41,068 research outputs found
Mechanical properties of a degradable phosphate glass fibre reinforced polymer composite for internal fracture fixation
NOTICE: this is the author’s version of a work that was accepted for publication in Materials Science and Engineering. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Materials Science and Engineering, [VOL 30, ISSUE 7, (2010)] DOI: 10.1016/j.msec.2010.04.017
Restrictions of generalized Verma modules to symmetric pairs
We initiate a new line of investigation on branching problems for generalized
Verma modules with respect to complex reductive symmetric pairs (g,k). Here we
note that Verma modules of g may not contain any simple module when restricted
to a reductive subalgebra k in general.
In this article, using the geometry of K_C orbits on the generalized flag
variety G_C/P_C, we give a necessary and sufficient condition on the triple
(g,k, p) such that the restriction X|_k always contains simple k-modules for
any g-module lying in the parabolic BGG category O^p attached to a
parabolic subalgebra p of g.
Formulas are derived for the Gelfand-Kirillov dimension of any simple
k-module occurring in a simple generalized Verma module of g. We then prove
that the restriction X|_k is multiplicity-free for any generic g-module X \in O
if and only if (g,k) is isomorphic to a direct sum of (A_n,A_{n-1}), (B_n,D_n),
or (D_{n+1},B_n). We also see that the restriction X|_k is multiplicity-free
for any symmetric pair (g, k) and any parabolic subalgebra p with abelian
nilradical and for any generic g-module X \in O^p. Explicit branching laws are
also presented.Comment: 31 pages, To appear in Transformation Group
NMR Evidence for Antiferromagnetic Transition in the Single-Component Molecular System, [Cu(tmdt)]
The magnetic state of the single-component molecular compound,
[Cu(tmdt)], is investigated by means of H-NMR. An abrupt spectral
broadening below 13 K and a sharp peak in nuclear spin-lattice relaxation rate,
, at 13 K are observed as clear manifestations of a second-order
antiferromagnetic transition, which is consistent with the previously reported
magnetic susceptibility and EPR measurement. The ordered moment is estimated at
/molecule. The temperature-dependence of
above the transition temperature indicates one-dimensional spin
dynamics and supports that the spins are on the central part of the molecule
differently from other isostructural compounds.Comment: 13pages, 5 figure
Relativistic stars in f(R) gravity, and absence thereof
Several f(R) modified gravity models have been proposed which realize the
correct cosmological evolution and satisfy solar system and laboratory tests.
Although nonrelativistic stellar configurations can be constructed, we argue
that relativistic stars cannot be present in such f(R) theories. This problem
appears due to the dynamics of the effective scalar degree of freedom in the
strong gravity regime. Our claim thus raises doubts on the viability of f(R)
models.Comment: 9 pages, 7 figures, v2: references added, minor corrections, version
accepted for publication in PR
Co-NMR Knight Shift of NaxCoO2 \dot yH2O Studied in Both Superconducting Regions of the Tc-nuQ3 Phase Diagram Divided by the Nonsuperconducting Phase
In the temperature (T)-nuQ3 phase diagram of NaxCoO2 \dot yH2O, there exist
two superconducting regions of nuQ3 separated by the nonsuperconducting region,
where nuQ3 is usually estimated from the peak position of the 59Co-NQR spectra
of the 5/2-7/2 transition and well-approximated here as nuQ3~3nuQ,nuQ being the
interaction energy between the nuclear quadrupole moment and the electric field
gradient. We have carried out measurements of the 59Co-NMR Knight shift (K) for
a single crystal in the higher-nuQ3 superconducting phase and found that K
begins to decrease with decreasing T at Tc for both magnetic field directions
parallel and perpendicular to CoO2-planes. The result indicates together with
the previous ones that the superconducting pairs are in the spin-singlet state
in both phases, excluding the possibility of the spin-triplet superconductivity
in this phase diagram. The superconductivity of this system spreads over the
wide nuQ3 regions, but is suppressed in the narrow region located at the middle
point of the region possibly due to charge instability.Comment: 8 pages, 5 figures, submitted to J. Phys. Soc. Jp
Dominant role of impurity scattering over crystalline anisotropy for magnetotransport properties in the quasi-1D Hollandite Ba1.2Rh8O16
Angular magnetotransport measurements have been performed to tackle the
origin of the magnetoresistance in the quasi-1D Hollandite Ba1.2Rh8O16. Three
samples of different impurities amount were measured. We observe that the low
temperature resistivity upturn is not due to a charge density wave transition,
and a dominant role of impurities scattering for low temperature transport
properties is instead demonstrated. The components of magnetoresistance were
separated by using the Kohler plot and the angular dependency of the resistance
under magnetic field. It shows the major contribution of an isotropic, likely
spin driven, negative magnetoresistance. Galvanomagnetic characteristics are
then consistent with a Kondo effect and appear to be essentially 3D at low
temperature.Comment: accepted for publication in PR
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