36,720 research outputs found
The effect of supersymmetry breaking in the Mass Varying Neutrinos
We discuss the effect of the supersymmetry breaking on the Mass Varying
Neutrinos(MaVaNs) scenario. Especially, the effect mediated by the
gravitational interaction between the hidden sector and the dark energy sector
is studied. A model including a chiral superfield in the dark sector and the
right handed neutrino superfield is proposed. Evolutions of the neutrino mass
and the equation of state parameter are presented in the model. It is remarked
that only the mass of a sterile neutrino is variable in the case of the
vanishing mixing between the left-handed and a sterile neutrino on cosmological
time scale. The finite mixing makes the mass of the left-handed neutrino
variable.Comment: 6 pages, 7 figures, RevTeX4, references added, discussions and
figures revise
Pre-K-Edge Structure on Anomalous X-Ray Scattering in LaMnO3
We study the pre-K-edge structure of the resonant X-ray scattering for
forbidden reflections (anomalous scattering) in LaMnO3, using the band
calculation based on the local density approximation. We find a two-peak
structure with an intensity approximately 1/100 of that of the main peak. This
originates from a mixing of 4p states of Mn to 3d states of neighboring Mn
sites. The effect is enhanced by an interference with the tail of the main
peak. The effect of the quadrupole transition is found to be one order of
magnitude smaller than that of the dipole transition, modifying slightly the
azimuthal-angle dependence.Comment: 4 pages, 5 figures, submitted to J. Phys. Soc. Jp
Superconducting pi qubit with a ferromagnetic Josephson junction
Solid-state qubits have the potential for the large-scale integration and for
the flexibility of layout for quantum computing. However, their short
decoherence time due to the coupling to the environment remains an important
problem to be overcome. We propose a new superconducting qubit which
incorporates a spin-electronic device: the qubit consists of a superconducting
ring with a ferromagnetic pi junction which has a metallic contact and a normal
Josephson junction with an insulating barrier. Thus, a quantum coherent
two-level state is formed without an external magnetic field. This feature and
the simple structure of the qubit make it possible to reduce its size leading
to a long decoherence time.Comment: 4 pages, 3 figure
Magnetic susceptibility and low-temperature specific-heat of integrable 1-D Hubbard model under open-boundary conditions
The magnetic susceptibility and the low-temperature specific heat of the
1-dimensional Hubbard model under the integrable open-boundary conditions are
discussed through the Bethe ansatz with the string hypothesis. The
contributions of the boundary fields to both the susceptibility and the
specific heat are obtained, and their exact expressions are analytically
derived.Comment: 14 pages, Latex, No figures, to appear in J. Phys. A: Gen. & Mat
Proximity-driven source of highly spin-polarized ac current on the basis of superconductor/weak ferromagnet/superconductor voltage-biased Josephson junction
We theoretically investigate an opportunity to implement a source of highly
spin-polarized ac current on the basis of superconductor/weak
ferromagnet/superconductor (SFS) voltage-biased junction in the regime of
essential proximity effect and calculate the current flowing through the probe
electrode tunnel coupled to the ferromagnetic interlayer region. It is shown
that while the polarization of the dc current component is generally small in
case of weak exchange field of the ferromagnet, there is an ac component of the
current in the system. This ac current is highly spin-polarized and entirely
originated from the non-equilibrium proximity effect in the interlayer. The
frequency of the current is controlled by the voltage applied to SFS junction.
We discuss a possibility to obtain a source of coherent ac currents with a
certain phase shift between them by tunnel coupling two probe electrodes at
different locations of the interlayer region.Comment: 8 pages, 5 figure
3-point off-shell vertex in scalar QED in arbitrary gauge and dimension
We calculate the complete one-loop off-shell three-point scalar-photon vertex
in arbitrary gauge and dimension for Scalar Quantum Electrodynamics. Explicit
results are presented for the particular cases of dimensions 3 and 4 both for
massive and massless scalars. We then propose non-perturbative forms of this
vertex that coincide with the perturbative answer to order .Comment: Uses axodra
Renormalization-Group Approach to Spin-Wave Theory of Quantum Heisenberg Ferromagnet
The renormalization-group method is used to analyze the low-temperature
behaviour of a two-dimentional, spin- quantum Heisenberg ferromagnet. A set
of recursion equations is derived in an one-loop approximation. The
low-temperature asymptotics of the correlation length and the uniform
susceptibility are obtained. For small spins () the results are
essentially different from those in the spin-wave theory.Comment: 9 pages, RevTex 3.0 fil
Template banks to search for compact binaries with spinning components in gravitational wave data
Gravitational waves from coalescing compact binaries are one of the most
promising sources for detectors such as LIGO, Virgo and GEO600. If the
components of the binary posess significant angular momentum (spin), as is
likely to be the case if one component is a black hole, spin-induced precession
of a binary's orbital plane causes modulation of the gravitational-wave
amplitude and phase. If the templates used in a matched-filter search do not
accurately model these effects then the sensitivity, and hence the detection
rate, will be reduced. We investigate the ability of several search pipelines
to detect gravitational waves from compact binaries with spin. We use the
post-Newtonian approximation to model the inspiral phase of the signal and
construct two new template banks using the phenomenological waveforms of
Buonanno, Chen and Vallisneri. We compare the performance of these template
banks to that of banks constructed using the stationary phase approximation to
the non-spinning post-Newtonian inspiral waveform currently used by LIGO and
Virgo in the search for compact binary coalescence. We find that, at the same
false alarm rate, a search pipeline using phenomenological templates is no more
effective than a pipeline which uses non-spinning templates. We recommend the
continued use of the non-spinning stationary phase template bank until the
false alarm rate associated with templates which include spin effects can be
substantially reduced.Comment: 11 pages, 3 figure
Direct observation of Fe spin reorientation in single crystalline YbFe6Ge6
We have grown single crystals of YbFe6Ge6 and LuFe6Ge6 and characterized
their anisotropic behaviour through low field magnetic susceptibility,
field-dependent magnetization, resistivity and heat capacity measurements. The
Yb+3 valency is confirmed by LIII XANES measurements. YbFe6Ge6 crystals exhibit
a field-dependent, sudden reorientation of the Fe spins at about 63 K, a unique
effect in the RFe6Ge6 family (R = rare earths) where the Fe ions order
anti-ferromagnetically with Neel temperatures above 450 K and the R ions'
magnetism appears to behave independently. The possible origins of this unusual
behaviour of the ordered Fe moments in this compound are discussed.Comment: 12 pages, 8 figures, accepted in J. Phys.: Cond. Matte
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