28,603 research outputs found
Induced top Yukawa coupling and suppressed Higgs mass parameters
In the scenarios with heavy top squarks, mass parameters of the Higgs field
must be fine-tuned due to a large logarithmic correction to the soft scalar
mass. We consider a new possibility that the top Yukawa coupling is small above
TeV scale. The large top mass is induced from strong Yukawa interaction of the
Higgs with another gauge sector, in which supersymmetry breaking parameters are
given to be small. Then it is found that the logarithmic correction to the
Higgs soft scalar mass is suppressed in spite of the strong coupling and the
fine-tuning is ameliorated. We propose an explicit model coupled to a
superconformal gauge theory which realizes the above situation.Comment: RevTeX4 style, 10 pages, 3 figure
Kamland Results
The LMA solution of the solar neutrino problem has been explored with the
1,000 ton liquid scinatillator detector, KamLAND. It utilizes nuclear power
reactors distributing effectively 180km from the experimental site. Comparing
observed neutrino rate with the calculation of reactor operation histories, an
evidence for reactor neutrino disapearance has been obtained from 162 ton-year
exposure data. This deficit is only compatible with the LMA solution and the
other solutions in the two neutrino oscillation hypotheisis are excluded at
99.95% confidence level.Comment: 8 pages, 5 figures, proceeding of the Moriond Conference "Electroweak
Interactions and Unified Thories
A possible signature of primordial stellar populations in Lyman emitters
Observations with Subaru telescope have detected surprisingly strong Lyman
continuum (LyC; \AA\ in the rest-frame) from some Lyman
emitters (LAEs) at . We have examined the stellar population which
simultaneously accounts for the strength of the LyC and the spectral slope of
non-ionizing ultraviolet of the LAEs. As a result, we have found that stellar
populations with metallicity can explain the observed LyC
strength only with a very top-heavy initial mass function (IMF; ). However, the critical metallicity for such an IMF is expected to be
much lower. A very young ( Myr) and massive ( )
extremely metal-poor () or metal-free (so-called
Population III) stellar population can also reproduce the observed LyC strength
if the mass fraction of such 'primordial' stellar population is % in
total stellar mass of the LAEs.Comment: 4 pages, 2 figures, First Stars IV in Kyoto conference (May 2012)
proceedin
Evolution of Dust-to-Metal Ratio in Galaxies
This paper investigates the evolution of the dust-to-metal ratio in galaxies
based on a simple evolution model for the amount of metal and dust with infall.
We take into account grain formation in stellar mass-loss gas, grain growth by
the accretion of metallic atoms in a cold dense cloud, and grain destruction by
SNe shocks. Especially, we propose that the accretion efficiency is independent
of the star-formation history. This predicts various evolutionary tracks in the
metallicity ()--dust-to-gas ratio () plane depending on the
star-formation history. In this framework, the observed linear --
relation of nearby spiral galaxies can be interpreted as a sequence of a
constant galactic age. We emphasize that an observational study of the
-- relation of galaxies at is very useful to constrain the
efficiencies of dust growth and destruction. We also suggest that the
Lyman break galaxies at have a very low dust-to-metal ratio,
typically \ltsim 0.1. Although the effect of infall on the evolutionary
tracks in the -- plane is quite small, the dispersion of the infall
rate can disturb the -- relation with a constant galactic age.Comment: 9 pages, accepted to appear in PASJ October issu
Method of manufacturing ceramic shaped articles
A method of manufacturing ceramic shaped articles, wherein tapes of ceramic powder material in mixture with a binder material and special additives are shaped and then articles are stamped out from said tapes and sintered in a sintering furnace is described
Structure and Stability of Magnetic Fields in Solar Active Region12192 Based on Nonlinear Force-Free Field Modeling
We analyze a three-dimensional (3D) magnetic structure and its stability in
large solar active region(AR) 12192, using the 3D coronal magnetic field
constructed under a nonlinear force-free field (NLFFF) approximation. In
particular, we focus on the magnetic structure that produced an X3.1-class
flare which is one of the X-class flares observed in AR 12192. According to our
analysis, the AR contains multiple-flux-tube system, {\it e.g.}, a large flux
tube, both of whose footpoints are anchored to the large bipole field, under
which other tubes exist close to a polarity inversion line (PIL). These various
flux tubes of different sizes and shapes coexist there. In particular, the
later are embedded along the PIL, which produces a favorable shape for the
tether-cutting reconnection and is related to the X-class solar flare. We
further found that most of magnetic twists are not released even after the
flare, which is consistent with the fact that no observational evidence for
major eruptions was found. On the other hand, the upper part of the flux tube
is beyond a critical decay index, essential for the excitation of torus
instability before the flare, even though no coronal mass ejections (CMEs) were
observed. We discuss the stability of the complicated flux tube system and
suggest the reason for the existence of the stable flux tube. In addition, we
further point out a possibility for tracing the shape of flare ribbons, on the
basis of a detailed structural analysis of the NLFFF before a flare.Comment: 24 pages, 9 figures, accepted for publication in The Astrophysical
Journa
Constraint on intergalactic dust from thermal history of intergalactic medium
This Letter investigates the amount of dust in the intergalactic medium
(IGM). The dust photoelectric heating can be the most efficient heating
mechanism in the IGM where the density is very small and there are a lot of
hard ultraviolet photons. Comparing the observational thermal history of IGM
with a theoretical one taking into account the dust photoelectric heating, we
can put an upper limit on the dust-to-gas ratio, , in the IGM. Since
the rate of the dust photoelectric heating depends on the size of dust, we find
the following results: If the grain size is \ga 100 \AA, at is \la 1/100 Galactic value corresponding to \Omega_{\rm dust}^{\rm
IGM}\la 10^{-5}. On the other hand, if the grain size is as small as
\AA, is \la 1/1000 Galactic value corresponding to \Omega_{\rm
dust}^{\rm IGM}\la 10^{-6}.Comment: 5 pages, 2 figures; accepted for publication in MNRAS pink page
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