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Thank you for the enlightening answer. I am trying to see what best can be said about $\tilde{E}$. Neverthless $\tilde{E}$ is not well defined, irrespective of how we choose the eigenvector matrix $\tilde{E}$, can we always say the following : Let $\Sigma$ is any constant diagonal matrix, as $\epsilon\to 0$, $\tilde{E}\Sigma\tilde{E}^T$ always converges to some matrix.
The crucial for the answer is the value $s$ and it is not the order of singularity of $A$. It depends on first $p$ matrices in the series and there is a procedure to determine $s$. pdfs.semanticscholar.org/106b/…