Resistance and Reactance of Monopole Fields Induced by a Test Charge Drifting Off-Axis in a Cold and Collisional Cylindrical Plasma

We study the interaction of a uniform, cold and collisional plasma with a test charged particle moving off-axis at a constant speed down a cylindrical tube with a resistive thick metallic wall. Upon matching the electromagnetic field components at all interfaces, the induced monopole electromagnetic fields in the plasma are obtained in the frequency domain. An expression for the plasma electric resistance and reactance is derived and analyzed numerically for some representative parameters. Near the plasma resonant frequency, the plasma resistance evolves with frequency like a parallel RLC resonator with peak resistance at the plasma frequency pe, while the plasma reactance can be capacitive or inductive in nature depending on the frequency under consideration.

Relic Gravitational Waves and Trans-Planckian Physics

Assuming that the effects of trans-Planckian physics are encoded in the choice of initial conditions, mode by mode, for vacuum states at the time when its wavelength becomes equal to the scale of new physics （Planck＇s scale for example）, we calculate the spectrum of energy densities of total relic gravitational waves from de Sitter inflation to the matter dominated universe. Our results show that the spectrum acquires corrections due to the consideration of trans-Planckian physics and these corrections depend sensitively on the vacuum state that was actually realized at the beginning of the inflation.

Finite Temperature Casimir Effect for Corrugated Plates

Using the path-integral method, the corrections to the Casimir energy due to the combined effect of surface roughness and the finite temperature are calculated. For the specific case of two sinusoidally corrugated plates, the lateral Casimir force at finite temperature is obtained. The amplitude of the lateral Casimir force has a maximum at an optimal wavelength of λ≈ 2H with the mean plate distance H. This optimal parameter relation is almost independent of temperature.

Spontaneous Emission of an Inertial Multi-Level Atom in a Spacetime with a Reflecting Plane Boundary

We calculate the contributions of the vacuum fluctuations and radiation reaction to the rate of change of the mean atomic energy for a multi-level hydrogen atom in the multipolar coupling scheme in a spacetime with a reflecting boundary. Our results show that, due to the presence of the boundary, the polarizations of the atom in the parallel direction and in the normal direction are weighted differently in terms of their contributions to the spontaneous emission rate, which is an oscillating function of the atom distance from the boundary. The possible experimental implications of our result are briefly discussed.

Lorentz Invariance and Brownian Motion of Test Particles with Constant Classical Velocity in Electromagnetic Vacuum

We show that the velocity and position dispersions of a test particle with a nonzero constant classical velocity undergoing Brownian motion caused by electromagnetic vacuum fluctuations in a space with plane boundaries can be obgained from those of the static case by Lorentz transformation. We explicitly derive the Lorentz transformations relating the dispersions of the two cases and then apply them to the case of the Brownian motion of a test particle with a constant classical velocity parallel to the boundary between two conducting planes. Our results show that the influence of a nonzero initial velocity is negligible for nonrelativistic test particles.

Effect of different carbon precursors on properties of LiFePO_4/C

The anoxic decomposition and influence of carbon precursors on the properties of LiFePO_4/C prepared by using Fe_2O_3 were investigated.X-ray powder diffractometry,Fourier transform infrared spectroscopy(FTIR),scanning electron microscopy(SEM) and carbon content and charge–discharge tests were applied to the characterization of the as-synthesized cathodes.Partial carbon is lost in the anaerobic decomposition of organic precursors and a high hydrogen content leads to a high residual carbon rate.Pyromellitic anhydride and citric acid participate in reactions before and in ball-milling.All the chosen carbon precursors are capable of producing LiFePO_4 with high degree of crystallinity and purity.The carbon derived from α-D-glucose,pyromellitic anhydride,soluble starch,citric acid and polyacrylamide has a loose and porous texture in LiFePO_4/C which forms conduction on and between LiFePO_4 particles.LiFePO_4/C prepared by using α-D-glucose,pyromellitic anhydride,citric acid and sucrose exhibits appreciable electrochemical performance.Graphite alone is able to enhance the electrochemical performance of LiFePO_4 to a limited extent but incapable of preparing practical cathode.