10,310 research outputs found
On the p-adic geometry of traces of singular moduli
The aim of this article is to show that p-adic geometry of modular curves is
useful in the study of p-adic properties of traces of singular moduli. In order
to do so, we partly answer a question by Ono. As our goal is just to illustrate
how p-adic geometry can be used in this context, we focus on a relatively
simple case, in the hope that others will try to obtain the strongest and most
general results. For example, for p=2, a result stronger than Thm.1 is proved
in [Boylan], and a result on some modular curves of genus zero can be found in
[Osburn] . It should be easy to apply our method, because of its local nature,
to modular curves of arbitrary level, as well as to Shimura curves.Comment: 3 pages, Late
Two mechanisms of pseudogap formation in Bi-2201: Evidence from the c-axis magnetoresistance
Measurements of the c-axis resistivity and magnetoresistance have been used
to investigate the pseudogap (PG) behavior in Bi_{2+z}Sr_{2-x-z}La_xCuO_y
(Bi-2201) crystals at various hole densities. While the PG opening temperature
T* increases with decreasing hole doping, the magnetic-field sensitivity of the
PG is found to have a very different trend: it appears at lower temperatures in
more underdoped samples and vanishes in non-superconducting samples. These data
suggest that besides the field-insensitive pseudogap emerging at T*, a distinct
one is formed above T_c as a precursor to superconductivity.Comment: 7 pages, 6 figures, accepted for publication in Europhysics Letters
(initially submitted to PRL on 14 June 2000
High-performance -type organic field-effect transistors with ionic liquid gates
High-performance -type organic field-effect transistors were developed
with ionic-liquid gates and N,N-bis(n-alkyl)-(1,7 and
1,6)-dicyanoperylene-3,4:9,10-bis(dicarboximide)s single-crystals. Transport
measurements show that these devices reproducibly operate in ambient atmosphere
with negligible gate threshold voltage and mobility values as high as 5.0
cm/Vs. These mobility values are essentially identical to those measured in
the same devices without the ionic liquid, using vacuum or air as the gate
dielectric. Our results indicate that the ionic-liquid and -type organic
semiconductor interfaces are suitable to realize high-quality -type organic
transistors operating at small gate voltage, without sacrificing electron
mobility
Core-tube morphology of multiwall carbon nanotubes
The present paper investigates the cross-sectional morphology of Multiwalled
Carbon Nanotubes (MWNTs) restrained radially and circumferentially by an
infinite surrounding elastic medium, subjected to uniform external hydrostatic
pressure. In this study, a two-dimensional plane strain model is developed,
assuming no variation of load and deformation along the tube axis. We find some
characteristic cross-sectional shapes from the elastic buckling analysis. The
effect of the surrounded elastic medium on the cross-sectional shape which
occurs due to pressure buckling is focused on by the comparison with the shape
for no elastic medium case in our discussion. It is suggested that in no
embedded elastic medium cases, the cross-sectional shapes of inner tubes
maintain circle or oval; on the other hand, an embedded medium may cause inner
tube corrugation modes especially when the number of shells for MWNTs is small.Comment: 7 figures, 2 figure
Effects of phytohemagglutinin on humoral antibody response, delayed hypersensitivity, and homograft rejection.
Evolution of the Hall Coefficient and the Peculiar Electronic Structure of the Cuprate Superconductors
Although the Hall coefficient R_H is an informative transport property of
metals and semiconductors, its meaning in the cuprate superconductors has been
ambiguous because of its unusual characteristics. Here we show that a
systematic study of R_H in La_{2-x}Sr_{x}CuO_{4} single crystals over a wide
doping range establishes a qualitative understanding of its peculiar evolution,
which turns out to reflect a two-component nature of the electronic structure
caused by an unusual development of the Fermi surface recently uncovered by
photoemission experiments.Comment: 4 pages, 5 figures, final version appeared in Phys. Rev. Let
Abrupt transition in quasiparticle dynamics at optimal doping in a cuprate superconductor system
We report time-resolved measurements of the photoinduced change in
reflectivity, Delta R, in the Bi2Sr2Ca(1-y)Dy(y)Cu2O(8+delta) (BSCCO) system of
cuprate superconductors as a function of hole concentration. We find that the
kinetics of quasiparticle decay and the sign of Delta R both change abruptly
where the superconducting transition temperature Tc is maximal. These
coincident changes suggest that a sharp transition in quasiparticle dynamics
takes place precisely at optimal doping in the BSCCO system.Comment: 10 pages, 4 figure
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