Deflection angle of light in an Ellis wormhole geometry

We reexamine the light deflection by an Ellis wormhole. The bending angle as a function of the ratio between the impact parameter and the throat radius of the wormhole is obtained in terms of a complete elliptic integral of the first kind. This result immediately yields asymptotic expressions in the weak field approximation. It is shown that an expression for the deflection angle derived (and used) in recent papers is valid at the leading order but it breaks down at the next order because of the nontrivial spacetime topology.Comment: 3 pages, accepted by PR

Coherent driving and freezing of bosonic matter wave in an optical Lieb lattice

While kinetic energy of a massive particle generally has quadratic dependence on its momentum, a flat, dispersionless energy band is realized in crystals with specific lattice structures. Such macroscopic degeneracy causes the emergence of localized eigenstates and has been a key concept in the context of itinerant ferromagnetism. Here we report the realization of a "Lieb lattice" configuration with an optical lattice, which has a flat energy band as the first excited state. Our optical lattice potential possesses various degrees of freedom about its manipulation, which enables coherent transfer of a Bose-Einstein condensate into the flat band. In addition to measuring lifetime of the flat band population for different tight-binding parameters, we investigate the inter-sublattice dynamics of the system by projecting the sublattice population onto the band population. This measurement clearly shows the formation of the localized state with the specific sublattice decoupled in the flat band, and even detects the presence of flat-band breaking perturbations, resulting in the delocalization. Our results will open up the possibilities of exploring physics of flat band with a highly controllable quantum system.Comment: 13 pages, 9 figures. v2: Title changed, 1 reference correcte

Low pressure DC-plasma system for the modification of polymeric membrane surfaces

The main objectives of this work were to develop a lab-scale direct current (DC) glow discharges plasma system for modification of organic and inorganic membranes. Characteristics of plasma system were presented under the discharge of five gases (Ar, N2, air, O2, and CO2). A Langmuir double probe was used for the evaluation of the electron temperature (Te) and electron density (ne) of plasmas. The current and voltage (I-V) characteristic curves were analyzed. Relationships between breakdown voltage (VB) of gases and products of gas pressure and inter-electrode gap (pd) were studied in form of Paschen curves. The results showed that Te of plasma in various gases was in the range of 4-13 eV, while the ne varied between 108 and 109 cm-3. The plasma generated at different gas pressure and applied voltage is in the normal and abnormal modes. Finally, the constructed DC-plasma system was utilized for modification of polymeric membrane surfaces. Treatment time, discharge power and type of gas were varied. The tailoring of membrane surfaces was analyzed through the water contact angle and percent-weight loss (PWL) measurements, DMTA, AFM, XPS and FTIR spectrum. It could be shown that DC-plasma from this system can be used to modify the surface of polymeric membranes

Swelling of a V-5Fe Alloy After Irradiation in JOYO

Void swelling behavior of a vanadium iron binary alloy has been studied using JOYO as an irradiation facility. The swelling at a damage level of approximately 14dpa was as high as 30% for 600℃ irradiation, which is qualitatively consistent with the large swelling observed after FFTF/MOTA irradiation about 30dpa. The evolution of dislocation microstructure is very fast and the sink strength ratio Q is much greater than unity except for the highest damage level studied, yet the swelling rate is more than 2%/dpa. Several possible mechanisms involving segregation effects have been discussed. It has been suggested that any successful model should be capable of predicting the observed swelling rate more than 2%/dpa under condition of Q value much greater than unity