Things Happen

Making Things Happen

We explore some logics of change, focusing on commands to change the world in such a way that certain elementary propositions become true or false. This investigation starts out from the following two simplifying assumptions: (1) the world is a collection of facts (Wittgenstein), and (2), the world can be changed by changing elementary facts (Marx). These assumptions allow us to study the logic...

How Things Happen

In the year 2008 I was honoured and delighted to be invited to write an editorial in OBESITY FACTS on the occasion of International Federation for the Surgery of Obesity and Metabolic Disorders – European Chapter (IFSO-EC) members joining the Editorial Board of OBESITY FACTS , and therefore the journal becoming an affiliated journal of the IFSO-EC. The 2008 editorial was entitled ‘The Circle Is...

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When bad things happen to good trees

When the edges in a tree or rooted tree fail with a certain fixed probability, the (greedoid) rank may drop. We compute the expected rank as a polynomial in p and as a real number under the assumption of uniform distribution. We obtain several different expressions for this expected rank polynomial for both trees and rooted trees, one of which is especially simple in each case. We also prove tw...

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