62,966 research outputs found
Analytical and scale model research aimed at improved hangglider design
Research consisted of a theoretical analysis which attempts to predict aerodynamic characteristics using lifting surface theory and finite-element structural analysis as well as an experimental investigation using 1/5 scale elastically similar models in the NASA Ames 2m x 3m (7' x 10') wind tunnel. Experimental data were compared with theoretical results in the development of a computer program which may be used in the design and evaluation of ultralight gliders
Custodial bulk Randall-Sundrum model and B->K* l+ l'-
The custodial Randall-Sundrum model based on SU(2)_L X SU(2)_R X U(1)_(B-L)
generates new flavor-changing-neutral-current (FCNC) phenomena at tree level,
mediated by Kaluza-Klein neutral gauge bosons. Based on two natural assumptions
of universal 5D Yukawa couplings and no-cancellation in explaining the observed
standard model fermion mixing matrices, we determine the bulk Dirac mass
parameters. Phenomenological constraints from lepton-flavor-violations are also
used to specify the model. From the comprehensive study of B->K* l+ l'-, we
found that only the B->K*ee decay has sizable new physics effects. The zero
value position of the forward-backward asymmetry in this model is also
evaluated, with about 5% deviation from the SM result. Other effective
observables are also suggested such as the ratio of two differential (or
partially integrated) decay rates of B->K*ee and B->K*mu mu. For the first KK
gauge boson mass of M_A^(1)=2-4 TeV, we can have about 10-20% deviation from
the SM results.Comment: references added with minor change
Spin states and persistent currents in a mesoscopic ring with an embedded magnetic impurity
Spin states and persistent currents are investigated theoretically in a
mesoscopic ring with an embedded magnetic ion under a uniform magnetic field
including the spin-orbit interactions. The magnetic impurity acts as a
spin-dependent -potential for electrons and results in gaps in the
energy spectrum, consequently suppresses the oscillation of the persistent
currents. The competition between the Zeeman splittings and the -
exchange interaction leads to a transition of the electron ground state in the
ring. The interplay between the periodic potential induced by the Rashba and
Dresselhaus spin-orbit interactions and the -potential induced by the
magnetic impurity leads to significant variation in the energy spectrum, charge
density distribution, and persistent currents of electrons in the ring.Comment: 8 pages, 11 figure
Direct detection of the relative strength of Rashba and Dresselhaus spin-orbit interaction: Utilizing the SU(2) symmetry
We propose a simple method to detect the relative strength of Rashba and
Dresselhaus spin-obit interactions in quantum wells (QWs) without relying on
the directional-dependent physical quantities. This method utilize the
asymmetry of critical gate voltages that leading to the remarkable signals of
SU(2) symmetry, which happens to reflect the intrinsic structure inversion
asymmetry of the QW. We support our proposal by the numerical calculation of
in-plane relaxation times based on the self-consistent eight-band Kane model.
We find that the two different critical gate voltages leading to the maximum
spin relaxation times [one effect of the SU(2) symmetry] can simply determine
the ratio of the coefficients of Rashba and Dresselhaus terms. Our proposal can
also be generalized to extract the relative strengths of the spin-orbit
interactions in quantum wire and quantum dot structures.Comment: 5 pages, 4 figure
Computing the Girth of a Planar Graph in Linear Time
The girth of a graph is the minimum weight of all simple cycles of the graph.
We study the problem of determining the girth of an n-node unweighted
undirected planar graph. The first non-trivial algorithm for the problem, given
by Djidjev, runs in O(n^{5/4} log n) time. Chalermsook, Fakcharoenphol, and
Nanongkai reduced the running time to O(n log^2 n). Weimann and Yuster further
reduced the running time to O(n log n). In this paper, we solve the problem in
O(n) time.Comment: 20 pages, 7 figures, accepted to SIAM Journal on Computin
- …