Google's Anti-competitive and Unfair Practices in Digital Leisure Markets

The purpose of this article is to reflect on the critical use of commitments in the Google case and to analyse and review the matrix of facts that have been highlighted in the academic and practitioner literature. Therefore, the core areas of reflection in this contribution are: relevant markets; barriers to entry; network and lock-in effects; dominance; and, potential anticompetitive, as well as unfair practices as regards commercial advertisements. The analysis of the online search-engine market is complemented by the comparative insights offered by the US class action against Google’s Android mobile applications. In the EU, a similar trend is noticeable in the complaining tone of Google’s competitors. When this is coupled with the transitional period of the mandate of the newly appointed Commissioner for Competition and the political sensitivity over the potential to misuse search-engine users’ personal data to serve commercial purposes, such as boosting its advertising revenues, the giant Google swims in uncertain waters

The Fence Complexity of Persistent Sets

This thesis studies fence complexity of concurrent sets in a non-volatile shared memory model. I consider the case where CPU registers and cache memory remain volatile while main memory is non-volatile. Flush instructions are required to force shared state to be written back to non-volatile memory. These flush instructions must be accompanied by the use of expensive fence instructions to enforce ordering among such flushes. Collectively I refer to a flush and a fence as a psync. In this model the system can crash at any time. When the system crashes the contents of volatile memory are lost. I consider lock-free implementations of the set abstract data type and the safety properties of strict linearizability and durable linearizability. Strict linearizability forces crashed operations to take effect before the crash or not take effect at all; the weaker property of durable linearizability enforces this requirement only for operations that have completed prior to the crash event. In this thesis, I consider classes of strict linearizable implementations that guarantee operations take effect at or before the point when the operation is persisted. I prove two lower bounds for lock-free implementations of the set abstract data type. First, I prove that it is impossible to implement strict linearizable lock-free sets in which read-only (or search) operations do not flush or fence. Second, I prove that for any durable-linearizable lock-free set there must exist an execution in which some process must perform at least one redundant psync as part of an update operation. I also present several implementations of persistent concurrent lock-free sets. I evaluate these implementations against existing persistent sets. This evaluation exposes the impact of algorithmic design and safety properties on psync complexity in practice as well as the cost of recovering the data structure following a system crash

Universal magneto-orbital ordering in the divalent AA-site quadruple perovskite manganites AAMn7_7O12_{12} (AA = Ca, Sr, Cd, and Pb)

Through analysis of variable temperature neutron powder diffraction data, we present solutions for the magnetic structures of SrMn$_7$O$_{12}$, CdMn$_7$O$_{12}$, and PbMn$_7$O$_{12}$ in all long-range ordered phases. The three compounds were found to have magnetic structures analogous to that reported for CaMn$_7$O$_{12}$. They all feature a higher temperature lock-in phase with \emph{commensurate} magneto-orbital coupling, and a delocked, multi-\textbf{k} magnetic ground state where \emph{incommensurate} magneto-orbital coupling gives rise to a constant-moment magnetic helix with modulated spin helicity. CdMn$_7$O$_{12}$ represents a special case in which the orbital modulation is commensurate with the crystal lattice and involves stacking of fully and partially polarized orbital states. Our results provide a robust confirmation of the phenomenological model for magneto-orbital coupling previously presented for CaMn$_7$O$_{12}$. Furthermore, we show that the model is universal to the $A^{2+}$ quadruple perovskite manganites synthesised to date, and that it is tunable by selection of the $A$-site ionic radius