2,685 research outputs found

    High-Resolution Simulations of Cosmic Microwave Background non-Gaussian Maps in Spherical Coordinates

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    We describe a new numerical algorithm to obtain high-resolution simulated maps of the Cosmic Microwave Background (CMB), for a broad class of non-Gaussian models. The kind of non-Gaussianity we account for is based on the simple idea that the primordial gravitational potential is obtained by a non-linear but local mapping from an underlying Gaussian random field, as resulting from a variety of inflationary models. Our technique, which is based on a direct realization of the potential in spherical coordinates and fully accounts for the radiation transfer function, allows to simulate non-Gaussian CMB maps down to the Planck resolution (max3,000\ell_{\rm max} \sim 3,000), with reasonable memory storage and computational time.Comment: 9 pages, 5 figures. Submitted to ApJ. A version with higher quality figures is available at http://www.pd.infn.it/~liguori/content.htm

    Galaxy-CMB Cross-Correlation as a Probe of Alternative Models of Gravity

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    Bekenstein's alternative to general relativity, TeVeS, reduces to Modified Newtonian Dynamics (MOND) in the galactic limit. On cosmological scales, the (potential well overdensity) relationship is quite different than in standard general relativity. Here we investigate the possibility of cross-correlating galaxies with the cosmic microwave background (CMB) to probe this relationship. At redshifts of order 2, the sign of the CMB-galaxy correlation differs in TeVeS from that in general relativity. We show that this effect is detectable and hence can serve as a powerful discriminator of these two models of gravity.Comment: 10 pages, 6 figures, revised version re-submitted to Phys. Rev.

    A quasi-static nonlinear analysis for assessing the fire resistance of 3d frames exploiting time-dependent yield surface

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    In this work an automatic procedure for evaluating the axial force-biaxial bending yield surface of reinforced concrete sections in fire is proposed. It provides an accurate time-dependent expression of the yield condition by a section analysis carried out once and for all, accounting for the strength reduction of the materials, which is a function of the fire duration. The equilibrium state of 3D frames with such yield conditions, once discretized using beam finite elements, is formulated as a nonlinear vectorial equation defining a curve in the hyperspace of the discrete variables and the fire duration. A generalized path-following strategy is proposed for tracing this curve and evaluating, if it exists, the limit fire duration, that is the time of exposure which leads to structural collapse. Compared to the previous proposals on the topic, which are limited to local sectional checks, this work is the first to present a global analysis for assessing the fire resistance of 3D frames, providing a time history of the fire event and taking account of the stress redistribution. Numerical examples are given to illustrate and validate the proposal

    Observational constraints on patch inflation in noncommutative spacetime

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    We study constraints on a number of patch inflationary models in noncommutative spacetime using a compilation of recent high-precision observational data. In particular, the four-dimensional General Relativistic (GR) case, the Randall-Sundrum (RS) and Gauss-Bonnet (GB) braneworld scenarios are investigated by extending previous commutative analyses to the infrared limit of a maximally symmetric realization of the stringy uncertainty principle. The effect of spacetime noncommutativity modifies the standard consistency relation between the tensor spectral index and the tensor-to-scalar ratio. We perform likelihood analyses in terms of inflationary observables using new consistency relations and confront them with large-field inflationary models with potential V \propto \vp^p in two classes of noncommutative scenarios. We find a number of interesting results: (i) the quartic potential (p=4) is rescued from marginal rejection in the class 2 GR case, and (ii) steep inflation driven by an exponential potential (p \to \infty) is allowed in the class 1 RS case. Spacetime noncommutativity can lead to blue-tilted scalar and tensor spectra even for monomial potentials, thus opening up a possibility to explain the loss of power observed in the cosmic microwave background anisotropies. We also explore patch inflation with a Dirac-Born-Infeld tachyon field and explicitly show that the associated likelihood analysis is equivalent to the one in the ordinary scalar field case by using horizon-flow parameters. It turns out that tachyon inflation is compatible with observations in all patch cosmologies even for large p.Comment: 16 pages, 11 figures; v2: updated references, minor corrections to match the Phys. Rev. D versio

    Vascular flora of Monte Sparviere (southern Italy, Pollino Massif)

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    Vascular Flora of Monte Sparviere (Southern Italy, Pollino Massif). A floristic survey of Monte Sparviere was carried out from 2012 to 2015, allowing us to record 377 specific and subspecific taxa, belonging to 229 genera and 64 families. The most represented families are Asteraceae (55 taxa), Poaceae (30), Fabaceae (28), Rosaceae (23) and Lamiaceae (19). Italian endemic species reach the 8.5% and no exotic species are recorded except three conifers used for reforestation. Biological spectrum shows a dominance of Hemicryptophytes, with a moderate percentage of Therophytes. The chorological analysis shows a dominance of species belonging to the Eurosibiric region, albeit Mediterranean region is also well represented. The ecological spectra are in agreement with climatic and geo-pedologic features, with variations mainly related to woody coverage and altitude. Finally, Potentilla pedata Willd. ex Hornem was confirmed for the flora of Basilicata; Dianthus sternbergii Capelli was excluded from the flora of Basilicata and Calabria whereas Dianthus hyssopifolius L. resulted new for both regions

    Anyonic Realization of the Quantum Affine Lie Superalgebra U_q(A(M,N)^{(1)})

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    We give a realization of the quantum affine Lie superalgebras U_q(A(M,N))^(1) in terms of anyons defined on a one or two-dimensional lattice, the deformation parameter q being related to the statistical parameter ν\nu of the anyons by q = exp(i\pi\nu). The construction uses anyons contructed from usual fermionic oscillators and deformed bosonic oscillators. As a byproduct, realization deformed in any sector of the quantum superalgebras U_q(A(M,N)) is obtained.Comment: 14p LaTeX Document (should be run twice

    Gauge-Invariant Quasi-Free States on the Algebra of the Anyon Commutation Relations

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    Let X=R2X=\mathbb R^2 and let qCq\in\mathbb C, q=1|q|=1. For x=(x1,x2)x=(x^1,x^2) and y=(y1,y2)y=(y^1,y^2) from X2X^2, we define a function Q(x,y)Q(x,y) to be equal to qq if x1y1x^1y^1, and to q\Re q if x1=y1x^1=y^1. Let x+\partial_x^+, x\partial_x^- (xXx\in X) be operator-valued distributions such that x+\partial_x^+ is the adjoint of x\partial_x^-. We say that x+\partial_x^+, x\partial_x^- satisfy the anyon commutation relations (ACR) if x+y+=Q(y,x)y+x+\partial^+_x\partial_y^+=Q(y,x)\partial_y^+\partial_x^+ for xyx\ne y and xy+=δ(xy)+Q(x,y)y+x\partial^-_x\partial_y^+=\delta(x-y)+Q(x,y)\partial_y^+\partial^-_x for (x,y)X2(x,y)\in X^2. In particular, for q=1q=1, the ACR become the canonical commutation relations and for q=1q=-1, the ACR become the canonical anticommutation relations. We define the ACR algebra as the algebra generated by operator-valued integrals of x+\partial_x^+, x\partial_x^-. We construct a class of gauge-invariant quasi-free states on the ACR algebra. Each state from this class is completely determined by a positive self-adjoint operator TT on the real space L2(X,dx)L^2(X,dx) which commutes with any operator of multiplication by a bounded function ψ(x1)\psi(x^1). In the case q0\Re q0), we discuss the corresponding particle density ρ(x):=x+x\rho(x):=\partial_x^+\partial_x^-. For q(0,1]\Re q\in(0,1], using a renormalization, we rigorously define a vacuum state on the commutative algebra generated by operator-valued integrals of ρ(x)\rho(x). This state is given by a negative binomial point process. A scaling limit of these states as κ\kappa\to\infty gives the gamma random measure, depending on parameter q\Re q

    Towards Runtime Verification via Event Stream Processing in Cloud Computing Infrastructures

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    Software bugs in cloud management systems often cause erratic behavior, hindering detection, and recovery of failures. As a consequence, the failures are not timely detected and notified, and can silently propagate through the system. To face these issues, we propose a lightweight approach to runtime verification, for monitoring and failure detection of cloud computing systems. We performed a preliminary evaluation of the proposed approach in the OpenStack cloud management platform, an “off-the-shelf” distributed system, showing that the approach can be applied with high failure detection coverage

    The pulsed electron deposition technique for biomedical applications: A review

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    The "pulsed electron deposition" (PED) technique, in which a solid target material is ablated by a fast, high-energy electron beam, was initially developed two decades ago for the deposition of thin films of metal oxides for photovoltaics, spintronics, memories, and superconductivity, and dielectric polymer layers. Recently, PED has been proposed for use in the biomedical field for the fabrication of hard and soft coatings. The first biomedical application was the deposition of low wear zirconium oxide coatings on the bearing components in total joint replacement. Since then, several works have reported the manufacturing and characterization of coatings of hydroxyapatite, calcium phosphate substituted (CaP), biogenic CaP, bioglass, and antibacterial coatings on both hard (metallic or ceramic) and soft (plastic or elastomeric) substrates. Due to the growing interest in PED, the current maturity of the technology and the low cost compared to other commonly used physical vapor deposition techniques, the purpose of this work was to review the principles of operation, the main applications, and the future perspectives of PED technology in medicine
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