Cellular Automata are Generic

Any algorithm (in the sense of Gurevich's abstract-state-machine axiomatization of classical algorithms) operating over any arbitrary unordered domain can be simulated by a dynamic cellular automaton, that is, by a pattern-directed cellular automaton with unconstrained topology and with the power to create new cells. The advantage is that the latter is closer to physical reality. The overhead of our simulation is quadratic.Comment: In Proceedings DCM 2014, arXiv:1504.0192

Complexity of Propositional Proofs under a Promise

We study -- within the framework of propositional proof complexity -- the problem of certifying unsatisfiability of CNF formulas under the promise that any satisfiable formula has many satisfying assignments, where ``many'' stands for an explicitly specified function \Lam in the number of variables $n$. To this end, we develop propositional proof systems under different measures of promises (that is, different \Lam) as extensions of resolution. This is done by augmenting resolution with axioms that, roughly, can eliminate sets of truth assignments defined by Boolean circuits. We then investigate the complexity of such systems, obtaining an exponential separation in the average-case between resolution under different size promises: 1. Resolution has polynomial-size refutations for all unsatisfiable 3CNF formulas when the promise is \eps\cd2^n, for any constant 0<\eps<1. 2. There are no sub-exponential size resolution refutations for random 3CNF formulas, when the promise is $2^{\delta n}$ (and the number of clauses is $o(n^{3/2})$), for any constant $0<\delta<1$.Comment: 32 pages; a preliminary version appeared in the Proceedings of ICALP'0

External networks and geographic clustering as sources of MNE advantages: Foreign and indigenous professional service firms in Central London

This study combines the theories of international business and management with network theory in order to examines the networking activities of foreign affiliates. It focuses on a specific kind of network, which is taking place between firms based in geographic proximity. A comparative analysis between foreign and indigenous firms in selected professional service industries located in Central London is used as the analytical tool to isolate the networking attributes of firms in general from those that are unique to foreign affiliates and emerge as a result of their specific characteristics. The findings suggest considerable differences between foreign and indigenous firms in terms of their network behaviour. MNE internal networks appear partially to replace the advantages provided by external networks, acting both to diminish the MNE's need for external linkages and channel it into somewhat different directions.networking, Multinational Enterprises, geographic clustering, Professional service firms, London

MNEs in the Digital Economy

Technological advances are changing many aspects of business activity and in particular the meaning of distance and geography. Such changes are likely to have profound impact on firms whose activities take place over distance, namely MNEs. Using the motivations for FDI identified in the literature as a theoretical framework, this study examines the motivations of firms producing and selling products that can be transferred electronically in real time and at little or no cost, to establish operations outside their home countries. The paper advances a set of hypotheses regarding the likely motivations for foreign activity under such circumstances and provides some statistical testing for their prevalence in US inward and outward FDI. The findings suggest that the investment motivations of firms operating in the digital economy differ from those of firms in the traditional world. The most important motivations for FDI in the digital economy appear to be efficiency and the quest for intangible assets, especially those embedded in human capital, while market seeking and the search for low cost export platforms appear to be the dominant motivations for FDI in the traditional economy.digital economy, FDI motivations, US FDI

Neo-Marshallian Nodes, Global Networks and Firm Competitiveness: The Media Cluster of Central London

The recent emphasis by some business scholars on processes taking place within locally-embedded production systems seems to undervalue the dynamics of global competition and the role played by TNCs in mobilising tangible and intangible assets across localised clusters. Using the external linkages of firms as the theoretical framework, this paper examines the interplay between global and local influences on the competitiveness of the cluster of media firms in Central London. The main findings are that the locality indeed plays a vital role in influencing the capabilities of these firms, but it is by no means the only relevant geographic area. This localised cluster is bound tightly into world-wide webs of interdependence, with TNCs playing a major role in mediating between local and global linkages. The latter are vital for the ability of the firms studied to compete successfully in international markets.