250 research outputs found
A Heat Kernel Approach to Interest Rate Models
We construct default-free interest rate models in the spirit of the
well-known Markov funcional models: our focus is analytic tractability of the
models and generality of the approach. We work in the setting of state price
densities and construct models by means of the so called propagation property.
The propagation property can be found implicitly in all of the popular state
price density approaches, in particular heat kernels share the propagation
property (wherefrom we deduced the name of the approach). As a related matter,
an interesting property of heat kernels is presented, too
Magnetic relaxation and collective vortex creep in FeTeSe single crystal
We study the vortex dynamics in high-quality FeTeSe single
crystal by performing magnetization measurements of the screening current
density \emph{J} and flux creep rate \emph{S}. Temperature dependence of
\emph{S} shows a plateau in the intermediate temperature region with a high
creep rate 0.03, which is interpreted in the framework of the collective
creep theory. A crossover from elastic to plastic creep is observed. The glassy
exponent and barrier height for flux creep are directly determined by extended
Maley's method. \emph{J} with flux creep, obtained from magnetic hysteresis
loops, is successfully reproduced based on the collective creep analysis. We
also approach critical current density without flux creep by means of the
generalized inversion scheme, which proves that the \emph{l} and
\emph{T} pinning coexist in FeTeSe single crystal.Comment: 6 pages, 5 figure
Magnetic and transport properties of iron-platinum arsenide Ca10(Pt4-{\delta}As8)(Fe2-xPtxAs2)5 single crystal
We report superconducting properties of single crystalline
Ca10(Pt4-{\delta}As8)(Fe2-xPtxAs2)5 by X-ray diffraction, magnetization,
resistivity, and magneto-optical imaging measurements. The magnetization
measurements reveal fish-tail hysteresis loop and relatively high critical
current density Jc ~ 0.8\times105 A/cm2 at low temperatures. The exponential
temperature dependence of Jc, which arises from nonlinear effective flux-creep
activation energy, has been observed. Upper critical field determined by
resistive transition shows a relatively large anisotropy. The magneto-optical
images reveal homogenous current flow within the crystal.Comment: 6 pages, 6 figures, Accepted for publication in Phys. Rev.
ナノ構造超伝導体における磁束侵入過程の観察
学位の種別:課程博士University of Tokyo(東京大学
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