52,095 research outputs found
Impact of sterile neutrinos on nuclear-assisted cLFV processes
We discuss charged lepton flavour violating processes occurring in the
presence of muonic atoms, such as muon-electron conversion in nuclei
, the (Coulomb enhanced) decay of muonic atoms
into a pair of electrons BR(, N), as well as Muonium
conversion and decay, and .
Any experimental signal of these observables calls for scenarios of physics
beyond the Standard Model. In this work, we consider minimal extensions of the
Standard Model via the addition of sterile fermions, providing the
corresponding complete analytical expressions for all the considered
observables. We first consider an "ad hoc" extension with a single sterile
fermion state, and investigate its impact on the above observables. Two well
motivated mechanisms of neutrino mass generation are then considered: the
Inverse Seesaw embedded into the Standard Model, and the MSM. Our study
reveals that, depending on their mass range and on the active-sterile mixing
angles, sterile neutrinos can give significant contributions to the above
mentioned observables, some of them even lying within present and future
sensitivity of dedicated cLFV experiments. We complete the analysis by
confronting our results to other (direct and indirect) searches for sterile
fermions.Comment: 32 pages, 11 figures. v2: minor revision, matches published version
on JHE
Effect of steriles states on lepton magnetic moments and neutrinoless double beta decay
We address the impact of sterile fermion states on the anomalous magnetic
moment of charged leptons, as well as their contribution to neutrinoless double
beta decays. We illustrate our results in a minimal, effective extension of the
Standard Model by one sterile fermion state, and in a well-motivated framework
of neutrino mass generation, embedding the Inverse Seesaw into the Standard
Model. The simple "3+1" effective case succeeds in alleviating the tension
related to the muon anomalous magnetic moment, albeit only at the 3
level, and for light sterile states (corresponding to a }cosmologically
disfavoured regime). Interestingly, our analysis shows that a future observation does not necessarily imply an inverted hierarchy for the
active neutrinos in this simple extension. Although the Inverse Seesaw
realisation here addressed could indeed ease the tension in , bounds
from lepton universality in kaon decays mostly preclude this from happening.
However, these scenarios can also have a strong impact on the interpretation of
a future signal regarding the hierarchy of the active neutrino
mass spectrum.Comment: 25 pages, 19 figure
Theory of Nonequilibrium Spin Transport and Spin Transfer Torque in Superconducting-Ferromagnetic Nanostructures
Spin transport currents and the spin-transfer torques in voltage-biased
superconducting-ferromagnetic nanopillars (SFNFS point contacts) are computed.
We develop and implement an algorithm based on the Ricatti formulation of the
quasiclassical theory of superconductivity to solve the time-dependent boundary
conditions for the nonequilibrium Green's functions for spin transport through
the ferromagnetic interfaces. A signature of the nonequilibrium torque is a
component perpendicular to the plane spanned by the two ferromagnetic moments.
The perpendicular component is absent in normal-metal-ferromagnetic nanopillars
(NFNFN) contacts, but is shown to have the same order of magnitude as the
in-plane torque for non-equilibrium SFNFS contacts. The out-of-plane torque is
due to the rotation of quasiparticle spin by the exchange fields of the
ferromagnetic layers. In the ballistic limit the equilibrium torque is related
to the spectrum of spin-polarized Andreev bound states, while the {\sl ac}
component, for small bias voltages, is determined by the nearly adiabatic
dynamics of the Andreev bound states. The nonlinear voltage dependence of the
non-equilibrium torque, including the subharmonic gap structure and the
high-voltage asymptotics, is attributed to the interplay between multiple
Andreev reflections, spin filtering and spin mixing. These properties of spin
angular momentum transport may be exploited to control the state of
nanomagnets.Comment: 15 pages, 14 figure
Broadcast Strategies with Probabilistic Delivery Guarantee in Multi-Channel Multi-Interface Wireless Mesh Networks
Multi-channel multi-interface Wireless Mesh Networks permit to spread the
load across orthogonal channels to improve network capacity. Although broadcast
is vital for many layer-3 protocols, proposals for taking advantage of multiple
channels mostly focus on unicast transmissions. In this paper, we propose
broadcast algorithms that fit any channel and interface assignment strategy.
They guarantee that a broadcast packet is delivered with a minimum probability
to all neighbors. Our simulations show that the proposed algorithms efficiently
limit the overhead
Fold-Saddle Bifurcation in Non-Smooth Vector Fields on the Plane
This paper presents results concerning bifurcations of 2D piecewise-smooth
dynamical systems governed by vector fields. Generic three parameter families
of a class of Non-Smooth Vector Fields are studied and its bifurcation diagrams
are exhibited. Our main result describes the unfolding of the so called
Fold-Saddle singularity
Agricultural Credit Interest Rate Equalization Policy: A Growth Subsidy?
The Brazilian Interest Rate Equalization System (IRES) subsidizes farmers by providing them with credit at lower than market interest rates. The objective of this research is to evaluate the IRES by comparing its monetary cost with its benefits as measured by Brazilian GDP growth. Estimates are carried out using input-output matrix. The results suggest that each Brazilian real spent by IRES to assist Brazilian family farms increases Brazilian GDP by R 3.57. The IRES is a subsidy that generates economic growth greater than its cost to society.IRES subsidy, growth, input-output matrix, Agricultural Finance, Q18, C67, O40, H81,
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