1,654 research outputs found
Classically Integrable Cosmological Models with a Scalar Field
New classes of classically integrable models in the cosmological theories
with a scalar field are obtained by using freedoms of defining time and fields.
In particular, some models with the sum of exponential potentials in the flat
spatial metric are shown to be integrable. The model with the Sine-Gordon
potential can be solved in terms of analytic continuation of the non-periodic
Toda field theory.Comment: 10 pages, Late
Sweeping the Space of Admissible Quark Mass Matrices
We propose a new and efficient method of reconstructing quark mass matrices
from their eigenvalues and a complete set of mixing observables. By a
combination of the principle of NNI (nearest neighbour interaction) bases which
are known to cover the general case, and of the polar decomposition theorem
that allows to convert arbitrary nonsingular matrices to triangular form, we
achieve a parameterization where the remaining freedom is reduced to one
complex parameter. While this parameter runs through the domain bounded by a
circle with radius R determined by the up-quark masses around the origin in the
complex plane one sweeps the space of all mass matrices compatible with the
given set of data.Comment: 18 page
Study of the Data Base Management System for Atomic and Molecular Processes in Nuclear Fusion Science
Effect of water vapor on the spallation of thermal barrier coating systems during laboratory cyclic oxidation testing.
The effect of water and water vapor on the lifetime of Ni-based superalloy samples coated with a typical thermal barrier coating system—b-(Ni,Pt)Al bond coat and yttria stabilized zirconia (YSZ) top coat deposited by electron beam physical vapor deposition (EB-PVD) was studied. Samples were thermally cycled to 1,150 C and subjected to a water-drop test in order to elucidate the effect of water vapor on thermal barrier coating (TBC) spallation. It was shown that the addition of water promotes spallation of TBC samples after a given number of cycles at 1,150 C. This threshold was found to be equal to 170 cycles for the present system. Systems based on b-NiAl bond coat or on Pt-rich c/c0 bond coat were also sensitive to the water-drop test. Moreover, it was shown that water vapor in ambient air after minutes or hours at room temperature, promotes also TBC spallation once the critical number of cycles has been reached. This desktop spalling (DTS) can be prevented by locking up the cycled samples in a dry atmosphere box. These results for TBC systems confirm and document Smialek’s theory about DTS and moisture induced delayed spalling (MIDS) being the same phenomenon. Finally, the mechanisms implying hydrogen embrittlement or surface tension modifications are discussed
Measurements of Primary and Atmospheric Cosmic-Ray Spectra with the BESS-TeV Spectrometer
Primary and atmospheric cosmic-ray spectra were precisely measured with the
BESS-TeV spectrometer. The spectrometer was upgraded from BESS-98 to achieve
seven times higher resolution in momentum measurement. We report absolute
fluxes of primary protons and helium nuclei in the energy ranges, 1-540 GeV and
1-250 GeV/n, respectively, and absolute flux of atmospheric muons in the
momentum range 0.6-400 GeV/c.Comment: 26 pages, 9 figures, 3 tables, Submitted to Phys. Lett.
On the Quantitative Impact of the Schechter-Valle Theorem
We evaluate the Schechter-Valle (Black Box) theorem quantitatively by
considering the most general Lorentz invariant Lagrangian consisting of
point-like operators for neutrinoless double beta decay. It is well known that
the Black Box operators induce Majorana neutrino masses at four-loop level.
This warrants the statement that an observation of neutrinoless double beta
decay guarantees the Majorana nature of neutrinos. We calculate these
radiatively generated masses and find that they are many orders of magnitude
smaller than the observed neutrino masses and splittings. Thus, some lepton
number violating New Physics (which may at tree-level not be related to
neutrino masses) may induce Black Box operators which can explain an observed
rate of neutrinoless double beta decay. Although these operators guarantee
finite Majorana neutrino masses, the smallness of the Black Box contributions
implies that other neutrino mass terms (Dirac or Majorana) must exist. If
neutrino masses have a significant Majorana contribution then this will become
the dominant part of the Black Box operator. However, neutrinos might also be
predominantly Dirac particles, while other lepton number violating New Physics
dominates neutrinoless double beta decay. Translating an observed rate of
neutrinoless double beta decay into neutrino masses would then be completely
misleading. Although the principal statement of the Schechter-Valle theorem
remains valid, we conclude that the Black Box diagram itself generates
radiatively only mass terms which are many orders of magnitude too small to
explain neutrino masses. Therefore, other operators must give the leading
contributions to neutrino masses, which could be of Dirac or Majorana nature.Comment: 18 pages, 4 figures; v2: minor corrections, reference added, matches
journal version; v3: typo corrected, physics result and conclusions unchange
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