In network theory, the Braunstein-Ghosh-Severini entropy (BGS entropy) of a network is the von Neumann entropy of a density matrix given by a normalized Laplacian matrix of the network. This definition of entropy does not have a clear thermodynamical interpretation. The BGS entropy has been used in the context of quantum gravity.
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Braunstein-Ghosh-Severini Entropy Wikipedia(Text) CC BY-SA