32,230 research outputs found
Solar neutrinos and the MSW effect for three-neutrino mixing
Researchers considered three-neutrino Mikheyev-Smirnov-Wolfenstein (MSW) mixing, assuming m sub 3 is much greater than m sub 2 is greater than m sub 1 as expected from theoretical consideration if neutrinos have mass. They calculated the corresponding mixing parameter space allowed by the Cl-37 and Kamiokande 2 experiments. They also calculated the expected depletion for the Ga-71 experiment. They explored a range of theoretical uncertainty due to possible astrophysical effects by varying the B-8 neutrino flux and redoing the MSW mixing calculation
Peculiar Hubble Flows in Our Local Universe
A formalism that simultaneously searches for the monopolar and dipolar
peculiar velocities is presented. The formalism is applied to (1) the Mark III
catalogue, (2) Lauer and Postman's Abell cluster catalogue, and (3) Riess et
al.'s Type Ia supernova sample. The emphasis is drawn to the monopolar peculiar
velocities, i.e., peculiar Hubble flows, within these samples. The samples show
inconsistent peculiar Hubble flows within a depth of Mpc.
Beyond a depth of Mpc, the Hubble flows of all samples converge
to the global Hubble flow to better than 10% at the level. The
results are compared with theoretical predictions. They at face value disfavor
models predicting smaller peculiar velocities such as the tilted Cold Dark
Matter model. Limitations of the catalogues are discussed, so are ways to
improve the catalogues so that an accurate map of Hubble flows in our local
universe can be drawn and be compared with theoretical predictions.Comment: 20 latex pages and 8 figures. Final versio
X-ray ptychography on low-dimensional hard-condensed matter materials
Tailoring structural, chemical, and electronic (dis-)order in heterogeneous media is one of the transformative opportunities to enable new functionalities and sciences in energy and quantum materials. This endeavor requires elemental, chemical, and magnetic sensitivities at the nano/atomic scale in two- and three-dimensional space. Soft X-ray radiation and hard X-ray radiation provided by synchrotron facilities have emerged as standard characterization probes owing to their inherent element-specificity and high intensity. One of the most promising methods in view of sensitivity and spatial resolution is coherent diffraction imaging, namely, X-ray ptychography, which is envisioned to take on the dominance of electron imaging techniques offering with atomic resolution in the age of diffraction limited light sources. In this review, we discuss the current research examples of far-field diffraction-based X-ray ptychography on two-dimensional and three-dimensional semiconductors, ferroelectrics, and ferromagnets and their blooming future as a mainstream tool for materials sciences
Study on the variation law of temperature field in three-roll skew rolling of variable diameter specimen
This paper takes the simplified high-speed train hollow axle variable diameter section sample as the research object, uses Simufact.Forming simulation software for simulation, analyze the rolling piece inner variable diameter section, equal diameter section, outer variable diameter section three stages in the forming process of temperature field distribution characteristics and variation, and discusses the causes of temperature field variation
Study on the variation law of temperature field in three-roll skew rolling of variable diameter specimen
This paper takes the simplified high-speed train hollow axle variable diameter section sample as the research object, uses Simufact.Forming simulation software for simulation, analyze the rolling piece inner variable diameter section, equal diameter section, outer variable diameter section three stages in the forming process of temperature field distribution characteristics and variation, and discusses the causes of temperature field variation
Neutrino-Mixing-Generated Lepton Asymmetry and the Primordial He Abundance
It has been proposed that an asymmetry in the electron neutrino sector may be
generated by resonant active-sterile neutrino transformations during Big Bang
Nucleosynthesis (BBN). We calculate the change in the primordial He yield
resulting from this asymmetry, taking into account both the time evolution
of the and distribution function and the spectral
distortions in these. We calculate this change in two schemes: (1) a lepton
asymmetry directly generated by mixing with a lighter right-handed
sterile neutrino ; and (2) a lepton asymmetry generated by a
or transformation
which is subsequently partially converted to an asymmetry in the
sector by a matter-enhanced active-active neutrino
transformation. In the first scheme, we find that the percentage change in
is between -1% and 9% (with the sign depending on the sign of the asymmetry),
bounded by the Majorana mass limit m_{\nu_e}\la 1 eV. In the second scheme,
the maximal percentage reduction in is 2%, if the lepton number asymmetry
in neutrinos is positive; Otherwise, the percentage increase in is \la 5%
for m^2_{\nu_\mu,\nu_\tau}-m^2_{\nu_s}\la 10^4 eV. We conclude that the
change in the primordial He yield induced by a neutrino-mixing-generated
lepton number asymmetry can be substantial in the upward direction, but limited
in the downward direction.Comment: 15 pages, 7 figures, submitted to PR
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