2,609 research outputs found
Comment on "Heavy element production in inhomogeneous big bang nucleosynthesis"
The work of Matsuura et al. [Phys. Rev. D 72, 123505 (2005);
astro-ph/0507439] claims that heavy nuclei could have been produced in a
combined p- and r-process in very high baryon density regions of an
inhomogeneous big bang. However, they do not account for observational
constraints and previous studies which show that such high baryon density
regions did not significantly contribute to big bang abundances.Comment: 2 pages, submitted to Phys. Rev. D on Feb 23, 200
One-parameter extension of the Doi-Peliti formalism and relation with orthogonal polynomials
An extension of the Doi-Peliti formalism for stochastic chemical kinetics is
proposed. Using the extension, path-integral expressions consistent with
previous studies are obtained. In addition, the extended formalism is naturally
connected to orthogonal polynomials. We show that two different orthogonal
polynomials, i.e., Charlier polynomials and Hermite polynomials, can be used to
express the Doi-Peliti formalism explicitly.Comment: 10 page
Current and fluctuation in a two-state stochastic system under non-adiabatic periodic perturbation
We calculate a current and its fluctuation in a two-state stochastic system
under a periodic perturbation. The system could be interpreted as a channel on
a cell surface or a single Michaelis-Menten catalyzing enzyme. It has been
shown that the periodic perturbation induces so-called pump current, and the
pump current and its fluctuation are calculated with the aid of the geometrical
phase interpretation. We give a simple calculation recipe for the statistics of
the current, especially in a non-adiabatic case. The calculation scheme is
based on the non-adiabatic geometrical phase interpretation. Using the Floquet
theory, the total current and its fluctuation are calculated, and it is
revealed that the average of the current shows a stochastic-resonance-like
behavior. In contrast, the fluctuation of the current does not show such
behavior.Comment: 7 pages, 1 figur
Noncyclic and nonadiabatic geometric phase for counting statistics
We propose a general framework of the geometric-phase interpretation for
counting statistics. Counting statistics is a scheme to count the number of
specific transitions in a stochastic process. The cumulant generating function
for the counting statistics can be interpreted as a `phase', and it is
generally divided into two parts: the dynamical phase and a remaining one. It
has already been shown that for cyclic evolution the remaining phase
corresponds to a geometric phase, such as the Berry phase or Aharonov-Anandan
phase. We here show that the remaining phase also has an interpretation as a
geometric phase even in noncyclic and nonadiabatic evolution.Comment: 12 pages, 1 figur
Spin-filter tunnel junction with matched Fermi surfaces
Efficient injection of spin-polarized current into a semiconductor is a basic
prerequisite for building semiconductor-based spintronic devices. Here, we use
inelastic electron tunneling spectroscopy to show that the efficiency of
spin-filter-type spin injectors is limited by spin scattering of the tunneling
electrons. By matching the Fermi-surface shapes of the current injection source
and target electrode material, spin injection efficiency can be significantly
increased in epitaxial ferromagnetic insulator tunnel junctions. Our results
demonstrate that not only structural but also Fermi-surface matching is
important to suppress scattering processes in spintronic devices.Comment: 5 pages, 4 figure
Roles of proton-neutron interactions in alpha-like four-nucleon correlations
An extended pairing plus QQ force model, which has been shown to successfully
explain the nuclear binding energy and related quantities such as the symmetry
energy, is applied to study the alpha-like four-nucleon correlations in
1f_{7/2} shell nuclei.
The double difference of binding energies, which displays a characteristic
behavior at , is interpreted in terms of the alpha-like
correlations. Important roles of proton-neutron interactions forming the
alpha-like correlated structure are discussed.Comment: 10 pages, 2 figures, RevTex, submitted to Phys. Rev.
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