3,241 research outputs found
Momentum-Dependent Hybridization Gap and dispersive in-gap state of The Kondo Semiconductor SmB6
We report the temperature-dependent three-dimensional angle-resolved
photoemission spectra of the Kondo semiconductor SmB. We found a difference
in the temperature dependence of the peaks at the X and points, due to
hybridization between the Sm 5d conduction band and the nearly localized Sm 4f
state. The peak intensity at the X point has the same temperature dependence as
the valence transition below 120 K, while that at the point is
consistent with the magnetic excitation at Q=(0.5,0.5,0.5) below 30 K. This
suggests that the hybridization with the valence transition mainly occurs at
the X point, and the initial state of the magnetic excitation is located at the
point.Comment: 5 pages, 3 figure
TeV Scale Mirage Mediation and Natural Little SUSY Hierarchy
TeV scale mirage mediation has been proposed as a supersymmetry breaking
scheme reducing the fine tuning for electroweak symmetry breaking in the
minimal supersymmetric extension of the standard model. We discuss a moduli
stabilization set-up for TeV scale mirage mediation which allows an
extra-dimensional interpretation for the origin of supersymmetry breaking and
naturally gives an weak-scale size of the Higgs B-parameter. The set-up
utilizes the holomorphic gauge kinetic functions depending on both the heavy
dilaton and the light volume modulus whose axion partners are assumed to be
periodic fields. We also examine the low energy phenomenology of TeV scale
mirage mediation, particularly the constraints from electroweak symmetry
breaking and FCNC processes.Comment: 44 pages, 14 figures; added references, extended discussions in
section
Naked singularities and quantum gravity
There are known models of spherical gravitational collapse in which the
collapse ends in a naked shell-focusing singularity for some initial data. If a
massless scalar field is quantized on the classical background provided by such
a star, it is found that the outgoing quantum flux of the scalar field diverges
in the approach to the Cauchy horizon. We argue that the semiclassical
approximation (i.e. quantum field theory on a classical curved background) used
in these analyses ceases to be valid about one Planck time before the epoch of
naked singularity formation, because by then the curvature in the central
region of the star reaches Planck scale. It is shown that during the epoch in
which the semiclassical approximation is valid, the total emitted energy is
about one Planck unit, and is not divergent. We also argue that back reaction
in this model does not become important so long as gravity can be treated
classically. It follows that the further evolution of the star will be
determined by quantum gravitational effects, and without invoking quantum
gravity it is not possible to say whether the star radiates away on a short
time scale or settles down into a black hole state.Comment: 16 pages, paper rewritten into sections, conclusions unchanged, 4
references added, to appear in Phys. Rev. D (Rapid Communication
磁気島の爆発的合体過程の粒子加速
An explosive reconnection process associated with the nonlinear evolution of the coalescence instability is found through studies of the electromagnetic particle simulation. The explosive coalescence is a process of magnetic collapse, in which we find the magnetic and electrostatic field energies and temperatures (ion temperature in the coalescing direction, in particular) explode toward the explosion time to as (t_0 - t)^, (t_0 - t)^, and (t_0 - t)^, respectively.Single-peak, double-peak, and triple-peak structures of magnetic energy, temperature, and electrostatic energy, respectively, are observed on the simulatton as overshoot amplitude oscillations and these features are theoretically explained. Rapid acceleration of particles binormal to the magnetic field and electric field becomes possible
磁気島の爆発的合体過程の流体モデル
Magnetohydrodynamic simulation of the explosive coalescence of magnetic islands is carried out. This result is in agreement with the electromagnetic particle simulation. A theoretical model to describe this process observed in our computer simulations is presented. The theory describes the magnetic collapse and is based on a self-similar solution to the two-fluid plasma equations, as the simulation exhibits temporal self-similarity. The master equation for the scale factor takes a from of the orbital equation in a Sagdeev potential
Log-aesthetic Curves as Similarity Geometric Analogue of Euler's Elasticae
In this paper we consider the log-aesthetic curves and their generalization
which are used in CAGD. We consider those curves under similarity geometry and
characterize them as stationary integrable flow on plane curves which is
governed by the Burgers equation. We propose a variational formulation of those
curves whose Euler-Lagrange equation yields the stationary Burgers equation.
Our result suggests that the log-aesthetic curves and their generalization can
be regarded as the similarity geometric analogue of Euler's elasticae
Emergent spatial correlations in stochastically evolving populations
We study the spatial pattern formation and emerging long range correlations
in a model of three species coevolving in space and time according to
stochastic contact rules. Analytical results for the pair correlation
functions, based on a truncation approximation and supported by computer
simulations, reveal emergent strategies of survival for minority agents based
on selection of patterns. Minority agents exhibit defensive clustering and
cooperative behavior close to phase transitions.Comment: 11 pages, 4 figures, Adobe PDF forma
Xenopus NM23-X4 regulates retinal gliogenesis through interaction with p27Xic1
Background. In Xenopus retinogenesis, p27Xic1, a Xenopus cyclin dependent kinase inhibitor, functions as a cell fate determinant in both gliogenesis and neurogenesis in a context dependent manner. This activity is essential for co-ordination of determination and cell cycle regulation. However, very little is known about the mechanism regulating the context dependent choice between gliogenesis versus neurogenesis. Results. We have identified NM23-X4, a NM23 family member, as a binding partner of p27Xic1. NM23-X4 is expressed at the periphery of the ciliary marginal zone of the Xenopus retina and the expression overlaps with p27Xic1 at the central side. Our in vivo functional analysis in Xenopus retina has shown that knockdown of NM23-X4 activates gliogenesis. Furthermore, co-overexpression of NM23-X4 with p27Xic1 results in the inhibition of p27Xic1-mediated gliogenesis, through direct interaction of NM23-X4 with the amino-terminal side of p27Xic1. This inhibitory effect on gliogenesis requires serine-150 and histidine-148, which correspond to the important residues for the kinase activities of NM23 family members. Conclusion. This study demonstrates that NM23-X4 functions as an inhibitor of p27Xic1-mediated gliogenesis in Xenopus retina and suggests that this activity contributes to the proper spatio-temporal regulation of gliogenesis
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