The Power of Natural Properties as Oracles

We study the power of randomized complexity classes that are given oracle access to a natural property of Razborov and Rudich (JCSS, 1997) or its special case, the Minimal Circuit Size Problem (MCSP). We show that in a number of complexity-theoretic results that use the SAT oracle, one can use the MCSP oracle instead. For example, we show that ZPEXP^{MCSP} !subseteq P/poly, which should be contrasted with the previously known circuit lower bound ZPEXP^{NP} !subseteq P/poly. We also show that, assuming the existence of Indistinguishability Obfuscators (IO), SAT and MCSP are equivalent in the sense that one has a ZPP algorithm if and only the other one does. We interpret our results as providing some evidence that MCSP may be NP-hard under randomized polynomial-time reductions

Synchronizing automata over nested words

We extend the concept of a synchronizing word from deterministic finite-state automata (DFA) to nested word automata (NWA): A well-matched nested word is called synchronizing if it resets the control state of any configuration, i. e., takes the NWA from all control states to a single control state. We show that although the shortest synchronizing word for an NWA, if it exists, can be (at most) exponential in the size of the NWA, the existence of such a word can still be decided in polynomial time. As our main contribution, we show that deciding the existence of a short synchronizing word (of at most given length) becomes PSPACE-complete (as opposed to NP-complete for DFA). The upper bound makes a connection to pebble games and Strahler numbers, and the lower bound goes via small-cost synchronizing words for DFA, an intermediate problem that we also show PSPACE-complete. We also characterize the complexity of a number of related problems, using the observation that the intersection nonemptiness problem for NWA is EXP-complete

The Competitiveness of Ports in Emerging Markets : The case of Durban, South Africa

This report provides a synthesis of main findings from the OECD Port-Cities Programme, created in 2010 in order to assess the impact of ports on their cities and provide policy recommendations to increase the positive impacts of ports on their cities. This Programme was directed by Olaf Merk, Administrator Port-Cities within the OECD Public Governance and Territorial Development Directorate. This synthesis report was directed and written by Olaf Merk; it draws on the work of a number of other contributors: César Ducruet, Jasper Cooper, Jing Li, Ihnji Jon, Maren Larsen and Lucie Billaud. The report has benefited from comments from Bill Tompson, Nils-Axel Braathen, Jane Korinek, Nicolas Mat and Juliette Cerceau. The synthesis report is based on findings from a series of OECD Port-Cities case studies. Such case studies were conducted for Le Havre/Rouen/Paris/Caen (France), Hamburg (Germany), Helsinki (Finland), Marseille (France), Mersin (Turkey), Rotterdam/Amsterdam (the Netherlands), Antofagasta (Chile), Bratislava/Komárno/Štúrova (Slovak Republic), Durban (South Africa) and Shanghai (China). Within the framework of these studies, study visits to these port-cities were conducted, which included a series of interviews with the port-city related actors and stakeholders in these places. The OECD Port-Cities Programme also benefited from visits to the following ports and port-cities and discussion with port-related actors in the following port-cities: Hong Kong, Shenzhen, Singapore, Casablanca, Venice, Trieste, Genoa, Valparaíso, Varna, Gdansk, Koper, Vienna, Antwerp, Felixstowe, Los Angeles, Long Beach, Sydney and Newcastle (Australia). Contributions and inputs into the OECD Port-Cities case studies and related working papers were provided by César Ducruet, Elvira Haezendonck, Michael Dooms, Patrick Dubarle, Markus Hesse, Géraldine Planque, Theo Notteboom, José Tongzon, Jörg Jocker, Oguz Bagis, Angela Bergantino, Claude Comtois, Nicolas Winicki, Thai Thanh Dang, Claudio Ferrari, Alessio Tei, Anna Bottasso, Maurizio Conti, Salvador Saz, Leandro Garcia-Menéndez, Zhen Hong, Zhao Nan, Angela Xu Mingying, Xie Wenqing, Du Xufeng, Wang Jinggai, Jing Li, Matthieu Bordes, Rachel Silberstein, Xiao Wang, Jean-Paul Rodrigue, Jasper Cooper, Marten van den Bossche, Carla Jong, Christelle Larsonneur, Walter Manshanden, Martijn Dröes, Evgueny Poliakov, Olli-Pekka Hilmola, Charlotte Lafitte, Caroline Guillet, Léonie Claeyman, Suzanne Chatelier. The Programme has been enriched through the interaction with these experts. Within the framework of the Programme, three different workshops in Paris were organised and benefited from presentations by: César Ducruet, Markus Hesse, Elvira Haezendonck, Claudio Ferrari, Jan Egbertsen, Ingo Fehrs, Stijn Effting, Michael Vanderbeek, Alessio Tei, Philippe Deiss, Birgit Liodden, Johan Woxenius, Hyong Mo Jeon, Dimitrios Theologitis, Carla Jong, Lorene Grandidier, Dominique Lebreton, Claude Comtois, Marten van den Bossche, Matt Bogdan, Alice Liu, Jan Green Rebstock. Within the framework of the Programme, the Administrator has provided presentations and interventions in conferences organised by: European Committee of the Regions (COTER), European Seaport Organisation (ESPO), Moroccan Association for Logistics (Amlog), International Association of Ports and Harbors (IAPH), Port of Long Beach Board of Harbor Commissioners, City of Shenzhen, Korean Transport Institute (KOTI), Korean Maritime Institute (KMI), French Association of Town Planners (FNAU), Italian Association of Transport Economists (SIET), World Conference of Transport Research Society (WCTRS-SIG2), Maersk, Port Finance International, BSR Clean Cargo Working Group, Infrastructure Australia, International Association Cities Ports (AIVP), Inter American Committee for Ports, International Transport Forum (ITF), Florence School of Regulation, Cargo Edições Lda, Logistics Portugal, International Forum on Shipping, Ports and Airports (IFSPA), Port of Amsterdam, Port of Rotterdam, Port of Hamburg, Université du Sud Toulon-Var, Colloque Axe Seine Acte II. The Programme has benefited from the support of: the Netherlands Ministry of Economy, City of Rotterdam, City of Amsterdam, Port of Amsterdam, Çukurova Development Agency, City of Helsinki, Port of Marseille, Slovak Ministry of Transport, Construction and Regional Development, Slovak Ministry of Foreign Affairs, City of Hamburg, Transnet South Africa, Provence-Alpes-Côte d’Azur Region, Bouches du Rhône Department, Syndicat mixte du Schéma de Cohérence Territoriale Ouest Étang de Berre, Communauté d’agglomération Marseille Provence Métropole, City of Marseille, Chamber of Commerce and Industry Marseille Provence, the Agence d’Urbanisme de Marseille, the Union Maritime et Fluviale, l’Agence d’Urbanisme de la Région du Havre et de l’Estuaire de la Seine (AURH), l’Agence d’Études d’Urbanisme de Caen Métropole (AUCAME), l’Atelier Parisien d’Urbanisme (APUR), l’Institut d’Aménagement et d’Urbanisme de la région d’Île de France (IAU IDF), l’Agence d'Urbanisme et de Développement de la Seine Aval (AUDAS), la Ville du Havre, la Communauté d’Agglomération Havraise (CODAH), la Communauté de l’Agglomération Rouen Elbeuf Austreberthe (CREA), le Grand Port Maritime du Havre (GPMH), le Grand Port Maritime de Rouen (GPMR), Ports de Paris. The report, as well as the Port-City case studies and related thematic papers can be downloaded from the OECD website: www.oecd.org/regional/portcities Further enquiries about this work in this area should be addressed to: Olaf Merk ([email protected]) of the OECD Public Governance and Territorial Development Directorate