47 research outputs found
Optimal liquidation of a call spread
We study the optimal liquidation strategy for a call spread in the case when an investor, who does not hedge, believes in a volatility that differs from the implied volatility. The liquidation problem is formulated as an optimal stopping problem, which we solve explicitly. We also provide a sensitivity analysis with respect to the model parameters
Optimal liquidation of a call spread
We study the optimal liquidation strategy for a call spread in the case when an investor, who does not hedge, believes in a volatility that differs from the implied volatility. The liquidation problem is formulated as an optimal stopping problem, which we solve explicitly. We also provide a sensitivity analysis with respect to the model parameters
Experimental secondary methyl mercury poisoning in the goshawk (Accipiter G. Gentilis L.)
Evidence for mutualism between a flower-piercing carpenter bee and ocotillo: use of pollen and nectar by nesting bees
The Implications of Paleontological Evidence for Theories of Ecological Communities and Species Richness
Abstract Palaeontological evidence raises several questions that relate to current explanations of ecological communities, to the classification of communities and to interpretations of species richness. The first question relates to the stability of species detected in the fossil record. Coupled with that is the issue of incidental association of species on the same trophic level through differential effects of climatic change on the different species. Such observations are seen to support the âindividualisticâ concept of communities. Recent statements about this concept leave unresolved questions about the acquisition of adaptation, and about the place of adaptation theory in theories of ecological communities and interpretations of âregional species richnessâ. At issue is whether there is justification for continuing to classify communities as a basis for understanding them. There is good reason to reject this approach for one in which questions about communities and âlocalâ and âregionalâ species richness are replaced by more specific and basic questions about the relationship between adaptation, distribution and abundance, and ecological interactions. Some recent efforts to incorporate species theory into community theory fail because their basis remains the flawed concept of âlocal communityâ