Fig. 2

The SLIP NES force \(f\left( \beta \right)\) and its corresponding force \(\overline{f}\left( \beta \right)\) for \(k_{\beta } = 1\) in (a) at \(\alpha = 2\), in (b) at \(\alpha = 1\), in (c) at \(\alpha = 0.5\) and in (d) at \(\alpha = - 1\).