Intraplanar couplings in the CuO_2 lattice of cuprate superconductors

We have investigated the doping dependencies of the basal areas in single-layer high-T_c cuprates La_{2-x}Sr_xCuO_4 and HgBa_2CuO_x, as well as in two-layer Y_{1-y}Ca_yBa_2Cu_3O_x and HgBa_2CaCu_2O_x. The basal areas not only tend to shrink on hole doping, as expected from single electron quantum chemistry, but exhibit also a "bulge'' around optimum doping. We attribute the "bulge'' to the effects of the strongly correlated quantum liquid on the CuO_2 lattice, rendering it nearly incompressible around optimum doping, but highly compressible in the weakly overdoped regime. Inhomogenous doping cannot account for this anomaly in the electronic compressibility of the CuO_2 lattice.Comment: 2 pages, 2 figures, to appear in Physica C (Proc. M2S-HTSC-VII

Dilatonic Inflation, Gravitino and Reheating in Modified Modular invariant Supergravity

A new modified string-inspired modular invariant supergravity model is proposed and is applied to realize the slow roll inflation in Einstein frame, so that the model explains WMAP observations very well. Gravitino mass and their production rate from scalar fields are estimated at certain values of parameters in the model. Seven cases of parameter choices are discussed here, among which some examples show the possibility of observation of gauginos by LHC experiments, which will give some hints of identity of dark matters. The reheating temperature, which is estimated by the stability condition of Boltzmann equation by using the decay rates of the dilaton $S$ into gauginos, is lower than the mass of gravitino. Therefore no thermal reproduction of gravitinos happens. The ratio between the scalar and tensor power spectrum is predicted to be almost the same for the seven cases under study, and its value $r \sim 6.8 \times 10^{-2}$ seems in the range possibly observed by the Planck satellite soon. The plausible supergravity model of inflation, which will be described here, will open the hope to construct a realistic theory of particles and cosmology in this framework, including yet undetected objects.Comment: 12 pages, 4 figures, 2 table

Supersymmetry Breaking and Gravitino Production after Inflation in Modular Invariant Supergravity

By using a string-inspired modular invariant supergravity, which was proved well to explain WMAP observations appropriately, a mechanism of supersymmetry breaking (SSB) and Gravitino Production just after the end of inflation are investigated. Supersymmetry is broken mainly by F-term of the inflaton superfield and the Goldstino is identified to be inflatino in this model, which fact is shown numerically. By using the canonically normalized and diagonalized scalars, the decay rates of these fields are calculated, for both the $T$ and $Y$ into gravitinos. Non-thermal production of gravitinos is not generated from the inflaton (dilaton), since the inflaton mass is lighter than gravitino, but they are produced by the decay of modular field $T$ and scalar field $Y$. Because the reheating temperature $T_R$ is about order $\sim O(10^{10})$ GeV and the mass of gravitino is $3.16 \times 10^{12}$ GeV, it is not reproduced after the reheating of the universe. The gravitinos are produced almost instantly just after the end of inflation through $Y$ and $T$, not from inflaton. Because the decay time appears very rapid, gravitinos disappear before the BBN stage of the universe. The effects of the lightest supersymmetric particles (LSP) produced by gravitinos may be important to investigate more carefully, if the LSP's are the candidate of dark matter.Comment: 11 pages, 1 figure

Stamina of a non-gasketed flange joint under combined internal pressure and axial loading

The performance of a bolted flange joint is characterized mainly by its 'strength' and 'sealing capability'. A number of numerical and experimental studies have been conducted to study these characteristics under internal pressure loading conditions alone. However, limited work is found in the literature under conditions of combined internal pressure and axial loading. The effect of external, axial loading pressure being unknown, the optimal performance of the bolted flange joint cannot be achieved. Current design codes do not address the effects of axial loading on structural integrity and sealing ability. To study joint strength and sealing capability under combined loading conditions, an extensive experimental and numerical study of a non-gasketed flange joint was carried out. Actual joint load capacity was determined at both design and test stages with the maximum external axial loading that can be applied for safe joint performance. Experimental and numerical results have been compared and overall joint performance and behaviour is discussed in detail

Glasslike vs. crystalline thermal conductivity in carrier-tuned Ba8Ga16X30 clathrates (X = Ge, Sn)

The present controversy over the origin of glasslike thermal conductivity observed in certain crystalline materials is addressed by studies on single-crystal x-ray diffraction, thermal conductivity k(T) and specific heat Cp(T) of carrier-tuned Ba8Ga16X30 (X = Ge, Sn) clathrates. These crystals show radically different low-temperature k(T) behaviors depending on whether their charge carriers are electrons or holes, displaying the usual crystalline peak in the former case and an anomalous glasslike plateau in the latter. In contrast, Cp(T) above 4 K and the general structural properties are essentially insensitive to carrier tuning. We analyze these combined results within the framework of a Tunneling/Resonant/Rayleigh scatterings model, and conclude that the evolution from crystalline to glasslike k(T) is accompanied by an increase both in the effective density of tunnelling states and in the resonant scattering level, while neither one of these contributions can solely account for the observed changes in the full temperature range. This suggests that the most relevant factor which determines crystalline or glasslike behavior is the coupling strength between the guest vibrational modes and the frameworks with different charge carriers.Comment: 8 pages, 4 figures, 4 tables, submitted to Phys. Rev.