Abstract
In this talk, I will discuss the different definitions that have been proposed in the literature to express that two states of a probabilistic system are similar (or bisimilar). Different intuitions and purposes led to conceptually various definitions.
I will show that most of the definitions have a logical counterpart, meaning that for each of them there exists a logical formalism which distinguishes two states if, and only if, they are not similar (or bisimilar).
When considering computational properties, the landscape turns out to be rather surprising: some definitions lead to efficient algorithms, while some others to undecidability.
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