10 research outputs found
Real spinors and real Dirac equation
We reexamine the minimal coupling procedure in the Hestenes' geometric
algebra formulation of the Dirac equation, where spinors are identified with
the even elements of the real Clifford algebra of spacetime. This point of
view, as we argue, leads naturally to a non-Abelian generalisation of the
electromagnetic gauge potential.Comment: 10 pages, 3 figure
Braiding Interactions in Anyonic Quantum Walks
The anyonic quantum walk is a dynamical model describing a single anyon
propagating along a chain of stationary anyons and interacting via mutual
braiding statistics. We review the recent results on the effects of braiding
statistics in anyonic quantum walks in quasi-one dimensional ladder geometries.
For anyons which correspond to spin-1/2 irreps of the quantum groups ,
the non-Abelian species gives rise to entanglement between the
walker and topological degrees of freedom which is quantified by quantum link
invariants over the trajectories of the walk. The decoherence is strong enough
to reduce the walk on the infinite ladder to classical like behaviour. We also
present numerical results on mixing times of or Ising model anyon
walks on cyclic graphs. Finally, the possible experimental simulation of the
anyonic quantum walk in Fractional Quantum Hall systems is discussed.Comment: 13 pages, submitted to Proceedings of the 2nd International
Conference on Theoretical Physics (ICTP 2012
Statistical dynamics of a non-Abelian anyonic quantum walk
We study the single particle dynamics of a mobile non-Abelian anyon hopping
around many pinned anyons on a surface. The dynamics is modelled by a discrete
time quantum walk and the spatial degree of freedom of the mobile anyon becomes
entangled with the fusion degrees of freedom of the collective system. Each
quantum trajectory makes a closed braid on the world lines of the particles
establishing a direct connection between statistical dynamics and quantum link
invariants. We find that asymptotically a mobile Ising anyon becomes so
entangled with its environment that its statistical dynamics reduces to a
classical random walk with linear dispersion in contrast to particles with
Abelian statistics which have quadratic dispersion.Comment: 7 pages, 5 figure
Cytokinin metabolism in maize: Novel evidence of cytokinin abundance, interconversions and formation of a new trans-zeatin metabolic product with a weak anticytokinin activity
Cytokinins (CKs) are an important group of phytohormones. Their tightly regulated and balanced levels are essential for proper cell division and plant organ development. Here we report precise quantification of CK metabolites and other phytohormones in maize reproductive organs in the course of pollination and kernel maturation. A novel enzymatic activity dependent on NADP(+) converting trans-zeatin (tZ) to 6-(3-methylpyrrol-1-yl)purine (MPP) was detected. MPP shows weak anticytokinin properties and inhibition of CK dehydrogenases due to their ability to bind to an active site in the opposite orientation than substrates. Although the physiological significance of tZ side-chain cyclization is not anticipated as the MPP occurrence in maize tissue is very low, properties of the novel CK metabolite indicate its potential for utilization in plant in vitro tissue culture. Furthermore, feeding experiments with different isoprenoid CKs revealed distinct preferences in glycosylation of tZ and cis-zeatin (cZ). While tZ is preferentially glucosylated at the N9 position, cZ forms mainly O-glucosides. Since O-glucosides, in contrast to N9-glucosides, are resistant to irreversible cleavage catalyzed by CK dehydrogenases, the observed preference of maize CK glycosyltransferases to O-glycosylate zeatin in the cis-position might be a reason why cZ derivatives are over-accumulated in different maize tissues and organs