7,232 research outputs found
Degeneracy between warm and coupled cold dark matter: A clarifying note
Wei et al [PRD 88, 043510 (2013)] have proposed the existence of a
cosmological degeneracy between warm dark matter (WDM), modified gravity and
coupled cold dark matter (CDM) cosmologies at both the background expansion and
the growth of density perturbation levels, i.e., corresponding cosmological
data would not be able to differentiate such scenarios. Here, we will focus on
the specific indistinguishability between a warm dark matter plus cosmological
constant () and coupled scalar field-CDM scenarios. Although the
statement of Wei et al is true for very specific conditions we present a more
complete discussion on this issue and show in more detail that these models are
indeed distinguishable. We show that the degeneracy breaks down since coupled
models leave a specific signature in the redshift space distortion data which
is absent in the uncoupled warm dark matter cosmologies. Furthermore, we
complement our claim by providing the reasons which suggest that even at
nonlinear level a breaking of such apparent equivalence is also expected.Comment: 6 pages, 1 Figure; revised version, section IV extended and enriched
with further discussion, title altered, typos corrected and new references
added. Version published in PR
Alterations in brain connectivity due to plasticity and synaptic delay
Brain plasticity refers to brain's ability to change neuronal connections, as
a result of environmental stimuli, new experiences, or damage. In this work, we
study the effects of the synaptic delay on both the coupling strengths and
synchronisation in a neuronal network with synaptic plasticity. We build a
network of Hodgkin-Huxley neurons, where the plasticity is given by the Hebbian
rules. We verify that without time delay the excitatory synapses became
stronger from the high frequency to low frequency neurons and the inhibitory
synapses increases in the opposite way, when the delay is increased the network
presents a non-trivial topology. Regarding the synchronisation, only for small
values of the synaptic delay this phenomenon is observed
Generalising the logistic map through the -product
We investigate a generalisation of the logistic map as (, )
where stands for a generalisation of the ordinary product, known as
-product [Borges, E.P. Physica A {\bf 340}, 95 (2004)]. The usual product,
and consequently the usual logistic map, is recovered in the limit ,
The tent map is also a particular case for . The
generalisation of this (and others) algebraic operator has been widely used
within nonextensive statistical mechanics context (see C. Tsallis, {\em
Introduction to Nonextensive Statistical Mechanics}, Springer, NY, 2009). We
focus the analysis for at the edge of chaos, particularly at the
first critical point , that depends on the value of . Bifurcation
diagrams, sensitivity to initial conditions, fractal dimension and rate of
entropy growth are evaluated at , and connections with
nonextensive statistical mechanics are explored.Comment: 12 pages, 23 figures, Dynamics Days South America. To be published in
Journal of Physics: Conference Series (JPCS - IOP
Diffraction and an infrared finite gluon propagator
We discuss some phenomenological applications of an infrared finite gluon
propagator characterized by a dynamically generated gluon mass. In particular
we compute the effect of the dynamical gluon mass on and
diffractive scattering. We also show how the data on photoproduction
and hadronic reactions can be derived from the and
forward scattering amplitudes by assuming vector meson dominance and
the additive quark model.Comment: 4 pages, 7 figures, added references and figures, changed structure.
Contribution to Proceedings of XVIIIth Reuniao de Trabalho sobre Interacoes
Hadronicas, Sao Paulo, Brazil, 22-24 May, 200
Modeling electrodialysis and a photochemical process for their integration in saline wastewater treatment.
Oxidation processes can be used to treat industrial wastewater containing non-biodegradable organic compounds. However, the presence of dissolved salts may inhibit or retard the treatment process. In this study, wastewater desalination by electrodialysis (ED) associated with an advanced oxidation process (photo-Fenton) was applied to an aqueous NaCl solution containing phenol. The influence of process variables on the demineralization factor was investigated for ED in pilot scale and a correlation was obtained between the phenol, salt and water fluxes with the driving force. The oxidation process was investigated in a laboratory batch reactor and a model based on artificial neural networks was developed by fitting the experimental data describing the reaction rate as a function of the input variables. With the experimental parameters of both processes, a dynamic model was developed for ED and a continuous model, using a plug flow reactor approach, for the oxidation process. Finally, the hybrid model simulation could validate different scenarios of the integrated system and can be used for process optimization
Scattering and Bound State Green's Functions on a Plane via so(2,1) Lie Algebra
We calculate the Green's functions for the particle-vortex system, for two
anyons on a plane with and without a harmonic regulator and in a uniform
magnetic field. These Green's functions which describe scattering or bound
states (depending on the specific potential in each case) are obtained exactly
using an algebraic method related to the SO(2,1) Lie group. From these Green's
functions we obtain the corresponding wave functions and for the bound states
we also find the energy spectra.Comment: 21 Latex pages. Typos corrected. Results unchanged. Version to appear
in JM
Phosphorus and Potassium Placement for No-Till Corn
The information presented is part of ongoing research to identify effective fertilizer placement methods and diagnostic tools for phosphorus (P) and potassium (K) in no-till and ridge-till corn and soybean. Results for no-till cornfields will be emphasized here. There is uncertainty about soil test interpretations and cost-effective methods of fertilizer application for the no-till system. Moreover, producers are uncertain about the value of soil testing in conservation tillage because of large variability and lack of knowledge concerning techniques for collection of samples. Broadcast placements are less costly than banded placements but they seem inefficient for no-till fields because fertilizers are not incorporated. Because of the reduced movement of P and K in soils, broadcast applications result in stratification of these nutrients and accumulations within the top 2 or 3 inches of the soils. Although residue cover usually improves root growth and root absorption efficiency at shallow soil layers, the stratification could result in lower P or K uptake by plants during dry periods
The Collins-Roscoe mechanism and D-spaces
We prove that if a space X is well ordered , or linearly
semi-stratifiable, or elastic then X is a D-space
Cultura Alternativa: Produção de laranjas e tangerinas sem sementes.
bitstream/item/59169/1/laranjas-Pedroso.pd
Improving the Knowledge on Seismogenic Sources in the Lower Tagus Valley for Seismic Hazard Purposes
The Lower Tagus Valley, that includes the metropolitan area of Lisbon, has been struck by several earthquakes which produced significant material damage and loss of lives. Their exact location remains unknown. Our goal is to shed some light into the seismogenic sources in the area using seismic reflection and geological data. In areas with no seismic coverage, potential-field data interpretation was carried out. Seismicity was overlaid to the potential seismogenic structures and high-resolution data was acquired in order to confirm which structures have been active into the Quaternary. Three major fault-zones affecting the Neogene were identified: V. F. Xira, Samora-Alcochete and Pinhal Novo. For the first fault, strong evidences suggest it is active. The other two fault-zones and other structures previously unknown can be correlated with several epicentres. Empirical relationships between maximum moment magnitude and fault area indicate that MW > 6.5 earthquakes can be expected for the larger structures
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