1,407 research outputs found
Pure and entangled N=4 linear supermultiplets and their one-dimensional sigma-models
"Pure" homogeneous linear supermultiplets (minimal and non-minimal) of the
N=4-Extended one-dimensional Supersymmetry Algebra are classified. "Pure" means
that they admit at least one graphical presentation (the corresponding
graph/graphs are known as "Adinkras"). We further prove the existence of
"entangled" linear supermultiplets which do not admit a graphical presentation,
by constructing an explicit example of an entangled N=4 supermultiplet with
field content (3,8,5). It interpolates between two inequivalent pure N=4
supermultiplets with the same field content. The one-dimensional N=4
sigma-model with a three-dimensional target based on the entangled
supermultiplet is presented. The distinction between the notion of equivalence
for pure supermultiplets and the notion of equivalence for their associated
graphs (Adinkras) is discussed. Discrete properties such as chirality and
coloring can discriminate different supermultiplets. The tools used in our
classification include, among others, the notion of field content, connectivity
symbol, commuting group, node choice group and so on.Comment: 20 pages, 5 figures. Two references adde
Stable Existence of Phase IV inside Phase II under Pressure in CeLaB
We investigate the pressure effect of the electrical resistivity and
magnetization of CeLaB. The situation in which phase IV
stably exists inside phase II at H=0 T could be realized by applying a pressure
above GPa. This originates from the fact that the stability of
phase II under pressure is larger than those of phases IV and III. The results
seem to be difficult to reproduce by taking the four interactions of
-type AFO, -type AFQ, -type AFO, and AF
exchange into account within a mean-field calculation framework.Comment: 4 pages, 5 figures, to appear in J. Phys. Soc. Jpn. 79 (2010) No.
Optical conductivity of the Kondo insulator YbB_12: Gap formation and low-energy excitations
Optical reflectivity experiments have been conducted on single crystals of
the Kondo insulator YbB_12 in order to obtain its optical conductivity,
\sigma(\omega). Upon cooling below 70 K, a strong supression of \sigma(\omega)
is seen in the far-infrared region, indicating the opening of an energy gap of
~ 25 meV. This gap development is coincident with a rapid decrease in the
magnetic susceptibility, which shows that the gap opening has significant
influence on magnetic properties. A narrow, asymmetric peak is observed at ~40
meV in \sigma(\omega), which is attributed to optical transitions between the
Yb 4f-derived states across the gap. In addition, a broad peak is observed at
~0.25 eV. This peak is attributed to transitions between Yb 4f-derived states
and p-d band, and is reminiscent of similar peaks previously observed for
rare-earth hexaborides.Comment: 4 pages, 4 figure
On General Off-Shell Representations of Worldline (1D) Supersymmetry
Every finite-dimensional unitary representation of the N-extended worldline
supersymmetry without central charges may be obtained by a sequence of
differential transformations from a direct sum of minimal Adinkras, simple
supermultiplets that are identifiable with representations of the Clifford
algebra. The data specifying this procedure is a sequence of subspaces of the
direct sum of Adinkras, which then opens an avenue for classification of the
continuum of so constructed off-shell supermultiplets.Comment: 21 pages, 5 illustrations; references update
Evidence for short-range antiferromagnetic fluctuations in Kondo-insulating YbB12
The spin dynamics of mixed-valence YbB12 has been studied by inelastic
neutron scattering on a high-quality single crystal. In the Kondo-insulating
regime realized at low temperature, the spectra exhibit a spin-gap structure
with two sharp, dispersive, in-gap excitations at E = 14.5 and approximately 20
meV. The lower mode is shown to be associated with short-range correlations
near the antiferromagnetic wave vector q0 = (1/2, 1/2, 1/2). Its properties are
in overall agreement with those expected for a "spin exciton'' branch in an
indirect hybridization gap semiconductor.Comment: 4 pages, 4 figures ; submitted to Physical Review Letter
Effective Symmetries of the Minimal Supermultiplet of N = 8 Extended Worldline Supersymmetry
A minimal representation of the N = 8 extended worldline supersymmetry, known
as the `ultra-multiplet', is closely related to a family of supermultiplets
with the same, E(8) chromotopology. We catalogue their effective symmetries and
find a Spin(4) x Z(2) subgroup common to them all, which explains the
particular basis used in the original construction. We specify a constrained
superfield representation of the supermultiplets in the ultra-multiplet family,
and show that such a superfield representation in fact exists for all adinkraic
supermultiplets. We also exhibit the correspondences between these
supermultiplets, their Adinkras and the E(8) root lattice bases. Finally, we
construct quadratic Lagrangians that provide the standard kinetic terms and
afford a mixing of an even number of such supermultiplets controlled by a
coupling to an external 2-form of fluxes.Comment: 13 Figure
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