Optical Evidence of Itinerant-Localized Crossover of 4f4f Electrons in Cerium Compounds

Cerium (Ce)-based heavy-fermion materials have a characteristic double-peak structure (mid-IR peak) in the optical conductivity [$\sigma(\omega)$] spectra originating from the strong conduction ($c$)--$f$ electron hybridization. To clarify the behavior of the mid-IR peak at a low $c$-$f$ hybridization strength, we compared the $\sigma(\omega)$ spectra of the isostructural antiferromagnetic and heavy-fermion Ce compounds with the calculated unoccupied density of states and the spectra obtained from the impurity Anderson model. With decreasing $c$-$f$ hybridization intensity, the mid-IR peak shifts to the low-energy side owing to the renormalization of the unoccupied $4f$ state, but suddenly shifts to the high-energy side owing to the $f$-$f$ on-site Coulomb interaction at a slight localized side from the quantum critical point (QCP). This finding gives us information on the change in the electronic structure across QCP.Comment: 6 pages, 4 figures. To appear in JPSJ (Letters

Little IIB Matrix Model

We study the zero-dimensional reduced model of D=6 pure super Yang-Mills theory and argue that the large N limit describes the (2,0) Little String Theory. The one-loop effective action shows that the force exerted between two diagonal blocks of matrices behaves as 1/r^4, implying a six-dimensional spacetime. We also observe that it is due to non-gravitational interactions. We construct wave functions and vertex operators which realize the D=6, (2,0) tensor representation. We also comment on other "little" analogues of the IIB matrix model and Matrix Theory with less supercharges.Comment: 17 pages, references adde

The phase separation behavior of poly(vinyl methyl ether)/polystyrene semi-IPN/

The effect of crosslinking on the phase stability and phase separation behavior of poly(vinyl methyl ether)/polystyrene semi-IPN was studied by light scattering. The cloud point temperature was measured as a function of degree of crosslinking and found to be constant within experimental precision. The result of this experiment was combined with a theoretical prediction of the phase diagram to determine conditions for the following experiment. Wide angle light scattering was used to quantitatively analyze the mechanism and dynamics of the thermally induced phase separation with respect to the crosslinking density and the thermal condition. An apparatus with a one dimensional diode array was used to simultaneously monitor a wide range of scattering angles. Analysis of the early stages of phase separation indicates that the spinodal temperature remained virtually constant whether or not crosslinks were present in the system. This was demonstrated to be consistent with theoretical prediction. However, the apparent diffusion coefficient decreased dramatically with the introduction of crosslinks thus the initial phase separation was slowed down significantly. The final scattering intensity was shown to decrease with increasing crosslinking density. The scattering vector dependence of the scattering intensity was negligible compared with its overall time dependence. A plateau region was observed for some of the scattering intensity data of the semi-IPN systems with respect to time. This indicates that the crosslinks restrict terminal phase contrast and not the size of phase

4/3-Law of Granular Particles Flowing through a Vertical Pipe

Density waves of granular material (sand) flowing through a vertical pipe have been investigated. Clear density waves emerge when the cock attached to bottom end of the pipe is closed. The FFT power spectra were found to show a stable power-law form $P(f) \sim f^{-\alpha}.$ The value of the exponent was evaluated as $\alpha \cong 4/3$. We also introduce a simple one-dimensional model which reproduces $\alpha = 4/3$ from both simulation and theoretical analysis. (to be published in Phys.Rev.Lett.)Comment: 4 pages, 4 figures, a style fil