11,510 research outputs found
A note on the birational geometry of tropical line bundles
Given a closed subvariety Y of a n-dimensional torus, we study how the
tropical line bundles of Trop(Y) can be induced by line bundles living on a
tropical compactification of Y in a toric variety, following the construction
of Jenia Tevelev. We then consider the general structure with respect to the
Zariski--Riemann space.Comment: Version
Ruled Fano fivefolds of index two
We classify Fano fivefolds of index two which are projectivization of rank
two vector bundles over four dimensional manifolds.Comment: 30 page
The forgotten monoid
We study properties of the forgotten monoid which appeared in work of Lascoux
and Schutzenberger and recently resurfaced in the construction of dual
equivalence graphs by Assaf. In particular, we provide an explicit
characterization of the forgotten classes in terms of inversion numbers and
show that there are n^2-3n+4 forgotten classes in the symmetric group S_n. Each
forgotten class contains a canonical element that can be characterized by
pattern avoidance. We also show that the sum of Gessel's quasi-symmetric
functions over a forgotten class is a 0-1 sum of ribbon-Schur functions.Comment: 13 pages; in version 3 the proof of Proposition 3 is correcte
Consumers' Willingness to Pay a Price for Organic Beef Meat
The goal of this paper is to estimate the maximum price consumers are willing to pay (MPWTP) for organic beef meat. To this purpose, a theoretical and econometric approach is presented, based on the RUM model and on a Contingent Valuation technique. The results show that consumers' MPWTP is quite high, thus suggesting that organic beef meat might gain an appreciable market share. This is also an encouraging signal for prospective producers of organic meat, who might compensate the likely increase in production costs with a substantial premium for the new good.Organic meat, Willingness to pay, Double bounded probit, Consumer/Household Economics,
Hopf Algebras of m-permutations, (m+1)-ary trees, and m-parking functions
The m-Tamari lattice of F. Bergeron is an analogue of the clasical Tamari
order defined on objects counted by Fuss-Catalan numbers, such as m-Dyck paths
or (m+1)-ary trees. On another hand, the Tamari order is related to the product
in the Loday-Ronco Hopf algebra of planar binary trees. We introduce new
combinatorial Hopf algebras based on (m+1)-ary trees, whose structure is
described by the m-Tamari lattices.
In the same way as planar binary trees can be interpreted as sylvester
classes of permutations, we obtain (m+1)-ary trees as sylvester classes of what
we call m-permutations. These objects are no longer in bijection with
decreasing (m+1)-ary trees, and a finer congruence, called metasylvester,
allows us to build Hopf algebras based on these decreasing trees. At the
opposite, a coarser congruence, called hyposylvester, leads to Hopf algebras of
graded dimensions (m+1)^{n-1}, generalizing noncommutative symmetric functions
and quasi-symmetric functions in a natural way. Finally, the algebras of packed
words and parking functions also admit such m-analogues, and we present their
subalgebras and quotients induced by the various congruences.Comment: 51 page
Willingness-to-pay in terms of price: an application to organic beef during and after the “mad cow” crisis
This paper aims at assessing consumers’ attitudes and willingness to pay for organic beef, an obvious alternative to regular beef in terms of safety, both immediately and at a longer term after the BSE crisis. It is based on two random telephone surveys in an Italian region, the first one conducted in 2001 (few months after the BSE crisis) and the second one in 2003. The analysis is based on an innovative methodology of contingent valuation, keeping into account the possibility for consumers to decide the quantity of their purchase when a price is proposed. The results show that though the effect of the BSE crisis weakened along with time distance, it left some permanent signs in consumers’ behaviour. The main conclusion is that the demand for organic beef reduced, but that in the meantime it became more inelastic.BSE, organic beef, willingness to pay, contingent valuation
Ideal Family Size and Fertility in Egypt: An Overview of Recent Trends
Egypt is already the most populous Arab country in the world with 93 million citizens in 2016 which may grow to about 120 million by 2030 if the same level of fertility continues. This paper aims to offer an overview of the evolution over time of the ideal number of children in Egypt, assessing previous researches and giving a particular emphasis on most recent data on such topic. In a context of raising fertility, whose causes are still unknown, we test the persistence of a high ideal number of children among younger cohorts
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