21 research outputs found
On positivity of Ehrhart polynomials
Ehrhart discovered that the function that counts the number of lattice points
in dilations of an integral polytope is a polynomial. We call the coefficients
of this polynomial Ehrhart coefficients, and say a polytope is Ehrhart positive
if all Ehrhart coefficients are positive (which is not true for all integral
polytopes). The main purpose of this article is to survey interesting families
of polytopes that are known to be Ehrhart positive and discuss the reasons from
which their Ehrhart positivity follows. We also include examples of polytopes
that have negative Ehrhart coefficients and polytopes that are conjectured to
be Ehrhart positive, as well as pose a few relevant questions.Comment: 40 pages, 7 figures. To appear in in Recent Trends in Algebraic
Combinatorics, a volume of the Association for Women in Mathematics Series,
Springer International Publishin
Quantificação de propágulos de Gibberella zeae no ar e infecção de anteras em trigo
Evaluation of crop coefficients, water productivity, and water balance components for wine grapes irrigated at different deficit levels by a sub-surface drip
The impact of foreign ownership and off-shore investing on technical efficiency: evidence from Chinese managed funds industry
In a landmark reform in the managed fund industry, China permitted foreign joint ventures as well as off-shore investing. Have these decisions helped improved the efficiency of the industry? We examine this hitherto unexamined question in the literature, using a robust method of efficiency analysis—bootstrap data envelopment analysis. We compute the bootstrap efficiency scores and regress them using truncated regression on environmental variables. We focus on 64 of 69 funds management companies in China from 2003 to 2011 using a unique dataset made available to us. We find that there is considerable room for funds management companies to improve technical efficiency to ultimately bring increased benefits to investors. We find that foreign ownership has not helped efficiency improvement. Similarly, off-shore investing had no impact on technical efficiency. A number of regulatory constraints still persist in China, which makes it hard for the previously measured to yield efficiency gains. We recommend further liberalization of the sector, for example, by removing restriction on distribution of foreign funds