191,211 research outputs found
Modulation of the Curie Temperature in Ferromagnetic/Ferroelectric Hybrid Double Quantum Wells
We propose a ferromagnetic/ferroelectric hybrid double quantum well
structure, and present an investigation of the Curie temperature (Tc)
modulation in this quantum structure. The combined effects of applied electric
fields and spontaneous electric polarization are considered for a system that
consists of a Mn \delta-doped well, a barrier, and a p-type ferroelectric well.
We calculate the change in the envelope functions of carriers at the lowest
energy sub-band, resulting from applied electric fields and switching the
dipole polarization. By reversing the depolarizing field, we can achieve two
different ferromagnetic transition temperatures of the ferromagnetic quantum
well in a fixed applied electric field. The Curie temperature strongly depends
on the position of the Mn \delta-doped layer and the polarization strength of
the ferroelectric well.Comment: 9 pages, 5 figures, to be published in Phys. Rev. B (2006) minor
revision: One of the line types is changed in Fig.
Pulsar Velocity with Three-Neutrino Oscillations in Non-adiabatic Processes
We have studied the position dependence of neutrino energy on the
Kusenko-Segr\`{e} mechanism as an explanation of the proper motion of pulsars.
The mechanism is also examined in three-generation mixing of neutrinos and in a
non-adiabatic case. The position dependence of neutrino energy requires the
higher value of magnetic field such as Gauss in order
to explain the observed proper motion of pulsars. It is shown that possible
non-adiabatic processes decrease the neutrino momentum asymmetry, whereas an
excess of electron neutrino flux over other flavor neutrino fluxes increases
the neutrino momentum asymmetry. It is also shown that a general treatment with
all three neutrinos does not modify the result of the two generation treatment
if the standard neutrino mass hierarchy is assumed.Comment: 8 pages, REVTEX, no figure
Entropy of the Randall-Sundrum brane world with the generalized uncertainty principle
By introducing the generalized uncertainty principle, we calculate the
entropy of the bulk scalar field on the Randall-Sundrum brane background
without any cutoff. We obtain the entropy of the massive scalar field
proportional to the horizon area. Here, we observe that the mass contribution
to the entropy exists in contrast to all previous results, which is independent
of the mass of the scalar field, of the usual black hole cases with the
generalized uncertainty principle.Comment: 12 pages. The improved version published in Phys. Rev.
Potential contributions of noncontact atomic force microscopy for the future Casimir force measurements
Surface electric noise, i.e., the non-uniform distribution of charges and
potentials on a surface, poses a great experimental challenge in modern
precision force measurements. Such a challenge is encountered in a number of
different experimental circumstances. The scientists employing atomic force
microscopy (AFM) have long focused their efforts to understand the
surface-related noise issues via variants of AFM techniques, such as Kelvin
probe force microscopy or electric force microscopy. Recently, the physicists
investigating quantum vacuum fluctuation phenomena between two closely-spaced
objects have also begun to collect experimental evidence indicating a presence
of surface effects neglected in their previous analyses. It now appears that
the two seemingly disparate science communities are encountering effects rooted
in the same surface phenomena. In this report, we suggest specific experimental
tasks to be performed in the near future that are crucial not only for
fostering needed collaborations between the two communities, but also for
providing valuable data on the surface effects in order to draw the most
realistic conclusion about the actual contribution of the Casimir force (or van
der Waals force) between a pair of real materials.Comment: The paper appeared in the Proceedings to the 12th International
Conference on Noncontact Atomic Force Microscopy (NC-AFM 2009) and Casimir
2009 Satellite Worksho
Electronic structures of layered perovskite Sr2MO4 (M=Ru, Rh, and Ir)
We investigated the electronic structures of the two-dimensional layered
perovskite Sr\textit{M}O (\textit{M}=4\textit{d} Ru, 4\textit{d}
Rh, and 5\textit{d} Ir) using optical spectroscopy and polarization-dependent O
1\textit{s} x-ray absorption spectroscopy. While the ground states of the
series of compounds are rather different, their optical conductivity spectra
exhibit similar interband transitions, indicative of the
common electronic structures of the 4\textit{d} and 5\textit{d} layered oxides.
The energy splittings between the two orbitals, ,
and , are about 2 eV, which is much larger
than those in the pseudocubic and 3\textit{d} layered perovskite oxides. The
electronic properties of the Sr\textit{M}O compounds are discussed
in terms of the crystal structure and the extended character of the 4\textit{d}
and 5\textit{d} orbitals
The Bowhead Whale, Balaena mysticetus: Its Historic and Current Status
The bowhead whale, Balaena mysticetus, is currently listed as endangered under the Endangered Species Act of 1973 and as depleted under the Marine Mammal Protection Act of 1972. Literature on the species is updated since 1984, and elements are reviewed that may contribute to the evaluation of the status of bowhead whale stocks
Note on the boundary terms in AdS/CFT correspondence for Rarita-Schwinger field
In this letter the boundary problem for massless and massive Rarita-Schwinger
field in the AdS/CFT correspondence is considered. The considerations are along
the lines of a paper by Henneaux (hep-th/9902137) and are based on the
requirement the solutions to be a stationary point for the action functional.
It is shown that this requirement, along with a definite asymptotic behavior of
the solutions, fixes the boundary term that must be added to the initial
Rarita-Schwinger action. It is also shown that the boundary term reproduce the
known two point correlation functions of certain local operators in CFT living
on the boundary.Comment: 12 pages, one more refernce added, some typos correcte
Free-stream turbulence and concave curvature effects on heated, transitional boundary layers, volume 1
An experimental investigation of the transition process on flat-plate and concave curved-wall boundary layers for various free-streem turbulence levels was performed. Where possible, sampling according to the intermittency function was made. Such sampling allowed segregation of the signal into two types of behavior: laminar-like and turbulent-like. The results from the investigation are discussed. Documentation is presented in two volumes. Volume one contains the text of the report including figures and supporting appendices. Volume two contains data reduction program listings and tabulated data
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