Patrons temporals de comportament tàctic en curses atlètiques de 5.000 metres

El comportament tàctic en curses atlètiques de fons ha estat residualment estudiat. En el present treball, al si de la metodologia observacional, s’ha construït un instrument d’observació que permet detectar patrons temporals de comportament tàctic –mitjançant el programari Theme, versió 5.0– en el mostratge observacional corresponent a les finals de Campionats Mundials París 2003 i Berlín 2009; Olimpíades d’Atenes 2004 i Pequín 2008; Campionats Europeus de Göteborg 2006 i Barcelona 2010, en la modalitat de 5.000 metres –categoria masculina–. Els resultats obtinguts mostren pautes comportamentals rellevants, relatives fonamentalment al ritme de la prova i a la interacció de l’atleta guanyador amb els seus competidors

Patrones temporales de comportamiento táctico en carreras atléticas de 5.000 metros

El comportamiento táctico en carreras atléticas de fondo ha sido residualmente estudiado. En el presente trabajo, en el seno de la metodología observacional, se ha construido un instrumento de observación que permite detectar patrones temporales de comportamiento táctico –mediante el software Theme, versión 5.0.–, en el muestreo observacional correspondiente a las finales de: Campeonatos Mundiales París 2003 y Berlín 2009; Olimpiadas de Atenas 2004 y Pekín 2008; Campeonatos Europeos de Goteborg 2006 y Barcelona 2010, en la modalidad de 5000 metros –categoría masculina–. Los resultados obtenidos muestran pautas comportamentales relevantes, relativas, fundamentalmente, al ritmo de la prueba y a la interacción del atleta ganador con sus competidores

Locally Cold Flows from Large-Scale Structure

We show that the "cold" Hubble flow observed for galaxies around the Milky Way does not represent a problem in cosmology but is due to the particular geometry and dynamics of our local wall. The behavior of the perturbed Hubble flow around the Milky Way is the result of two main factors: at small scales (R < 1 Mpc) the inflow is dominated by the gravitational influence of the Milky Way. At large scales (R > 1 Mpc) the out flow reflects the expansion of our local wall which "cools down" the peculiar velocities. This is an intrinsic property of walls and is independent of cosmology. We find the dispersion of the local Hubble flow (1 < R < 3 Mpc) around simulated "Milky Way" haloes located at the centre of low-density cosmological walls to be {\sigma}_H ~ 30 km/s, in excellent agreement with observations. The expansion of our local wall is also reflected in the value of the measured local Hubble constant. For "Milky Way" haloes inside walls, we find super-Hubble flows with h_local \simeq 0.77 - 1.13. The radius of equilibrium (R_0) depends not only on the mass of the central halo and the Hubble expansion but also on the dynamics given by the local LSS geometry. The super-Hubble flow inside our local wall has the effect of reducing the radius at which the local expansion balances the gravitational influence of the Milky Way. By ignoring the dynamical effect of the local wall, the mass of the Milky Way estimated from R_0 can be underestimated by as much as ~ 30%.Comment: 5 pages, 3 figures, Submitted to MNRA

Origami constraints on the initial-conditions arrangement of dark-matter caustics and streams

In a cold-dark-matter universe, cosmological structure formation proceeds in rough analogy to origami folding. Dark matter occupies a three-dimensional 'sheet' of free- fall observers, non-intersecting in six-dimensional velocity-position phase space. At early times, the sheet was flat like an origami sheet, i.e. velocities were essentially zero, but as time passes, the sheet folds up to form cosmic structure. The present paper further illustrates this analogy, and clarifies a Lagrangian definition of caustics and streams: caustics are two-dimensional surfaces in this initial sheet along which it folds, tessellating Lagrangian space into a set of three-dimensional regions, i.e. streams. The main scientific result of the paper is that streams may be colored by only two colors, with no two neighbouring streams (i.e. streams on either side of a caustic surface) colored the same. The two colors correspond to positive and negative parities of local Lagrangian volumes. This is a severe restriction on the connectivity and therefore arrangement of streams in Lagrangian space, since arbitrarily many colors can be necessary to color a general arrangement of three-dimensional regions. This stream two-colorability has consequences from graph theory, which we explain. Then, using N-body simulations, we test how these caustics correspond in Lagrangian space to the boundaries of haloes, filaments and walls. We also test how well outer caustics correspond to a Zel'dovich-approximation prediction.Comment: Clarifications and slight changes to match version accepted to MNRAS. 9 pages, 5 figure

Radio Emission in the Cosmic Web

We explore the possibility of detecting radio emission in the \emph{cosmic web} by analyzing shock waves in the MareNostrum cosmological simulation. This requires a careful calibration of shock finding algorithms in Smoothed-Particle Hydrodynamics simulations, which we present here. Moreover, we identify the elements of the cosmic web, namely voids, walls, filaments and clusters with the use of the SpineWeb technique, a procedure that classifies the structure in terms of its topology. Thus, we are able to study the Mach number distribution as a function of its environment. We find that the median Mach number, for clusters is $\mathcal{M}_{\mathrm{clusters}}\approx1.8$, for filaments is $\mathcal{M}_{\mathrm{filaments}}\approx 6.2$, for walls is $\mathcal{M}_{\mathrm{walls}}\approx 7.5$, and for voids is $\mathcal{M}_{\mathrm{voids}}\approx 18$. We then estimate the radio emission in the cosmic web using the formalism derived in Hoeft & Br\"{u}ggen (2007). We also find that in order to match our simulations with observational data (e.g., NVSS radio relic luminosity function), a fraction of energy dissipated at the shock of $\xi_{\mathrm{e}}=0.0005$ is needed, in contrast with the $\xi_{\mathrm{e}}=0.005$ proposed by Hoeft et al. (2008). We find that 41% of clusters with $M \ge 10^{14} M_{\odot}$ host diffuse radio emission in the form of radio relics. Moreover, we predict that the radio flux from filaments should be $S_{150 MHz}\sim 0.12$ $\mu$Jy at a frequency of 150 MHz.Comment: 19 pages, 17 figures, accepted for publication in MNRAS. Minor changes to tex fil

The Spine of the Cosmic Web

We present the SpineWeb framework for the topological analysis of the Cosmic Web and the identification of its walls, filaments and cluster nodes. Based on the watershed segmentation of the cosmic density field, the SpineWeb method invokes the local adjacency properties of the boundaries between the watershed basins to trace the critical points in the density field and the separatrices defined by them. The separatrices are classified into walls and the spine, the network of filaments and nodes in the matter distribution. Testing the method with a heuristic Voronoi model yields outstanding results. Following the discussion of the test results, we apply the SpineWeb method to a set of cosmological N-body simulations. The latter illustrates the potential for studying the structure and dynamics of the Cosmic Web.Comment: Accepted for publication HIGH-RES version: http://skysrv.pha.jhu.edu/~miguel/SpineWeb

The persistent cosmic web and its filamentary structure I: Theory and implementation

We present DisPerSE, a novel approach to the coherent multi-scale identification of all types of astrophysical structures, and in particular the filaments, in the large scale distribution of matter in the Universe. This method and corresponding piece of software allows a genuinely scale free and parameter free identification of the voids, walls, filaments, clusters and their configuration within the cosmic web, directly from the discrete distribution of particles in N-body simulations or galaxies in sparse observational catalogues. To achieve that goal, the method works directly over the Delaunay tessellation of the discrete sample and uses the DTFE density computed at each tracer particle; no further sampling, smoothing or processing of the density field is required. The idea is based on recent advances in distinct sub-domains of computational topology, which allows a rigorous application of topological principles to astrophysical data sets, taking into account uncertainties and Poisson noise. Practically, the user can define a given persistence level in terms of robustness with respect to noise (defined as a "number of sigmas") and the algorithm returns the structures with the corresponding significance as sets of critical points, lines, surfaces and volumes corresponding to the clusters, filaments, walls and voids; filaments, connected at cluster nodes, crawling along the edges of walls bounding the voids. The method is also interesting as it allows for a robust quantification of the topological properties of a discrete distribution in terms of Betti numbers or Euler characteristics, without having to resort to smoothing or having to define a particular scale. In this paper, we introduce the necessary mathematical background and describe the method and implementation, while we address the application to 3D simulated and observed data sets to the companion paper.Comment: A higher resolution version is available at http://www.iap.fr/users/sousbie together with complementary material. Submitted to MNRA