The accuracy of parameters determined with the core-sampling method: application to Voronoi tessellations

The large-scale matter distribution represents a complex network of structure elements such as voids, clusters, filaments, and sheets. This network is spanned by a point distribution. The global properties of the point process can be measured by different statistical methods, which, however, do not describe directly the structure elements. The morphology of structure elements is an important property of the point distribution. Here we apply the core-sampling method to various Voronoi tessellations. Using the core-sampling method we identify one- and two-dimensional structure elements (filaments and sheets) in these Voronoi tessellations and reconstruct their mean separation along random straight lines. We compare the results of the core-sampling method with the a priori known structure elements of the Voronoi tessellations under consideration and find good agreement between the expected and found structure parameters, even in the presence of substantial noise. We conclude that the core-sampling method is a potentially powerful tool to investigate the distribution of such structure elements like filaments and walls of galaxies.Comment: 14 pages (Latex) with 6 figures, the complete paper with 8 figures is available at http://kosmos.aip.de/~got/projects.html {Characteristical scales in point distributions}, Astronomy and Astrophysics Supplement Series, accepte

The Cross Correlation between the Gravitational Potential and the Large Scale Matter Distribution

The large scale gravitational potential distribution and its influence on the large-scale matter clustering is considered on the basis of six simulations. It is found that the mean separation between zero levels of the potential along random straight lines coincides with the theoretical expectations, but it scatters largely. A strong link of the initial potential and the structure evolution is shown. It is found that the under-dense and over-dense regions correlate with regions of positive and negative gravitational potential at large redshifts. The over-dense regions arise due to a slow matter flow into the negative potential regions, where more pronounced non-linear structures appear. Such regions are related to the formation of huge super-large scale structures seen in the galaxy distribution.Comment: 14 pages LaTeX with 14 postscript figures included. To be publishes in Astron. Astroph. (accepted 17 July 1997

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements