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authorJaron Kent-Dobias <jaron@kent-dobias.com>2024-06-30 14:43:52 +0200
committerJaron Kent-Dobias <jaron@kent-dobias.com>2024-06-30 14:43:52 +0200
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@@ -1577,6 +1577,32 @@ energy in a nontrivial way. The figure also shows the dominant stability,
which is the stability associated with the dominant complexity and coincides
with the marginal stability only at the threshold energy.
+\begin{figure}
+ \includegraphics{figs/most_squares_complex.pdf}
+ \caption{
+ Real and imaginary parts of the complexity $\Sigma_0(E,\mu)$ with fixed
+ minimum eigenvalue $\lambda^*=0$ as a function of $\mu$ in the nonlinear
+ sum of squares problem with $\alpha=\frac32$, $f(q)=q^2+q^3$, and
+ $E\simeq-6.47$. The vertical line depicts the value of the marginal
+ stability $\mu_\mathrm m$.
+ } \label{fig:ls.reim}
+\end{figure}
+
+Because this version of the model has no signal, we were able to use the heuristic
+\eqref{eq:marginal.stability} to fix the marginal stability. However, we could
+also have used the more general method for finding a pseudogapped Hessian
+spectrum by locating the value of $\mu$ at which the complexity develops an
+imaginary part, as described in Section \ref{sec:pseudogap} and pictured in
+Fig.~\ref{fig:large.dev}. The real and imaginary parts of the complexity
+$\Sigma_0(E,\mu)$ are plotted in Fig.~\ref{fig:ls.reim} as a function of $\mu$
+at fixed energy. The figure also shows the marginal stability $\mu_\mathrm m$
+predicted by the variational approach \eqref{eq:marginal.stability}. The
+marginal stability corresponds to precisely the point at which an imaginary
+part develops in the complexity. This demonstrates that the principles we used
+to determine the marginal stability continue to hold even in non-Gaussian cases
+where the complexity and the condition to fix the minimum eigenvalue are
+tangled together.
+
In our companion paper, we use a sum of squared random functions model to explore the relationship between the marginal
complexity and the performance of two generic algorithms:
gradient descent and approximate message passing