miércoles, 24 de octubre de 2007

Does Sex Induce a Phase Transition?


We discovered a dynamic phase transition induced by sexual reproduc tion. The dynamics is a pure Darwinian rule applied to diploid bit-strings with both fundamental ingredients to drive Darwin’s evolution: 1) random mutations and crossings which act in the sense of increasing the entropy (or diversity); and 2) selection which acts in the opposite sense by limiting the entropy explosion. Selection wins this competition if mutations performed at birth are few enough, and thus the wild genotype dominates the steady-state population. By slowly increasing the average number m of mutations, however, the population suddenly undergoes a muta tional degradation precisely at a transition point mc . Above this point, the “bad” alleles (represented by 1-bits) spread over the genetic pool of the population, overcoming the selection pressure. Individuals become selectively alike, and evolution stops. Only below this point, m < mc , evolutionary life is possible.

The finite-size-scaling behaviour of this transition is exhibited for large enough “chromosome” lengths L, through lengthy computer simulations. One important and surprising observation is the L-independence of the transition curves, for large L. They are also independent on the population size. Another is that mc is near unity, i.e. life cannot be stable with much more than one mutation per diploid genome, independent of the chromosome length, in agreement with reality. One possible consequence is that an eventual evolutionary jump towards larger L enabling the storage of more genetic information would demand an improved DNA copying machinery in order to keep the same total number of mutations per offspring.

Referencia: http://arxiv.org/abs/0710.1357

Para que vean ustedes las cosas tan interesantes que se pueden investigar sabiendo fisica, que no solo de atomos y galaxias viven los cientificos de ciencias duras! Por si el anterior articulo no convence, ahi van otros:

Self-organizing, two-temperature Ising model describing human segregation

A two-temperature Ising-Schelling model is introduced and studied for describing human segregation. The self-organized Ising model with Glauber kinetics simulated by M¨uller et al. exhibits a phase transition between segregated and mixed phases mimicking the change of tolerance (local temperature) of individuals. The effect of external noise is considered here as a second temperature added to the decision of individuals who consider change of accommodation. A numerical evidence is presented for a discontinuous phase transition of the magnetization.

Referencia: http://arxiv.org/abs/0710.1496

Googling social interactions: Web search engine based social network construction

Recently, massive digital records have made it possible to analyze a huge amount of data in social sciences such as social network theory. We investigate social networks between people by extracting information on the World Wide Web. Using famous search engines such as Google, we quantify relatedness between two people as the number of Web pages including both of their names and construct weighted social relatedness networks. The weight and strength distributions are found to be quite broad. A class of measure called the R´enyi disparity, characterizing the homogeneity of weight distribution for each node, is presented. We introduce the maximum relatedness subnetwork, which extracts the most essential relation for each individual. We analyze the members of the 109th United States Senate as an example and demonstrate that the methods of construction and analysis are applicable to various other social groups and weighted networks.

Referencia: http://arxiv.org/abs/0710.3268


7 comentarios:

Montag dijo...

¿Pero qué es eso tan extrañisísimo?.

Eustaquio dijo...

Es algo que encontre y que me divirtio bastante, por lo menos el titulo (menuda carcajada cuando lo lei). Luego resulto no ser exactamente lo que pensaba. En fin, para no hacer el post muy corto decidi poner tambien el abstract y otros dos articulos, pero creo que no me ha quedado muy bien.

Herodoto dijo...

Mi ingles es regularcillo. Aun así no suelo tener muchos problemas para leer un texto en ese idioma. Pero aquí, no me he enterado de nada.

Eustaquio dijo...

Tampoco yo me he enterado de nada, y eso que me queda relativamente cerca. Lo ponia como curiosidad, para que se vean los derroteos que pueden tomar algunas cosas.

Agua dijo...

Pues nada, como yo no me he enterado de nada, puedo unirme a la conversación :)

Montag dijo...

Yo tampoco me he enterado de nada. No me he enterado de nada pero por supuesto no estoy de acuerdo con nada de lo que dice. Por eso creo que vosotros, que tampoco os habéis enterado de nada, estáis equivocados en el planteamiento de la cuestión.

Agua dijo...

Discrepo, Montag