JONSWAP sea states is presented\, inspired b
 y the analysis. In particular\, the (in)stability of inhomogeneities is fo
 r the first time tracked directly.&nbsp\; Key findings include the fact th
 at nonlinear evolution is surprisingly analogous to that of the classical 
 MI\, and allows to make more precise the relationship between generalised 
 MI and rogue waves.\nIncludes work joint with G. Athanassoulis (NTUA)\, T.
  Sapsis (MIT)\, M. Ptashnyk (Heriot-Watt) and O. Gramstad (DNV).
LOCATION:Seminar Room 1\, Newton Institute
END:VEVENT
END:VCALENDAR