Abstract
Let G be a simple graph with vertex set \(V\left( G\right) \).
A set \(S\subseteq V\left( G\right) \) is independent if no two vertices from S are adjacent, and by \(\mathrm {Ind}(G)\) we mean the family of all independent sets of G.
The number \(d\left( X\right) =\) \(\left| X\right| -\left| N(X)\right| \) is the difference of \(X\subseteq V\left( G\right) \), and a set \(A\in \mathrm {Ind}(G)\) is critical if \(d(A)=\max \{d\left( I\right) :I\in \mathrm {Ind}(G)\}\) [34].
Let us recall the following definitions:
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\(\mathrm {core}\left( G\right) = {\displaystyle \bigcap } \left\{ S:S\textit{ is a maximum independent set}\right\} \) [16],
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\(\mathrm {corona}\left( G\right) = {\displaystyle \bigcup } \left\{ S:S\textit{ is a maximum independent set}\right\} \) [5],
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\(\mathrm {\ker }(G)= {\displaystyle \bigcap } \left\{ S:S\textit{ is a critical independent set}\right\} \) [18],
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\(\mathrm {nucleus}(G)= {\displaystyle \bigcap } \left\{ S:S\textit{ is a maximum critical independent set}\right\} \) [12]
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\(\mathrm {diadem}(G)= {\displaystyle \bigcup } \left\{ S:S\textit{ is a (maximum) critical independent set}\right\} \) [24].
In this paper we focus on interconnections between \(\ker \), core, corona, \(\mathrm {nucleus}\), and diadem.
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The first author would like to thank the organizers of the Mathematical Optimization Theory and Operations Research Conference - MOTOR2019 for an opportunity to deliver an invited lecture on critical independent sets.
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Levit, V.E., Mandrescu, E. (2019). Critical and Maximum Independent Sets Revisited. In: Khachay, M., Kochetov, Y., Pardalos, P. (eds) Mathematical Optimization Theory and Operations Research. MOTOR 2019. Lecture Notes in Computer Science(), vol 11548. Springer, Cham. https://doi.org/10.1007/978-3-030-22629-9_1
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