Through multiple-scales and symmetry arguments we derive a model set of amplitude equations describing the interaction of two steady-state pattern-forming instabilities, in the case that the wavelengths of the instabilities are nearly in the ratio 1:2. In the case of exact 1:2 resonance the amplitude equations are ODEs; here they are PDEs. We discuss the stability of spatially periodic solutions to long-wavelength disturbances. By including these modulational effects we are able to explore the relevance of the exact 1:2 results to spatially extended physical systems for parameter values near to this codimension-two bifurcation point. These new instabilities can be described in terms of reduced 'normal form' PDEs near various secondary codimension-two points. The robust heteroclinic cycle in the ODEs is destabilised by long-wavelength perturbations and a stable periodic orbit is generated that lies close to the cycle. An analytic expression giving the approximate period of this orbit is derived.

Original languageEnglish
Pages (from-to)1-30
Number of pages30
JournalPhysica D: Nonlinear Phenomena
Issue number1-2
Publication statusPublished - 15 Apr 2004


  • Bifurcation
  • Heteroclinic cycle
  • Mode interaction
  • Pattern
  • Symmetry

ASJC Scopus subject areas

  • Statistical and Nonlinear Physics
  • Condensed Matter Physics


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