995 research outputs found
A_4 Symmetry and Lepton Masses and Mixing
Stimulated by Ma's idea which explains the tribimaximal neutrino mixing by
assuming an A_4 flavor symmetry, a lepton mass matrix model is investigated. A
Frogatt-Nielsen type model is assumed, and the flavor structures of the masses
and mixing are caused by the VEVs of SU(2)_L-singlet scalars \phi_i^u and
\phi_i^d (i=1,2,3), which are assigned to {\bf 3} and ({\bf 1}, {\bf 1}',{\bf
1}'') of A_4, respectively.Comment: 13 pages including 1 table, errors in Sec.7 correcte
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The impact of aerosol hygroscopic growth on the single-scattering albedo and its application on the NO2 photolysis rate coefficient
Hygroscopic growth of aerosol particles can significantly affect their single-scattering albedo (ω), and consequently alters the aerosol effect on tropospheric photochemistry. In this study, the impact of aerosol hygroscopic growth on ω and its application to the NO2 photolysis rate coefficient (JNO2) are investigated for a typical aerosol particle population in the North China Plain (NCP). The variations of aerosol optical properties with relative humidity (RH) are calculated using a Mie theory aerosol optical model, on the basis of field measurements of number–size distribution and hygroscopic growth factor (at RH values above 90%) from the 2009 HaChi (Haze in China) project. Results demonstrate that ambient ω has pronouncedly different diurnal patterns from ω measured at dry state, and is highly sensitive to the ambient RHs. Ambient ω in the NCP can be described by a dry state ω value of 0.863, increasing with the RH following a characteristic RH dependence curve. A Monte Carlo simulation shows that the uncertainty of ω from the propagation of uncertainties in the input parameters decreases from 0.03 (at dry state) to 0.015 (RHs > 90%). The impact of hygroscopic growth on ω is further applied in the calculation of the radiative transfer process. Hygroscopic growth of the studied aerosol particle population generally inhibits the photolysis of NO2 at the ground level, whereas accelerates it above the moist planetary boundary layer. Compared with dry state, the calculated JNO2 at RH of 98% at the height of 1 km increases by 30.4%, because of the enhancement of ultraviolet radiation by the humidified scattering-dominant aerosol particles. The increase of JNO2 due to the aerosol hygroscopic growth above the upper boundary layer may affect the tropospheric photochemical processes and this needs to be taken into account in the atmospheric chemical models
The dependence of the EIT wave velocity on the magnetic field strength
"EIT waves" are a wavelike phenomenon propagating in the corona, which were
initially observed in the extreme ultraviolet (EUV) wavelength by the EUV
Imaging Telescope (EIT). Their nature is still elusive, with the debate between
fast-mode wave model and non-wave model. In order to distinguish between these
models, we investigate the relation between the EIT wave velocity and the local
magnetic field in the corona. It is found that the two parameters show
significant negative correlation in most of the EIT wave fronts, {\it i.e.},
EIT wave propagates more slowly in the regions of stronger magnetic field. Such
a result poses a big challenge to the fast-mode wave model, which would predict
a strong positive correlation between the two parameters. However, it is
demonstrated that such a result can be explained by the fieldline stretching
model, \emph{i.e.,} that "EIT waves" are apparently-propagating brightenings,
which are generated by successive stretching of closed magnetic field lines
pushed by the erupting flux rope during coronal mass ejections (CMEs).Comment: 11 pages, 8 figures, accepted for publication in Solar Phy
Formability limits and process window based on fracture analysis of 5A02-O aluminium alloy in splitting spinning
Splitting spinning or rotary flow splitting is an advanced forming process for manufacturing axisymmetric integrated parts with bifurcated features and unique characteristics of high-performance and low-weight. During the process, under the kinematic effects of mandrel rotational movement and roller radial feed, plastic deformation occurs accompanied usually by undesirable fracture, which reduces the formability limit (FL). In this study, the kinematic effects on the FL of a 5A02-O aluminium alloy in the splitting spinning process were systematically investigated by finite element simulation based on a modified Lemaitre criterion and physical experiments. The results show that at a given roller feed speed or mandrel rotational speed (forming speed), the FL has a nonlinear relationship with forming speed, which increases firstly and then decreases. With the increase of forming speed, the maximum FL decreases, which appears at the larger forming speed. These variations of FL show that there exists a combined effect of the roller feed speed and mandrel rotational speed, thus a ratio between them, named as the roller feed ratio, is then used to investigate FL. It is found that there exists a critical roller feed ratio of approximately 2 mm/rev, independent of the speeds of roller and mandrel. Below this critical value, the FL increases with the roller feed ratio. While over the critical value, the FL decreases. In addition, the decrease of FL becomes more remarkable with the increase of mandrel rotational speed. Furthermore, the variations of stress triaxiality and tensile plastic strain were analyzed to see their effects on FL. The analyses show that the decrease of tensile plastic strain with the increasing roller feed ratio is dominant the increase of FL below the critical roller feed ratio value. The increase in the stress triaxiality is dominant in the decrease of FL when the roller feed ratio is over the critical value in combination with not too high forming speed, whereas both increases are dominant in the decrease of FL when it is over the critical roller feed ratio value in combination with high forming speed. Based on the kinematic effects of mandrel and roller, the process windows of the splitting spinning process were obtained to improve the FL. It is found that under the condition of the roller feed ratio within 1–2.5 mm/rev, the mandrel rotational speed within 8–100 rev/min and the roller feed speed within 0.5–4 mm/s are helpful to get high FL values. The experiments were carried out to verify the prediction on the FL and the process window. The research provides an in-depth understanding of FL and its affecting factors, and thus lays a basis for process optimization and process parameter configuration
S_3 Symmetry and Neutrino Masses and Mixings
Based on a universal seesaw mass matrix model with three scalars \phi_i, and
by assuming an S_3 flavor symmetry for the Yukawa interactions, the lepton
masses and mixings are investigated systematically. In order to understand the
observed neutrino mixing, the charged leptons (e, \mu, \tau) are regarded as
the 3 elements (e_1, e_2, e_3) of S_3, while the neutrino mass-eigenstates are
regarded as the irreducible representation (\nu_\eta, \nu_\sigma, \nu_\pi) of
S_3, where (\nu_\pi, \nu_\eta) and \nu_\sigma are a doublet and a singlet,
respectively, which are composed of the 3 elements (\nu_1, \nu_2, \nu_3) of
S_3.Comment: 16 pages, no figure, version to appear in EPJ-
Tri-Bimaximal Mixing from Twisted Friedberg-Lee Symmetry
We investigate the Friedberg-Lee (FL) symmetry and its promotion to include
the symmetry, and call that the twisted FL symmetry.Based on the
twisted FL symmetry, two possible schemes are presented toward the realistic
neutrino mass spectrum and the tri-bimaximal mixing.In the first scheme, we
suggest the semi-uniform translation of the FL symmetry.The second one is based
on the permutation family symmetry.The breaking terms, which are twisted
FL symmetric, are introduced.Some viable models in each scheme are also
presented.Comment: 14 pages, no figure. v2: 16 pages, modified some sentences, appendix
added, references added. v3: 14 pages, composition simplified, accepted
version in EPJ
A SUSY SU(5) Grand Unified Model of Tri-Bimaximal Mixing from A4
We discuss a grand unified model based on SUSY SU(5) in extra dimensions and
on the flavour group A4xU(1) which, besides reproducing tri-bimaximal mixing
for neutrinos with the accuracy required by the data, also leads to a natural
description of the observed pattern of quark masses and mixings.Comment: 19 page
The 3-3-1 model with S_4 flavor symmetry
We construct a 3-3-1 model based on family symmetry S_4 responsible for the
neutrino and quark masses. The tribimaximal neutrino mixing and the diagonal
quark mixing have been obtained. The new lepton charge \mathcal{L} related to
the ordinary lepton charge L and a SU(3) charge by L=2/\sqrt{3} T_8+\mathcal{L}
and the lepton parity P_l=(-)^L known as a residual symmetry of L have been
introduced which provide insights in this kind of model. The expected vacuum
alignments resulting in potential minimization can origin from appropriate
violation terms of S_4 and \mathcal{L}. The smallness of seesaw contributions
can be explained from the existence of such terms too. If P_l is not broken by
the vacuum values of the scalar fields, there is no mixing between the exotic
and the ordinary quarks at the tree level.Comment: 20 pages, revised versio
Deviation of Atmospheric Mixing from Maximal and Structure in the Leptonic Flavor Sector
I attempt to quantify how far from maximal one should expect the atmospheric
mixing angle to be given a neutrino mass-matrix that leads, at zeroth order, to
a nu_3 mass-eigenstate that is 0% nu_e, 50% nu_mu, and 50% nu_tau. This is done
by assuming that the solar mass-squared difference is induced by an
"anarchical" first order perturbation, an approach than can naturally lead to
experimentally allowed values for all oscillation parameters. In particular,
both |cos 2theta_atm| (the measure for the deviation of atmospheric mixing from
maximal) and |U_e3| are of order sqrt(Delta m^2_sol/Delta m^2_atm) in the case
of a normal neutrino mass-hierarchy, or of order Delta m^2_sol/Delta m^2_atm in
the case of an inverted one. Hence, if any of the textures analyzed here has
anything to do with reality, next-generation neutrino experiments can see a
nonzero cos 2theta_atm in the case of a normal mass-hierarchy, while in the
case of an inverted mass-hierarchy only neutrino factories should be able to
see a deviation of sin^2 2theta_atm from 1.Comment: 12 pages, no figures, references and acknowledgments adde
Energy Independent Solution to the Solar Neutrino Anomaly including the SNO data
The global data on solar neutrino rates and spectrum, including the SNO
charged current rate, can be explained by LMA, LOW or the energy independent
solution -- corresponding to near-maximal mixing. All the three favour a mild
upward renormalisation of the Cl rate. A mild downward shift of the
neutrino flux is favoured by the energy independent and to a lesser extent the
LOW solution, but not by LMA. Comparison with the ratio of SK elastic and SNO
charged current scattering rates favours the LMA over the other two solutions,
but by no more than .Comment: 18 pages, latex, 3 figure
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