689 research outputs found
Vector and Spinor Decomposition of SU(2) Gauge Potential, their quivalence and Knot Structure in SU(2) Chern-Simons Theory
In this paper, spinor and vector decomposition of SU(2) gauge potential are
presented and their equivalence is constructed using a simply proposal. We also
obtain the action of Faddeev nonlinear O(3) sigma model from the SU(2) massive
gauge field theory which is proposed according to the gauge invariant
principle. At last, the knot structure in SU(2) Chern-Simons filed theory is
discussed in terms of the --mapping topological current theory. The
topological charge of the knot is characterized by the Hopf indices and the
Brouwer degrees of -mapping.Comment: 10 pages, ni figur
Topological Excitation in Skyrme Theory
Based on the -mapping topological current theory and the decomposition
of gauge potential theory, we investigate knotted vortex lines and monopoles in
Skyrme theory and simply discuss the branch processes (splitting, merging and
intersection) during the evolution of the monopoles.Comment: 10 pages, 0 figure
Knotlike Cosmic Strings in The Early Universe
In this paper, the knotlike cosmic strings in the Riemann-Cartan space-time
of the early universe are discussed. It has been revealed that the cosmic
strings can just originate from the zero points of the complex scalar
quintessence field. In these strings we mainly study the knotlike
configurations. Based on the integral of Chern-Simons 3-form a topological
invariant for knotlike cosmic strings is constructed, and it is shown that this
invariant is just the total sum of all the self-linking and linking numbers of
the knots family. Furthermore, it is also pointed out that this invariant is
preserved in the branch processes during the evolution of cosmic strings
Statistical significance of fine structure in the frequency spectrum of Aharonov-Bohm conductance oscillations
We discuss a statistical analysis of Aharonov-Bohm conductance oscillations
measured in a two-dimensional ring, in the presence of Rashba spin-orbit
interaction. Measurements performed at different values of gate voltage are
used to calculate the ensemble-averaged modulus of the Fourier spectrum and, at
each frequency, the standard deviation associated to the average. This allows
us to prove the statistical significance of a splitting that we observe in the
h/e peak of the averaged spectrum. Our work illustrates in detail the role of
sample specific effects on the frequency spectrum of Aharonov-Bohm conductance
oscillations and it demonstrates how fine structures of a different physical
origin can be discriminated from sample specific features.Comment: accepted for publication in PR
Spin-dependent (magneto)transport through a ring due to spin-orbit interaction
Electron transport through a one-dimensional ring connected with two external
leads, in the presence of spin-orbit interaction (SOI) of strength \alpha and a
perpendicular magnetic field is studied. Applying Griffith's boundary
conditions we derive analytic expressions for the reflection and transmission
coefficients of the corresponding one-electron scattering problem. We
generalize earlier conductance results by Nitta et al. [Appl. Phys. Lett. 75,
695 (1999)] and investigate the influence of \alpha, temperature, and a weak
magnetic field on the conductance. Varying \alpha and temperature changes the
position of the minima and maxima of the magnetic-field dependent conductance,
and it may even convert a maximum into a minimum and vice versa.Comment: 19 pages, 9 figure
Density Matrix in Quantum Mechanics and Distinctness of Ensembles Having the Same Compressed Density Matrix
We clarify different definitions of the density matrix by proposing the use
of different names, the full density matrix for a single-closed quantum system,
the compressed density matrix for the averaged single molecule state from an
ensemble of molecules, and the reduced density matrix for a part of an
entangled quantum system, respectively. We show that ensembles with the same
compressed density matrix can be physically distinguished by observing
fluctuations of various observables. This is in contrast to a general belief
that ensembles with the same compressed density matrix are identical. Explicit
expression for the fluctuation of an observable in a specified ensemble is
given. We have discussed the nature of nuclear magnetic resonance quantum
computing. We show that the conclusion that there is no quantum entanglement in
the current nuclear magnetic resonance quantum computing experiment is based on
the unjustified belief that ensembles having the same compressed density matrix
are identical physically. Related issues in quantum communication are also
discussed.Comment: 26 pages. To appear in Foundations of Physics, 36 (8), 200
Institutional pedagogical waypoints : reflections on doctoral journeys between Taiwan and Australia
Spatial, social and academic journeys undertaken between Taiwan and Australia for doctoral education are the focus of reflection here. The discussion centres on the authors’ experiences of, on the one hand, the development of a Faculty of Education’s doctoral pedagogies in the early 2000s to reflect its international PhD candidature profile – especially from Taiwan – and, on the other, of Taiwanese doctoral candidates’ journeys through their PhDs in the Faculty. The authors write from their particular perspectives: Evans as an Australian academic and a manager of doctoral studies, and Liou as a Taiwanese academic pursuing her doctorate in an Australian university. The article considers the Australian and Taiwanese doctoral contexts between which the students transited. The institutional pedagogical strategies, from pre-enrolment to completion, are examined as waypoints on the doctoral journey for both staff and candidates
Effects of fertilizer application rate and planting density on photosynthetic characteristics, yield and yield components in waxy wheat
Waxy wheat (Triticum aestivum L.) is grown throughout the world for its specific quality. Fertilization and planting density are two crucial factors that affect waxy wheat yield and photosynthetic capacity. The objectives of the research were to determine the effects of fertilization and planting density on photosynthetic characteristics, yield, and yield components of waxy wheat, including Yield, SSR, TGW, GNPP, GWPP, PH, HI, Pn, Gs, Ci, E and WUE using the method of field experiment, in which there were three levels (150, 300, and 450 kg haâ1) of fertilizer application rate and three levels (1.35, 1.8, and 2.25 Ă 106 plants haâ1) of planting density. The results suggested that photosynthetic characteristics, yield, and yield components had close relationship with fertilization levels and planting density. Under the same plant density, with the increase of fertilization, Yield, SSR, TGW, GNPP, GWPP, HI, Pn, Gs, E and WUE increased and then decreased, PH increased, but Ci decreased. Under the same fertilization, with the increase of plant density, Yield, SSR, TGW, GNPP, GWPP, HI increased and then decreased, PH, Pn, Gs and E increased, PH and WUE declined. The results also showed that F2 (300 kg haâ1) and D2 (1.8 Ă 106 plants haâ1) was a better match in this experiment, which could obtain a higher grain yield 4961.61 kg haâ1. Consequently, this combination of fertilizer application rate and plant densities are useful to get high yield of waxy wheat
Electroweak Corrections to the Charged Higgs Boson Decay into Chargino and Neutralino
The electroweak corrections to the partial widths of the decays including one-loop
diagrams of the third generation quarks and squarks, are investigated within
the Supersymmetric Standard Model. The relative corrections can reach the
values about 10%, therefore they should be taken into account for the precise
experimental measurement at future colliders.Comment: 21 pages, 6 eps figures, 1 Latex fil
Direct characterization of photo-induced lattice dynamics in BaFeâAsâ
Ultrafast light pulses can modify electronic properties of quantum materials by perturbing the underlying, intertwined degrees of freedom. In particular, iron-based superconductors exhibit a strong coupling among electronic nematic fluctuations, spins and the lattice, serving as a playground for ultrafast manipulation. Here we use time-resolved X-ray scattering to measure the lattice dynamics of photoexcited BaFeAs. On optical excitation, no signature of an ultrafast change of the crystal symmetry is observed, but the lattice oscillates rapidly in time due to the coherent excitation of an A mode that modulates the FeâAsâFe bond angle. We directly quantify the coherent lattice dynamics and show that even a small photoinduced lattice distortion can induce notable changes in the electronic and magnetic properties. Our analysis implies that transient structural modification can be an effective tool for manipulating the electronic properties of multi-orbital systems, where electronic instabilities are sensitive to the orbital character of bands
- âŠ