7,262 research outputs found
Singlet Fermionic Dark Matter with Dark
We present a fermionic dark matter model mediated by the hidden gauge boson.
We assume the QED-like hidden sector which consists of a Dirac fermion and
U(1) gauge symmetry, and introduce an additional scalar electroweak doublet
field with the U(1) charge as a mediator. The hidden U(1) symmetry is
spontaneously broken by the electroweak symmetry breaking and there exists a
massive extra neutral gauge boson in this model which is the mediator between
the hidden and visible sectors. Due to the U(1) charge, the additional
scalar doublet does not couple to the Standard Model fermions, which leads to
the Higgs sector of type I two Higgs doublet model. The new gauge boson couples
to the Standard Model fermions with couplings proportional to those of the
ordinary boson but very suppressed, thus we call it the dark boson. We
study the phenomenology of the dark boson and the Higgs sector, and show
the hidden fermion can be the dark matter candidate.Comment: 10 pages, 3 figure
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Spatiomechanical Modulation of EphB4-Ephrin-B2 Signaling in Neural Stem Cell Differentiation.
Interactions between EphB4 receptor tyrosine kinases and their membrane-bound ephrin-B2 ligands on apposed cells play a regulatory role in neural stem cell differentiation. With both receptor and ligand constrained to move within the membranes of their respective cells, this signaling system inevitably experiences spatial confinement and mechanical forces in conjunction with receptor-ligand binding. In this study, we reconstitute the EphB4-ephrin-B2 juxtacrine signaling geometry using a supported-lipid-bilayer system presenting laterally mobile and monomeric ephrin-B2 ligands to live neural stem cells. This experimental platform successfully reconstitutes EphB4-ephrin-B2 binding, lateral clustering, downstream signaling activation, and neuronal differentiation, all in a configuration that preserves the spatiomechanical aspects of the natural juxtacrine signaling geometry. Additionally, the supported bilayer system allows control of lateral movement and clustering of the receptor-ligand complexes through patterns of physical barriers to lateral diffusion fabricated onto the underlying substrate. The results from this study reveal a distinct spatiomechanical effect on the ability of EphB4-ephrin-B2 signaling to induce neuronal differentiation. These observations parallel similar studies of the EphA2-ephrin-A1 system in a very different biological context, suggesting that such spatiomechanical regulation may be a common feature of Eph-ephrin signaling
Constraints on the dark Z model from the Higgs boson phenomenology
We study constraints on the hidden sector model mediated by an additional
SU(2) Higgs doublet from the phenomenology of Higgs bosons. The hidden sector
is assumed to contain a hidden U(1) gauge symmetry and the hidden U(1) gauge
boson gets the mass by the electroweak symmetry breaking to be a dark Z boson.
The Higgs sector of the model is similar to that of the two Higgs doublet model
of type I except for the absence of the CP-odd scalar boson. Using the programs
of HiggsBounds and HiggsSignals, we incorporate current experimental limits
from LEP, Tevatron and LHC to examine the Higgs sector in our model and derive
constraints on model parameters. We also discuss the implications of the model
on the dark matter phenomenology.Comment: 18 pages, 7 figure
Water-Soluble Epitaxial NaCl Thin Film for Fabrication of Flexible Devices
We studied growth mechanisms of water-soluble NaCl thin films on single crystal substrates. Epitaxial growth of NaCl(100) on Si(100) and domain-matched growth of NaCl(111) on c-sapphire were obtained at thicknesses below 100 nm even at room temperature from low lattice mismatches in both cases. NaCl thin film, which demonstrates high solubility selectivity for water, was successfully applied as a water-soluble sacrificial layer for fabrication of several functional materials, such as WO3 nano-helix and Sn doped In2O3 nano-branches.111Ysciescopu
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Controlling the Magnetic Anisotropy of the van der Waals Ferromagnet Fe3GeTe2 through Hole Doping.
Identifying material parameters affecting properties of ferromagnets is key to optimized materials that are better suited for spintronics. Magnetic anisotropy is of particular importance in van der Waals magnets, since it not only influences magnetic and spin transport properties, but also is essential to stabilizing magnetic order in the two-dimensional limit. Here, we report that hole doping effectively modulates the magnetic anisotropy of a van der Waals ferromagnet and explore the physical origin of this effect. Fe3-xGeTe2 nanoflakes show a significant suppression of the magnetic anisotropy with hole doping. Electronic structure measurements and calculations reveal that the chemical potential shift associated with hole doping is responsible for the reduced magnetic anisotropy by decreasing the energy gain from the spin-orbit induced band splitting. Our findings provide an understanding of the intricate connection between electronic structures and magnetic properties in two-dimensional magnets and propose a method to engineer magnetic properties through doping
Glueball Spectrum and Matrix Elements on Anisotropic Lattices
The glueball-to-vacuum matrix elements of local gluonic operators in scalar,
tensor, and pseudoscalar channels are investigated numerically on several
anisotropic lattices with the spatial lattice spacing ranging from 0.1fm -
0.2fm. These matrix elements are needed to predict the glueball branching
ratios in radiative decays which will help identify the glueball
states in experiments. Two types of improved local gluonic operators are
constructed for a self-consistent check and the finite volume effects are
studied. We find that lattice spacing dependence of our results is very weak
and the continuum limits are reliably extrapolated, as a result of improvement
of the lattice gauge action and local operators. We also give updated glueball
masses with various quantum numbers.Comment: 22 pages, 16 figures, revtex
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