C. O. Dorso

Dengue epidemics and human mobility

In this work we explore the effects of human mobility on the dispersion of a vector borne disease. We combine an already presented stochastic model for dengue with a simple representation of the daily motion of humans on a schematic city of 20 × 20 blocks with 100 inhabitants in each block. The pattern of motion of the individuals is described in terms of complex networks in which links connect different blocks and the link length distribution is in accordance with recent findings on human mobility. It is shown that human mobility can turn out to be the main driving force of the disease dispersal.

Quasiclassical model of intermediate velocity particle production in asymmetric heavy ion reactions

The particle emission at intermediate velocities in mass asymmetric reactions is studied within the framework of classical molecular dynamics. Two reactions in the Fermi energy domain were modeled,

Temperature and energy partition in fragmentation

{}^{58}\mathrm{N}\mathrm{i}+\mathrm{C}

The critical exponent of nuclear fragmentation

and

COMMUNITY DETECTION IN NETWORKS

{}^{58}\mathrm{N}\mathrm{i}+\mathrm{A}\mathrm{u}

Lectures Notes on Phase Transformations in Nuclear Matter

at 34.5 MeV/nucleon. The availability of microscopic correlations at all times allowed a detailed study of the fragment formation process. Special attention was paid to the physical origin of fragments and emission timescales, which allowed us to disentangle the different processes involved in the midrapidity particle production. Consequently, a clear distinction between a prompt preequilibrium emission and a delayed aligned asymmetric breakup of the heavier partner of the reaction was achieved.

Time dependence of critical behavior in multifragmentation

We study fragmentation of small atomistic clusters via molecular dynamics. We calculate the time scales related to fragment formation and emission. We also show that some degree of thermalization is achieved during the expansion process, which allows the determination of a local temperature. In this way we can calculate the break-up temperature as a function of excitation energy, i.e. the fragmentation caloric curve. Fragmentation appears as a rather constant temperature region of the caloric curve. Furthermore, we show that different definitions of temperature, related to different degrees of freedom, yield very similar values.

Classical drop phase diagram and correlations in phase space

Nuclei colliding at energies in the MeV’s break into fragments in a process that resembles a liquid-to-gas phase transition of the excited nuclear matter. If this is the case, phase changes occurring near the critical point should yield a “droplet” mass distribution of the form ≈A−T, with T (a critical exponent universal to many processes) within 2≤T≤3. This critical phenomenon, however, can be obscured by the finiteness in space of the nuclei and in time of the reaction. With this in mind, this work studies the possibility of having critical phenomena in small “static” systems (using percolation of cubic and spherical grids), and on small “dynamic” systems (using molecular dynamics simulations of nuclear collisions in two and three dimensions). This is done investigating the mass distributions produced by these models and extracting values of critical exponents. The specific conclusion is that the obtained values of T are within the range expected for critical phenomena, i.e. around 2.3, and the grand conclusion is that phase changes and critical phenomena appear to be possible in small and fast breaking systems, such as in collisions between heavy ions.

Collective coordinates as open systems: (I). Existence conditions for frictional hamiltonians

The problem of community detection is relevant in many disciplines of science. A community is usually defined, in a qualitative way, as a subset of nodes of a network which are more connected among themselves than to the rest of the network. In this article, we introduce a new method for community detection in complex networks. We define new merit factors based on the weak and strong community definitions formulated by Radicchi et al. [2004] and we show that this local definition properly describes the communities observed experimentally in two typical social networks.

Enhancement of kinetic energy fluctuations due to expansion

The free nucleon gas a simple nuclear equation of state the road toward mixed phases critical phenomena in finite system heavy ion reactions. Appendices: nonlinear aspects of fragmentation computer codes.