6,592 research outputs found
Axion and Right-handed Neutrino in the Minimal SUSY SO(10) Model
The connection between the axion and right-handed neutrinos is explored in
the framework of the minimal SUSY SO(10) model. The former is related to the
Peccei-Quinn (PQ) solution to the strong CP problem and the latter is to the
light Majorana neutrinos through the see-saw mechanism. In this model, a
relative phase between and multiplets of becomes a physical degree of freedom identified with the
axion. Then, the PQ symmetry breaking scale () and the
symmetry breaking scale () coincide through the VEV of . The scalar partner of the lightest right-handed neutrino is
regarded as the inflaton, which gives a consistent density fluctuation for the
CMB.Comment: 8 pages, no figure; the version to appear in JHE
Construction of a Versatile Ultra-Low Temperature Scanning Tunneling Microscope
We constructed a dilution-refrigerator (DR) based ultra-low temperature
scanning tunneling microscope (ULT-STM) which works at temperatures down to 30
mK, in magnetic fields up to 6 T and in ultrahigh vacuum (UHV). Besides these
extreme operation conditions, this STM has several unique features not
available in other DR based ULT-STMs. One can load STM tips as well as samples
with clean surfaces prepared in a UHV environment to an STM head keeping low
temperature and UHV conditions. After then, the system can be cooled back to
near the base temperature within 3 hours. Due to these capabilities, it has a
variety of applications not only for cleavable materials but also for almost
all conducting materials. The present ULT-STM has also an exceptionally high
stability in the presence of magnetic field and even during field sweep. We
describe details of its design, performance and applications for low
temperature physics.Comment: 6 pages, 9 figures. accepted for publication in Rev. Sci. Instru
Study on successive superconducting transitions in TaSC from electrical resistivity and nonlinear AC magnetic susceptibility
TaSC compound undergoes superconducting transitions at K and K. The nature of successive
superconducting transitions has been studied from electrical resistivity,
linear and nonlinear AC magnetic susceptibilities. The resistivity at
= 0 shows a local maximum near , a kink-like behavior around
, and reduces to zero at below = 2.1 K. The dependence
of is observed at = 50 kOe at low temperatures, which is due to
two-dimensional weak-localization effect. Below a two-dimensional
superconducting phase occurs in each TaC layer. The linear and nonlinear
susceptibilities , ,
, and as well as the difference
() between the FC and ZFC
susceptibilities, start to appear below 6.0 K, the onset temperature of
irreversibility. A drastic growth of the in-plane superconducting coherence
length below 6.0 K gives rise to a three-dimensional superconducting phase
below , through interplanar Josephson couplings between adjacent TaC
layers. The oscillatory behavior of ,
, and below is
related to the nonlinear behavior arising from the thermally activated flux
flow.Comment: 11 pages, 10 figures, Physical Review B (accepted for publication
On the Mott glass in the one-dimensional half-filled charge density waves
We study the effect of impurity pinning on a one-dimensional half-filled
electron system, which is expressed in terms of a phase Hamiltonian with the
charge degree of freedom. Within the classical treatment, the pinned state is
examined numerically. The Mott glass, which has been pointed out by Orignac et
al. [Phys. Rev. Lett 83 (1999) 2378], appears in the intermediate region where
the impurity potential competes with the commensurate potential. Such a state
is verified by calculating the soliton formation energy, the local restoring
force around the pinned state and the optical conductivity.Comment: 13 pages, 5 figures, to be published in J. Phys. Soc. Jpn. 72 No.11
(2003
Non-thermal Leptogenesis and a Prediction of Inflaton Mass in a Supersymmetric SO(10) Model
The gravitino problem gives a severe constraint on the thermal leptogenesis
scenario. This problem leads us to consider some alternatives to it if we try
to keep the gravitino mass around the weak scale GeV. We
consider, in this paper, the non-thermal leptogenesis scenario in the framework
of a minimal supersymmetric SO(10) model. Even if we start with the same
minimal SO(10) model, we have different predictions for low-energy
phenomenologies dependent on the types of seesaw mechanism. This is the case
for leptogenesis: it is shown that the type-I see-saw model gives a consistent
scenario for the non-thermal leptogenesis but not for type-II. The predicted
inflaton mass needed to produce the observed baryon asymmetry of the universe
is found to be GeV for the reheating temperature
GeV.Comment: 9 pages, 2 figures; the version to appear in JCA
Theoretical Study of Friction: A Case of One-Dimensional Clean Surfaces
A new method has been proposed to evaluate the frictional force in the
stationary state. This method is applied to the 1-dimensional model of clean
surfaces. The kinetic frictional force is seen to depend on velocity in
general, but the dependence becomes weaker as the maximum static frictional
force increases and in the limiting case the kinetic friction gets only weakly
dependent on velocity as described by one of the laws of friction. It is also
shown that there is a phase transition between state with vanishing maximum
static frictional force and that with finite one. The role of randomness at the
interface and the relation to the impurity pinning of the sliding
Charge-Density-Wave are discussed. to appear in Phys.Rev.B. abstract only. Full
text is available upon request. E-mail: [email protected]: 2 pages, Plain TEX, OUCMT-94-
The charged lepton mass matrix and non-zero with TeV scale New Physics
We provide an explicit structure of the charged lepton mass matrix which is
2-3 symmetric except for a single breaking of this symmetry by the muon mass.
We identify a flavor symmetric limit for the mass matrices where the first
generation is decoupled from the other two in the charged lepton sector while
in the neutrino sector the third generation is decoupled from the first two
generations. The leptonic mixing in the symmetric limit can be, among other
structures, the bi-maximal (BM) or the tri-bimaximal (TBM) mixing. Symmetry
breaking effects are included both in the charged lepton and the neutrino
sector to produce corrections to the leptonic mixing and explain the recent
measurements. A model that extends the SM by three right handed
neutrinos, an extra Higgs doublet, and two singlet scalars is introduced to
generate the leptonic mixing.Comment: 28 pages, 24 figures. arXiv admin note: substantial text overlap with
arXiv:1111.307
CP Violations in Lepton Number Violation Processes and Neutrino Oscillations
We examine the constraints on the MNS lepton mixing matrix from the present
and future experimental data of the neutrino oscillation and lepton number
violation processes. We introduce a graphical representation of the CP
violation phases which appear in the lepton number violation processes such as
neutrinoless double beta decay, the conversion, and the K decay,
Using this graphical representation, we derive the
constraints on the CP violation phases in the lepton sector.Comment: 21pp, REVTeX, 9 Figure
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