Abstract

Scaling symmetries arise in different branches of physics, and symmetry-based approaches are powerful tools for studying scaling-invariant models since they can provide conservation laws that are not obvious by inspection. In this framework, the class of variable-coefficients nonlinear dispersive equations vc$K(m,n)$, which contains several important evolution equations modeling nonlinear phenomena, is considered. For some of its scaling-invariant subclasses, we study its nonlinear self-adjointness and construct eight new local conservation laws associated with scaling symmetries by using a general theorem on conservation laws and the multipliers method. The property of scale invariance of those equations led to five conservation laws with a direct physical interpretation: energy, center of mass, and mass are the conserved quantities obtained in some cases.

Highlights

  • Scaling symmetries have wide applications in science and in engineering and are far from being a special case in physics - they can be found, for instance, in quantum physics, fluid mechanics, turbulence, elasticity, heat diffusion, convection, filtration, gas dynamics, and in the theory of detonation and combustion

  • In this paper we seek for conservation laws associated with scaling symmetries for scalinginvariant subclasses of a generalized vcK(m, n)

  • We highlight that conservation laws associated with scaling symmetries can be obtained via multipliers method by computing fluxes with no integration involved [3, 8, 14]

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Summary

INTRODUCTION

Scaling symmetries have wide applications in science and in engineering and are far from being a special case in physics - they can be found, for instance, in quantum physics, fluid mechanics, turbulence, elasticity, heat diffusion, convection, filtration, gas dynamics, and in the theory of detonation and combustion (see [12] and references therein). The relations between Ibragimov’s approach and the direct method are well known [4,46,47], and the latter is largely employed to build up conservation laws for nonlinearly self-adjoint equations [7, 13, 15, 22, 30, 44]. In this paper we seek for conservation laws associated with scaling symmetries for scalinginvariant subclasses of a generalized vcK(m, n). To this end, we shall consider the expanded form of vcK(m, n) (1.1), ut + α0(t, x, u) + α1(t, x, u)ux + α2(t, x, u)u2x + α3(t, x, u)u3x +α4(t, x, u)uxuxx + α5(t, x, u)uxx + α6(t, x, u)uxxx = 0 ,. We highlight that conservation laws associated with scaling symmetries can be obtained via multipliers method by computing fluxes with no integration involved [3, 8, 14]

NONLINEAR SELF-ADJOINTNESS CLASSIFICATION
Time-dependent mKdV
Time-dependent Schamel
CONSERVATION LAWS BY USING A GENERAL THEOREM ON CONSERVATION LAWS
Time-dependent KdV
Cylindrical KdV
CONSERVATION LAWS BY USING THE MULTIPLIERS METHOD
CONCLUDING REMARKS
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