Renormalization of NN-Scattering with One Pion Exchange and Boundary Conditions

A non perturbative renormalization scheme for Nucleon-Nucleon interaction based on boundary conditions at short distances is presented and applied to the One Pion Exchange Potential. It is free of off-shell ambiguities and ultraviolet divergences, provides finite results at any step of the calculation and allows to remove the short distance cut-off in a suitable way. Low energy constants and their non-perturbative evolution can directly be obtained from experimental threshold parameters in a completely unique and model independent way when the long range explicit pion effects are eliminated. This allows to compute scattering phase shifts which are, by construction consistent with the effective range expansion to a given order in the C.M. momentum $p$. In the singlet $^1S_0$ and triplet $^3S_1- ^3D_1$ channels ultraviolet fixed points and limit cycles are obtained respectively for the threshold parameters. Data are described satisfactorily up to CM momenta of about $p \sim m_\pi$.Comment: 22 pages, 10 figures, revte

Evaluation of CupCarbon Network Simulator for Wireless Sensor Networks

[EN] Wireless sensor networks (WSNs) are a technology in continuous evolution with great future and a huge quantity of applications. The implementation and deployment of a WSN imply important expenses, so it is interesting to simulate the operation of our design before deploying it. In addition, WSNs are limited by a set of parameters such as the low processing capacity, low storing capacity or limited energy. Energy consumption is the most limiting parameter since the network stability and availability depends on the survival of the nodes. To check the correct operation of a network, currently, there are several network simulators and day by day new proposals are launched. This paper presents the evaluation of a new network simulator called CupCarbon. Along the document, we present the main characteristics of this simulator and check its operation by an example. To evaluate the ease of use of this new network simulator, we propose a modified version of Dijkstra algorithm. In addition of considering the cost route to calculate the best route, it considers the remaining energy in nodes as an additional parameter to evaluate the best route. CupCarbon allows implementing our proposal and the results show that our proposal is able to offer a more stable network with an increase of the network lifetime of the 20%. Finally, to extract some conclusions from our experiences, we compare the characteristics and results of CupCarbon with the most common network simulators currently used by researchers. Our conclusions point out that CupCarbon can be used as a complementary tool for those simulators that are not able to monitor the energy consumption in nodes. However, it needs some improvements to reach the level of functionality of the most used simulators. CupCarbon could be an interesting option for academic environments.López-Pavón, C.; Sendra, S.; Valenzuela-Valdés, JF. (2018). Evaluation of CupCarbon Network Simulator for Wireless Sensor Networks. Network Protocols and Algorithms. 10(2):1-27. https://doi.org/10.5296/npa.v10i2.13201S12710

Methodology for characterization, evaluation and optimization of acoustic environments

Currently we are working on methodologies to characterize, evaluate and optimize acoustic environments with different approaches. One methodology is based on the evaluation of temporal energetic behavior of acoustic environment through the use of parameters associated with the autocorrelation function (ACF). In this case the main objective is to verify the variability of the temporal behavior of urban acoustic environment depending of sounds sources that are part of them. We evaluate the temporal energetic behavior in 10 urban acoustic environments using ACF in two main cities, Brasilia (Brazil) and Bogotá (Colombia). The second methodology is based on the design of an experiment to improve and optimize acoustic environments on the basis of the auditory subjective experiences of the people. It has been designed a LabVIEW application for psychoacoustic laboratory tests to evaluate the subjective perception of people. The main objective is to evaluate how adding sound signals in acoustics environments with traffic noise couls improve the experience of the users

Bulk viscous cosmology with causal transport theory

We consider cosmological scenarios originating from a single imperfect fluid with bulk viscosity and apply Eckart's and both the full and the truncated M\"uller-Israel-Stewart's theories as descriptions of the non-equilibrium processes. Our principal objective is to investigate if the dynamical properties of Dark Matter and Dark Energy can be described by a single viscous fluid and how such description changes when a causal theory (M\"uller-Israel-Stewart's, both in its full and truncated forms) is taken into account instead of Eckart's non-causal theory. To this purpose, we find numerical solutions for the gravitational potential and compare its behaviour with the corresponding LambdaCDM case. Eckart's and the full causal theory seem to be disfavoured, whereas the truncated theory leads to results similar to those of the LambdaCDM model for a bulk viscous speed in the interval 10^{-11} << c_b^2 < 10^{-8}. Tentatively relating such value to a square propagation velocity of the order of T/m of perturbations in a non-relativistic gas of particles with mass m at the epoch of matter-radiation equality, this may be compatible with a mass range 0.1 GeV < m << 100 GeV.Comment: 23 pages, 7 figure

Selección de variables en la predicción de llamadas en un centro de atención telefónica

En este artículo se ilustra la importancia de la selección de variables independientes para modelos neuronales destinados a la predicción de la demanda en un centro de atención telefónica. Los modelos tienen como objetivo ayudar en la planificación semanal del personal del centro, tarea que se realiza con 14 días de antelación. Los modelos requeridos pueden hacer uso de gran cantidad de variables independientes. Sin embargo, el número de casos que pueden ser usados para obtener los parámetros del modelo es escaso debido a los cambios socio-económicos. Esto plantea la necesidad de seleccionar cuidadosamente las variables independientes y utilizar el menor número posible de ellas, de otro modo la generalización del modelo se degradaría. Para resolver el problema se utiliza un método mixto que permite trabajar con un alto número de variables candidatas, en una primera fase, y seleccionar más cuidadosamente un número menor de variables en una segunda fase. Los resultados obtenidos por los modelos resultantes de aplicar el método propuesto y sus variantes son analizados utilizando datos reales de un centro de atención telefónica. Los resultados de la comparación muestran que la correcta selección de variables independientes es vital para este tipo de aplicación.Unión Europea HYCON FP6-511368

Synergistic warm inflation

We consider an alternative warm inflationary scenario in which $n$ scalar fields coupled to a dissipative matter fluid cooperate to produce power--law inflation. The scalar fields are driven by an exponential potential and the bulk dissipative pressure coefficient is linear in the expansion rate. We find that the entropy of the fluid attains its asymptotic value in a characteristic time proportional to the square of the number of fields. This scenario remains nearly isothermal along the inflationary stage. The perturbations in energy density and entropy are studied in the long--wavelength regime and seen to grow roughly as the square of the scale factor. They are shown to be compatible with COBE measurements of the fluctuations in temperature of the CMB.Comment: 13 pages, Revtex 3 To be published in Physical Review

Precision cosmology as a test for statistics

We compute the shift in the epoch of matter-radiation equality due to the possible existence of a different statistical (non-extensive) background. The shift is mainly caused by a different neutrino-photon temperature ratio. We then consider the prospects to use future large galaxy surveys and cosmic microwave background measurements to constrain the degree of non-extensivity of the universe.Comment: to appear in Physica

Simulating elliptic flow with viscous hydrodynamics

In this work we simulate a viscous hydrodynamical model of non-central Au-Au collisions in 2+1 dimensions, assuming longitudinal boost invariance. The model fluid equations were proposed by \"{O}ttinger and Grmela \cite{OG}. Freezeout is signaled when the viscous corrections become large relative to the ideal terms. Then viscous corrections to the transverse momentum and differential elliptic flow spectra are calculated. When viscous corrections to the thermal distribution function are not included, the effects of viscosity on elliptic flow are modest. However, when these corrections are included, the elliptic flow is strongly modified at large $p_T$. We also investigate the stability of the viscous results by comparing the non-ideal components of the stress tensor ($\pi^{ij}$) and their influence on the $v_2$ spectrum to the expectation of the Navier-Stokes equations (\pi^{ij} = -\eta \llangle \partial_i u_j \rrangle). We argue that when the stress tensor deviates from the Navier-Stokes form the dissipative corrections to spectra are too large for a hydrodynamic description to be reliable. For typical RHIC initial conditions this happens for \eta/s \gsim 0.3.Comment: 34 pages, 40 figures added references, updated figure 1

Le Chatelier-Braun principle in cosmological physics

Assuming that dark energy may be treated as a fluid with a well defined temperature, close to equilibrium, we argue that if nowadays there is a transfer of energy between dark energy and dark matter, it must be such that the latter gains energy from the former and not the other way around.Comment: 6 pages, revtex file, no figures; version accepted for publication in General Relativity and Gravitatio

Exact inhomogeneous cosmologies whose source is a radiation-matter mixture with consistent thermodynamics

We derive a new class of exact solutions of Einstein's equations providing a physically plausible hydrodynamical description of cosmological matter in the radiative era ($10^6 K > T > 10^3 K$), between nucleosynthesis and decoupling. The solutions are characterized by the Lema\^{\i}tre-Tolman -Bondi metric with a viscous fluid source, subjected to the following conditions: (a) the equilibrium state variables satisfy the equation of state of a mixture of an ultra-relativistic and a non-relativistic ideal gases, where the internal energy of the latter has been neglected, (b) the particle numbers of the mixture components are independently conserved, (c) the viscous stress is consistent with the transport equation and entropy balance law of Extended Irreversible Thermodynamics, with the coefficient of shear viscosity provided by Kinetic Theory for the `radiative gas' model. The fulfilment of (a), (b) and (c) restricts initial conditions in terms of an initial value function, $\Delta_i^{(s)}$, related to the average of spatial gradients of the fluctuations of photon entropy per baryon in the initial hypersurface. Constraints on the observed anisotropy of the microwave cosmic radiation and the condition that decoupling occurs at $T=T_{_D}\approx 4\times 10^3$ K yield an estimated value: $|\Delta_i^{(s)}|\approx 10^{-8}$ which can be associated with a bound on promordial entropy fluctuations. The Jeans mass at decoupling is of the same order of magnitude as that of baryon dominated perturbation models ($\approx 10^{16} M_\odot$)Comment: LaTeX with revtex (PRD macros). Contains 9 figures (ps). To be published in Physics Review