Maxwell's other demons

Of the Hennessy-Milner Property and other Demons

We relate three different, but equivalent, ways to characterise behavioural equivalence for set coalgebras. These are: using final coalgebras, using coalgebraic languages that have the HennessyMilner property and using coalgebraic languages that have “logical congruences”. On the technical side the main result of our paper is a straightforward construction of the final T -coalgebra of a set fun...

On Demons and Oracles

Implementing Demons and Ratchets

Experimental results show that ratchets may be implemented in semiconductor and chemical systems, bypassing the second law and opening up huge gains in energy production. This paper summarizes or describes experiments and results on systems that effect demons and ratchets operating in chemical or electrical domains. One creates temperature differences that can be harvested by a heat engine. A s...

Demons in Physics

Maxwell’s ”finite being” was born in 1867, as one ”who knows the paths and velocities of all the molecules” ([7], p.213), and who, unlike us, is ”clever enough” ([7], p.213), and can violate the second law of thermodynamics. It was baptized as a demon by Lord Kelvin ([7], p. 214), and ever since has fueled the discussions in the foundations of statistical mechanics. Since its inception, and con...

Nested sampling with demons

This article looks at Skilling’s nested sampling from a physical perspective and interprets it as a microcanonical demon algorithm. Using key quantities of statistical physics we investigate the performance of nested sampling on complex systems such as Ising, Potts and protein models. We show that releasing multiple demons helps to smooth the truncated prior and eases sampling from it because t...