18,680 research outputs found
The acoustic cut-off frequency of the Sun and the solar magnetic activity cycle
The acoustic cut-off frequency -the highest frequency for acoustic solar
eigenmodes- is an important parameter of the solar atmosphere as it determines
the upper boundary of the p-mode resonant cavities. At frequencies beyond this
value, acoustic disturbances are no longer trapped but traveling waves.
Interference amongst them give rise to higher-frequency peaks -the pseudomodes-
in the solar acoustic spectrum. The pseudomodes are shifted slightly in
frequency with respect to p modes making possible the use of pseudomodes to
determine the acoustic cut-off frequency. Using data from GOLF and VIRGO
instruments on board the SOHO spacecraft, we calculate the acoustic cut-off
frequency using the coherence function between both the velocity and intensity
sets of data. By using data gathered by these instruments during the entire
lifetime of the mission (1996 till the present), a variation in the acoustic
cut-off frequency with the solar magnetic activity cycle is found.Comment: Paper accepted in ApJ. 26 Pages, 9 figure
Strangeness on the nucleon
Observables from parity violation in elastic electron-nucleon scattering and
neutral current quasi-elastic neutrino-nucleus scattering are employed as tools
to improve the current knowledge on the strangeness content in the nucleon.Comment: Proceedings of International Scientific Meeting on Nuclear Physics,
9-13th September 2012. La R\'abida, Huelva, Spai
Pion production within the hybrid relativistic plane wave impulse approximation model at MiniBooNE and MINERvA kinematics
The hybrid model for electroweak single-pion production (SPP) off the
nucleon, presented in [Gonz\'alez-Jim\'enez et al., Phys. Rev. D 95, 113007
(2017)], is extended here to the case of incoherent pion-production on the
nucleus. Combining a low-energy model with a Regge approach, this model
provides valid predictions in the entire energy region of interest for current
and future accelerator-based neutrino-oscillation experiments. The Relativistic
Mean-Field model is used for the description of the bound nucleons while the
outgoing hadrons are considered as plane waves. This approach, known as
Relativistic Plane-Wave Impulse Approximation (RPWIA), is a first step towards
the development of more sophisticated models, it is also a test of our current
understanding of the elementary reaction. We focus on the charged-current
()-nucleus interaction at MiniBooNE and MINERvA kinematics. The
effect on the cross sections of the final-state interactions, which affect the
outgoing hadrons on their way out of the nucleus, is judged by comparing our
results with those from the NuWro Monte Carlo event generator. We find that the
hybrid-RPWIA predictions largely underestimate the MiniBooNE data. In the case
of MINERvA, our results fall below the -induced 1 production data,
while a better agreement is found for -induced 1 and
-induced 1 production.Comment: 13 pages, 10 figure
The effect of pension rules on retirement monetary incentives with an application to pension reforms in Spain
In this work we theoretically disentangle the effects of pension provisions on a variety of financial incentives to retirement, trying to reconcile them with some key Spanish retirement patterns. We find that the "average" individual, who is never affected by any cap of contributions or benefits, has weak incentives to retire early and strong incentives to retire at the normal retirement age. Alternatively, individuals at the bottom of the wage distribution have strong incentives to retire as early as possible, because ot the interaction between age-related penalties and the minimun pension. Both findings perfectly accommodate the retirement hazard of medium and low earners respectively. In contrast, high earners (those that have their contributions capped) despite having strong incentives to retire at the Early Retirement Age, do not do so. This is because, for those workers, financial incentives are not a good proxy for the marginal utility from working. Finally, we analyze the reasons behind the failure of the 1997 reform in improving the sustainability of the Spanish public pension system
Spike-based control monitoring and analysis with Address Event Representation
Neuromorphic engineering tries to mimic biological
information processing. Address-Event Representation (AER) is
a neuromorphic communication protocol for spiking neurons
between different chips. We present a new way to drive robotic
platforms using spiking neurons. We have simulated spiking
control models for DC motors, and developed a mobile robot
(Eddie) controlled only by spikes. We apply AER to the robot
control, monitoring and measuring the spike activity inside the
robot. The mobile robot is controlled by the AER-Robot tool,
and the AER information is sent to a PC using the
USBAERmini2 interface.Junta de Andalucía P06-TIC-01417Ministerio de Educación y Ciencia TEC2006-11730-C03-0
THE EFFECT OF PENSION RULES ON RETIREMENT MONETARY INCENTIVES WITH AN APPLICATION TO PENSION REFORMS IN SPAIN
In this work we theoretically disentangle the effects of pension provisions on a variety of financial incentives to retirement, trying to reconcile them with some key Spanish retirement patterns. We find that the “average” individual, who is never affected by any cap of contributions or benefits, has weak incentives to retire early and strong incentives to retire at the normal retirement age. Alternatively, individuals at the bottom of the wage distribution have strong incentives to retire as early as possible, because ot the interaction between age-related penalties and the minimun pension. Both findings perfectly accommodate the retirement hazard of medium and low earners respectively. In contrast, high earners (those that have their contributions capped) despite having strong incentives to retire at the Early Retirement Age, do not do so. This is because, for those workers, financial incentives are not a good proxy for the marginal utility from working. Finally, we analyze the reasons behind the failure of the 1997 reform in improving the sustainability of the Spanish public pension system.
An evaluation of the life-cycle effects of minimum pensions on retirement behavior
In this paper we explore the effects of the minimum pension program on welfare and retirement in Spain. This is done with a stylized life-cycle model which provides a convenient analytical characterization of optimal behavior. We use data from the Spanish Social Security to estimate the behavioral parameters of the model and then simulate the changes induced by the minimum pension in aggregate retirement patterns. The impact is substantial: there is threefold increase in retirement at 60 (the age of first entitlement) with respect to the economy without minimum pensions, and total early retirement (before or at 60) is almost 50% larger.Retirement, life cycle model, minimum pension, structural estimation
Parity violation in quasielastic electron-nucleus scattering within the relativistic impulse approximation
We study parity violation in quasielastic (QE) electron-nucleus scattering
using the relativistic impulse approximation. Different fully relativistic
approaches have been considered to estimate the effects associated with the
final-state interactions. We have computed the parity-violating quasielastic
(PVQE) asymmetry and have analyzed its sensitivity to the different ingredients
that enter in the description of the reaction mechanism: final-state
interactions, nucleon off-shellness effects, current gauge ambiguities.
Particular attention has been paid to the description of the weak neutral
current form factors. The PVQE asymmetry is proven to be an excellent
observable when the goal is to get precise information on the axial-vector
sector of the weak neutral current. Specifically, from measurements of the
asymmetry at backward scattering angles good knowledge of the radiative
corrections entering in the isovector axial-vector sector can be gained.
Finally, scaling properties shown by the interference nuclear
responses are also analyzed.Comment: 15 pages, 11 figure
Parity violation and dynamical relativistic effects in reactions
It is well known that coincidence quasielastic reactions are
not appropriate to analyze effects linked to parity violation due the presence
of the fifth electromagnetic (EM) response . Nevertheless, in this
work we develop a fully relativistic approach to be applied to parity-violating
(PV) quasielastic processes. This is of importance as a
preliminary step in the subsequent study of inclusive quasielastic PV
reactions. Moreover, our present analysis allows us to
disentangle effects associated with the off-shell character of nucleons in
nuclei, gauge ambiguities and the role played by the lower components in the
nucleon wave functions, i.e., dynamical relativistic effects. This study can
help in getting clear information on PV effects. Particular attention is paid
to the relativistic plane-wave impulse approximation where the explicit
expressions for the PV single-nucleon responses are shown for the first time.Comment: 39 pages, 9 figure
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