Speaker
Ruben Moreno Bote

Description Neuronal activity in cortex is variable both spontaneously and during stimulation, and this variability is correlated across neurons. We will show that both variability and correlations have important impact on our knowledge about the underlying neuronal circuits and about the functions these circuits carry on. In particular, we will show in spontaneously active networks in monkey V1 that correlations imply that the underlying circuits have long-range connections with invariant-scale properties, although correlations per se decay fast with distance. Then, we will stress that the type of variability that we encounter in cortex (Poisson-like) is hard to reconcile with the behavior obtained from state of art balanced neuronal networks, unless probabilistic synapses are included. This suggests that the major source of variability in cortex arises from probabilistic synapses, begging the question of why the brain introduces noise. Finally, we will show that this injected noise has surprising computational implications, allowing to the cortical circuits to explore their states in a contrast-invariant manner.

Speaker
Joan Serrà

Description Popular music is a key cultural asset whose regularities and dynamics remain still largely unknown. In this talk I will outline the recent research we have been performing at the intersection between complex systems, computer science, and music. In particular, we have been analyzing audio content descriptions from nearly half a million songs, finding several patterns and regularities, among them the Zipf's law and interesting complex network structures. Most importantly, we have been studying the evolution of these patterns and regularities from 1955 to 2010. Our results show that there are some important trends in popular music, including the restriction of pitch transitions, the homogenization of the timbral palette, and the growing loudness levels. In the end of the talk we will revise some of the implications of such results. Bibliography: M. Haro, J. Serrà, P. Herrera, and Á. Corral. Zipf's law in short-time timbral codings of speech, music, and environmental sound signals. PLoS ONE 7(3): e33993 (2012). J. Serrà, Á. Corral, M. Boguñá, M. Haro, and J. Ll. Arcos. Measuring the evolution of contemporary western popular music. In preparation.

Speaker
Jörg Enderlein

Description When placing a molecule close to a dielectric surface or a metal structure, one changes the local density of states of the electromagnetic field with profound consequences for the excitation and emission properties of fluorescing molecules. A perfect theoretical understanding of this electromagnetic coupling of a single fluorescing molecule to its environment is the basis for many exciting experimental applications. After giving a brief introduction into the subject, the presentation will focus on three topics: (i) defocused imaging of single molecules for measuring three-dimensional molecular orientation and rotation; (ii) interaction of single molecules with metallic nanocavities; (iii) nanometer accuracy distance measurements of single from surfaces.

Speaker
Pere Puig

Speaker
Bernat Corominas Murtra

Description In this talk I will outline a general, model-free demonstration of the emergence of Zipf's law in a generic, wide class of Complex Systems. We start from a rigorous characterization of a "Growing System between Order and Disorder". Then, we variationally introduce evolution -and thus, path dependence- by means of the Kullback's minimum Information discrimination principle, a generalization of Jaynes' maxEnt principle. We demonstrate that, under such very general assumptions, Zipf's law emerges as the unique possible system's configuration at the limit of large sizes. The strong conclusion of the result, considering the low conditions imposed over the system, might explain the ubiquity of such law in nature. We will finally revise the implications of the result. Bibliography: Universality of Zipf's law. Bernat Corominas-Murtra and Ricard V. Solé. Physical Review E 82, 11102 (2010); Emergence of Zipf’s Law in the Evolution of Communication. Bernat Corominas-Murtra, Jordi Fortuny and Ricard V. Solé. Physical Review E 83, 32767 (2011) Notice change in time. It will start at 14:30