11,352 research outputs found
Equations, inequations and inequalities characterizing the configurations of two real projective conics
Couples of proper, non-empty real projective conics can be classified modulo
rigid isotopy and ambient isotopy.
We characterize the classes by equations, inequations and inequalities in the
coefficients of the quadratic forms defining the conics.
The results are well--adapted to the study of the relative position of two
conics defined by equations depending on parameters.Comment: 31 pages. See also
http://emmanuel.jean.briand.free.fr/publications/twoconics/ Added references
to important prior work on the subject. The title changed accordingly. Some
typos and imprecisions corrected. To be published in Applicable Algebra in
Engineering, Communication and Computin
TO INFORM THEIR DISCRETION: POLICY EDUCATION AND DEMOCRATIC POLITICS
Political Economy,
Marginal Cost Versus Average Cost Pricing with Climatic Shocks in Senegal: A Dynamic Computable General Equilibrium Model Applied to Water
The model simulates on a 20-year horizon, a first phase of increase in the water resource availability taking into account the supply policies by the Senegalese government and a second phase with hydrologic deficits due to demand evolution (demographic growth). The results show that marginal cost water pricing (with a subsidy ensuring the survival of the water production sector) makes it possible in the long term to absorb the shock of the resource shortage, GDP, investment and welfare increase. Unemployment drops and the sectors of rain rice, market gardening and drinking water distribution grow. In contrast, the current policy of average cost pricing of water leads the long-term economy in a recession with an agricultural production decrease, a strong degradation of welfare and a rise of unemployment. This result questions the basic tariff (average cost) on which block water pricing is based in Senegal.Computable General Equilibrium Model, Dynamic, Imperfect Competition, Water, Pricing, Sub Saharan Africa
Crystallization of self-propelled hard-discs : a new scenario
We experimentally study the crystallization of a monolayer of vibrated discs
with a built-in polar asymmetry, a model system of active liquids, and contrast
it with that of vibrated isotropic discs. Increasing the packing fraction
, the quasi-continuous crystallization reported for isotropic discs is
replaced by a transition, or a crossover towards a "self-melting" crystal.
Increasing the packing fraction from the liquid phase, clusters of dense
hexagonally-ordered packed discs spontaneously form, melt, split and merge
leading to a highly intermittent and heterogeneous dynamics. The resulting
steady state cluster size distribution decreases monotonically. For packing
fraction larger than , a few large clusters span the system size and
the cluster size distribution becomes non monotonic, the transition being
signed by a power-law. The system is however never dynamically arrested. The
clusters permanently melt from place to place forming droplets of active liquid
which rapidly propagate across the system. This state of affair remains up to
the highest possible packing fraction questioning the stability of the crystal
for active discs, unless at ordered close packing.Comment: 4 pages, 4 figures, 1 Supp Mat
Quadratic BSDEs with convex generators and unbounded terminal conditions
In a previous work, we proved an existence result for BSDEs with quadratic
generators with respect to the variable z and with unbounded terminal
conditions. However, no uniqueness result was stated in that work. The main
goal of this paper is to fill this gap. In order to obtain a comparison theorem
for this kind of BSDEs, we assume that the generator is convex with respect to
the variable z. Under this assumption of convexity, we are also able to prove a
stability result in the spirit of the a priori estimates stated in the article
of N. El Karoui, S. Peng and M.-C. Quenez. With these tools in hands, we can
derive the nonlinear Feynman--Kac formula in this context
Combinatorial proof for a stability property of plethysm coefficients
Plethysm coefficients are important structural constants in the representation the-
ory of the symmetric groups and general linear groups. Remarkably, some sequences
of plethysm coefficients stabilize (they are ultimately constants). In this paper we
give a new proof of such a stability property, proved by Brion with geometric representation theory techniques. Our new proof is purely combinatorial: we decompose
plethysm coefficients as a alternating sum of terms counting integer points in poly-
topes, and exhibit bijections between these sets of integer points.Ministerio de Ciencia e InnovaciĂłn MTM2010â19336Junta de AndalucĂa FQMâ333Junta de AndalucĂa P12âFQMâ269
On the growth of the Kronecker coefficients
We study the rate of growth experienced by the Kronecker coefficients as we
add cells to the rows and columns indexing partitions. We do this by moving to
the setting of the reduced Kronecker coefficients.Comment: Extended version, Containing 4 appendice
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