350,445 research outputs found
Mass neutrino flavor evolution in spacetime with torsion
In the framework of the spacetime with torsion, we obtain the flavor
evolution equation of the mass neutrino oscillation in vacuum. A comparison
with the result of general relativity case, it shows that the flavor
evolutionary equations in Riemann spacetime and Weitzenb\"ock spacetimes are
equivalent in the spherical symmetric Schwarzschild spacetime, but turns out to
be different in the case of the axial symmetry.Comment: 8 papes, no fiur
Observation of Terahertz Radiation via the Two-Color Laser Scheme with Uncommon Frequency Ratios
In the widely-studied two-color laser scheme for terahertz (THz) radiation
from a gas, the frequency ratio of the two lasers is usually fixed at
1:2. We investigate THz generation with uncommon frequency
ratios. Our experiments show, for the first time, efficient THz generation with
new ratios of 1:4 and 2:3. We observe that the THz
polarization can be adjusted by rotating the longer-wavelength laser
polarization and the polarization adjustment becomes inefficient by rotating
the other laser polarization; the THz energy shows similar scaling laws with
different frequency ratios. These observations are inconsistent with multi-wave
mixing theory, but support the gas-ionization model. This study pushes the
development of the two-color scheme and provides a new dimension to explore the
long-standing problem of the THz generation mechanism.Comment: 6 pages, 3 figure
Atmospheric Charged Ratio and Measurement of Muon Annual Modulation with a Liquid Scintillation Detector at Soudan
We report a measurement of muon annual modulation in a 12-liter liquid
scintillation detector with a live-time of more than 4 years at the Soudan
Underground Laboratory. Muon minimum ionization in the detector is identified
by its observed pulse shape and large energy deposition. The measured muon rate
in the detector is 28.692.09 muons per day with a modulation amplitude of
2.66 1.0\% and a phase at Jul 22 36.2 days. This annual modulation
is correlated with the variation of the effective atmospheric temperature in
the stratosphere. The correlation coefficient, , is determined to
be . This can be interpreted as a measurement of the
atmospheric charged kaon to pion (/) ratio of 0.094
for 7 TeV, consistent with the measurement from the MINOS far
detector. To further constrain the value of / ratio, a Geant4
simulation of the primary cosmic-ray protons with energy up to 100 TeV is
implemented to study the correlation of / ratio and the muon annual
modulation for muon energy greater than 0.5 TeV. We find out that a charged
/ ratio of 0.1598, greater than the upper bound (0.138) from this work
at the production point 30 km above the Earth surface in the stratosphere
cannot induce muon annual modulation at the depth of Soudan.Comment: 6 pages and 11 figure
A Conservative Discontinuous Galerkin Scheme With O(N-2) Operations In Computing Boltzmann Collision Weight Matrix
In the present work, we propose a deterministic numerical solver for the homogeneous Boltzmann equation based on Discontinuous Galerkin (DG) methods. The weak form of the collision operator is approximated by a quadratic form in linear algebra setting. We employ the property of >shifting symmetry> in the weight matrix to reduce the computing complexity from theoretical O(N-3) down to O(N-2), with N the total number of freedom for d-dimensional velocity space. In addition, the sparsity is also explored to further reduce the storage complexity. To apply lower order polynomials and resolve loss of conserved quantities, we invoke the conservation routine at every time step to enforce the conservation of desired moments (mass, momentum and/or energy), with only linear complexity. Due to the locality of the DG schemes, the whole computing process is well parallelized using hybrid OpetiMP and MPI. The current work only considers integrable angular cross-sections under elastic and/or inelastic interaction laws. Numerical results on 2-D and 3-D problems are shown.Mathematic
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