The group of causal automorphisms

The group of causal automorphisms on Minkowski space-time is given and its structure is analyzed

The q-component static model : modeling social networks

We generalize the static model by assigning a q-component weight on each vertex. We first choose a component $(\mu)$ among the q components at random and a pair of vertices is linked with a color $\mu$ according to their weights of the component $(\mu)$ as in the static model. A (1-f) fraction of the entire edges is connected following this way. The remaining fraction f is added with (q+1)-th color as in the static model but using the maximum weights among the q components each individual has. This model is motivated by social networks. It exhibits similar topological features to real social networks in that: (i) the degree distribution has a highly skewed form, (ii) the diameter is as small as and (iii) the assortativity coefficient r is as positive and large as those in real social networks with r reaching a maximum around $f \approx 0.2$.Comment: 5 pages, 6 figure

Polyhedral graph abstractions and an approach to the Linear Hirsch Conjecture

We introduce a new combinatorial abstraction for the graphs of polyhedra. The new abstraction is a flexible framework defined by combinatorial properties, with each collection of properties taken providing a variant for studying the diameters of polyhedral graphs. One particular variant has a diameter which satisfies the best known upper bound on the diameters of polyhedra. Another variant has superlinear asymptotic diameter, and together with some combinatorial operations, gives a concrete approach for disproving the Linear Hirsch Conjecture.Comment: 16 pages, 4 figure

Particle Correlation Results from the ALICE Experiment at LHC

Measurements of two-particle correlations of inclusive and identified charged particles performed with the ALICE detector in Pb--Pb collisions at $\sqrt{s_{NN}} = 2.76 TeV$ are presented. The near-side jet shape is analyzed in the low $p_{\rm T}$ regions ($1<$p_{\rm T}$<8GeV/c$). While the RMS of the peak in $\Delta\varphi$-direction is independent of centrality within uncertainties, we find significant broadening in $\Delta\eta$-direction from peripheral to central collisions. The near-side $p/\pi$ ratio of particles associated to a trigger particle from jet fragmentation in the central Pb--Pb collisions is consistent with vacuum fragmentation in the measured momentum region ($1.5<$p_{\rm T}<4.5GeV\c).Comment: 8 pages, 6 figures, proceeding for Physics at LHC 2012, vancouver, Canad