Hypergeometric Functions over Finite Fields and their relations to Algebraic Curves

In this work we present an explicit relation between the number of points on a family of algebraic curves over \F_{q} and sums of values of certain hypergeometric functions over \F_{q}. Moreover, we show that these hypergeometric functions can be explicitly related to the roots of the zeta function of the curve over \F_{q} in some particular cases. A general conjecture relating these last two is presented and advances toward its proof are shown in the last section.Comment: 24 page

On string integrability. A journey through the two-dimensional hidden symmetries in the AdS/CFT dualities

One of the main topics in the modern String Theory are the AdS/CFT dualities. Proving such conjectures is extremely difficult since the gauge and string theory perturbative regimes do not overlap. In this perspective, the discovery of infinitely many conserved charges, i.e. the integrability, in the planar AdS/CFT has allowed us to reach immense progresses in understanding and confirming the duality. We review the fundamental concepts and properties of integrability in two-dimensional sigma-models and in the AdS/CFT context. The first part is focused on the AdS_5/CFT_4 duality, especially the classical and quantum integrability of the type IIB superstring on AdS_5 x S^5 are discussed in both pure spinor and Green-Schwarz formulations. The second part is dedicated to the AdS_4/CFT_3 duality with particular attention to the type IIA superstring on AdS_4 x CP^3 and its integrability. This review is based on a shortened and revised version of the author's PhD thesis, discussed at Uppsala University in September 2009.Comment: 116 pages, 11 figures, to be published in Advances in High Energy Physics, Special Issue on ''Gauge/String Duality'

PERFORMANCE AND GOVERNANCE OF COMMUNITY DEVELOPMENT FINANCIAL INSTITUTIONS

This paper investigates the influence of board size and board diversity on the performance of Community Development Financial Institutions' operating in the Southeast. The results indicate that at present many CDFI boards are larger than optimal. The results also show that CDFIs generally have well diversified boards and that these organizations' performance is unlikely to improve by further diversifying their boards. However, CDFIs performance may be improved by promoting smaller boards.Financial Economics,

Governance and Performance of Microfinance Institutions in Central and Eastern Europe and the Newly Independent States

This paper studies how various governance mechanisms affect the performance of microfinance institutions in Central and Eastern Europe and the Newly Independent States. Results show that managerial compensation matters, that market forces are becoming important disciplining device, and that board size, diversification and independence affect both outreach and sustainability.Financial Economics,

Rating in Microfinance: Cross Country Evidence

This paper focuses on the ability of microfinance rating agencies to impose market discipline on microfinance institutions by rating these organizations' performance. Results indicate that not all rating agencies are equal as only one rater was able to impose market discipline by promoting better sustainability, while rating by another agency caused MFIs to slack off. In addition, while rating in general lead to better outreach, this effect was annulled if MFIs received financial aid in order to get rated. Finally, only one rater provided rating that allowed MFIs to raise additional debtFinancial Economics,