77,065 research outputs found
Stability of Kronecker coefficients via discrete tomography
In this paper we give a new sufficient condition for a general stability of
Kronecker coefficients, which we call it additive stability. It was motivated
by a recent talk of J. Stembridge at the conference in honor of Richard P.
Stanley's 70th birthday, and it is based on work of the author on discrete
tomography along the years. The main contribution of this paper is the
discovery of the connection between additivity of integer matrices and
stability of Kronecker coefficients. Additivity, in our context, is a concept
from discrete tomography. Its advantage is that it is very easy to produce lots
of examples of additive matrices and therefore of new instances of stability
properties. We also show that Stembridge's hypothesis and additivity are
closely related, and prove that all stability properties of Kronecker
coefficients discovered before fit into additive stability.Comment: 22 page
Heavy quark asymmetries with DELPHI
The measurements of the forward-backward asymmetry in Z -> c cbar and Z -> b
bbar decays are among the most precise determinations of sin^2(theta)_W. In
this paper the results obtained by the DELPHI experiment at LEP with three
different analyses are reviewed together with the impact of the combined LEP
result on the global Electroweak fit.Comment: 7 pages, RevTeX, fonts changed in 2 eps file
Isotropization of non-diagonal Bianchi I spacetimes with collisionless matter at late times assuming small data
Assuming that the space-time is close to isotropic in the sense that the
shear parameter is small and that the maximal velocity of the particles is
bounded, we have been able to show that for non-diagonal Bianchi I-symmetric
spacetimes with collisionless matter the asymptotic behaviour at late times is
close to the special case of dust. We also have been able to show that all the
Kasner exponents converge to 1/3 and an asymptotic expression for the induced
metric has been obtained. The key was a bootstrap argument.Comment: V3 18 p. 3 fig. typos corrected, conclusions part extended,
references added. To appear in Classical and Quantum Gravit
Spectral Scaling in Complex Networks
A complex network is said to show topological isotropy if the topological
structure around a particular node looks the same in all directions of the
whole network. Topologically anisotropic networks are those where the local
neighborhood around a node is not reproduced at large scale for the whole
network. The existence of topological isotropy is investigated by the existence
of a power-law scaling between a local and a global topological characteristic
of complex networks obtained from graph spectra. We investigate this structural
characteristic of complex networks and its consequences for 32 real-world
networks representing informational, technological, biological, social and
ecological systems.Comment: 9 pages, 3 figure
Structural patterns in complex networks through spectral analysis
The study of some structural properties of networks is introduced from a graph spectral perspective. First, subgraph centrality of nodes is defined and used to classify essential proteins in a proteomic map. This index is then used to produce a method that allows the identification of superhomogeneous networks. At the same time this method classify non-homogeneous network into three universal classes of structure. We give examples of these classes from networks in different real-world scenarios. Finally, a communicability function is studied and showed as an alternative for defining communities in complex networks. Using this approach a community is unambiguously defined and an algorithm for its identification is proposed and exemplified in a real-world network
Communicability in temporal networks
A first-principles approach to quantify the communicability between pairs of nodes in temporal networks is proposed. It corresponds to the imaginary-time propagator of a quantum random walk in the temporal network, which accounts for unique structural and temporal characteristics of both streaming and nonstreaming temporal networks. The influence of the system's temperature on the perdurability of information and how the communicability identifies patterns of communication hidden in the temporal and topological structure of the networks are also studied for synthetic and real-world systems
- …