| Contents |
| We develop a Hamilton-Krein instability index, which allows one to treat KdV like eigenvalue problems. Note that the classical indices, including the Grillakis-Shatah-Strauss theory require a gap between the zero eigenvalue and the continuous spectrum, which we do not. As an application, we completely characterize the stability of travelling waves of certain fractional KdV and BBM versions of the classical models. |
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