15,103 research outputs found
The Fermi surface of CeCoIn5: dHvA
Measurements of the de Haas - van Alphen effect in the normal state of the
heavy Fermion superconductor CeCoIn5 have been carried out using a torque
cantilever at temperatures ranging from 20 to 500 mK and in fields up to 18
tesla. Angular dependent measurements of the extremal Fermi surface areas
reveal a more extreme two dimensional sheet than is found in either CeRhIn5 or
CeIrIn5. The effective masses of the measured frequencies range from 9 to 20
m*/m0.Comment: 4 pages, 2 figures, submitted to PRB Rapid
Dynamical coupled-channel model of meson production reactions in the nucleon resonance region
A dynamical coupled-channel model is presented for investigating the nucleon
resonances in the meson production reactions induced by pions and photons. The
model is based on an energy-independent Hamiltonian which is derived from a set
of Lagrangians by using a unitary transformation method. By applying the
projection operator techniques,we derive a set of coupled-channel equations
which satisfy the unitarity conditions within the channel space spanned by the
considered two-particle meson-baryon states and the three-particle
state. We present and explain in detail a numerical method based on a
spline-function expansion for solving the resulting coupled-channel equations
which contain logarithmically divergent one-particle-exchange driving terms
resulted from the unitarity cut. We show that this driving term can
generate rapidly varying structure in the reaction amplitudes associated with
the unstable particle channels. It also has large effects in determining the
two-pion production cross sections. Our results indicate that cautions must be
taken to interpret the parameters extracted from using models which do
not include cut effects.Comment: 73 pages, 20 figure
Collective motions in globally coupled tent maps with stochastic updating
We study a generalization of globally coupled maps, where the elements are
updated with probability . When is below a threshold , the
collective motion vanishes and the system is the stationary state in the large
size limit. We present the linear stability analysis.Comment: 6 pages including 5 figure
A generalization of Gabriel's Galois covering functors and derived equivalences
Let be a group acting on a category . We give a definition
for a functor to be a -covering and
three constructions of the orbit category , which generalizes
the notion of a Galois covering of locally finite-dimensional categories with
group whose action on is free and locally bonded defined by
Gabriel. Here is defined for any category and we
do not require that the action of is free or locally bounded. We show that
a -covering is a universal "-invariant" functor and is essentially given
by the canonical functor . By using this we
improve a covering technique for derived equivalence. Also we prove theorems
describing the relationships between smash product construction and the orbit
category construction by Cibils and Marcos (2006) without the assumption that
the -action is free. The orbit category construction by a cyclic group
generated by an auto-equivalence modulo natural isomorphisms (e.g., the
construction of cluster categories) is justified by a notion of the "colimit
orbit category". In addition, we give a presentation of the orbit category of a
category with a monoid action by a quiver with relations, which enables us to
calculate many examples.Comment: Title changed. Definitions of and
in section 6 were corrected. Proof of Theorem 8.1
is slightly changed to make it more readable. Other minor change
Two energy scales and slow crossover in YbAl3
Experimental results for the susceptibility, specific heat, 4f occupation
number, Hall effect and magnetoresistance for single crystals of YbAl
show that, in addition to the Kondo energy scale 670K,
there is a low temperature scale K for the onset of coherence.
Furthermore the crossover from the low temperature Fermi liquid regime to the
high temperature local moment regime is slower than predicted by the Anderson
impurity model. These effects may reflect the behavior of the Anderson Lattice
in the limit of low conduction electron density.Comment: Ten pages, including three figure
A new median-based formula for the Black-Scholes-Merton Theory
The Black-Scholes-Merton (BSM) theory for price variation has been well
established in mathematical financial engineering. However, it has been
recognized that long-term outcomes in practice may divert from the
Black-Scholes formula, which is the expected value of the stochastic process of
price changes. While the expected value is expected for the long-run average of
infinite realizations of the same stochastic process, it may give an erroneous
picture of nearly every realization when the probability distribution is
skewed, as is the case for prices. Here we propose a new formula of the BSM
theory, which is based on the median of the stochastic process. This formula
makes a more realistic prediction for the long-term outcomes than the current
Black-Scholes formula
Physical Phenomenology of Phyllotaxis
We propose an evolutionary mechanism of phyllotaxis, regular arrangement of
leaves on a plant stem. It is shown that the phyllotactic pattern with the
Fibonacci sequence has a selective advantage, for it involves the least number
of phyllotactic transitions during plant growth
Large N reduction for Chern-Simons theory on S^3
We study a matrix model which is obtained by dimensional reduction of
Chern-Simon theory on S^3 to zero dimension. We find that expanded around a
particular background consisting of multiple fuzzy spheres, it reproduces the
original theory on S^3 in the planar limit. This is viewed as a new type of the
large N reduction generalized to curved space.Comment: 4 pages, 2 figures, references added, typos correcte
Domestic canonical algebras and simple Lie algebras
For each simply-laced Dynkin graph we realize the simple complex Lie
algebra of type as a quotient algebra of the complex degenerate
composition Lie algebra of a domestic canonical algebra
of type by some ideal of that is
defined via the Hall algebra of , and give an explicit form of .
Moreover, we show that each root space of has a basis
given by the coset of an indecomposable -module with root easily
computed by the dimension vector of .Comment: 43 pages, 5 figures, revised versio
A theoretical analysis on highly spin-polarized transport of iron nitride Fe_4N
In order to propose a ferromagnet exhibiting highly spin-polarized transport,
we theoretically analyzed the spin polarization ratio of the conductivity of
the bulk FeN with a perovskite type structure, in which N is located at the
body center position of fcc-Fe. The spin polarization ratio is defined by , with being the conductivity at zero
temperature of the up spin (down spin). The conductivity is obtained by using
the Kubo formula and the Slater-Koster tight binding model, where parameters
are determined from the least-square fitting of the dispersion curves by the
tight binding model to those by the first principles calculation. In the
vicinity of the Fermi energy, takes almost 1.0, indicating perfectly
spin-polarized transport. In addition, by comparing FeN to fcc-Fe
(FeN) in the ferromagnetic state with the equilibrium lattice constant
of FeN, it is shown that the non-magnetic atom N plays an important role in
increasing .Comment: 4 pages, 2 figures, accepted for publication in Phys. Rev.
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