The non-Gaussian Cold Spot in WMAP: significance, morphology and foreground contribution

The non--Gaussian cold spot in the 1-year WMAP data, described in Vielva et al. and Cruz et al., is analysed in detail in the present paper. First of all, we perform a more rigorous calculation of the significance of the non-zero kurtosis detected in WMAP maps by Vielva et al. in wavelet space, mainly generated by the Spot. We confirm the robustness of that detection, since the probability of obtaining this deviation by chance is 0.69%. Afterwards, the morphology of the Spot is studied by applying Spherical Mexican Hat Wavelets with different ellipticities. The shape of the Spot is found to be almost circular. Finally, we discuss if the observed non-Gaussianity in wavelet space can arise from bad subtracted foreground residues in the WMAP maps. We show that the flat frequency dependence of the Spot cannot be explained by a thermal Sunyaev-Zeldovich effect. Based on our present knowledge of Galactic foreground emissions, we conclude that the significance of our detection is not affected by Galactic residues in the region of the Spot. Considering different Galactic foreground estimates, the probability of finding such a big cold spot in Gaussian simulations is always below 1%.Comment: 13 pages, 8 figures, minor changes, accpeted in MNRA

Optimal mobility-aware admission control in content delivery networks

This paper addresses the problem of mobility management in Content Delivery Networks (CDN). We introduce a CDN architecture where admission control is performed at mobility aware access routers. We formulate a Markov Modulated Poisson Decision Process for access control that captures the bursty nature of data and packetized traffic together with the heterogeneity of multimedia services. The optimization of performance parameters, like the blocking probabilities and the overall utilization, is conducted and the structural properties of the optimal solutions are also studied. Heuristics are proposed to encompass the computational difficulties of the optimal solution when several classes of multimedia traffic are considered

Social learning and information sharing: an evolutionary simulation model of foraging in Norway rats

Social learning is distinguished from innate behaviour and individual learning as a behavioural strategy. We investigate simple mechanisms for social learning in an evolutionary simulation of food-preference copying in Norway rats. These animals learn preferences by interacting with conspecifics, but, unexpectedly, they fail to learn aversions after interacting with a poisoned demonstrator. They also follow each other for food sites. Simulation results show that failure to discriminate between sick and healthy demonstrators may be due to food toxicity in foraging environments. A seemingly complex instance of social information transmission is explained through the action of simple behaviours in an appropriately structured environment

Cross-correlation of the CMB and radio galaxies in real, harmonic and wavelet spaces: detection of the integrated Sachs-Wolfe effect and dark energy constraints

We report the first detection of the ISW effect in wavelet space, at scales in the sky around 7 degrees with a significance of around 3.3 sigma, by cross-correlating the WMAP first-year data and the NRAO VLA Sky Survey (NVSS). In addition, we present a detailed comparison among the capabilities of three different techniques for two different objectives: to detect the ISW and to put constraints in the nature of the dark energy. The three studied techniques are: the cross-angular power spectrum (CAPS, harmonic space), the correlation function (CCF, real space) and the covariance of the Spherical Mexican Hat Wavelet (SMHW) coefficients (CSMHW, wavelet space). We prove that the CSMHW is expected to provide a higher detection of the ISW effect for a certain scale. This prediction has been corroborated by the analysis of the data. The SMHW analysis shows that the cross-correlation signal is caused neither by systematic effects nor foreground contamination. However, by taking into account the information encoded in all the multipoles/scales/angles, the CAPS provides slightly better constraints than the SMHW in the cosmological parameters that define the nature of the dark energy. The limits provided by the CCF are wider than for the other two methods. Two different cases have been studied: 1) a flat Lambda-CDM universe and 2) a flat universe with an equation of state parameter different from -1. In the first case, the CAPS provides (for a bias value of b = 1.6) 0.59 < Lambda density < 0.84 (at 1 sigma CL). Moreover, the CAPS rejects the range Lambda density < 0.1 at 3.5 sigma, which is the highest detection of the dark energy reported up to date. In the second case, the CAPS gives 0.50 < dark energy density < 0.82 and -1.16 < w < 0.43 (at 1 sigma CL).Comment: 12 pages, 7 figures, accepted for publication in MNRAS. Analysis redone. Changes in the estimation of the cosmological parametres. Additional comparison between wavelets and more standard technique

SUPPLY CHAIN MANAGEMENT AND THE ROMANIAN TRANSITION

Supply Chain Management (SCM), defined here as the construction of productive systems spanning over organizational borders with suppliers and customers and integrated via human-based and information technology systems to satisfy final customer requirements, is introduced as a key concept to accelerate Romania’s economic transition as it approaches EU membership, as well as to develop a modern supplier network. We introduce SCM from a system perspective along three broad areas: input, operations, output and system integration activities. We close by introducing constraints to SCM implementation in Romania. The first major constraint involves a lack of appropriate physical and human capital. Modernization of antiquated equipment and training employees in modern operations practices are prime requisites. The second major constraint, and perhaps the more difficult to change, deals with a lack of social capital among Romanian firms and adapting to appropriate managerial and worker values and attitudes.Supply Chain Management; Social Capital; Transition Economy; Economic Development.

Agent-based modeling of interdependent critical infrastructures

Critical interdependent infrastructures are complex systems, that if damaged or disrupted can seriously compromise the welfare of our society. This research, part of the CRESCO project, deal with the problem of interdependent critical infrastructures analysis, proposing an agent-based modelling and simulation solution. The approach we put forward, named Federated-ABMS, relies on discrete agent-based modelling and simulation and federated simulation. Federated-ABMS provides a formalism to model compound complex systems, composed of interacting systems, as federation of interacting agents and sector specific simulation models. This paper describes the formal model as well it outlines the steps that characterise the Federated-ABMS methodology, here applied to a target system, composed of a communication network and of a power grid. Moreover we conclude the paper with a thorough discussion of implementation issues

1.4 GHz polarimetric observations of the two fields imaged by the DASI experiment

We present results of polarization observations at 1.4 GHz of the two fields imaged by the DASI experiment ($\alpha = 23^{\rm h} 30^{\rm m}$, $\delta = -55^{\circ}$ and $\alpha = 00^{\rm h} 30^{\rm m}$, $\delta = -55^{\circ}$, respectively). Data were taken with the Australia Telescope Compact Array with 3.4 arcmin resolution and $\sim 0.18$ mJy beam$^{-1}$ sensitivity. The emission is dominated by point sources and we do not find evidence for diffuse synchrotron radiation even after source subtraction. This allows to estimate an upper limit of the diffuse polarized emission. The extrapolation to 30 GHz suggests that the synchrotron radiation is lower than the polarized signal measured by the DASI experiment by at least 2 orders of magnitude. This further supports the conclusions drawn by the DASI team itself about the negligible Galactic foreground contamination in their data set, improving by a factor $\sim 5$ the upper limit estimated by Leitch et al. (2005). The dominant point source emission allows us to estimate the contamination of the CMB by extragalactic foregrounds. We computed the power spectrum of their contribution and its extrapolation to 30 GHz provides a framework where the CMB signal should dominate. However, our results do not match the conclusions of the DASI team about the negligibility of point source contamination, suggesting to take into account a source subtraction from the DASI data.Comment: 7 pages, six figures, submitted to MNRA

Internet Industry Competition Dynamics: Peering Limitations, Exposure, and Counter Strategies

The Internet industry is vertically integrated with Internet Backbone Providers (IBPs) and Internet Service Providers (ISPs.) Although there are many ISPs and IBPs in each stream, both markets are considered independent oligopolies in that there are a few dominant competitors in each market. It is generally accepted that the Internet industry structure has evolved into a four-tier hierarchical structure. The synergistic and codependent nature of the Internet industry is the key element in understanding the competitive environment in which both IBP’s and ISP’s cooperate. Peering is an efficient way to exchange traffic freely within the access tier, nevertheless competitive constraints limit within tier exchanges. This paper combines the value chain model, competitive force model and a game model to illustrate the interconnection competitive perspective between IBP and ISPs and demonstrate why peering is difficult in the local access market

The CIB-lensing bispectrum: impact on primordial non-Gaussianity and detectability for the Planck mission

We characterize the cosmic infrared background (CIB)-lensing bispectrum which is one of the contributions to the three-point functions of cosmic microwave background (CMB) maps in harmonic space. We show that the CIB-lensing bispectrum has a considerable strength and that it can be detected with high significance in the Planck high-frequency maps. We also present forecasts of the contamination on different shapes of the primordial non-Gaussianity fnl parameter produced by the CIB-lensing bispectrum and by the extragalactic point sources bispectrum in the Planck high-resolution CMB anisotropy maps. The local, equilateral and orthogonal shapes are considered for ‘raw' single-frequency (i.e. without applying any component separation technique) and foreground-reduced Planck temperature maps. The CIB-lensing correlation seems to mainly affect orthogonal shapes of the bispectrum - with $\Delta f_{\rm nl}^{\rm (ort)} =-21$ and −88 for the 143 and 217 GHz bands, respectively - while point sources mostly impact equilateral shapes, with $\Delta f_{\rm nl}^{\rm (eq)} =160, 54$ and 60 at 100, 143 and 217 GHz. However, the results indicate that these contaminants do not induce any relevant bias on Planck fnl estimates when foreground-reduced maps are considered: using SEVEM for the component separation, we obtain $\Delta f_{\rm nl}^{\rm (ort)} =10.5$ due to the CIB-lensing and $\Delta f_{\rm nl}^{\rm (eq)}=30.4$ due to point sources, corresponding to 0.3σ and 0.45σ in terms of the Planck 2013 fnl uncertainty. The component separation technique is, in fact, able to partially clean the extragalactic source contamination and the bias is reduced for all the shapes. We have further developed single- and multiple-frequency estimators based on the Komatsu, Spergel & Wandelt formalism that can be implemented to efficiently detect this signa