138 research outputs found
A thermodynamic counterpart of the Axelrod model of social influence: The one-dimensional case
We propose a thermodynamic version of the Axelrod model of social influence.
In one-dimensional (1D) lattices, the thermodynamic model becomes a coupled
Potts model with a bonding interaction that increases with the site matching
traits. We analytically calculate thermodynamic and critical properties for a
1D system and show that an order-disorder phase transition only occurs at T = 0
independent of the number of cultural traits q and features F. The 1D
thermodynamic Axelrod model belongs to the same universality class of the Ising
and Potts models, notwithstanding the increase of the internal dimension of the
local degree of freedom and the state-dependent bonding interaction. We suggest
a unifying proposal to compare exponents across different discrete 1D models.
The comparison with our Hamiltonian description reveals that in the
thermodynamic limit the original out-of-equilibrium 1D Axelrod model with noise
behaves like an ordinary thermodynamic 1D interacting particle system.Comment: 19 pages, 5 figure
Spin triplet superconductivity in Sr2RuO4
Sr2RuO4 is at present the best candidate for being a superconducting analogue
of the triplet superfluidity in ^3He. This material is a good (albeit
correlated) Fermi liquid in the normal state and an exotic superconductor below
Tc. The mechanism of superconductivity and symmetry of the order parameter are
the main puzzling issues of on-going research. Here we present the results of
our search for a viable description of the superconducting state realised in
this material. Our calculations are based on a three-dimensional effective
three-band model with a realistic band structure. We have found a state with
non-zero order parameter on each of the three sheets of the Fermi surface. The
corresponding gap in the quasi-particle spectrum has line or point nodes on the
alpha and beta sheets and is complex with no nodes on the gamma sheet. This
state describes remarkably well a number of existing experiments including
power low temperature dependence of the specific heat, penetration depth,
thermal conductivity etc. The stability of the state with respect to disorder
and different interaction parameters are also analyzed briefly.Comment: 8 pages, 5 figures (to appear in Physica Status Solidi A
Fulde-Ferrel-Larkin-Ovchinnikov State due to Antisymmetric Spin-Orbit-Coupling in Noncentrosymmetric Superconductivity CePtSi
When the inversion symmetry is broken, the spin-orbit coupling reduces the
transition temperature of some types of spin triplet superconductivity, which
is similar to the case that magnetic field reduces the spin singlet
superconductivity due to Zeeman splitting. It is well known that
Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) state of spin singlet superconductivity
is realized near the Pauli limit (or Chandrasekhar-Clogston limit) of external
magnetic field. In FFLO state the amplitude of the order parameter is not
uniform in space. In this paper we study the FFLO state in the spin triplet
superconductivity in the absence of magnetic field due to the spin-orbit
coupling. Although the FFLO state is not realized in the simple model with
spherical Fermi surface, it will be stabilized if some condition is favorable
for it. We discuss the possibility of FFLO state in CePtSi in the absence
of external magnetic field.Comment: 2 pages, 1 figure, M2S-HTSC VII
Cluster size entropy in the Axelrod model of social influence: small-world networks and mass media
We study the Axelrod's cultural adaptation model using the concept of cluster
size entropy, that gives information on the variability of the cultural
cluster size present in the system. Using networks of different topologies,
from regular to random, we find that the critical point of the well-known
nonequilibrium monocultural-multicultural (order-disorder) transition of the
Axelrod model is unambiguously given by the maximum of the
distributions. The width of the cluster entropy distributions can be used to
qualitatively determine whether the transition is first- or second-order. By
scaling the cluster entropy distributions we were able to obtain a relationship
between the critical cultural trait and the number of cultural
features in regular networks. We also analyze the effect of the mass media
(external field) on social systems within the Axelrod model in a square
network. We find a new partially ordered phase whose largest cultural cluster
is not aligned with the external field, in contrast with a recent suggestion
that this type of phase cannot be formed in regular networks. We draw a new
phase diagram for the Axelrod model in regular networks.Comment: 21 pages, 7 figure
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