961 research outputs found

    The evolutionary ecology of interactive synchronism: The illusion of the optimal phenotype

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    In this article, we discuss some ecological-evolutionary strategies that allow synchronization of organisms, resources, and conditions. Survival and reproduction require synchronization of life cycles of organisms with favourable environmental and ecological features and conditions. This interactive synchronization can occur directly, through pairwise or diffuse co-evolution, or indirectly, for example, as a result of actions of ecosystem engineers and facilitator species. Observations of specific interactions, especially those which have coevolved, may give the false impression that evolution results in optimal genotypes or phenotypes. However, some phenotypes may arise under evolutionary constraints, such as simultaneous evolution of multiple traits, lack of a chain of fit transitional forms leading to an optimal phenotype, or by limits inherent in the process of selection, set by the number of selective deaths and by interference between linked variants. Although there are no optimal phenotypes, optimization models applied to particular species may be useful for a better understanding of the nature of adaptations. The evolution of adaptive strategies results in variable life histories. These strategies can minimize adverse impacts on the fitness of extreme or severe environmental conditions on survival and reproduction, and may include reproductive strategies such as semelparity and iteroparity, or morphological, physiological, or behavioural traits such as diapause, seasonal polyphenism, migration, or bet-hedging. However, natural selection cannot indefinitely maintain intra-population variation, and lack of variation can ultimately extinguish populations

    Book Review: Avant D, Fennimore, M. & Sell, S.K, 2010. Who Governs the Globe? New York: Cambridge University Press.

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    For those immersed in grand International Relations (IR) theory couched in the structural/ functional paradigm of the 80's, this book is indeed iconoclastic. The paradigm informing traditional International Relations theory supported the bi-polar world view during the cold war. It then proceeded to support the shift to a multipolar view based on the geo-political power balance among leading states, their clubs and then the inclusion of state groupings as the non-aligned nations and more recently emerging countries such as those making up the BRICS cluster. Modern IR theory represented by this book has essentially replaced the key concept of balanced geo-political state power with global governance based on pluralism of global players

    Academic Panel: Can Self-Managed Systems be trusted?

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    Trust can be defined as to have confidence or faith in; a form of reliance or certainty based on past experience; to allow without fear; believe; hope: expect and wish; and extend credit to. The issue of trust in computing has always been a hot topic, especially notable with the proliferation of services over the Internet, which has brought the issue of trust and security right into the ordinary home. Autonomic computing brings its own complexity to this. With systems that self-manage, the internal decision making process is less transparent and the ‘intelligence’ possibly evolving and becoming less tractable. Such systems may be used from anything from environment monitoring to looking after Granny in the home and thus the issue of trust is imperative. To this end, we have organised this panel to examine some of the key aspects of trust. The first section discusses the issues of self-management when applied across organizational boundaries. The second section explores predictability in self-managed systems. The third part examines how trust is manifest in electronic service communities. The final discussion demonstrates how trust can be integrated into an autonomic system as the core intelligence with which to base adaptivity choices upon

    Type-4 spinors: transmuting from Elko to single-helicity spinors

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    In this communication we briefly report an unexpected theoretical discovery which emerge from the mapping of Elko mass-dimension-one spinors into single helicity spinors. Such procedure unveils a class of spinor which is classified as type-4 spinor field within Lounesto classification. In this paper we explore the underlying physical and mathematical contents of the type-4 spinor.Comment: 9 pages, 0 figure

    Can neutrino-assisted early dark energy models ameliorate the H0H_0 tension in a natural way?

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    The idea of neutrino-assisted early dark energy (ν\nuEDE), where a coupling between neutrinos and the scalar field that models early dark energy (EDE) is considered, was introduced with the aim of reducing some of the fine-tuning and coincidence problems that appear in usual EDE models. In order to be relevant in ameliorating the H0H_0 tension, the contribution of EDE to the total energy density (fEDEf_\text{EDE}) should be around 10\% near the redshift of matter-radiation equality. We verify under which conditions ν\nuEDE models can fulfill these requirements for a model with a quartic self-coupling of the EDE field and an exponential coupling to neutrinos. We find that in the situation where the EDE field is frozen initially, the contribution to fEDEf_\text{EDE} can be significant but it is not sensitive to the neutrino-EDE coupling and does not address the EDE coincidence problem. On the other hand, if the EDE field starts already dynamical at the minimum of the effective potential, it tracks this time-dependent minimum that presents a feature triggered by the neutrino transition from relativistic to nonrelativistic particles. This feature generates fEDEf_\text{EDE} in a natural way at around this transition epoch, that roughly coincides with the matter-radiation equality redshift. For the set of parameters that we considered we did not find values that satisfy the requirements on the background cosmological evolution to mitigate the Hubble tension in a natural way in this particular ν\nuEDE model.Comment: 6 pages, 4 figures. New version with more detailed analysi
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