A crucial question is how objective and classical behavior arises from a fundamental physical theory. Here we provide natural definition of decoherence process valid in all causal theories, show its can be extremely different the quantum one. Remarkably, despite this, prove that so-called spectrum broadcast structure characterizes states every theory, exactly as mechanics. Our results stark con...

Lawvere theories and monads have been the two main category theoretic formulations of universal algebra, Lawvere theories arising in 1963 and the connection with monads being established a few years later. Monads, although mathematically the less direct and less malleable formulation, rapidly gained precedence. A generation later, the definition of monad began to appear extensively in theoretic...

Logic programming has favored universal Horn theories for several reasons. An advantage of consistent universal Horn theories, compared with arbitrary consistent theories, is the fact that they possess a “typical” model-the least Herbrand model. More precisely, in order to verify that a sentence of the form 3 X, . . . 3 x, A, where A is a conjunction of atomic formulas (i.e. positive literals),...

The theories of gravity which violate local Lorentz invariance do not admit a universal maximum speed of signal-propagation. Different field excitations see a different effective metric and hence a different light cone. In these theories, although one can define the Killing horizon in a conventional way, this definition does not capture the notion of a black hole. This is so because there exist...

Theories of rational belief revision recently proposed by Alchourrón, Gärdenfors, Makinson, and Nebel illuminate many important issues but impose unnecessarily strong standards for correct revisions and make strong assumptions about what information is available to guide revisions. We reconstruct these theories according to an economic standard of rationality in which preferences are used to se...