Diagram Fase Sistem Spin Ising Antiferomagnet Pada Jaringan Kompleks

Diagram fase dari sistem spin Ising antiferomagnet pada jaringan bebas skala yang rapat konektivitasnya bervariasi ditelaah dengan menggunakan metoda Monte Carlo algoritma pertukaran replika. Besaran fisis yang dihitung meliputi parameter pertindihan dan parameter Binder, keduanya bergantung pada temperatur. Jumlah simpul dalam jaringan bervariasi. Dengan menggunakan penyekalaan ukuran berhingga, temperatur peralihan fase untuk masing-masing rapat konektivitas dapat ditentukan, dan selanjutnya digambarkan diagram fasenya. Hasil yang diperoleh menunjukkan bahwa hingga rapat konektivitas tertentu, fase gelas spin kuat akan tetapi melemah pada keadaan konektivitas yang mendekati batas medan rerata, yaitu sistem kisi terkoneksi sempurna

Scale-free networks in complex systems

In the past few years, several studies have explored the topology of interactions in different complex systems. Areas of investigation span from biology to engineering, physics and the social sciences. Although having different microscopic dynamics, the results demonstrate that most systems under consideration tend to self-organize into structures that share common features. In particular, the networks of interaction are characterized by a power law distribution, $P(k)\sim k^{-\alpha}$, in the number of connections per node, $k$, over several orders of magnitude. Networks that fulfill this propriety of scale-invariance are referred to as ``scale-free''. In the present work we explore the implication of scale-free topologies in the antiferromagnetic (AF) Ising model and in a stochastic model of opinion formation. In the first case we show that the implicit disorder and frustration lead to a spin-glass phase transition not observed for the AF Ising model on standard lattices. We further illustrate that the opinion formation model produces a coherent, turbulent-like dynamics for a certain range of parameters. The influence, of random or targeted exclusion of nodes is studied.Comment: 9 pages, 4 figures. Proceeding to "SPIE International Symposium Microelectronics, MEMS, and Nanotechnology", 11-15 December 2005, Brisbane, Australi

Towards a mean-field kinetic model of electroweak baryogenesis

We explore the dynamic symmetry breaking between the mass of two annihilating species entrapped within a condensing droplet of a third phase-changing species. The symmetry breaking is induced by different diffusivities and/or diffebet source terms acting at the droplet interface. Potential implications for the problem of electroweak baryogenesis are sketched out