639,819 research outputs found
Comment on "Modified Coulomb Law in a Strongly Magnetized Vacuum"
This is a comment on Phys. Rev. Lett. 98, 180403 (2007) [arXiv:0704.2162].Comment: 1 page, comment on arXiv:0704.2162, published versio
On the convergence of autonomous agent communities
This is the post-print version of the final published paper that is available from the link below. Copyright @ 2010 IOS Press and the authors.Community is a common phenomenon in natural ecosystems, human societies as well as artificial multi-agent systems such as those in web and Internet based applications. In many self-organizing systems, communities are formed evolutionarily in a decentralized way through agents' autonomous behavior. This paper systematically investigates the properties of a variety of the self-organizing agent community systems by a formal qualitative approach and a quantitative experimental approach. The qualitative formal study by applying formal specification in SLABS and Scenario Calculus has proven that mature and optimal communities always form and become stable when agents behave based on the collective knowledge of the communities, whereas community formation does not always reach maturity and optimality if agents behave solely based on individual knowledge, and the communities are not always stable even if such a formation is achieved. The quantitative experimental study by simulation has shown that the convergence time of agent communities depends on several parameters of the system in certain complicated patterns, including the number of agents, the number of community organizers, the number of knowledge categories, and the size of the knowledge in each category
Twistings, crossed coproducts and Hopf-Galois coextensions
Let be a Hopf algebra. Ju and Cai introduced the notion of twisting of an
-module coalgebra. In this note, we study the relationship between
twistings, crossed coproducts and Hopf-Galois coextensions. In particular, we
show that a twisting of an -Galois coextension remains -Galois if the
twisting is invertible.Comment: 20 page
Cosmological model of the interaction between dark matter and dark energy
In this paper, we test the dark matter-dark energy interacting cosmological
model with a dynamic equation of state , using
type Ia supernovae (SNe Ia), Hubble parameter data, baryonic acoustic
oscillation (BAO) measurements, and the cosmic microwave background (CMB)
observation. This interacting cosmological model has not been studied before.
The best-fitted parameters with uncertainties are , , and
with . At the
confidence level, we find , which means that the energy transfer
prefers from dark matter to dark energy. We also find that the SNe Ia are in
tension with the combination of CMB, BAO and Hubble parameter data. The
evolution of indicates that this interacting model is a
good approach to solve the coincidence problem, because the
decrease with scale factor . The transition redshift is in this model.Comment: 6 pages, 6 figures, published in A&
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