A 3D Numerical Method for Studying Vortex Formation Behind a Moving Plate

In this paper, we introduce a three-dimensional numerical method for computing the wake behind a flat plate advancing perpendicular to the flow. Our numerical method is inspired by the panel method of J. Katz and A. Plotkin [J. Katz and A. Plotkin, Low-speed Aerodynamics, 2001] and the 2D vortex blob method of Krasny [R. Krasny, Lectures in Appl. Math., 28 (1991), pp. 385--402]. The accuracy of the method will be demonstrated by comparing the 3D computation at the center section of a very high aspect ratio plate with the corresponding two-dimensional computation. Furthermore, we compare the numerical results obtained by our 3D numerical method with the corresponding experimental results obtained recently by Ringuette [M. J. Ringuette, Ph.D. Thesis, 2004] in the towing tank. Our numerical results are shown to be in excellent agreement with the experimental results up to the so-called formation time

Origin of superconductivity in nominally "undoped" T'-La2−x_{2-x}Yx_{x}CuO4_{4} films

We have systematically studied the transport properties of the La$_{2-x}$Y$_{x}$CuO$_{4}$(LYCO) films of T'-phase ($0.05\leq x \leq 0.30$). In this nominally "undoped" system, superconductivity was acquired in certain Y doping range ($0.10\leq x \leq 0.20$). Measurements of resistivity, Hall coefficients in normal states and resistive critical field ($H^\rho_{c2}$)in superconducting states of the T'-LYCO films show the similar behavior as the known Ce-doped n-type cuprate superconductors, indicating the intrinsic electron-doping nature. The charge carriers are induced by oxygen deficiency. Non-superconducting Y-doped Pr- or Nd-based T'-phase cuprate films were also investigated for comparison, suggesting the crucial role of the radii of A-site cations in the origin of superconductivity in the nominally "undoped" cuptates. Based on a reasonable scenario in the microscopic reduction process, we put forward a self-consistent interpretation of these experimental observations.Comment: 8 pages, 9 figure

Quantum-Fluctuation-Initiated Coherence in Multi-Octave Raman Optical Frequency Combs

We show experimentally and theoretically that the spectral components of a multi-octave frequency comb spontaneously created by stimulated Raman scattering in a hydrogen-filled hollow-core photonic crystal fiber exhibit strong self coherence and mutual coherence within each 12 ns driving laser pulse. This coherence arises in spite of the field's initiation being from quantum zero-point fluctuations, which causes each spectral component to show large phase and energy fluctuations. This points to the possibility of an optical frequency comb with nonclassical correlations between all comb lines.Comment: Accepted for publication, Physical Review Letters, 201

Two Higgs Bi-doublet Left-Right Model With Spontaneous P and CP Violation

A left-right symmetric model with two Higgs bi-doublet is shown to be a consistent model for both spontaneous P and CP violation. The flavor changing neutral currents can be suppressed by the mechanism of approximate global U(1) family symmetry. We calculate the constraints from neural $K$ meson mass difference $\Delta m_K$ and demonstrate that a right-handed gauge boson $W_2$ contribution in box-diagrams with mass well below 1 TeV is allowed due to a cancellation caused by a light charged Higgs boson with a mass range $150 \sim 300$ GeV. The $W_2$ contribution to $\epsilon_K$ can be suppressed from appropriate choice of additional CP phases appearing in the right-handed Cabbibo-Kobayashi-Maskawa matrix. The model is also found to be fully consistent with $B^0$ mass difference $\Delta m_B$, and the mixing-induced CP violation quantity $\sin2\beta_{J/\psi}$, which is usually difficult for the model with only one Higgs bi-doublet. The new physics beyond the standard model can be directly searched at the colliders LHC and ILC.Comment: 25 pages, 6 figures, typos corrected, 1 figure added, published versio

Thermodynamic properties of Ba1-xMxFe2As2 (M = La and K)

The specific heat $C(T)$ of BaFe$_2$As$_2$ single crystal, electron-doped Ba$_{0.7}$La$_{0.3}$Fe$_2$As$_2$ and hole-doped Ba$_{0.5}$K$_{0.5}$Fe$_2$As$_2$ polycrystals were measured. For undoped BaFe$_2$As$_2$ single crystal, a very sharp specific heat peak was observed at 136 K. This is attributed to the structural and antiferromagnetic transitions occurring at the same temperature. $C(T)$ of the electron-doped non-superconducting Ba$_{0.7}$La$_{0.3}$Fe$_2$As$_2$ also shows a small peak at 120 K, indicating a similar but weaker structural/antiferromagnetic transition. For the hole-doped superconducting Ba$_{0.5}$K$_{0.5}$Fe$_2$As$_2$, a clear peak of $C/T$ was observed at $T_c$ = 36 K, which is the highest peak seen at superconducting transition for iron-based high-$T_c$ superconductors so far. The electronic specific heat coefficient $\gamma$ and Debye temperature $\Theta_D$ of these compounds were obtained from the low temperature data

Novel dynamical effects and glassy response in strongly correlated electronic system

We find an unconventional nucleation of low temperature paramagnetic metal (PMM) phase with monoclinic structure from the matrix of high-temperature antiferromagnetic insulator (AFI) phase with tetragonal structure in strongly correlated electronic system $BaCo_{0.9}Ni_{0.1}S_{1.97}$. Such unconventional nucleation leads to a decease in resistivity by several orders with relaxation at a fixed temperature without external perturbation. The novel dynamical process could arise from the competition of strain fields, Coulomb interactions, magnetic correlations and disorders. Such competition may frustrate the nucleation, giving rise to a slow, nonexponential relaxation and "physical aging" behavior.Comment: 5 pages, 4 figure