1,978 research outputs found
Hermitian clifford analysis
This paper gives an overview of some basic results on Hermitian Clifford analysis, a refinement of classical Clifford analysis dealing with functions in the kernel of two mutually adjoint Dirac operators invariant under the action of the unitary group. The set of these functions, called Hermitian monogenic, contains the set of holomorphic functions in several complex variables. The paper discusses, among other results, the Fischer decomposition, the Cauchy–Kovalevskaya extension problem, the axiomatic radial algebra, and also some algebraic analysis of the system associated with Hermitian monogenic functions. While the Cauchy–Kovalevskaya extension problem can be carried out for the Hermitian monogenic system, this system imposes severe constraints on the initial Cauchy data. There exists a subsystem of the Hermitian monogenic system in which these constraints can be avoided. This subsystem, called submonogenic system, will also be discussed in the paper
Cosmogenic neutrino fluxes under the effect of active-sterile secret interactions
Ultra High Energy cosmogenic neutrinos may represent a unique opportunity to
unveil possible new physics interactions once restricted to the neutrino sector
only. In the present paper we study the observable effects of a secret
active-sterile interactions, mediated by a pseudoscalar, on the expected flux
of cosmogenic neutrinos. The results show that for masses of sterile neutrinos
and pseudoscalars of hundreds MeV, necessary to evade cosmological,
astrophysical and elementary particle constraints, the presence of such new
interactions can significantly change the energy spectrum of cosmogenic
neutrinos at Earth in the energy range from PeV to ZeV. Interestingly, the
distortion of the spectrum results to be detectable at GRAND apparatus if the
scalar mediator mass is around 250 MeV and the UHECRs are dominated by the
proton component. Larger mediator masses or a chemical composition of UHECRs
dominated by heavier nuclei would require much larger cosmic rays apparatus
which might be available in future.Comment: 10 pages, 3 figure
An anisotropic numerical model for thermal hydraulic analyses: application to liquid metal flow in fuel assemblies
A CFD analysis has been carried out to study the thermal–hydraulic behavior of liquid metal coolant in a fuel assembly of triangular lattice. In order to obtain fast and accurate results, the isotropic two-equation RANS approach is often used in nuclear engineering applications. A different approach is provided by Non-Linear Eddy Viscosity Models (NLEVM), which try to take into account anisotropic effects by a nonlinear formulation of the Reynolds stress tensor. This approach is very promising, as it results in a very good numerical behavior and in a potentially better fluid flow description than classical isotropic models. An Anisotropic Shear Stress Transport (ASST) model, implemented into a commercial software, has been applied in previous studies, showing very trustful results for a large variety of flows and applications. In the paper, the ASST model has been used to perform an analysis of the fluid flow inside the fuel assembly of the ALFRED lead cooled fast reactor. Then, a comparison between the results of wall-resolved conjugated heat transfer computations and the results of a decoupled analysis using a suitable thermal wall-function previously implemented into the solver has been performed and presented
Bump-hunting in the diffuse flux of high-energy cosmic neutrinos
The origin of the bulk of the high-energy astrophysical neutrinos seen by
IceCube, with TeV--PeV energies, is unknown. If they are made in photohadronic,
i.e., proton-photon, interactions in astrophysical sources, this may manifest
as a bump-like feature in their diffuse flux, centered around a characteristic
energy. We search for evidence of this feature, allowing for variety in its
shape and size, in 7.5 years of High-Energy Starting Events (HESE) collected by
the IceCube neutrino telescope, and make forecasts using larger data samples
from upcoming neutrino telescopes. Present-day data reveals no evidence of
bump-like features, which allows us to constrain candidate populations of
photohadronic neutrino sources. Near-future forecasts show promising potential
for stringent constraints or decisive discovery of bump-like features. Our
results provide new insight into the origins of high-energy astrophysical
neutrinos, complementing those from point-source searches.Comment: 29 pages, 13 figure
Hunting for bumps in the diffuse high-energy neutrino flux
The origin of the TeV--PeV astrophysical neutrinos seen by the IceCube
telescope is unknown. If they are made in proton-photon interactions in
astrophysical sources, their spectrum may show bump-like features. We search
for such features in the 7.5-years High-Energy Starting Events (HESE), and
forecast the power of such searches using larger data samples expected from
upcoming telescopes. Present-day data reveals no evidence of bump-like
features, which allows us to constrain candidate populations of photohadronic
neutrino sources. Near-future forecasts show promising potential for stringent
constraints or decisive discovery of bump-like features. Our results provide
new insight into the origins of high-energy astrophysical neutrinos,
complementing those from point-source searches.Comment: Submitted as a proceeding for ICRC 2023. arXiv admin note:
substantial text overlap with arXiv:2301.0002
Slow and fast collective neutrino oscillations: Invariants and reciprocity
The flavor evolution of a neutrino gas can show ''slow'' or ''fast''
collective motion. In terms of the usual Bloch vectors to describe the
mean-field density matrices of a homogeneous neutrino gas, the slow two-flavor
equations of motion (EOMs) are
,
where , , is a unit vector in the mass direction in
flavor space, and . For an
axisymmetric angle distribution, the fast EOMs are
, where
is the Bloch vector for lepton number, is the
velocity along the symmetry axis, , and
. We discuss similarities and differences
between these generic cases. Both systems can have pendulum-like instabilities
(soliton solutions), both have similar Gaudin invariants, and both are
integrable in the classical and quantum case. Describing fast oscillations in a
frame comoving with (which itself may execute pendulum-like
motions) leads to transformed EOMs that are equivalent to an abstract slow
system. These conclusions carry over to three flavors.Comment: 16 pages; typo below Eq. (5) and in Eq. (47) correcte
Kinematic Foot Types in Youth with Equinovarus Secondary to Hemiplegia
Background Elevated kinematic variability of the foot and ankle segments exists during gait among individuals with equinovarus secondary to hemiplegic cerebral palsy (CP). Clinicians have previously addressed such variability by developing classification schemes to identify subgroups of individuals based on their kinematics. Objective To identify kinematic subgroups among youth with equinovarus secondary to CP using 3-dimensional multi-segment foot and ankle kinematics during locomotion as inputs for principal component analysis (PCA), and K-means cluster analysis. Methods In a single assessment session, multi-segment foot and ankle kinematics using the Milwaukee Foot Model (MFM) were collected in 24 children/adolescents with equinovarus and 20 typically developing children/adolescents. Results PCA was used as a data reduction technique on 40 variables. K-means cluster analysis was performed on the first six principal components (PCs) which accounted for 92% of the variance of the dataset. The PCs described the location and plane of involvement in the foot and ankle. Five distinct kinematic subgroups were identified using K-means clustering. Participants with equinovarus presented with variable involvement ranging from primary hindfoot or forefoot deviations to deformtiy that included both segments in multiple planes. Conclusion This study provides further evidence of the variability in foot characteristics associated with equinovarus secondary to hemiplegic CP. These findings would not have been detected using a single segment foot model. The identification of multiple kinematic subgroups with unique foot and ankle characteristics has the potential to improve treatment since similar patients within a subgroup are likely to benefit from the same intervention(s)
Gestational diabetes: An overview with attention for developing countries
AbstractGestational diabetes mellitus (GDM) is defined as a glucose intolerance that occurs for the first time or it is first identified during pregnancy. The GDM etiology is multifactorial. It has not completely been established yet and several known risk factors may contribute to its onset. To date, there are no shared guidelines on the management and follow-up, especially regarding the low-income countries. In this paper, we describe the state of art about epidemiology, physiopathology, diagnosis, and management of GDM. Moreover, we focus on the current state in low income countries trying to outline basis for further research
Collective neutrino-antineutrino oscillations in dense neutrino environments?
The paradigm-changing possibility of collective neutrino-antineutrino
oscillations was recently advanced in analogy to collective flavor
oscillations. However, the amplitude for the backward scattering process
is helicity-suppressed and vanishes for massless neutrinos, implying that there
is no off-diagonal refractive index between and of a
single flavor of massless neutrinos. For a nonvanishing mass, collective
helicity oscillations are possible, representing de-facto --
oscillations in the Majorana case. However, such phenomena are suppressed by
the smallness of neutrino masses as discussed in the previous literature.Comment: 3 pages, 2 figures, with appendice
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