Artículos con la etiqueta ‘sistemas dinamicos’

Are Deterministic Descriptions And Indeterministic Descriptions Observationally Equivalent?

Por • 14 oct, 2013 • Category: Ciencia y tecnología

The central question of this paper is: are deterministic and indeterministic descriptions observationally equivalent in the sense that they give the same predictions? I tackle this question for measure-theoretic deterministic systems and stochastic processes, both of which are ubiquitous in science. I first show that for many measure-theoretic deterministic systems there is a stochastic process which is observationally equivalent to the deterministic system. Conversely, I show that for all stochastic processes there is a measure-theoretic deterministic system which is observationally equivalent to the stochastic process. Still, one might guess that the measure-theoretic deterministic systems which are observationally equivalent to stochastic processes used in science do not include any deterministic systems used in science. I argue that this is not so because deterministic systems used in science even give rise to Bernoulli processes. Despite this, one might guess that measure-theoretic deterministic systems used in science cannot give the same predictions at every observation level as stochastic processes used in science. By proving results in ergodic theory, I show that also this guess is misguided: there are several deterministic systems used in science which give the same predictions at every observation level as Markov processes. All these results show that measure-theoretic deterministic systems and stochastic processes are observationally equivalent more often than one might perhaps expect. Furthermore, I criticise the claims of the previous philosophy papers Suppes (1993, 1999), Suppes and de Barros (1996) and Winnie (1998) on observational equivalence.

Justifying Definitions in Mathematics—Going Beyond Lakatos

Por • 9 oct, 2013 • Category: Educacion

This paper addresses the actual practice of justifying definitions in mathematics. First, I introduce the main account of this issue, namely Lakatos’s proof-generated definitions. Based on a case study of definitions of randomness in ergodic theory, I identify three other common ways of justifying definitions: natural-world-justification, condition-justification and redundancy-justification. Also, I clarify the interrelationships between the different kinds of justification. Finally, I point out how Lakatos’s ideas are limited: they fail to show that various kinds of justification can be found and can be reasonable, and they fail to acknowledge the interplay between the different kinds of justification.

When periodicities enforce aperiodicity

Por • 25 sep, 2013 • Category: Ciencia y tecnología

Aperiodic tilings are non-periodic tilings defined by local rules. They are widely used to model quasicrystals, and a central question is to understand which of the non-periodic tilings are actually aperiodic. Among tilings, those by rhombi can be easily seen as approximations of surfaces in higher dimensional spaces. In particular, those which approximate irrational planes are non-periodic. But which ones are also aperiodic? This paper introduces the notion of subperiod, which links algebraic properties of a plane with geometric properties of the tilings that approximate it. A necessary and sufficient condition is obtained for tilings that can be seen in the four dimensional Euclidean space. This result is then applied to some examples in higher codimensions, notably tilings with n-fold rotational symmetry

Dynamical systems and categories

Por • 3 ago, 2013 • Category: Crítica

We study questions motivated by results in the classical theory of dynamical systems in the context of triangulated and A-infinity categories. First, entropy is defined for exact endofunctors and computed in a variety of examples. In particular, the classical entropy of a pseudo-Anosov map is recovered from the induced functor on the Fukaya category. Second, the density of the set of phases of a Bridgeland stability condition is studied and a complete answer is given in the case of bounded derived categories of quivers. Certain exceptional pairs in triangulated categories, which we call Kronecker pairs, are used to construct stability conditions with density of phases. Some open questions and further directions are outlined as well

Periodic Sequences of Arbitrage: A Tale of Four Currencies

Por • 2 ene, 2012 • Category: Opinion

This paper investigates arbitrage chains involving four currencies and four foreign exchange trader-arbitrageurs. In contrast with the three-currency case, we find that arbitrage operations when four currencies are present may appear periodic in nature, and not involve smooth convergence to a «balanced» ensemble of exchange rates in which the law of one price holds. The goal of this article is to understand some interesting features of sequences of arbitrage operations, features which might well be relevant in other contexts in finance and economics

Stable Parallel Looped Networks – A New Systems Framework for the Evolution of Order

Por • 13 feb, 2011 • Category: Ambiente

When attempting to explain the creation of a highly ordered system from a disordered one for living beings, in addition to identifying the sequential or iterative sequences of steps, we need to address which laws and mechanisms guide all the necessary components to indeed follow these sequences of steps.

an Lagrangian Systems be Better than Hamiltonian Systems at Approximating Biological Evolution?

Por • 7 feb, 2011 • Category: Ambiente

Evolutionary processes and their major features have commonalities with a diverse range of physical phenomena. Models of fitness or adaptation currently used in theoretical biology are similar to Hamiltonian-based representations of dynamical systems in terms of inspiration and major assumptions.