6,231 research outputs found
Fermion Masses and Mixings in a String Inspired Model
In the context of Calabi-Yau string models we explore the origin of
characteristic pattern of quark-lepton masses and the CKM matrix. The discrete
-symmetry is introduced and the is assigned to the
-parity. The gauge symmetry at the string scale, , is
broken into the standard model gauge group at a very large intermediate energy
scale. At energies below the intermediate scale down-type quarks and also
leptons are mixed with unobserved heavy states, respectively. On the other
hand, there are no such mixings for up-type quarks. Due to the large mixings
between light states and heavy ones we can derive phenomenologically viable
fermion mass hierarchies and the CKM matrix. Mass spectra for
intermediate-scale matter beyond the MSSM are also determined. Within this
framework proton lifetime is long enough to be consistent with experimental
data. As for the string scale unification of gauge couplings, however,
consistent solutions are not yet found.Comment: 49 pages, 1 figure, Latex Revised version includes discussion on FCNC
problems. Final version to appear in Prog. Theor. Phys. Vol.96 No.
Titanium and water-rich metamorphic olivine in high-pressure serpentinites from the Voltri Massif (Ligurian Alps, Italy): evidence for deep subduction of high-field strength and fluid-mobile elements
Titanium- and water-rich metamorphic olivine (Fo 86-88) is reported from partially dehydrated serpentinites from the Voltri complex, Ligurian Alps. The rocks are composed of mostly antigorite and olivine in addition to magnetite, chlorite, clinopyroxene and Ti-clinohumite. In situ secondary ion mass spectrometry (SIMS) data show that metamorphic olivine has very high and strongly correlated H2O (up to 0.7 wt%) and TiO2 contents (up to 0.85 wt%). Ti-rich olivine shows colourless to yellow pleochroism. Olivine associated with Ti-clinohumite contains low Ti, suggesting that Ti-rich olivine is not the breakdown product of Ti-clinohumite. Fourier transform infrared spectroscopy (FTIR) absorption spectra show peaks of serpentine, Ti-clinohumite and OH-related Si vacancies. Combining FTIR and SIMS data, we suggest the presence of clustered planar defects or nanoscale exsolutions of Ti-clinohumite in olivine. These defects or exsolutions contain more H2O (x similar to 0.1 in the formula 4Mg(2)SiO(4)center dot(1-x)Mg(OH, F)(2)center dot xTiO(2)) than Ti-clinohumite in the sample matrix (x = 0.34-0.46). In addition to TiO2 and H2O, secondary olivine contains significant Li (2-60 ppm), B (10-20 ppm), F (10-130 ppm) and Zr (0.9-2.1 ppm). It is enriched in B-11 (delta B-11 = +17 to +23 parts per thousand). Our data indicate that secondary olivine may play a significant role in transporting water, high-field strength and fluid-mobile elements into the deeper mantle as well as introduce significant B isotope anomalies. Release of hydrogen from H2O-rich olivine subducted into the deep mantle may result in strongly reduced mantle domains.OAIID:oai:osos.snu.ac.kr:snu2014-01/102/0000043439/1SEQ:1PERF_CD:SNU2014-01EVAL_ITEM_CD:102USER_ID:0000043439ADJUST_YN:YEMP_ID:A076886DEPT_CD:3345CITE_RATE:3.476FILENAME:de hoog et al-14-cmp-titanium- and water-ric.pdfDEPT_NM:지구환경과학부SCOPUS_YN:NCONFIRM:
How Can We Obtain a Large Majorana-Mass in Calabi-Yau Models ?
In a certain type of Calabi-Yau superstring models it is clarified that the
symmetry breaking occurs by stages at two large intermediate energy scales and
that two large intermediate scales induce large Majorana-masses of right-handed
neutrinos. Peculiar structure of the effective nonrenormalizable interactions
is crucial in the models. In this scheme Majorana-masses possibly amount to
O(10^{9 \sim 10}\gev) and see-saw mechanism is at work for neutrinos. Based
on this scheme we propose a viable model which explains the smallness of masses
for three kind of neutrinos .
Special forms of the nonrenormalizable interactions can be understood as a
consequence of an appropriate discrete symmetry of the compactified manifold.Comment: 30-pages + 6-figures, LaTeX, Preprint DPNU-94-02, AUE-01-9
Bipolaron-SO(5) Non-Fermi Liquid in a Two-channel Anderson Model with Phonon-assisted Hybridizations
We analyze non-Fermi liquid (NFL) properties along a line of critical points
in a two-channel Anderson model with phonon-assisted hybridizations. We succeed
in identifying hidden nonmagnetic SO(5) degrees of freedom for
valence-fluctuation regime and analyze the model on the basis of boundary
conformal field theory. We find that the NFL spectra along the critical line,
which is the same as those in the two-channel Kondo model, can be alternatively
derived by a fusion in the nonmagnetic SO(5) sector. The leading irrelevant
operators near the NFL fixed points vary as a function of Coulomb repulsion U;
operators in the spin sector dominate for large U, while those in the SO(5)
sector do for small U, and we confirm this variation in our numerical
renormalization group calculations. As a result, the thermodynamic singularity
for small U differs from that of the conventional two-channel Kondo problem.
Especially, the impurity contribution to specific heat is proportional to
temperature and bipolaron fluctuations, which are coupled electron-phonon
fluctuations, diverge logarithmically at low temperatures for small U.Comment: 16 pages, 4 figures, 3 table
Possible Evidence for Metal Accretion onto the Surfaces of Metal-Poor Main-Sequence Stars
The entire evolution of the Milky Way, including its mass-assembly and
star-formation history, is imprinted onto the chemo-dynamical distribution
function of its member stars, f(x, v, [X/H]), in the multi-dimensional phase
space spanned by position, velocity, and elemental abundance ratios. In
particular, the chemo-dynamical distribution functions for low-mass stars
(e.g., G- or K-type dwarfs) are precious tracers of the earliest stages of the
Milky Way's formation, since their main-sequence lifetimes approach or exceed
the age of the universe. A basic tenet of essentially all previous analyses is
that the stellar metallicity, usually parametrized as [Fe/H], is conserved over
time for main-sequence stars (at least those that have not been polluted due to
mass transfer from binary companions). If this holds true, any correlations
between metallicity and kinematics for long-lived main-sequence stars of
different masses, effective temperatures, or spectral types must strictly be
the same, since they reflect the same mass-assembly and star-formation
histories. By analyzing a sample of nearby metal-poor halo and thick-disk stars
on the main sequence, taken from Data Release 8 of the Sloan Digital Sky
Survey, we find that the median metallicity of G-type dwarfs is systematically
higher (by about 0.2 dex) than that of K-type dwarfs having the same median
rotational velocity about the Galactic center. If it can be confirmed, this
finding may invalidate the long-accepted assumption that the atmospheric
metallicities of long-lived stars are conserved over time.Comment: 12 pages, 7 figures, ApJ accepted, comments welcom
Very Metal-Poor Outer-Halo Stars with Round Orbits
The orbital motions of halo stars in the Milky Way reflect the orbital
motions of the progenitor systems in which they formed, making it possible to
trace the mass-assembly history of the Galaxy. Direct measurement of
three-dimensional velocities, based on accurate proper motions and
line-of-sight velocities, has revealed that the majority of halo stars in the
inner-halo region move on eccentric orbits. However, our understanding of the
motions of distant, in-situ halo-star samples is still limited, due to the lack
of accurate proper motions for these stars. Here we explore a model-independent
analysis of the line-of-sight velocities and spatial distribution of a recent
sample of 1865 carefully selected halo blue horizontal-branch (BHB) stars
within 30 kpc of the Galactic center. We find that the mean rotational velocity
of the very metal-poor ([Fe/H] < -2.0) BHB stars significantly lags behind that
of the relatively more metal-rich ([Fe/H] > -2.0) BHB stars. We also find that
the relatively more metal-rich BHB stars are dominated by stars with eccentric
orbits, as previously observed for other stellar samples in the inner-halo
region. By contrast, the very metal-poor BHB stars are dominated by stars on
rounder, lower-eccentricity orbits. Our results indicate that the motion of the
progenitor systems of the Milky Way that contributed to the stellar populations
found within 30 kpc correlates directly with their metal abundance, which may
be related to their physical properties such as gas fractions. These results
are consistent with the existence of an inner/outer halo structure for the halo
system, as advocated by Carollo et al. (2010).Comment: 5 pages, 3 figures, ApJ Letter accepted, comments welcom
Transition density of diffusion on Sierpinski gasket and extension of Flory's formula
Some problems related to the transition density u(t,x) of the diffusion on
the Sierpinski gasket are considerd, based on recent rigorous results and
detailed numerical calculations. The main contents are an extension of Flory's
formula for the end-to-end distance exponent of self-avoiding walks on the
fractal spaces, and an evidence of the oscillatory behavior of u(t,x) on the
Sierpinski gasket.Comment: 11 pages, REVTEX, 2 postscript figure
The semantic effects of verb raising and its consequences in second language grammars
This article considers whether highly proficient second language speakers of English can distinguish meaning contrasts associated with constructions where there is a raising be, and constructions where there is a non-raising thematic verb, as illustrated in the difference between (1a) and (1b): 1a. Kim is reading a novel (`event-in-progress/existential ? interpretation
Cooperative Effect of Coulomb Interaction and Electron-Phonon Coupling on the Heavy Fermion State in the Two-Orbital Periodic Anderson Model
We investigate the two-orbital periodic Anderson model, where the local
orbital fluctuations of f-electrons couple with a two-fold degenerate
Jahn-Teller phonon, by using the dynamical mean-field theory. It is found that
the heavy fermion state caused by the Coulomb interaction between f-electrons U
is largely enhanced due to the electron-phonon coupling g, in contrast to the
case with the single-orbital periodic Anderson model where the effects of U and
g compete to each other. In the heavy fermion state for large and g, both
the orbital and lattice fluctuations are enhanced, while the charge (valence)
and spin fluctuations are suppressed. In the strong coupling regime, a sharp
soft phonon mode with a large spectral weight is observed for small U, while a
broad soft phonon mode with a small spectral weight is observed for large U.
The cooperative effect of U and g for half-filling with two f-electrons per
atom is more pronounced than that for quarter-filling with .Comment: 8 pages, 11 figures, accepted for publication in JPS
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