591 research outputs found
THE CHEAPEST HEDGE:A PORTFOLIO DOMINANCE APPROACH
Investors often wish to insure themselves against the payoff of their portfolios falling below a certain value. One way of doing this is by purchasing an appropriate collection of traded securities. However, when the derivatives market is not complete, an investor who seeks portfolio insurance will also be interested in the cheapest hedge that is marketed. Such insurance will not exactly replicate the desired insured-payoff, but it is the cheapest that can be achieved using the market. Analytically, the problem of finding a cheapest insuring portfolio is a linear programming problem. The present paper provides an alternative portfolio dominance approach to solving the minimum-premium insurance portfolio problem. This affords remarkably rich and intuitive insights to determining and describing the minimum-premium insurance portfolios.
On dominant contractions and a generalization of the zero-two law
Zaharopol proved the following result: let T,S:L^1(X,{\cf},\m)\to
L^1(X,{\cf},\m) be two positive contractions such that . If
then for all n\in\bn. In the present paper we
generalize this result to multi-parameter contractions acting on . As an
application of that result we prove a generalization of the "zero-two" law.Comment: 10 page
The structure of reversible computation determines the self-duality of quantum theory
Predictions for measurement outcomes in physical theories are usually
computed by combining two distinct notions: a state, describing the physical
system, and an observable, describing the measurement which is performed. In
quantum theory, however, both notions are in some sense identical: outcome
probabilities are given by the overlap between two state vectors - quantum
theory is self-dual. In this paper, we show that this notion of self-duality
can be understood from a dynamical point of view. We prove that self-duality
follows from a computational primitive called bit symmetry: every logical bit
can be mapped to any other logical bit by a reversible transformation.
Specifically, we consider probabilistic theories more general than quantum
theory, and prove that every bit-symmetric theory must necessarily be
self-dual. We also show that bit symmetry yields stronger restrictions on the
set of allowed bipartite states than the no-signalling principle alone,
suggesting reversible time evolution as a possible reason for limitations of
non-locality.Comment: 4 pages, 1 figure. v2: published version. Title slightly changed,
interpretation of Theorem 2 correcte
Gut microbiota induce IGF-1 and promote bone formation and growth
New interventions are needed to improve bone health and reduce the risk for osteoporosis and fracture. Dysbiosis is increasingly linked to metabolic abnormalities, although the effect of the microbiota on skeletal health is poorly understood. Previous studies suggest microbiota are detrimental to bone by increasing resorption. In this report, we show that the gut resident microbiota promote bone formation, as well as resorption, with long-term exposure to microbiota resulting in net skeletal growth. Microbiota induce the hormone insulin-like growth factor 1 (IGF-1), which promotes bone growth and remodeling. Short-chain fatty acids (SCFAs), produced when microbiota ferment fiber, also induce IGF-1, suggesting a mechanism by which microbiota affect bone health. Manipulating the microbiome or its metabolites may afford opportunities to optimize bone health and growth
Self-Similar Random Processes and Infinite-Dimensional Configuration Spaces
We discuss various infinite-dimensional configuration spaces that carry
measures quasiinvariant under compactly-supported diffeomorphisms of a manifold
M corresponding to a physical space. Such measures allow the construction of
unitary representations of the diffeomorphism group, which are important to
nonrelativistic quantum statistical physics and to the quantum theory of
extended objects in d-dimensional Euclidean space. Special attention is given
to measurable structure and topology underlying measures on generalized
configuration spaces obtained from self-similar random processes (both for d =
1 and d > 1), which describe infinite point configurations having accumulation
points
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