469 research outputs found
Peccei-Quinn Symmetry Breaking via Asymptotically Safe Dynamical Scalegenesis: A Walking Axicolor and Axion
Pecci-Quinn (PQ) symmetry breaking by perturbative dynamics would suffer from
a hierarchy problem, just like the electroweak symmetry breaking in the
standard model. The dynamics of the axion, associated with the PQ symmetry
breaking, would also involve a triviality problem. We provide a paradigm to
resolve those two problems potentially existing in the PQ symmetry breaking
scenario, with keeping successful axion relaxation for the QCD strong CP phase.
The proposed theory includes an axicolor dynamics with the axicolored fermions
partially gauged by the QCD color, and is shown to be governed by an
asymptotically safe (AS) fixed point: quantum scale invariance is built. The AS
axicolor is actually a ``walking" dynamics, which dynamically breaks a PQ
symmetry, a part of the chiral symmetry carried by the axicolored fermions. The
PQ scale generation is then triggered by the nonperturbative dimensional
transmutation in the ``walking" dynamics. A composite axion emerges as the
assosiated Nambu-Goldstone boson. That is, no hierarchy or triviality problem
is present there. The composite axion can potentially be light due to the
characteristic feature of the AS axicolor (``walking" axicolor), becomes the
QCD axion in the anti-Veneziano limit, and gets heavier by the subleading
correction. The composite axion relaxes the QCD theta parameter, involving
heavier relaxation partners such as axicolored pseudoscalar mesons, and the
ultraviolet correction to the relaxation mechanism is protected by the
established (near) scale invariance during the ``walking" regime.Comment: 19 pages, 1 figure; minor revisions mad
Gravitational wave footprints from Higgs-portal scalegenesis with multiple dark chiral scalars
We discuss the gravitational wave (GW) spectra predicted from the electroweak
scalegenesis of the Higgs portal type with a large number of dark chiral
flavors, which many flavor QCD would underlie and give the dynamical
explanation of the negative Higgs portal coupling required to trigger the
electroweak symmetry breaking. We employ the linear-sigma model as the
low-energy description of dark many flavor QCD and show that the model
undergoes ultra-supercooling due to the produced strong first-order thermal
phase transition along the (approximately realized) flat direction based on the
Gildener-Weinberg mechanism. Passing through evaluation of the bubble
nucleation/percolation, we address the reheating and relaxation processes,
which are generically non-thermal and nonadiabatic. Parametrizing the reheating
epoch in terms of the e-folding number, we propose proper formulae for the
redshift effects on the GW frequencies and signal spectra. It then turns out
that the ultra-supercooling predicted from the Higgs-portal scalegenesis
generically yields none of GW signals with the frequencies as low as nano Hz,
unless the released latent heat is transported into another sector other than
reheating the universe. Instead, models of this class prefer to give the higher
frequency signals and still keeps the future prospected detection sensitivity,
like at LISA, BBO, and DECIGO, etc. We also find that with large flavors in the
dark sector, the GW signals are made further smaller and the peak frequencies
higher. Characteristic phenomenological consequences related to the multiple
chiral scalars include the prediction of dark pions with the mass much less
than TeV scale, which is also briefly addressed.Comment: 14 pages, 4 figure
Dynamical realization of the small field inflation in the post supercooled universe
The small field inflation (SFI) of Coleman-Weinberg (CW) type suffers from
precise tuning of the initial inflaton field value to be away from the true
vacuum one. We propose a dynamical trapping mechanism to solve this problem: an
ultra-supercooling caused by an almost scale-invariant CW potential traps the
inflaton at the false vacuum, far away from the true vacuum dominantly created
by the quantum scale anomaly, and allows the inflaton to dynamically start the
slow-roll down due to a classical explicit-scale breaking effect. To be
concrete, we employ a successful CW-SFI model and show that the proposed
mechanism works consistently with the observed bounds on the inflation
parameters. The proposed new mechanism thus provides new insights for
developing small field inflation models.Comment: 6 pages, 2 figure
Photoelectron detection from transient species in organic semiconducting thin films by dual laser pulse irradiation
An Nd3+:YAG pulsed laser was employed as a light source for two-photon photoemission from organic semiconducting thin films in low vacuum and air. Photoionization by the two-photon process was confirmed in both the environments by measuring photoemission current. By constructing a pump–probe system, photoemissions from transient species formed by the pump light irradiation were detected by probe light irradiation as a result of a linear increase in the photocurrent with the pump power via a one-photon process. Thus, we propose a novel method called two-photon photoelectron yield spectroscopy to determine the excited-state energy levels in ambient environments
Chemical and isotopic compositions in acid residues from three meteorites
Chemical compositions of acid residues obtained from three types of meteorites, 1) Canyon Diablo (IA), 2) Allende (CV3) and 3) Nuevo Mercurio (H5) were determined. Refractory elements were generally enriched in these acid residues. The results match the features that acid residues contain primary condensates from the cooling solar gas as well as extra-solar grains. In the cases of Allende and Canyon Diablo, the contents of a series of refractory siderophile elements such as W, Re, Os, Ir, Mo, Ru and Pt were determined by INAA and AAS. Particularly, in acid residue of Allende, enrichment factors of these elements relative to CI are generally higher (7-20 times/CI), whereas in the cases of W and Mo, they are slightly depleted compared with those of Canyon Diablo. Since both elements would be the first metals to be oxidized under high oxygen fugacity, acid residue of Allende should contain fractions that were produced under oxidizing conditions. In these samples, the isotopic compositions of Ru have been measured by thermal ionization mass spectrometry. So far, in the measurements of acid residue of Allende, all Ru isotope ratios were found to be indistinguishable from terrestrial values within the experimental errors, though errors were large because of small Ru ion beam intensities
Application of compound-specific 14C dating to IODP Exp.318 U1357A core
第3回極域科学シンポジウム 横断セッション「海・陸・氷床から探る後期新生代の南極寒冷圏環境変動」11月27日(火) 国立国語研究所 2階講
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