Connection Between the Exact Moving Solutions of the Negative Korteweg-de Vries (nKdV) Equation and the Negative Modified Korteweg-de Vries (nmKdV) Equation and the Static Solutions of 1+1 Dimensional $ϕ^4$ Field Theory

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Main Authors: Khare, Avinash, Cooper, Fred, Saxena, Avadh
Format: Preprint
Published: 2025
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author Khare, Avinash
Cooper, Fred
Saxena, Avadh
author_facet Khare, Avinash
Cooper, Fred
Saxena, Avadh
contents The negative order KdV (nKdV) and the modified KdV (nmKdV) equations have two different formulations based on different hierarchy operators. Both equations can be written in terms of a nonlinear differential equation for a field $u(x,t)$ which we call the ``Lou form" of the equation. We find that for moving solutions of the nKdV equation and the nmKdV equation written in the ``Lou form" with $u(x,t) \rightarrow u (x-ct)= u(ξ) $, the equation for $u(ξ)$ can be mapped to the equation for the static solutions of the 1+1 dimensional $ϕ^4$ field theory. Using this mapping we obtain a large number of solutions of the nKdV and the nmKdV equation, most of which are new. We also show that the nKdV equation can be derived from an Action Principle for both of its formulations. Furthermore, for both forms of the nmKdV equations as well as for both focusing and defocusing cases, we show that with a suitable ansatz one can decouple the $x$ and $t$ dependence of the nmKdV field $u(x,t)$ and obtain novel solutions in all the cases. We also obtain novel rational solutions of both the nKdV and the nmKdV equations.
format Preprint
id arxiv_https___arxiv_org_abs_2505_09811
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Connection Between the Exact Moving Solutions of the Negative Korteweg-de Vries (nKdV) Equation and the Negative Modified Korteweg-de Vries (nmKdV) Equation and the Static Solutions of 1+1 Dimensional $ϕ^4$ Field Theory
Khare, Avinash
Cooper, Fred
Saxena, Avadh
Exactly Solvable and Integrable Systems
Mathematical Physics
Pattern Formation and Solitons
The negative order KdV (nKdV) and the modified KdV (nmKdV) equations have two different formulations based on different hierarchy operators. Both equations can be written in terms of a nonlinear differential equation for a field $u(x,t)$ which we call the ``Lou form" of the equation. We find that for moving solutions of the nKdV equation and the nmKdV equation written in the ``Lou form" with $u(x,t) \rightarrow u (x-ct)= u(ξ) $, the equation for $u(ξ)$ can be mapped to the equation for the static solutions of the 1+1 dimensional $ϕ^4$ field theory. Using this mapping we obtain a large number of solutions of the nKdV and the nmKdV equation, most of which are new. We also show that the nKdV equation can be derived from an Action Principle for both of its formulations. Furthermore, for both forms of the nmKdV equations as well as for both focusing and defocusing cases, we show that with a suitable ansatz one can decouple the $x$ and $t$ dependence of the nmKdV field $u(x,t)$ and obtain novel solutions in all the cases. We also obtain novel rational solutions of both the nKdV and the nmKdV equations.
title Connection Between the Exact Moving Solutions of the Negative Korteweg-de Vries (nKdV) Equation and the Negative Modified Korteweg-de Vries (nmKdV) Equation and the Static Solutions of 1+1 Dimensional $ϕ^4$ Field Theory
topic Exactly Solvable and Integrable Systems
Mathematical Physics
Pattern Formation and Solitons
url https://arxiv.org/abs/2505.09811