Phase transitions in Ising models on directed networks

We examine Ising models with heat-bath dynamics on directed networks. Our simulations show that Ising models on directed triangular and simple cubic lattices undergo a phase transition that most likely belongs to the Ising universality class. On the directed square lattice the model remains paramagnetic at any positive temperature as already reported in some previous studies. We also examine random directed graphs and show that contrary to undirected ones, percolation of directed bonds does not guarantee ferromagnetic ordering. Only above a certain threshold can a random directed graph support finite-temperature ferromagnetic ordering. Such behavior is found also for out-homogeneous random graphs, but in this case the analysis of magnetic and percolative properties can be done exactly. Directed random graphs also differ from undirected ones with respect to zero-temperature freezing. Only at low connectivity do they remain trapped in a disordered configuration. Above a certain threshold, however, the zero-temperature dynamics quickly drives the model toward a broken symmetry (magnetized) state. Only above this threshold, which is almost twice as large as the percolation threshold, do we expect the Ising model to have a positive critical temperature. With a very good accuracy, the behavior on directed random graphs is reproduced within a certain approximate scheme.

Medienart:

E-Artikel

Erscheinungsjahr:

2015

Erschienen:

2015

Enthalten in:

Zur Gesamtaufnahme - volume:92

Enthalten in:

Physical review. E, Statistical, nonlinear, and soft matter physics - 92(2015), 5 vom: 15. Nov., Seite 052811

Sprache:

Englisch

Beteiligte Personen:

Lipowski, Adam [VerfasserIn]
Ferreira, António Luis [VerfasserIn]
Lipowska, Dorota [VerfasserIn]
Gontarek, Krzysztof [VerfasserIn]

Links:

Volltext

Themen:

Journal Article

Anmerkungen:

Date Completed 30.08.2016

Date Revised 15.12.2015

published: Print-Electronic

Citation Status PubMed-not-MEDLINE

doi:

10.1103/PhysRevE.92.052811

funding:

Förderinstitution / Projekttitel:

PPN (Katalog-ID):

NLM255418205