841 research outputs found
Is the New Resonance Spin 0 or 2? Taking a Step Forward in the Higgs Boson Discovery
The observation of a new boson of mass \sim 125\gev at the CERN LHC may
finally have revealed the existence of a Higgs boson. Now we have the
opportunity to scrutinize its properties, determining its quantum numbers and
couplings to the standard model particles, in order to confirm or not its
discovery. We show that by the end of the 8 TeV run, combining the entire data
sets of ATLAS and CMS, it will be possible to discriminate between the
following discovery alternatives: a scalar or a tensor
particle with minimal couplings to photons, at a statistical
confidence level at least, using only diphotons events. Our results are based
on the calculation of a center-edge asymmetry measure of the reconstructed {\it
sPlot} scattering polar angle of the diphotons. The results based on
asymmetries are shown to be rather robust against systematic uncertainties with
comparable discrimination power to a log likelihood ratio statistic.Comment: 11 pages, 6 figures, 1 table. References added, minor typos correcte
A novel approach to study realistic navigations on networks
We consider navigation or search schemes on networks which are realistic in
the sense that not all search chains can be completed. We show that the
quantity , where is the average dynamic shortest distance
and the success rate of completion of a search, is a consistent measure
for the quality of a search strategy. Taking the example of realistic searches
on scale-free networks, we find that scales with the system size as
, where decreases as the searching strategy is improved.
This measure is also shown to be sensitive to the distintinguishing
characteristics of networks. In this new approach, a dynamic small world (DSW)
effect is said to exist when . We show that such a DSW indeed
exists in social networks in which the linking probability is dependent on
social distances.Comment: Text revised, references added; accepted version in Journal of
Statistical Mechanic
Proximity Drawings of High-Degree Trees
A drawing of a given (abstract) tree that is a minimum spanning tree of the
vertex set is considered aesthetically pleasing. However, such a drawing can
only exist if the tree has maximum degree at most 6. What can be said for trees
of higher degree? We approach this question by supposing that a partition or
covering of the tree by subtrees of bounded degree is given. Then we show that
if the partition or covering satisfies some natural properties, then there is a
drawing of the entire tree such that each of the given subtrees is drawn as a
minimum spanning tree of its vertex set
Pseudospin-Resolved Transport Spectroscopy of the Kondo Effect in a Double Quantum Dot
We report measurements of the Kondo effect in a double quantum dot (DQD),
where the orbital states act as pseudospin states whose degeneracy contributes
to Kondo screening. Standard transport spectroscopy as a function of the bias
voltage on both dots shows a zero-bias peak in conductance, analogous to that
observed for spin Kondo in single dots. Breaking the orbital degeneracy splits
the Kondo resonance in the tunneling density of states above and below the
Fermi energy of the leads, with the resonances having different pseudospin
character. Using pseudospin-resolved spectroscopy, we demonstrate the
pseudospin character by observing a Kondo peak at only one sign of the bias
voltage. We show that even when the pseudospin states have very different
tunnel rates to the leads, a Kondo temperature can be consistently defined for
the DQD system.Comment: Text and supplementary information. Text: 4 pages, 5 figures.
Supplementary information: 4 pages, 4 figure
Asymptotic behavior of the Kleinberg model
We study Kleinberg navigation (the search of a target in a d-dimensional
lattice, where each site is connected to one other random site at distance r,
with probability proportional to r^{-a}) by means of an exact master equation
for the process. We show that the asymptotic scaling behavior for the delivery
time T to a target at distance L scales as (ln L)^2 when a=d, and otherwise as
L^x, with x=(d-a)/(d+1-a) for ad+1. These
values of x exceed the rigorous lower-bounds established by Kleinberg. We also
address the situation where there is a finite probability for the message to
get lost along its way and find short delivery times (conditioned upon arrival)
for a wide range of a's
Search in Complex Networks : a New Method of Naming
We suggest a method for routing when the source does not posses full
information about the shortest path to the destination. The method is
particularly useful for scale-free networks, and exploits its unique
characteristics. By assigning new (short) names to nodes (aka labelling) we are
able to reduce significantly the memory requirement at the routers, yet we
succeed in routing with high probability through paths very close in distance
to the shortest ones.Comment: 5 pages, 4 figure
Transport in networks with multiple sources and sinks
We investigate the electrical current and flow (number of parallel paths)
between two sets of n sources and n sinks in complex networks. We derive
analytical formulas for the average current and flow as a function of n. We
show that for small n, increasing n improves the total transport in the
network, while for large n bottlenecks begin to form. For the case of flow,
this leads to an optimal n* above which the transport is less efficient. For
current, the typical decrease in the length of the connecting paths for large n
compensates for the effect of the bottlenecks. We also derive an expression for
the average flow as a function of n under the common limitation that transport
takes place between specific pairs of sources and sinks
Defect formation and local gauge invariance
We propose a new mechanism for formation of topological defects in a U(1)
model with a local gauge symmetry. This mechanism leads to definite
predictions, which are qualitatively different from those of the Kibble-Zurek
mechanism of global theories. We confirm these predictions in numerical
simulations, and they can also be tested in superconductor experiments. We
believe that the mechanism generalizes to more complicated theories.Comment: REVTeX, 4 pages, 2 figures. The explicit form of the Hamiltonian and
the equations of motion added. To appear in PRL (http://prl.aps.org/
Limited path percolation in complex networks
We study the stability of network communication after removal of
links under the assumption that communication is effective only if the shortest
path between nodes and after removal is shorter than where is the shortest path before removal. For a large
class of networks, we find a new percolation transition at
, where and
is the node degree. Below , only a fraction of
the network nodes can communicate, where , while above , order nodes can
communicate within the limited path length . Our analytical results
are supported by simulations on Erd\H{o}s-R\'{e}nyi and scale-free network
models. We expect our results to influence the design of networks, routing
algorithms, and immunization strategies, where short paths are most relevant.Comment: 11 pages, 3 figures, 1 tabl
The evolution of interdisciplinarity in physics research
Science, being a social enterprise, is subject to fragmentation into groups
that focus on specialized areas or topics. Often new advances occur through
cross-fertilization of ideas between sub-fields that otherwise have little
overlap as they study dissimilar phenomena using different techniques. Thus to
explore the nature and dynamics of scientific progress one needs to consider
the large-scale organization and interactions between different subject areas.
Here, we study the relationships between the sub-fields of Physics using the
Physics and Astronomy Classification Scheme (PACS) codes employed for
self-categorization of articles published over the past 25 years (1985-2009).
We observe a clear trend towards increasing interactions between the different
sub-fields. The network of sub-fields also exhibits core-periphery
organization, the nucleus being dominated by Condensed Matter and General
Physics. However, over time Interdisciplinary Physics is steadily increasing
its share in the network core, reflecting a shift in the overall trend of
Physics research.Comment: Published version, 10 pages, 8 figures + Supplementary Informatio
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