Artículos con la etiqueta ‘teoría de la información’

An information-processing approach to the origin of life

Por • 20 dic, 2012 • Category: Ambiente

“To a physicist or chemist life seems like ‘magic matter,’” Davies explained. “It behaves in extraordinary ways that are unmatched in any other complex physical or chemical system. Such lifelike properties include autonomy, adaptability and goal-oriented behavior — the ability to harness chemical reactions to enact a pre-programmed agenda, rather than being a slave to those reactions. “We believe the transition in the informational architecture of chemical networks is akin to a phase transition in physics, and we place special emphasis on the top-down information flow in which the system as a whole gains causal purchase over its components, This approach will reveal how the logical organization of biological replicators differs crucially from trivial replication associated with crystals (non-life). By addressing the causal role of information directly, many of the baffling qualities of life are explained.”

Urban characteristics attributable to density-driven tie formation

Por • 26 oct, 2012 • Category: sociologia

Motivated by empirical evidence on the interplay between geography, population density and societal interaction, we propose a generative process for the evolution of social structure in cities. Our analytical and simulation results predict both super-linear scaling of social tie density and information flow as a function of the population. We demonstrate that our model provides a robust and accurate fit for the dependency of city characteristics with city size, ranging from individual-level dyadic interactions (number of acquaintances, volume of communication) to population-level variables (contagious disease rates, patenting activity, economic productivity and crime) without the need to appeal to modularity, specialization, or hierarchy.

Quantum Theory, namely the pure and reversible theory of information

Por • 27 sep, 2012 • Category: Opinion

After more than a century since its birth, Quantum Theory still eludes our understanding. If asked to describe it, we have to resort to abstract and ad hoc principles about complex Hilbert spaces. How is it possible that a fundamental physical theory cannot be described using the ordinary language of Physics? Here we offer a contribution to the problem from the angle of Quantum Information, providing a short non-technical presentation of a recent derivation of Quantum Theory from information-theoretic principles. The broad picture emerging from the principles is that Quantum Theory is the only standard theory of information compatible with the purity and reversibility of physical processes.

Is the Information Entropy the Same as the Statistical Mechanical Entropy?

Por • 27 sep, 2012 • Category: Crítica

It is shown that the standard expression for the information entropy, originally due to Shannon, is only valid for a particular set of states. For the general case of statistical mechanics, one needs to include an additional term in the expression for the entropy as a function of the probability. A simple derivation of the general formula is given.

Three-dimensionality of space and the quantum bit: how to derive both from information-theoretic postulates

Por • 10 jun, 2012 • Category: Leyes

It is sometimes pointed out as a curiosity that the state space of quantum theory and actual physical space seem related in a surprising way: not only is space three-dimensional and Euclidean, but so is the Bloch ball which describes quantum two-level systems. In this paper, we show how this observation can be turned into a rigorous mathematical result: suppose that physics takes place in d spatial dimensions, and that some events happen probabilistically (not assuming quantum theory in any way). Furthermore, suppose there are systems that in some sense behave as “units of direction information”, interacting via some continuous reversible time evolution. We prove that this uniquely determines spatial dimension d=3 and quantum theory on two qubits (including entanglement, unitary time evolution and complementarity), and that it allows observers to infer local spatial geometry from probability measurements

Information Theory of DNA Sequencing

Por • 4 abr, 2012 • Category: Ciencia y tecnología

DNA sequencing is the basic workhorse of modern day biology and medicine. Shotgun sequencing is the dominant technique used: many randomly located short fragments called reads are extracted from the DNA sequence, and these reads are assembled to reconstruct the original sequence. A basic question is: given a sequencing technology and the statistics of the DNA sequence, what is the minimum number of reads required for reliable reconstruction? This number provides a fundamental limit to the performance of any assembly algorithm. By drawing an analogy between the DNA sequencing problem and the classic communication problem, we formulate this question in terms of an information theoretic notion of sequencing capacity. This is the asymptotic ratio of the length of the DNA sequence to the minimum number of reads required to reconstruct it reliably. We compute the sequencing capacity explicitly for a simple statistical model of the DNA sequence and the read process. Using this framework, we also study the impact of noise in the read process on the sequencing capacity.

Neuropsychological constraints to human data production on a global scale

Por • 3 dic, 2011 • Category: Opinion

Which are the factors underlying human information production on a global level? In order to gain an insight into this question we study a corpus of 252-633 Million publicly available data files on the Internet corresponding to an overall storage volume of 284-675 Terabytes. Analyzing the file size distribution for several distinct data types we find indications that the neuropsychological capacity of the human brain to process and record information may constitute the dominant limiting factor for the overall growth of globally stored information, with real-world economic constraints having only a negligible influence. This supposition draws support from the observation that the files size distributions follow a power law for data without a time component, like images, and a log-normal distribution for multimedia files, for which time is a defining qualia.

Comments on “Disproof of Bell’s theorem”

Por • 11 jul, 2011 • Category: Filosofía

In a series of very interesting papers [1-7], Joy Christian constructed a counterexample to Bell’s theorem. This counterexample does not have the same assumptions as the original Bell’s theorem, and therefore it does not represent a genuine disproof in a strict mathematical sense. However, assuming the physical relevance of the new assumptions, the counterexample is shown to be a contextual hidden variable theory.