Yu Hong-Wei

The Motion of a Gyroscope Freely Falling Along the Radial Geodesic in the Space-Time of a Black Hole with a Global Monopole

By means of the orthonormal frame, the motion of the axis of a gyroscope freely falling along the radial geodesic in the space-time of a black hole with a global monopole is investigated. It is shown that the axis of the gyroscope rotates about the radial direction as it falls into the black hole.

Gravitational Field of a Rotating, Arbitrarily Accelerating Mass

A new metric depending on five arbitrary parameters is obtained by the method of complex coordinate transformations. It gives the gravitational field of a mass source with both arbitrary acceleration and rotation.

Fabrication of rhenium Josephson junctions

Rhenium is a superconductor with a relatively weak tendency to oxidize, which is advantageous in superconducting quantum circuit and qubit applications. In this work, Re/Al—AlOx/Re Josephson tunnel junctions were fabricated using a selective film-etching process similar to that developed in Nb trilayer technology. The Re films had a superconducting transition temperature of 4.8 K and a transition width of 0.2 K. The junctions were found to be highly reproducible using the fabrication process and their characteristics had good quality with a low leakage current and showed a superconducting gap of 0.55 meV.

Vacuum polarization of scalar electrodynamics in flat space-time with nontrivial topology

The one-loop vacuum polarization is calculated for scalar electrodynamics in a flat space-time with the topology S1×R3. The effect of vacuum polarization upon photon propagation is considered. It is found that photon propagation becomes anisotropic with some photon modes acquiring a positive topological mass and thus travelling at a subluminal speed.

Back Reaction of Evaporating Black Holes Attached to Global Monopoles

The back reaction of evaporating black holes with internal global monopoles is studied by examining the Klein-Gordon equation near the event horizon and computing the renormalized expectation value of the stress-energy tensor for conformally invariant massless scalar fields in two dimensions. The effective radiation temperature up to O() is found.

Inflationary dynamics in the braneworld scenarios

We analyze the attractor behaviour of the inflation field in braneworld scenarios using the Hamilton—Jacobi formalism, where the Friedmann equation has the form of or H2 = ρ+ρ2/2σ, with = ±1. We find that in all models the linear homogeneous perturbation can decay exponentially as the scalar field rolls down its potential. However, in the case of a −ρ2 correction to the standard cosmology with ρ 1. Our results show that the perturbation decays more quickly in models with positive-energy correction than in the standard cosmology, which is opposite to the case of negative-energy correction. Thus, the positive-energy modification rather than the negative one can assist the inflation and widen the range of initial conditions.

Restrictions on negative energy density for the Dirac field in flat spacetime

This paper investigates the quantum Dirac field in n+1-dimensional flat spacetime and derives a lower bound in the form of quantum inequality on the energy density averaged against spacetime sampling functions. The state-independent quantum inequality derived in the present paper is similar to the temporal quantum energy inequality and it is stronger for massive field than for massless one. It also presents the concrete results of the quantum inequality in 2 and 4-dimensional spacetimes.

Vacuum Polarization of Twisted Scalars in a Non-simply Connected Space-time and Its Effects

The vacuum polarization due to twisted scalar fields is investigated in a non-simply connected space-time. It is found that some photon modes acquire an imaginary topological mass, thus travelling at a superluminal speed. Topological bi-refringence is expected for photons propagating perpendicularly to the compactification direction. The effect of a topological photon mass on the static properties of electromagnetic fields is also considered for the cases of both twisted and untwisted scalar fields. Our result shows that in the untwisted case the magnetic field is screened along the radial direction for massive photon modes, while in the twisted case no screening occurs and the magnetic fields merely oscillate.