255 research outputs found
One-loop unitarity of scalar field theories on Poincare invariant commutative nonassociative spacetimes
We study scalar field theories on Poincare invariant commutative
nonassociative spacetimes. We compute the one-loop self-energy diagrams in the
ordinary path integral quantization scheme with Feynman's prescription, and
find that the Cutkosky rule is satisfied. This property is in contrast with
that of noncommutative field theory, since it is known that noncommutative
field theory with space/time noncommutativity violates unitarity in the above
standard scheme, and the quantization procedure will necessarily become
complicated to obtain a sensible Poincare invariant noncommutative field
theory. We point out a peculiar feature of the non-locality in our
nonassociative field theories, which may explain the property of the unitarity
distinct from noncommutative field theories. Thus commutative nonassociative
field theories seem to contain physically interesting field theories on
deformed spacetimes.Comment: 25 pages, 9 figures ; appendix and references adde
Effects of Orthogonal Rotating Electric Fields on Electrospinning Process
Electrospinning is a nanotechnology process whereby an external electric
field is used to accelerate and stretch a charged polymer jet, so as to produce
fibers with nanoscale diameters. In quest of a further reduction in the cross
section of electrified jets hence of a better control on the morphology of the
resulting electrospun fibers, we explore the effects of an external rotating
electric field orthogonal to the jet direction. Through extensive particle
simulations, it is shown that by a proper tuning of the electric field
amplitude and frequency, a reduction of up to a in the aforementioned
radius can be obtained, thereby opening new perspectives in the design of
future ultra-thin electrospun fibres. Applications can be envisaged in the
fields of nanophotonic components as well as for designing new and improved
filtration materials.Comment: 22 pages, 8 figure
The Cutkosky rule of three dimensional noncommutative field theory in Lie algebraic noncommutative spacetime
We investigate the unitarity of three dimensional noncommutative scalar field
theory in the Lie algebraic noncommutative spacetime [x^i,x^j]=2i kappa
epsilon^{ijk}x_k. This noncommutative field theory possesses a SL(2,R)/Z_2
group momentum space, which leads to a Hopf algebraic translational symmetry.
We check the Cutkosky rule of the one-loop self-energy diagrams in the
noncommutative phi^3 theory when we include a braiding, which is necessary for
the noncommutative field theory to possess the Hopf algebraic translational
symmetry at quantum level. Then, we find that the Cutkosky rule is satisfied if
the mass is less than 1/(2^(1/2)kappa).Comment: 24 pages, 13 figures, a minor clarification, references adde
Epitaxial contact Andreev reflection spectroscopy of NbN/Co<sub>2</sub>FeSi layered devices
We investigated the spin polarization P of Co-based Heusler alloy Co2FeSi by epitaxial contact Andreev reflection (ECAR) spectroscopy using epitaxially grown superconductor NbN and Heusler alloy Co2FeSi layered devices. Ferromagnetic Co2FeSi possesses the highest Curie temperature (TC ? 1100 K) and the largest spontaneous magnetic moment (ps ? 6 μB) in the class of Heusler alloys. The ECAR measurements revealed that the P value of Co2FeSi was 54 ± 2% with a finite barrier parameter Z, indicating that an intrinsic P value in ECAR spectroscopy would exceed reported values in point-contact Andreev reflection spectroscopy. We therefore established not only the epitaxial integration of ferromagnetic Co2FeSi with superconductor NbN on an MgO substrate but also the fabrication and evaluation techniques of their ECAR devices. This highly versatile superconducting spintronic system enables fundamental superconducting spintronic studies, and it is also a candidate for practical superconducting spintronic devices
Stau Kinks at the LHC
The kink signature of charged tracks is predicted in some SUSY models, and it
is very characteristic signal at collider experiments. We study the kink
signature at LHC using two models, SUSY models with a gravitino LSP and a stau
NLSP, and R-parity violating SUSY models with a stau (N)LSP. We find that a
large number of kink events can be discovered in a wide range of the SUSY
parameters, when the decay length is O(10-10^5)mm. Model discrimination by
identifying the daughter particles of the kink tracks is also discussed.Comment: 19 pages, 4 figures; Version published in JHEP; abstract refined,
reference added and several minor corrections in tex
- …