Ghost imaging without beam splitter

Many significant results have been achieved in the fields of ghost imaging, in which the beam splitter is an indispensable optical component. This paper introduces a method to realize ghost imaging without beam splitter. And we study this method experimentally and theoretically. Finally, we suggest that our device can be applied to implement the ghost imaging when we use the Sun light as the light source

A New HDG Method for Dirichlet Boundary Control of Convection Diffusion PDEs II: Low Regularity

In the first part of this work, we analyzed a Dirichlet boundary control problem for an elliptic convection diffusion PDE and proposed a new hybridizable discontinuous Galerkin (HDG) method to approximate the solution. For the case of a 2D polygonal domain, we also proved an optimal superlinear convergence rate for the control under certain assumptions on the domain and on the target state. In this work, we revisit the convergence analysis without these assumptions; in this case, the solution can have low regularity and we use a different analysis approach. We again prove an optimal convergence rate for the control, and present numerical results to illustrate the convergence theory

Energy Spectra of Anti-nucleons in Finite Nuclei

The quantum vacuum in a many-body system of finite nuclei has been investigated within the relativistic Hartree approach which describes the bound states of nucleons and anti-nucleons consistently. The contributions of the Dirac sea to the source terms of the meson-field equations are taken into account up to the one-nucleon loop and one-meson loop. The tensor couplings for the $\omega$- and $\rho$-meson are included in the model. The overall nucleon spectra of shell-model states are in agreement with the data. The calculated anti-nucleon spectra in the vacuum differ about 20 -- 30 MeV with and without the tensor-coupling effects.Comment: 4 pages, to appear in the Proceedings of MENU 2004 (Beijing, Aug. 29 -- Sept. 4, 2004

Improved cosmological constraints on the curvature and equation of state of dark energy

We apply the Constitution compilation of 397 supernova Ia, the baryon acoustic oscillation measurements including the $A$ parameter, the distance ratio and the radial data, the five-year Wilkinson microwave anisotropy probe and the Hubble parameter data to study the geometry of the universe and the property of dark energy by using the popular Chevallier-Polarski-Linder and Jassal-Bagla-Padmanabhan parameterizations. We compare the simple $\chi^2$ method of joined contour estimation and the Monte Carlo Markov chain method, and find that it is necessary to make the marginalized analysis on the error estimation. The probabilities of $\Omega_k$ and $w_a$ in the Chevallier-Polarski-Linder model are skew distributions, and the marginalized $1\sigma$ errors are $\Omega_m=0.279^{+0.015}_{-0.008}$, $\Omega_k=0.005^{+0.006}_{-0.011}$, $w_0=-1.05^{+0.23}_{-0.06}$, and $w_a=0.5^{+0.3}_{-1.5}$. For the Jassal-Bagla-Padmanabhan model, the marginalized $1\sigma$ errors are $\Omega_m=0.281^{+0.015}_{-0.01}$, $\Omega_k=0.000^{+0.007}_{-0.006}$, $w_0=-0.96^{+0.25}_{-0.18}$, and $w_a=-0.6^{+1.9}_{-1.6}$. The equation of state parameter $w(z)$ of dark energy is negative in the redshift range $0\le z\le 2$ at more than $3\sigma$ level. The flat $\Lambda$CDM model is consistent with the current observational data at the $1\sigma$ level.Comment: 10 figures, 12 pages, Classical and Quantum Gravity in press; v2 to match the pulished versio

Seething Horizontal Magnetic Fields in the Quiet Solar Photosphere

The photospheric magnetic field outside of active regions and the network has a ubiquitous and dynamic line-of-sight component that strengthens from disk center to limb as expected for a nearly horizontal orientation. This component shows a striking time variation with an average temporal rms near the limb of 1.7 G at ~3" resolution. In our moderate resolution observations the nearly horizontal component has a frequency variation power law exponent of -1.4 below 1.5 mHz and is spatially patchy on scales up to ~15 arcsec. The field may be a manifestation of changing magnetic connections between eruptions and evolution of small magnetic flux elements in response to convective motions. It shows no detectable latitude or longitude variations.Comment: 7 pages, 6 figures, submitted to ApJ letters, quality of figures significantly degraded here by compression requirement

Non-Parametric Estimation of Copula Parameters: Testing for Time-Varying Correlation

The correlation structure of financial assets is a key input with regard to portfolio and risk management. In this paper, we propose a non-parametric estimation method for the time-varying copula parameter. This is achieved in two steps: first, displaying the marginal distributions of financial asset returns by applying the empirical distribution function; second, by implementing the local likelihood method to estimate the copula parameters. The method for obtaining the optimal bandwidth through a maximum pseudo likelihood function and a statistical test on whether the copula parameter is time-varying are also introduced. A simulation study is conducted to show that our method is superior to its contender. Finally, we verify the proposed estimation methodology and time-varying statistical test by analysing the dynamic linkages between the Shanghai, Shenzhen and Hong Kong stock markets