5,573 research outputs found
CBBN in the CMSSM
Catalyzed big bang nucleosynthesis (CBBN) can lead to an overproduction of
^6Li in gravitino dark matter scenarios in which the lighter stau is the
lightest Standard Model superpartner. Based on a treatment using the
state-of-the-art result for the catalyzed ^6Li production cross section, we
update the resulting constraint within the framework of the constrained minimal
supersymmetric Standard Model (CMSSM). We confront our numerical findings with
recently derived conservative limits on the gaugino mass parameter and the
reheating temperature.Comment: 4 pages, 4 figures; Submitted for the SUSY07 proceeding
Landau Migdal Theory of Interacting Fermi Systems: A Framework for Effective Theories in Nuclear Structure Physics
We review Migdal's Theory of Finite Fermi Systems and its application to the
structure of nuclei. The theory is an extension of Landau's Theory of
Interacting Fermi Systems. In the first part the basic formulas are derived
within the many body Green functions approach. The theory is applied to
isovector electric giant resonances in medium and heavy mass nuclei. The
parameterizations of the enormalized effective ph-interaction and the effective
operators are discussed. It is shown that the number of free parameters are
restricted due to conservation laws. We also present an extension of Migdal's
theory, where the low-lying phonons are considered in a consistent manner. The
extended theory is again applied to the same isovector electric giant
resonances and to the analysis of reaction data. We
point out that the extended theory is the appropriate frame for self consistent
nuclear structure calculations starting from effective Lagrangians and
Hamiltonians.Comment: 6 figure
Brown-von Neumann-Nash Dynamics: The Continuous Strategy Case
In John Nash’s proofs for the existence of (Nash) equilibria based on Brouwer’s theorem, an iteration mapping is used. A continuous— time analogue of the same mapping has been studied even earlier by Brown and von Neumann. This differential equation has recently been suggested as a plausible boundedly rational learning process in games. In the current paper we study this Brown—von Neumann—Nash dynamics for the case of continuous strategy spaces. We show that for continuous payoff functions, the set of rest points of the dynamics coincides with the set of Nash equilibria of the underlying game. We also study the asymptotic stability properties of rest points. While strict Nash equilibria may be unstable, we identify sufficient conditions for local and global asymptotic stability which use concepts developed in evolutionary game theory.Learning in games; evolutionary stability; BNN
Brown-von Neumann-Nash Dynamics: The Continuous Strategy Case
In John Nash’s proofs for the existence of (Nash) equilibria based on Brouwer’s theorem, an iteration mapping is used. A continuous— time analogue of the same mapping has been studied even earlier by Brown and von Neumann. This differential equation has recently been suggested as a plausible boundedly rational learning process in games. In the current paper we study this Brown—von Neumann—Nash dynamics for the case of continuous strategy spaces. We show that for continuous payoff functions, the set of rest points of the dynamics coincides with the set of Nash equilibria of the underlying game. We also study the asymptotic stability properties of rest points. While strict Nash equilibria may be unstable, we identify sufficient conditions for local and global asymptotic stability which use concepts developed in evolutionary game theory.
Estimating optimal conservation in agricultural landscapes when costs and benefits of conservation measures are heterogeneous in space and over time
Designing agri-environmental schemes targeted at conservation poses the key question of how many financial resources should be allocated to address a particular aim such as the conservation of an endangered species. Economists can contribute to an answer by estimating the 'optimal level of species conservation'. This requires an assessment of the supply and the demand curve for conservation and a comparison of the two curves to identify the optimal conservation level. In a case study we estimate the optimal conservation level of Large Blue butterflies (protected by the EU Habitats Directive) in the region of Landau, Germany. The difference to other studies estimating optimal conservation is that a problem is addressed where costs and benefits of conservation measures are heterogeneous in space and over time. In our case study we find a corner solution where the highest proposed level of butterfly conservation is optimal. Although our results are specific to the area and species studied, the methodology is generally applicable to estimate how many financial resources should be allocated to conserve an endangered species in the context of agri-environmental schemes. --agri-environmental policy,biodiversity,optimal conservation,spatial heterogeneity,willingness-to-pay
Stability of the Replicator Equation for a Single-Species with a Multi-Dimensional Continuous Trait Space
The replicator equation model for the evolution of individual behaviors in a single-species with a multi-dimensional continuous trait space is developed as a dynamics on the set of probability measures. Stability of monomorphisms in this model using the weak topology is compared to more traditional methods of adaptive dynamics. For quadratic fitness functions and initial normal trait distributions, it is shown that the multi-dimensional CSS (Continuously Stable Strategy) of adaptive dynamics is often relevant for predicting stability of the measure-theoretic model but may be too strong in general. For general fitness functions and trait distributions, the CSS is related to dominance solvability which can be used to characterize local stability for a large class of trait distributions that have no gaps in their supports whereas the stronger NIS (Neighborhood Invader Strategy) concept is needed if the supports are arbitrary.Adaptive dynamics, CSS, NIS, replicator equation, local superiority, strategy dominance, measure dynamics, weak topology
Brown-von Neumann-Nash dynamics : the continuous strategy case
In John Nash’s proofs for the existence of (Nash) equilibria based on Brouwer’s theorem, an iteration mapping is used. A continuous- time analogue of the same mapping has been studied even earlier by Brown and von Neumann. This differential equation has recently been suggested as a plausible boundedly rational learning process in games. In the current paper we study this Brown-von Neumann-Nash dynamics for the case of continuous strategy spaces. We show that for continuous payoff functions, the set of rest points of the dynamics coincides with the set of Nash equilibria of the underlying game. We also study the asymptotic stability properties of rest points. While strict Nash equilibria may be unstable, we identify sufficient conditions for local and global asymptotic stability which use concepts developed in evolutionary game theory
Origins and fate of fungi and bacteria in the gut of Lumbricus terrestris L. studied by image analysis
The effect of the passage through the gut of the earthworm Lumbricus terrestris L. on fungi and bacteria ingested with decomposing leaves of Taraxacum officinale and with soil was quantified using image analysis tools. Both leaf and soil material were labeled with fluorescent latex microbeads to allow a quantification of the food sources in the fore-, mid-, and hindgut of the earthworms. The content of leaf material in the gut varied in a range between 4 and 59% of the total gut content in different earthworms and the different parts of the intestine of individual animals. Filamentous fungi in the gut compartments were found to originate mainly from leaf material (7700±1800 μg (g leaf (dry wt.))−1), however, the major part was disrupted before arriving in the intestine. Remaining hyphae in the foregut with a biomass of up to 900±150 μg (g gut content (dry wt.))−1 were completely digested during passage through the earthworm gut. Spores of fungi were not detected in our studies. Bacterial cell numbers in the gut compartments ranged from 63±5×108 to 327±16×108 (g gut content (dry wt.))−1 and were significantly higher than the numbers found in the soil (50±1×108 cells (g soil (dry wt.))−1). Cell numbers usually increased from fore- to hindgut. This increase was not correlated to contents of organic material and only partially due to a multiplication of bacterial cells. Numbers of dividing cells accounted in total for approximately 12% of all bacteria, increasing significantly from fore- to hindgut, counts were from 10±1×108 to 25±2×108 (g gut content (dry wt.))−1, respectively. Average cell volumes of bacteria calculated from cell size distributions in leaf and soil material differed significantly, being 0.197 and 0.063 μm3, respectively. In the gut compartments, average cell volumes ranged from 0.043 to 0.070 μm3, which may indicate the disruption of large cells originating from the leaves before arriving in the foregu
Thermal Gravitino Production and Collider Tests of Leptogenesis
Considering gravitino dark matter scenarios, we obtain the full
gauge-invariant result for the relic density of thermally produced gravitinos
to leading order in the Standard Model gauge couplings. For the temperatures
required by thermal leptogenesis, we find gaugino mass bounds which will be
probed at future colliders. We show that a conceivable determination of the
gravitino mass will allow for a unique test of the viability of thermal
leptogenesis in the laboratory.Comment: 5 pages, 3 figures, revised version matches published versio
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