arXiv subjects

Osame Kinouchi

Publications and source records attributed to Osame Kinouchi.

44 records · Page 3Linked to original sources

arXiv2001

Persistence solves Fermi Paradox but challenges SETI projects

Persistence phenomena in colonization processes could explain the negative results of SETI search preserving the possibility of a galactic civilization. However, persistence phenomena also indicates that search of technological civilizations in stars in the neighbourhood of Sun is a misdirected SETI strategy. This last conclusion is also suggested by a weaker form of the Fermi paradox. A simple model of a branching colonization which includes emergence, decay and branching of civilizations is proposed. The model could also be used in the context of ant nests diffusion.

cond-mat.dis-nn↗

arXiv2001

Extended dynamical range as a collective property of excitable cells

Receptor cells with electrically coupled axons can improve both their input sensitivity and dynamical range due to collective non-linear wave properties. This mechanism is illustrated by a network of axons modeled by excitable maps subjected to a Poison signal process with rate r. We find that, in a network of N cells, the amplification factor A (number of cells excited by a single signal event) decreases smoothly from A= O(N) to A=1 as r increases, preventing saturation in a self-organized way and leading to a Weber-Fechner law behavior. This self-limited amplification mechanism is generic for excitable media and could be implemented in other biological contexts and artificial sensor devices.

cond-mat.dis-nn↗

arXiv2000

Deterministic walks in random media: evidence of generic scale invariance

Deterministic walks over a random set of points in one and two dimensions (d=1,2) are considered. Points (``cities'') are randomly scattered in R^d following a uniform distribution. A walker (a ``tourist''), at each time step, goes to the nearest neighbor city that has not been visited in the past τsteps. Each initial city leads to a trajectory composed of a transient part and a final p-cycle attractor. The distribution of transient times, p-cycles and number of cities per attractor are studied. It is shown numerically that transient times (for d=1,2) follow a Poisson law with a $τ$ dependent decay but the density of p-cycles follows a power law D(p) \propto p^{-α(τ)} for d=2. For large τ, the expoent tends to α~ 5/2. Some analytical results are given for the d=1 case. Since the power law is robust and does not depend on free parameters, this system presents ``generic scale invariance''. Applications to animal exploratory behavior and other local minimization problems are suggested.

cond-mat.dis-nn↗

arXiv1999

On the robustness of scale invariance in SOC models

A random neighbor extremal stick-slip model is introduced. In the thermodynamic limit, the distribution of states has a simple analytical form and the mean avalanche size, as a function of the coupling parameter, is exactly calculable. The system is critical only at a special point Jc in the coupling parameter space. However, the critical region around this point, where approximate scale invariance holds, is very large, suggesting a mechanism for explaining the ubiquity of scale invariance in Nature.

cond-mat.stat-mech↗

arXiv1998

On the random neighbor Olami-Feder-Christensen slip-stick model

We reconsider the treatment of Lise and Jensen (Phys. Rev. Lett. 76, 2326 (1996)) on the random neighbor Olami-Feder-Christensen stik-slip model, and examine the strong dependence of the results on the approximations used for the distribution of states p(E).

cond-mat.stat-mech↗

arXiv1998

Self-organized (quasi-)criticality: the extremal Feder and Feder model

A simple random-neighbor SOC model that combines properties of the Bak-Sneppen and the relaxation oscillators (slip-stick) models is introduced. The analysis in terms of branching processes is transparent and gives insight about the development of large but finite mean avalanche sizes in dissipative models. In the thermodynamic limit, the distribution of states has a simple analytical form and the mean avalanche size, as a function of the coupling parameter strength, is exactly calculable.

cond-mat.dis-nn↗

arXiv1998

Statistical Mechanics of Online Learning of Drifting Concepts : A Variational Approach

We review the application of Statistical Mechanics methods to the study of online learning of a drifting concept in the limit of large systems. The model where a feed-forward network learns from examples generated by a time dependent teacher of the same architecture is analyzed. The best possible generalization ability is determined exactly, through the use of a variational method. The constructive variational method also suggests a learning algorithm. It depends, however, on some unavailable quantities, such as the present performance of the student. The construction of estimators for these quantities permits the implementation of a very effective, highly adaptive algorithm. Several other algorithms are also studied for comparison with the optimal bound and the adaptive algorithm, for different types of time evolution of the rule.

cond-mat.dis-nn↗

arXiv1997

Learning a spin glass: determining Hamiltonians from metastable states

We study the problem of determining the Hamiltonian of a fully connected Ising Spin Glass of $N$ units from a set of measurements, whose sizes needs to be ${\cal O}(N^2)$ bits. The student-teacher scenario, used to study learning in feed-forward neural networks, is here extended to spin systems with arbitrary couplings. The set of measurements consists of data about the local minima of the rugged energy landscape. We compare simulations and analytical approximations for the resulting learning curves obtained by using different algorithms.

cond-mat.dis-nn↗