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In the first part of the article, we characterize distribution-invariant risk measures with convex
acceptance and rejection sets on the level of distributions. It is shown that these risk measures
are closely related to utility-based shortfall risk.
In the second part of the paper, we provide an axiomatic characterization for distribution-invariant
dynamic risk measures of terminal payments. We prove a representation theorem and
investigate the relation to static risk measures. A key insight of the paper is that dynamic consistency
and the notion of "measure convex sets of probability measures" are intimately related.
This result implies that under weak conditions dynamically consistent dynamic risk measures can
be represented by static utility-based shortfall risk.
We derive a continuous time approximation of the evolutionary market selection model of Blume &
Easley (1992). Conditions on the payoff structure of the assets are identified that guarantee convergence. We show that the continuous
time approximation equals the solution of an integral equation
in a random environment. For constant asset returns, the integral equation reduces to an autonomous
ordinary differential equation. We analyze its long-run asymptotic behavior using techniques related to
Lyapunov functions, and compare our results to the benchmark of profit-maximizing investors.
Deformable surface models are often represented as triangular meshes in image segmentation applications. For a fast and easily regularized deformation onto the target object boundary, the vertices of the mesh are commonly moved along line segments (typically surface normals). However, in case of high mesh curvature, these lines may intersect with the target boundary at “non-corresponding” positions, or may not intersect at all. Consequently, certain deformations cannot be achieved. We propose omnidirectional displacements for deformable surfaces (ODDS) to overcome this limitation. ODDS allow each vertex to move not only along a line segment but within a surrounding sphere, and achieve globally optimal deformations subject to local regularization con-
straints. However, allowing a ball-shaped instead of a linear range of motion per vertex significantly increases runtime and memory. To alleviate this drawback, we propose a hybrid approach, fastODDS, with improved runtime and reduced memory requirements. Furthermore, fastODDS can also cope with simultaneous segmentation of multiple objects. We show the theoretical benefits of ODDS with experiments on synthetic data, and evaluate ODDS and fastODDS quantitatively on clinical image data of the mandible and the hip bones. There, we assess both the global segmentation accuracy as well as local accuracy in high curvature regions, such as the tip-shaped mandibular coronoid processes and the ridge-shaped acetabular rims of
the hip bones.