3,868 research outputs found
Tunable Exchange Interaction in Quantum Dot Devices
We theoretically discuss the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction
between semiconductor quantum dots (QDs). When each QD having a local spin is
coupled to the conduction electrons in semiconductors, an indirect exchange
interaction, i.e., the RKKY interaction, is induced between two local spins.
The RKKY interaction between QDs, which is mediated by the Fermi sea in
semiconductors, is modulated by changing the Fermi energy, and the magnitude or
even the sign of the exchange interaction can be tuned, which leads to a
tunable magnetic transition in QD devices. We estimate the magnitude of the
RKKY interaction in QDs as a function of the electron density and the inter-dot
distance
(2 + 1) noncommutative gravity and conical spacetimes
We solve (2+1) noncommutative gravity coupled to point-like sources. We find
continuity with Einstein gravity since we recover the classical gravitational
field in the limit or at large distance from the source. It
appears a limitation on the mass which is twice than expected. Since the
distance is not gauge invariant, the measure of the deficit angle near the
source is intrinsically ambiguous, with the gauge group playing the role of
statistical ensemble. Einstein determinism can be recovered only at large
distance from the source, compared with the scale of the noncommutative
parameter .Comment: 19 pages, LaTeX, no figure
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Laser Sintering of Stainless Steel using Resin Powder
We tried laser sintering of 316L stainless steel powder using resin powder. The laser
sintering conditions such as laser power, scan speed and scan pitch with a YAG laser, and the
influence of additional resin powder on the density and the tensile properties of the sintered alloy
were investigated experimentally. The tensile specimen was laser-sintered with a YAG laser, and
then debound and sintered in a vacuum furnace. The tensile specimen was successfully fabricated.
The relative density and the tensile strength varied with the additional resin powder, and the
optimum weight percentage of additional resin powder was around 4%.The relative density of the
sintered alloy was approximately 85%, and the tensile strength and elongation of the sintered
alloy were more than 280 MPa and 15% respectively.Mechanical Engineerin
Elliptic algebra U_{q,p}(^sl_2): Drinfeld currents and vertex operators
We investigate the structure of the elliptic algebra U_{q,p}(^sl_2)
introduced earlier by one of the authors. Our construction is based on a new
set of generating series in the quantum affine algebra U_q(^sl_2), which are
elliptic analogs of the Drinfeld currents. They enable us to identify
U_{q,p}(^sl_2) with the tensor product of U_q(^sl_2) and a Heisenberg algebra
generated by P,Q with [Q,P]=1. In terms of these currents, we construct an L
operator satisfying the dynamical RLL relation in the presence of the central
element c. The vertex operators of Lukyanov and Pugai arise as `intertwiners'
of U_{q,p}(^sl_2) for level one representation, in the sense to be elaborated
on in the text. We also present vertex operators with higher level/spin in the
free field representation.Comment: 49 pages, (AMS-)LaTeX ; added an explanation of integration contours;
added comments. To appear in Comm. Math. Phys. Numbering of equations is
correcte
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