2,420 research outputs found
Elliptic flow at high transverse momentum in Pb-Pb collisions at TeV with the ALICE experiment
An observable that can be used to better constrain the mechanism responsible
for the parton energy loss is the elliptic azimuthal event anisotropy, .
We report on measurements of for inclusive and identified charged
particles in Pb-Pb collisions at TeV recorded by the
ALICE experiment at the LHC. is presented for a wide range of particle
transverse momentum up to GeV/c. The particle is finite,
positive and approximately constant for GeV/c. The proton is
higher than that of the pion up to about GeV/c. The results are
compared to the measurements at lower energy reported by RHIC experiments.Comment: 4 pages, QM 2011 proceeding
Phase Transition in a Self-repairing Random Network
We consider a network, bonds of which are being sequentially removed; that is
done at random, but conditioned on the system remaining connected
(Self-Repairing Bond Percolation SRBP). This model is the simplest
representative of a class of random systems for which forming of isolated
clusters is forbidden. It qualitatively describes the process of fabrication of
artificial porous materials and degradation of strained polymers. We find a
phase transition at a finite concentration of bonds , at which the
backbone of the system vanishes; for all the network is a dense
fractal.Comment: 4 pages, 4 figure
The topological relationship between the large-scale attributes and local interaction patterns of complex networks
Recent evidence indicates that the abundance of recurring elementary
interaction patterns in complex networks, often called subgraphs or motifs,
carry significant information about their function and overall organization.
Yet, the underlying reasons for the variable quantity of different subgraph
types, their propensity to form clusters, and their relationship with the
networks' global organization remain poorly understood. Here we show that a
network's large-scale topological organization and its local subgraph structure
mutually define and predict each other, as confirmed by direct measurements in
five well studied cellular networks. We also demonstrate the inherent existence
of two distinct classes of subgraphs, and show that, in contrast to the
low-density type II subgraphs, the highly abundant type I subgraphs cannot
exist in isolation but must naturally aggregate into subgraph clusters. The
identified topological framework may have important implications for our
understanding of the origin and function of subgraphs in all complex networks.Comment: pape
Minimum spanning trees on random networks
We show that the geometry of minimum spanning trees (MST) on random graphs is
universal. Due to this geometric universality, we are able to characterise the
energy of MST using a scaling distribution () found using uniform
disorder. We show that the MST energy for other disorder distributions is
simply related to . We discuss the relationship to invasion
percolation (IP), to the directed polymer in a random media (DPRM) and the
implications for the broader issue of universality in disordered systems.Comment: 4 pages, 3 figure
Random-field Ising model on complete graphs and trees
We present exact results for the critical behavior of the RFIM on complete
graphs and trees, both at equilibrium and away from equilibrium, i.e., models
for hysteresis and Barkhausen noise. We show that for stretched exponential and
power law distributions of random fields the behavior on complete graphs is
non-universal, while the behavior on Cayley trees is universal even in the
limit of large co-ordination.Comment: 4 pages, 4 figure
Coarse-Graining and Self-Dissimilarity of Complex Networks
Can complex engineered and biological networks be coarse-grained into smaller
and more understandable versions in which each node represents an entire
pattern in the original network? To address this, we define coarse-graining
units (CGU) as connectivity patterns which can serve as the nodes of a
coarse-grained network, and present algorithms to detect them. We use this
approach to systematically reverse-engineer electronic circuits, forming
understandable high-level maps from incomprehensible transistor wiring: first,
a coarse-grained version in which each node is a gate made of several
transistors is established. Then, the coarse-grained network is itself
coarse-grained, resulting in a high-level blueprint in which each node is a
circuit-module made of multiple gates. We apply our approach also to a
mammalian protein-signaling network, to find a simplified coarse-grained
network with three main signaling channels that correspond to cross-interacting
MAP-kinase cascades. We find that both biological and electronic networks are
'self-dissimilar', with different network motifs found at each level. The
present approach can be used to simplify a wide variety of directed and
nondirected, natural and designed networks.Comment: 11 pages, 11 figure
Using graph concepts to understand the organization of complex systems
Complex networks are universal, arising in fields as disparate as sociology,
physics, and biology. In the past decade, extensive research into the
properties and behaviors of complex systems has uncovered surprising
commonalities among the topologies of different systems. Attempts to explain
these similarities have led to the ongoing development and refinement of
network models and graph-theoretical analysis techniques with which to
characterize and understand complexity. In this tutorial, we demonstrate
through illustrative examples, how network measures and models have contributed
to the elucidation of the organization of complex systems.Comment: v(1) 38 pages, 7 figures, to appear in the International Journal of
Bifurcation and Chaos v(2) Line spacing changed; now 23 pages, 7 figures, to
appear in the Special Issue "Complex Networks' Structure and Dynamics'' of
the International Journal of Bifurcation and Chaos (Volume 17, Issue 7, July
2007) edited by S. Boccaletti and V. Lator
Long-lived stops in MSSM scenarios with a neutralino LSP
This work investigates the possibility of a long-lived stop squark in
supersymmetric models with the neutralino as the lightest supersymmetric
particle (LSP). We study the implications of meta-stable stops on the sparticle
mass spectra and the dark matter density. We find that in order to obtain a
sufficiently long stop lifetime so as to be observable as a stable R-hadron at
an LHC experiment, we need to fine tune the mass degeneracy between the stop
and the LSP considerably. This increases the stop-neutralino coanihilation
cross section, leaving the neutralino relic density lower than what is expected
from the WMAP results for stop masses ~1.5 TeV/c^2. However, if such scenarios
are realised in nature we demonstrate that the long-lived stops will be
produced at the LHC and that stop-based R-hadrons with masses up to 1 TeV/c^2
can be detected after one year of running at design luminosity
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