23,099 research outputs found
Optimality and strong stability of control systems
Optimality and strong stability of control syste
Singlet portal extensions of the standard seesaw models to dark sector with local dark symmetry: An alternative to the new minimal standard model
Assuming dark matter is absolutely stable due to unbroken dark gauge symmetry
and singlet operators are portals to the dark sector, we present a simple
extension of the standard seesaw model that can accommodate all the
cosmological observations as well as terrestrial experiments available as of
now, including leptogenesis, extra dark radiation of (resulting in
the effective number of neutrino species), Higgs
inflation, small and large scale structure formation, and current relic density
of scalar DM (). The Higgs signal strength is equal to one as in the SM for
unbroken case with a scalar dark matter, but it could be less than one
independent of decay channels if the dark matter is a dark sector fermion or if
is spontaneously broken, because of a mixing with a new neutral scalar
boson in the models.Comment: Presented at the 9th PATRAS Workshop on Axions, WIMPs and WISP
Surface Spectral Function of Momentum-dependent Pairing Potentials in a Topological Insulator: Application to CuBiSe
We propose three possible momentum-dependent pairing potentials for candidate
of topological superconductor (for example CuBiSe), and calculate
the surface spectral function and surface density of state with these pairing
potentials. We find that the first two can give the same spectral functions as
the fully-gapped and node-contacted pairing potentials given in [Phys. Rev.
Lett. 105, 097001], and that the third one can obtain topological non-trivial
case which exists flat Andreev bound state and preserves the rotation
symmetry. We hope our proposals and results be judged by future experiment.Comment: 5 pages, 3 figure
Possible origin of the 0.5 plateau in the ballistic conductance of quantum point contacts
A non-equilibrium Green function formalism (NEGF) is used to study the
conductance of a side-gated quantum point contact (QPC) in the presence of
lateral spin-orbit coupling (LSOC). A small difference of bias voltage between
the two side gates (SGs) leads to an inversion asymmetry in the LSOC between
the opposite edges of the channel. In single electron modeling of transport,
this triggers a spontaneous but insignificant spin polarization in the QPC.
However, the spin polarization of the QPC is enhanced substantially when the
effect of electron-electron interaction is included. The spin polarization is
strong enough to result in the occurrence of a conductance plateau at 0.5G0 (G0
= 2e2/h) in the absence of any external magnetic field. In our simulations of a
model QPC device, the 0.5 plateau is found to be quite robust and survives up
to a temperature of 40K. The spontaneous spin polarization and the resulting
magnetization of the QPC can be reversed by flipping the polarity of the source
to drain bias or the potential difference between the two SGs. These numerical
simulations are in good agreement with recent experimental results for
side-gated QPCs made from the low band gap semiconductor InAs
Ultrafast Magneto-Acoustics in Nickel Films
We report about the existence of magneto-acoustic pulses propagating in a
200-nm-thick ferromagnetic nickel film excited with 120 fs laser pulses. They
result from the coupling between the magnetization of the ferromagnetic film
and the longitudinal acoustic waves associated to the propagation of the
lattice deformation induced by the femtosecond laser pulses. The
magneto-acoustic pulses are detected from both the front and back sides of the
film, using the time-resolved magneto-optical Kerr technique, measuring both
the time dependent rotation and ellipticity. We show that the propagating
acoustic pulse couples efficiently to the magnetization and is strong enough to
induce a precession of the magnetization. It is due to a transient change of
the crystalline anisotropy associated to the lattice deformation. It is shown
that the results can be interpreted by combining the concepts of acoustic pulse
propagation and ultrafast magnetization dynamics.Comment: 4 pages, 3 figures, Submitted to Physical Review Letters on November
30th 201
Global Cosmological Parameters Determined Using Classical Double Radio Galaxies
A sample of 20 powerful extended radio galaxies with redshifts between zero
and two were used to determine constraints on global cosmological parameters.
Data for six radio sources were obtained from the VLA archive, analyzed, and
combined with the sample of 14 radio galaxies used previously by Guerra & Daly
to determine cosmological parameters. The results are consistent with our
previous results, and indicate that the current value of the mean mass density
of the universe is significantly less than the critical value. A universe with
of unity is ruled out at 99.0% confidence, and the best fitting
values of in matter are and
assuming zero space curvature and zero cosmological
constant, respectively. Note that identical results obtain when the low
redshift bin, which includes Cygnus A, is excluded; these results are
independent of whether the radio source Cygnus A is included. The method does
not rely on a zero-redshift normalization.
The radio properties of each source are also used to determine the density of
the gas in the vicinity of the source, and the beam power of the source. The
six new radio sources have physical characteristics similar to those found for
the original 14 sources. The density of the gas around these radio sources is
typical of gas in present day clusters of galaxies. The beam powers are
typically about .Comment: 39 pages includes 21 figures, accepted to Ap
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