2,227 research outputs found
Critical Droplets and Phase Transitions in Two Dimensions
In two space dimensions, the percolation point of the pure-site clusters of
the Ising model coincides with the critical point T_c of the thermal transition
and the percolation exponents belong to a special universality class. By
introducing a bond probability p_B<1, the corresponding site-bond clusters keep
on percolating at T_c and the exponents do not change, until
p_B=p_CK=1-exp(-2J/kT): for this special expression of the bond weight the
critical percolation exponents switch to the 2D Ising universality class. We
show here that the result is valid for a wide class of bidimensional models
with a continuous magnetization transition: there is a critical bond
probability p_c such that, for any p_B>=p_c, the onset of percolation of the
site-bond clusters coincides with the critical point of the thermal transition.
The percolation exponents are the same for p_c<p_B<=1 but, for p_B=p_c, they
suddenly change to the thermal exponents, so that the corresponding clusters
are critical droplets of the phase transition. Our result is based on Monte
Carlo simulations of various systems near criticality.Comment: Final version for publication, minor changes, figures adde
Bound states in the 3d Ising model and implications for QCD at finite temperature and density
We study the spectrum of bound states of the three dimensional Ising model in
the (h,beta) plane near the critical point. We show the existence of an
unbinding line, defined as the boundary of the region where bound states exist.
Numerical evidence suggests that this line coincides with the beta=beta_c axis.
When the 3D Ising model is considered as an effective description of hot QCD at
finite density, we conjecture the correspondence between the unbinding line and
the line that separates the quark-gluon plasma phase from the superconducting
phase. The bound states of the Ising model are conjectured to correspond to the
diquarks of the latter phase of QCD.Comment: Lattice2001(hightemp
Interview with Laura Fortunato, Winner of the 2011 Gabriel W. Lasker Prize
An international jury composed of Michael Crawford (University of Kansas, USA), Dennis O\u27Rourke (University of Utah, USA), and Stephen Shennan (University College London, UK) has awarded the Gabriel Ward Lasker Prize 2011 to Dr. Laura Fortunato for her articles entitled Reconstructing the History of Residence Strategies in Indo-European–Speaking Societies and Reconstructing the History of Marriage Strategies in Indo-European–Speaking Societies considered as the best contribution to the 83rd volume of Human Biology (2011). Laura Fortunato is an Omidyar Fellow at the Santa Fe Institute in Santa Fe, New Mexico. She received her Ph.D. in anthropology from University College London in 2009; her doctoral research focused on the evolution of kinship and marriage systems. In particular, she has investigated the evolution of marriage strategies, wealth transfers at marriage, residence strategies, and inheritance strategies. Laura\u27s current research activities apply conceptual and methodological tools developed in evolutionary biology to a diverse range of topics in anthropology, from matrilineal kinship organization to cultural evolution
A Comparison of Blocking Methods for Record Linkage
Record linkage seeks to merge databases and to remove duplicates when unique
identifiers are not available. Most approaches use blocking techniques to
reduce the computational complexity associated with record linkage. We review
traditional blocking techniques, which typically partition the records
according to a set of field attributes, and consider two variants of a method
known as locality sensitive hashing, sometimes referred to as "private
blocking." We compare these approaches in terms of their recall, reduction
ratio, and computational complexity. We evaluate these methods using different
synthetic datafiles and conclude with a discussion of privacy-related issues.Comment: 22 pages, 2 tables, 7 figure
Spectral centrality measures in complex networks
Complex networks are characterized by heterogeneous distributions of the
degree of nodes, which produce a large diversification of the roles of the
nodes within the network. Several centrality measures have been introduced to
rank nodes based on their topological importance within a graph. Here we review
and compare centrality measures based on spectral properties of graph matrices.
We shall focus on PageRank, eigenvector centrality and the hub/authority scores
of HITS. We derive simple relations between the measures and the (in)degree of
the nodes, in some limits. We also compare the rankings obtained with different
centrality measures.Comment: 11 pages, 10 figures, 5 tables. Final version published in Physical
Review
The impact of partially missing communities~on the reliability of centrality measures
Network data is usually not error-free, and the absence of some nodes is a
very common type of measurement error. Studies have shown that the reliability
of centrality measures is severely affected by missing nodes. This paper
investigates the reliability of centrality measures when missing nodes are
likely to belong to the same community. We study the behavior of five commonly
used centrality measures in uniform and scale-free networks in various error
scenarios. We find that centrality measures are generally more reliable when
missing nodes are likely to belong to the same community than in cases in which
nodes are missing uniformly at random. In scale-free networks, the betweenness
centrality becomes, however, less reliable when missing nodes are more likely
to belong to the same community. Moreover, centrality measures in scale-free
networks are more reliable in networks with stronger community structure. In
contrast, we do not observe this effect for uniform networks. Our observations
suggest that the impact of missing nodes on the reliability of centrality
measures might not be as severe as the literature suggests
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