Effect of higher harmonics in quarter-filled Su-Schrieffer-Heeger model

The role of the higher harmonics of the order parameter in the ground state of the quarter-filled Su-Schrieffer-Heeger model is investigated. The lowest energy is obtained when the 4k_F order parameter Δ₂ vanishes. Furthermore, as far as the uniform excitations are concerned, the energy of the system has a minimum at a finite value of Δ₂ when the phase of the fundamental (or 2k_F) order parameter deviates from its ground state values.     

Metal-to-insulator crossover in the low-temperature normal state of Bi(2)Sr(2-x)La(x)CuO(6+delta)

We measure the normal-state in-plane resistivity of Bi(2)Sr(2-x)La(x)CuO(6+delta) single crystals at low temperatures by suppressing superconductivity with 60 T pulsed magnetic fields. With decreasing hole doping, we observe a crossover from a metallic to an insulating behavior in the low-temperature normal state. This crossover is estimated to occur near 1/8 doping, well inside the underdoped regime, and not at optimum doping as reported for other cuprates. The insulating regime is marked by a logarithmic temperature dependence of the resistivity over two decades of temperature, suggesting that a peculiar charge localization is common to the cuprates.     

Eichler–Shimura theory for mock modular forms

We use mock modular forms to compute generating functions for the critical values of modular $L$ -functions, and we answer a generalized form of a question of Kohnen and Zagier by deriving the “extra relation” that is satisfied by even periods of weakly holomorphic cusp forms. To obtain these results we derive an Eichler–Shimura theory for weakly holomorphic modular forms and mock modular forms. This includes two “Eichler–Shimura isomorphisms”, a “multiplicity two” Hecke theory, a correspondence between mock modular periods and classical periods, and a “Haberland-type” formula which expresses Petersson’s inner product and a related antisymmetric inner product on $M_{k}^{!}$ in terms of periods.     

On the Existence of p-Bases and -Adic p-Bases of a Semi-Local Ring Extension

Let R ^p  ? R′ ? R be a tower of Noetherian semi-local rings of prime characteristic p. When R has locally p-bases over R′ which consist of countably infinite elements, we show the existence of a countably infinite subset {? _i } _i?? of R such that {? _i } _i?? is p-independent over R′, R′[? _i ] _i?? is Noetherian, and R = R′[? _i ] _i?? + ? ^{′ l} R for all l ? ?, where ?′ is the Jacobson radical of R′. Moreover, we consider the existence of p-bases in the case of a tower of semi-local affine k-algebras.     

Anomalous resistance ridges along filling factor nu=4i

We report anomalous structure in the magnetoresistance of SiO(2)/Si(100)/SiO(2) quantum wells. When Landau levels of opposite valleys are driven through coincidence at the Fermi level, the longitudinal resistance displays elevations at filling factors that are integer multiples of 4 (nu=4i) accompanied by suppression on either side of nu=4i. This persists when either the magnetic field or the valley splitting is swept, leading to resistance ridges running along nu=4i. The range of field over which they are observed points to the role of spin degeneracy, which is directly confirmed by their disappearance with the addition of an in-plane magnetic field. The data suggest a new type of many-body effect arising from the combined degeneracy due to the valley and the spin degrees of freedom.     

10 GHz regeneratively mode-locked semiconductor optical amplifier fiber ring laser and its linewidth characteristics

A 10 GHz regeneratively mode-locked semiconductor optical amplifier fiber ring laser with a picosecond pulse duration was newly constructed, and the linewidth change of a longitudinal mode was measured for various laser cavity lengths using a delayed self-heterodyne detection method. The detected line shape was approximately Gaussian for cavity lengths of 3.4-171 m. This result indicates that the laser linewidth depends strongly on thermal or acoustic cavity length fluctuations. The linewidth was proportional to the inverse square root of the cavity length, and a linewidth of 1.7 kHz was obtained for a cavity length of 171 m.     

Two new steroid glycosides and a new sesquiterpenoid glycoside from the underground parts of Trillium kamtschaticum

Two new steroid glycosides, named trikamsterosides A and B, and a new sesquiterpenoid glycoside named trikamsesuquiside A were isolated from the underground parts of Trillium kamtschaticum PALL. along with 18 known compounds comprising 12 steroids, one sesquiterpenoid glycoside, one phenylpropanoid, one flavonoid glycoside, and three phenylpropanoid sucrose esters. Their chemical structures were determined on the basis of spectroscopic data and chemical evidence. Among them, one phenylpropanoid sucrose ester showed almost the same radical-scavenging effect on 1,1-diphenyl-2-picrylhydrazyl as that of alpha-tocopherol.