On Approximating the Sum-Rate for Multiple-Unicasts

We study upper bounds on the sum-rate of multiple-unicasts. We approximate the Generalized Network Sharing Bound (GNS cut) of the multiple-unicasts network coding problem with $k$ independent sources. Our approximation algorithm runs in polynomial time and yields an upper bound on the joint source entropy rate, which is within an $O(\log^2 k)$ factor from the GNS cut. It further yields a vector-linear network code that achieves joint source entropy rate within an $O(\log^2 k)$ factor from the GNS cut, but \emph{not} with independent sources: the code induces a correlation pattern among the sources. Our second contribution is establishing a separation result for vector-linear network codes: for any given field $\mathbb{F}$ there exist networks for which the optimum sum-rate supported by vector-linear codes over $\mathbb{F}$ for independent sources can be multiplicatively separated by a factor of $k^{1-\delta}$, for any constant ${\delta>0}$, from the optimum joint entropy rate supported by a code that allows correlation between sources. Finally, we establish a similar separation result for the asymmetric optimum vector-linear sum-rates achieved over two distinct fields $\mathbb{F}_{p}$ and $\mathbb{F}_{q}$ for independent sources, revealing that the choice of field can heavily impact the performance of a linear network code.Comment: 10 pages; Shorter version appeared at ISIT (International Symposium on Information Theory) 2015; some typos correcte

The crisis in Greece: the semi-rentier state hypothesis

This article offers an alternative explanation of the ‘Greek crisis’ by using the rentier-state theory. Past explanations referred to domestic pitfalls of the Greek economic development or to external constraints such as the incomplete architecture of the Eurozone. Without rejecting these interpretations, we offer a complementary interpretation underlining the facility and large scale with which external funds have flowed into Greece. This pattern was reminiscent of cases of resource-rich countries of the developing world and have created a semi-rentier state. External resources have spread a ‘rentier mentality’ among state actors and a ‘get-rich-quick mentality’ among business entrepreneurs and interest groups. Political decisions were characterised by riskaverse attitudes, while private actors spent their energy in seeking political protection rather than in initiating new enterprises. Three factors that played a significant role in shaping the Greek crisis and continue to plague Greece are foreign loans, EU funds and tax evasion

Looking for an oasis of support: Greece and the Gulf states

This paper examines Greece’s relations with the Gulf Cooperation Council [GCC] countries: Bahrain, Kuwait, Oman, Qatar, Saudi Arabia and the United Arab Emirates. Greek-Arab ties have a long history that goes back to 1947, when Greece voted against the partition of Palestine in the UN General Assembly. In the post-1974 era, these relations have been strengthened, reflecting Athens’ efforts to gain support in the dispute with Turkey and secure oil supplies. Within the last ten years, such security objectives of Greek foreign policy have moved to the background and economic priorities have come to the fore. This has made relations with the Gulf States a crucial economic and diplomatic goal that has not been undermined by its ties to Iran and Israel. While the country’s commercial relations with the GCC are regulated through the EU framework, it is through bilateral relations that Greece seeks to build its ties to the Gulf. Until now, the high expectations cultivated on the Greek side have not been fulfilled. Greece’s relations with the GCC countries have remained anemic and investment limited.While a possible Grexit may have initially dampened investors’ interest, the main obstacle continues to be one of domestic nature, reflecting the fragmentation and lack of coordination within Greek institutions themselves