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 $\omega_2/\omega_1=$1:2. We investigate THz generation with uncommon frequency ratios. Our experiments show, for the first time, efficient THz generation with new ratios of $\omega_2/\omega_1=$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 K/πK/\pi 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 28.69$\pm$2.09 muons per day with a modulation amplitude of 2.66$\pm$ 1.0\% and a phase at Jul 22 $\pm$ 36.2 days. This annual modulation is correlated with the variation of the effective atmospheric temperature in the stratosphere. The correlation coefficient, $\alpha_{T}$, is determined to be $0.898 \pm 0.025$. This can be interpreted as a measurement of the atmospheric charged kaon to pion ($K$/$\pi$) ratio of 0.094$^{+0.044}_{-0.061}$ for $E_{p} >$ 7 TeV, consistent with the measurement from the MINOS far detector. To further constrain the value of $K$/$\pi$ ratio, a Geant4 simulation of the primary cosmic-ray protons with energy up to 100 TeV is implemented to study the correlation of $K$/$\pi$ ratio and the muon annual modulation for muon energy greater than 0.5 TeV. We find out that a charged $K$/$\pi$ 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