5,080 research outputs found
Modified Reconstruction of Standard Model in Non-Commutative Differential Geometry
Sogami recently proposed the new idea to express Higgs particle as a kind of
gauge particle by prescribing the generalized covariant derivative with gauge
and Higgs fields operating on quark and lepton fields. The field strengths for
both the gauge and Higgs fields are defined by the commutators of the covariant
derivative by which he could obtain the Yang-Mills Higgs Lagrangian in the
standard model. Inspired by Sogami's work, we present a modification of our
previous scheme to formulate the spontaneously broken gauge theory in
non-commutative geometry on the discrete space; Minkowski space multiplied by
two points space by introducing the generation mixing matrix in operation of
the generalized derivative on the more fundamental fields a_i(x,y) which
compose the gauge and Higgs fields. The standard model is reconstructed
according to the modified scheme, which does not yields not only any special
relations between the particle masses but also the special restriction on the
Higgs potential.Comment: 21 page
BRST invariant Lagrangian of spontaneously broken gauge theories in noncommutative geometry
The quantization of spontaneously broken gauge theories in noncommutative
geometry(NCG) has been sought for some time, because quantization is crucial
for making the NCG approach a reliable and physically acceptable theory. Lee,
Hwang and Ne'eman recently succeeded in realizing the BRST quantization of
gauge theories in NCG in the matrix derivative approach proposed by Coquereaux
et al. The present author has proposed a characteristic formulation to
reconstruct a gauge theory in NCG on the discrete space .
Since this formulation is a generalization of the differential geometry on the
ordinary manifold to that on the discrete manifold, it is more familiar than
other approaches. In this paper, we show that within our formulation we can
obtain the BRST invariant Lagrangian in the same way as Lee, Hwang and Ne'eman
and apply it to the SU(2)U(1) gauge theory.Comment: RevTeX, page
Orbital Order, Structural Transition and Superconductivity in Iron Pnictides
We investigate the 16-band d-p model for iron pnictide superconductors in the
presence of the electron-phonon coupling g with the orthorhombic mode which is
crucial for reproducing the recently observed ultrasonic softening. Within the
RPA, we obtain the ferro-orbital order below TQ which induces the
tetragonal-orthorhombic structural transition at Ts = TQ, together with the
stripe-type antiferromagnetic order below TN. Near the phase transitions, the
system shows the s++ wave superconductivity due to the orbital fluctuation for
a large g case with TQ > TN, while the s+- wave due to the magnetic fluctuation
for a small g case with TQ < TN. The former case is consistent with the phase
diagram of doped iron pnictides with Ts > TN.Comment: 5 pages, 5 figures, minor changes, published in J. Phys. Soc. Jp
A High-Density SSR Linkage Map of Red Clover and Its Transferability to Other Legumes
A high-density linkage map of red clover was constructed based on SSR and RFLP markers. In order to construct a linkage map with user (breeder) friendly markers; i.e. informative and easy detection, two policies were adopted for marker development. One was that the markers should be derived from cDNA or gene-rich regions, and the other was that the SSR markers should be detected polymorphisms on agarose gels. We also discuss the transferability of the markers on the map to other red clover germplasm and legumes. Such highly transferable markers could be used to screen anchor markers for both on a consensus map of red clover and other legume species
First Detection of 12CO (1--0) Emission from Two Narrow-Line Seyfert 1 Galaxies
In order to investigate how the growth of galactic bulges progresses with the
growth of central black holes (BHs), we observed molecular gas (fuel for the
coming star formation) in possibly young active galaxies, narrow-line Seyfert 1
galaxies (NLS1s). We present the results of radio observations of 12CO(1--0)
using the Nobeyama Millimeter Array (with 2--4 kpc spatial resolution) for two
FIR-bright NLS1s, yielding the first detection of their CO emission.
Corresponding molecular--gas masses M(H2) of (1-3) X 109 Msun are the 2nd and
4th largest ones among NLS1s. By estimating dynamical masses and bulge masses
M(bulge) for these two NLS1s using CO channel map and CO line widths, we found
M(H2) amount to 0.13--0.35 of these masses. Taking account the star formation
efficiency (~ 0.1), the increase in M(bulge) in those NLS1s in the near future
(~< 10^{7.5} yr) is expected not to be a huge fraction (1--5% of the
preexisting stars). Bulge growth may have finished before BH growth, or
bulge--BH coevolution may proceed with many, occasional discrete events, where
one coevolution event produces only a small amount of mass growth of BHs and of
bulges. We also discuss the ratios of star-formation rate--to--gas accretion
rate onto BHs, finding that two NLS1s have very small ratios (~ 1) compared
with the M(bulge)/M(BH) ratios found in active and inactive galaxies (~ 700).
This huge difference suggests either the non-overlapped coevolution, long star
formation duration or temporarily high accretion rate during NLS1 phase.Comment: 29 pages, 8 figures, Accepted for publication in The Astrophysical
Journa
GOODS-: identification of the individual galaxies responsible for the 80-290m cosmic infrared background
We propose a new method of pushing to its faintest detection
limits using universal trends in the redshift evolution of the far infrared
over 24m colours in the well-sampled GOODS-North field. An extension to
other fields with less multi-wavelength information is presented. This method
is applied here to raise the contribution of individually detected
sources to the cosmic infrared background (CIRB) by a factor 5 close to its
peak at 250m and more than 3 in the 350m and 500m bands. We
produce realistic mock images of the deep PACS and SPIRE images of
the GOODS-North field from the GOODS- Key Program and use them to
quantify the confusion noise at the position of individual sources, i.e.,
estimate a "local confusion noise". Two methods are used to identify sources
with reliable photometric accuracy extracted using 24m prior positions.
The clean index (CI), previously defined but validated here with simulations,
which measures the presence of bright 24m neighbours and the photometric
accuracy index (PAI) directly extracted from the mock images. After
correction for completeness, thanks to our mock images, individually
detected sources make up as much as 54% and 60% of the CIRB in the PACS bands
down to 1.1 mJy at 100m and 2.2 mJy at 160m and 55, 33, and 13% of
the CIRB in the SPIRE bands down to 2.5, 5, and 9 mJy at 250m, 350m,
and 500m, respectively. The latter depths improve the detection limits of
by factors of 5 at 250m, and 3 at 350m and 500m as
compared to the standard confusion limit. Interestingly, the dominant
contributors to the CIRB in all bands appear to be distant siblings
of the Milky Way (0.96 for 300m) with a stellar mass
of 910M.Comment: 22 pages, 16 figures. Accepted for publication by Astronomy and
Astrophysic
Unidentified Infrared Emission Bands in the Diffuse Interstellar Medium
Using the Mid-Infrared Spectrometer on board the Infrared Telescope in Space
and the low-resolution grating spectrometer (PHT-S) on board the Infrared Space
Observatory, we obtained 820 mid-infrared (5 to 12 m) spectra of the
diffuse interstellar medium (DIM) in the Galactic center, W51, and Carina
Nebula regions. These spectra indicate that the emission is dominated by the
unidentified infrared (UIR) emission bands at 6.2, 7.7, 8.6, and 11.2 m.
The relative band intensities (6.2/7.7 m, 8.6/7.7 m, and 11.2/7.7
m) were derived from these spectra, and no systematic variation in these
ratios was found in our observed regions, in spite of the fact that the
incident radiation intensity differs by a factor of 1500. Comparing our results
with the polycyclic aromatic hydrocarbons (PAHs) model for the UIR band
carriers, PAHs in the DIM have no systematic variation in their size
distribution, their degree of dehydrogenation is independent of the strength of
UV radiation field, and they are mostly ionized. The latter finding is
incompatible with past theoretical studies, in which a large fraction of
neutral PAHs is predicted in this kind of environment. A plausible resolution
of this discrepancy is that the recombination coefficients for electron and
large PAH positive ion are by at least an order of magnitude less than those
adopted in past theoretical studies. Because of the very low population of
neutral state molecules, photoelectric emission from interstellar PAHs is
probably not the dominant source of heating of the diffuse interstellar gas.
The present results imply constant physical and chemical properties of the
carriers of the UIR emission bands in the DIM.Comment: 13 pages, 6 figures. Accepted for publication in Ap
Characterization and Improvement of the Image Quality of the Data Taken with the Infrared Camera (IRC) Mid-Infrared Channels onboard AKARI
Mid-infrared images frequently suffer artifacts and extended point spread
functions (PSFs). We investigate the characteristics of the artifacts and the
PSFs in images obtained with the Infrared Camera (IRC) onboard AKARI at four
mid-infrared bands of the S7 (7{\mu}m), S11 (11{\mu}m), L15 (15{\mu}m), and L24
(24 {\mu}m). Removal of the artifacts significantly improves the reliability of
the ref- erence data for flat-fielding at the L15 and L24 bands. A set of
models of the IRC PSFs is also constructed from on-orbit data. These PSFs have
extended components that come from diffraction and scattering within the
detector arrays. We estimate the aperture correction factors for point sources
and the surface brightness correction factors for diffuse sources. We conclude
that the surface brightness correction factors range from 0.95 to 0.8, taking
account of the extended component of the PSFs. To correct for the extended PSF
effects for the study of faint structures, we also develop an image
reconstruction method, which consists of the deconvolution with the PSF and the
convolution with an appropriate Gaussian. The appropriate removal of the
artifacts, improved flat-fielding, and image reconstruction with the extended
PSFs enable us to investigate de- tailed structures of extended sources in IRC
mid-infrared images.Comment: 35 pages, 15 figures, accepted for publication in PAS
Reconstruction of the eruptive history of Usu volcano, Hokkaido, Japan, inferred from petrological correlation between tephras and dome lavas
Usu volcano has erupted nine times since 1663. Most eruptive events started with an explosive eruption, which was followed by the formation of lava domes. However, the ages of several summit lava domes and craters remain uncertain. The petrological features of tephra deposits erupted from 1663 to 1853 are known to change systematically. In this study, we correlated lavas with tephras under the assumption that lava and tephra samples from the same event would have similar petrological features. Although the initial explosive eruption in 1663 was not accompanied by lava effusion, lava dome or cryptodome formation was associated with subsequent explosive eruptions. We inferred the location of the vent associated with each event from the location of the associated lava dome and the pyroclastic flow deposit distribution and found that the position of the active vent within the summit caldera differed for each eruption from the late 17th through the 19th century. Moreover, we identified a previously unrecognized lava dome produced by a late 17th century eruption; this dome was largely destroyed by an explosive eruption in 1822 and was replaced by a new lava dome during a later stage of the 1822 event at nearly the same place as the destroyed dome. This new interpretation of the sequence of events is consistent with historical sketches and documents. Our results show that petrological correlation, together with geological evidence, is useful not only for reconstructing volcanic eruption sequences but also for gaining insight into future potential disasters
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