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Item Structure of force networks in tapped particulate systems of disks and pentagons II Persistence analysis(American Physical Society, 2016) Kondic, L.; Kramar, M.; Pugnaloni, Luis; Carlevaro, Manuel; Mischaikow, K.In the companion paper [Pugnaloni et al., Phys. Rev. E 93, 062902 (2016)], we use classical measures based on force probability density functions (PDFs), as well as Betti numbers (quantifying the number of components, related to force chains, and loops), to describe the force networks in tapped systems of disks and pentagons. In the present work, we focus on the use of persistence analysis, which allows us to describe these networks in much more detail. This approach allows us not only to describe but also to quantify the differences between the force networks in different realizations of a system, in different parts of the considered domain, or in different systems. We show that persistence analysis clearly distinguishes the systems that are very difficult or impossible to differentiate using other means. One important finding is that the differences in force networks between disks and pentagons are most apparent when loops are considered: the quantities describing properties of the loops may differ significantly even if other measures (properties of components, Betti numbers, force PDFs, or the stress tensor) do not distinguish clearly or at all the investigated systems.Item Exact predictions from Edwards ensemble vs realistic simulations of tapped narrow two dimensional granular columns(Journal of Statistical Mechanics: Theory and Experiment, 2013) Irastorza, Ramiro; Carlevaro, Manuel; Pugnaloni, LuisWe simulate, via a discrete element method, the tapping of a narrow column of disks under gravity. For frictionless disks, this system has a simple analytical expression for the density of states in the Edwards volume ensemble. We compare the predictions of the ensemble at constant compactivity against the results for the steady states obtained in the simulations. We show that the steady states cannot be properly described since the microstates sampled are not in correspondence with the predicted distributions, suggesting that the postulates of flat measure and ergodicity are, either or both, invalid for this simple realization of a static granular system. However, we show that certain qualitative features of the volume fluctuations which are difficult to predict from simple arguments are captured by the theory.