2,271 research outputs found
Fractal Conductance Fluctuations of Classical Origin
In mesoscopic systems conductance fluctuations are a sensitive probe of
electron dynamics and chaotic phenomena. We show that the conductance of a
purely classical chaotic system with either fully chaotic or mixed phase space
generically exhibits fractal conductance fluctuations unrelated to quantum
interference. This might explain the unexpected dependence of the fractal
dimension of the conductance curves on the (quantum) phase breaking length
observed in experiments on semiconductor quantum dots.Comment: 5 pages, 4 figures, to appear in PR
The domain of a cannibal dark matter
We consider a scenario in which the dark matter is alone in a hidden sector
and consists of a real scalar particle with a manifest or spontaneously broken
symmetry, at a temperature which differs from the one of the
visible sector, . While similar models with general couplings have
already been studied in the literature, the special case of a model with
spontaneous symmetry breaking constitutes a non-trivial limit of these results,
since it features vanishing tree-level amplitudes for the processes with at threshold, thus making the cross-section governing
dark-matter freeze-out velocity suppressed. We carefully determine the
thermally averaged dark-matter annihilation cross-section in this scenario,
including the possible effects of one-loop corrections and Bose-Einstein
statistics, while also reporting our results in the domain of thermal dark
matter candidates, vs. with being
the hidden-sector temperature at decoupling. We show that for fixed quartic
coupling, due to entropy conservation, the thermal candidates lie along a curve
with anomalous scaling . Furthermore, we demonstrate
that this scaling is valid for a broad class of cannibal DM scenarios, with or
without symmetry breaking. In addition, we also discuss the relevant
cosmological and astrophysical constraints.Comment: 26 pages, 6 figures; v2: added discussion on domain-wall formation,
matches published versio
Rainforests at the beginning of the 21st century
Rainforests are situated at low latitude where forests enjoy steady and strong radiation.
Biodiversity in rainforests has been very high, for historical and climatic reasons. The number of species
is very high and tends to increase with precipitation and decrease with seasonality. Disturbance, soil
fertility and forest stature also influence the species richness and high turnover of species contribute to
diversity. Field observation and studies revealed that large scale deforestation could alter the regional and
global climate significantly. Deforestation alters the surface albedo which leads to climate change.
Regional land use contributes to climate change through surface-energy budget, as well as the carbon
cycle. Forest fragmentation, logging, overhunting, fire and the expanding agriculture threaten the
biodiversity. Rainforest covered area has significantly shrunk in the last decades. It is hard to protect the
forests because of the growing demand for agricultural area and forest-derived products. Most measures
proved ineffective to slow down the destruction. Hence, more forest will be lost in the future.
Conservationists should take into consideration the secondary forests because biodiversity can be high
enough and it is worth protecting them
Desiccation of the resurrection plant Craterostigma plantagineum induces dynamic changes in protein phosphorylation
Speech Communication
Contains reports on five research projects.C.J. LeBel FellowshipKurzweil Applied IntelligenceNational Institutes of Health (Grant 5 T32 NS07040)National Institutes of Health (Grant 5 R01 NS04332)National Science Foundation (Grant 1ST 80-17599)Systems Development FoundationU.S. Navy - Office of Naval Research (Contract N00014-82-K-0727
Speech Communication
Contains reports on eight research projects.C.J. LeBel FellowshipSystems Development FoundationNational Institutes of Health (Grant 5 T32 NS 07040-08)National Institutes of Health (Grant 5 R01 NS 04332-20)National Science Foundation (Grant 1ST 80-1759)National Science Foundation (Grant 1ST 80-17599 and MCS-8112899)U.S. Navy - Office of Naval Research (Contract N00014-82-K-0727
Fractal fluctuations in quantum integrable scattering
We theoretically and numerically demonstrate that completely integrable
scattering processes may exhibit fractal transmission fluctuations, due to
typical spectral properties of integrable systems.
Similar properties also occur with scattering processes in the presence of
strong dynamical localization, thus explaining recent numerical observations of
fractality in the latter class of systems.Comment: revtex, 4 pages, 3 eps figure
Speech Communication
Contains reports on eight research projects.C.J. LeBel FellowshipSystems Development FoundationNational Institutes of Health (Grant 5 T32 NS07040)National Institutes of Health (Grant 5 R01 NS04332)National Science Foundation (Grant 1ST 80-17599)U.S. Navy - Office of Naval Research (Contract N00014-82-K-0727
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