4,901 research outputs found
Single and Double Universal Seesaw Mechanisms with Universal Strength for Yukawa Couplings
Single and double universal seesaw mechanisms and the hypothesis of universal
strength for Yukawa couplings are applied to formulate a unified theory of
fermion mass spectrum in a model based on an extended Pati-Salam symmetry. Five
kinds of Higgs fields are postulated to mediate scalar interactions among
electroweak doublets of light fermions and electroweak singlets of heavy exotic
fermions with relative Yukawa coupling constants of exponential form. At the
first-order seesaw approximation, quasi-democratic mass matrices with equal
diagonal elements are derived for all charged fermion sectors and a diagonal
mass matrix is obtained for the neutrino sector under an additional ansatz.
Assuming the vacuum neutrino oscillation, the problems of solar and atmospheric
neutrino anomalies are investigated.Comment: 13 pages, LaTeX; a reference adde
Approximate Sum Rules of CKM Matrix Elements from Quasi-Democratic Mass Matrices
To extract sum rules of CKM matrix elements, eigenvalue problems for
quasi-democratic mass matrices are solved in the first order perturbation
approximation with respect to small deviations from the democratic limit. Mass
spectra of up and down quark sectors and the CKM matrix are shown to have clear
and distinctive hierarchical structures. Numerical analysis shows that the
absolute values of calculated CKM matrix elements fit the experimental data
quite well. The order of the magnitude of the Jarlskog parameter is estimated
by the relation .Comment: Latex, 15 pages, no figure
Nuclear Excitations Described by Randomly Selected Multiple Slater Determinants
We propose a new stochastic method to describe low-lying excited states of
finite nuclei superposing multiple Slater determinants without assuming
generator coordinates a priori. We examine accuracy of our method by using
simple BKN interaction.Comment: Talk at International Symposium on Correlation Dynamics in Nuclei,
Tokyo, Japan, 31 Jan.-- 4 Feb. 200
Reading the Number of Extra Dimensions in the Spectrum of Hawking Radiation
After a brief review of the production and decay of Schwarzschild-like
(4+n)-dimensional black holes in the framework of theories with Large Extra
Dimensions, we proceed to derive the greybody factors and emission rates for
scalars, fermions and gauge bosons on the brane. We present and discuss
analytic and numerical methods for obtaining the above results, and demonstrate
that both the amount and type of Hawking radiation emitted by the black hole
can help us to determine the number of spacelike dimensions that exist in
nature.Comment: 8 pages, Latex file, 1 figure, to appear in the proceedings of the
String Phenomenology 2003 Conference, Durham, UK, 29th July-4th August, 200
Light emission patterns from stadium-shaped semiconductor microcavity lasers
We study light emission patterns from stadium-shaped semiconductor (GaAs)
microcavity lasers theoretically and experimentally. Performing systematic wave
calculations for passive cavity modes, we demonstrate that the averaging by
low-loss modes, such as those realized in multi-mode lasing, generates an
emission pattern in good agreement with the ray model's prediction. In
addition, we show that the dependence of experimental far-field emission
patterns on the aspect ratio of the stadium cavity is well reproduced by the
ray model.Comment: 5 pages, 4 figure
High-Tc superconductivity in entirely end-bonded multi-walled carbon nanotubes
We report that entirely end-bonded multi-walled carbon nanotubes (MWNTs) can
show superconductivity with the transition temperature Tc as high as 12K that
is approximately 40-times larger than those reported in ropes of single-walled
nanotubes. We find that emergence of this superconductivity is very sensitive
to junction structures of Au electrode/MWNTs. This reveals that only MWNTs with
optimal numbers of electrically activated shells, which are realized by the
end-bonding, can allow the superconductivity due to inter shell effects.Comment: 5 page
Transition of amorphous to crystalline oxide film in initial oxide overgrowth on liquid metals
It is important to understand the mechanism of oxidation in the initial stage on the free surface of liquid metals. Mittemeijer and co-workers recently developed a thermodynamic model to study the oxide overgrowth on a solid metal surface. Based on this model, we have developed a thermodynamic model to analyse the thermodynamic stability of oxide overgrowth on liquid metals. The thermodynamic model calculation revealed that the amorphous oxide phase is thermodynamically preferred up to 1.3 and 0.35 nm respectively, in the initial oxide overgrowth on liquid Al and Ga at the corresponding melting point. However, the amorphous phase is thermodynamically unstable in the initial oxide overgrowth on liquid Mg. The thermodynamic stability of amorphous phase in the Al and Ga oxide systems is attributed to lower sums of surface and interfacial energies for amorphous phases, compared to that of the corresponding crystalline phases.Financial support under grant EP/H026177/1 from the EPSRC was used
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