126,434 research outputs found
Codes Cross-Correlation Impact on S-curve Bias and Data-Pilot Code Pairs Optimization for CBOC Signals
The aim of this paper is to analyze the impact of spreading codes cross-correlation on code tracking performance, and to optimize the data-pilot code pairs of Galileo E1 Open Service (OS) Composite Binary Offset Carrier (CBOC) signals. The distortion of the discriminator function (i.e., S-curve), due to data and pilot spreading codes cross-correlation properties, is evaluated when only the data or pilot components of CBOC signals are tracked, considering the features of the modulation schemes. Analyses show that the S-curve bias also depends on the receiver configuration (e.g., the tracking algorithm and correlator spacing). In this paper, two methods are proposed to optimize the data-pilot code pairs of Galileo E1 OS. The optimization goal is to obtain minimum average S-curve biases when tracking only the pilot components of CBOC signals for the specific correlator spacing. The S-curve biases after optimization processes are analyzed and compared with the un-optimized results. It is shown that the optimized data-pilot code pairs could significantly mitigate the intra-channel (i.e., data and pilot) codes cross-correlation,and then improve the code tracking performance of CBOC signals
Intrinsic Spin and Orbital-Angular-Momentum Hall Effect
A generalized definition of intrinsic and extrinsic transport coefficients is
introduced. We show that transport coefficients from the intrinsic origin are
solely determined by local electronic structure, and thus the intrinsic spin
Hall effect is not a transport phenomenon. The intrinsic spin Hall current is
always accompanied by an equal but opposite intrinsic orbital-angular-momentum
Hall current. We prove that the intrinsic spin Hall effect does not induce a
spin accumulation at the edge of the sample or near the interface.Comment: References update
Wave packet transmission of Bloch electron manipulated by magnetic field
We study the phenomenon of wave packet revivals of Bloch electrons and
explore how to control them by a magnetic field for quantum information
transfer. It is showed that the single electron system can be modulated into a
linear dispersion regime by the "quantized" flux and then an electronic wave
packet with the components localized in this regime can be transferred without
spreading. This feature can be utilized to perform the high-fidelity transfer
of quantum information encoded in the polarization of the spin. Beyond the
linear approximation, the re-localization and self-interference occur as the
novel phenomena of quantum coherence.Comment: 6 pages, 5 figures, new content adde
Spin filtering implemented through Rashba and weak magnetic modulations
We present two theoretical schemes for spin filters in one-dimensional
semiconductor quantum wires with spatially modulated Rashba spin-orbit coupling
(SOC) as well as weak magnetic potential. For case I, the SOC is periodic and
the weak magnetic potential is applied uniformly along the wire. Full spin
polarizations with opposite signs are obtained within two separated energy
intervals. For case II, the weak magnetic potential is periodic while the SOC
is uniform. An ideal negative/positive switching effect for spin polarization
is realized by tuning the strength of SOC. The roles of SOC, magnetic
potential, and their coupling on the spin filtering are analyzed.Comment: 4 pages, 4 figure
Dimerization-assisted energy transport in light-harvesting complexes
We study the role of the dimer structure of light-harvesting complex II (LH2)
in excitation transfer from the LH2 (without a reaction center (RC)) to the LH1
(surrounding the RC), or from the LH2 to another LH2. The excited and
un-excited states of a bacteriochlorophyll (BChl) are modeled by a quasi-spin.
In the framework of quantum open system theory, we represent the excitation
transfer as the total leakage of the LH2 system and then calculate the transfer
efficiency and average transfer time. For different initial states with various
quantum superposition properties, we study how the dimerization of the B850
BChl ring can enhance the transfer efficiency and shorten the average transfer
time.Comment: 11 pages, 6 figure
Baryons as Solitons in Three Dimensional Quantum Chromodynamics
We show that baryons of three dimensional Quantum Chromodynamics can be
understood as solitons of its effective lagrangian. In the parity preserving
phase we study, these baryons are fermions for odd and bosons for even
, never anyons. We quantize the collective variables of the solitons and
there by calculate the flavor quantum numbers, magnetic moments and mass
splittings of the baryon. The flavor quantum numbers are in agreement with
naive quark model for the low lying states. The magnetic moments and mass
splittings are smaller in the soliton model by a factor of . We also show that there is a dibaryon solution that is an analogue
of the deuteron. These solitons can describe defects in a quantum
anti--ferromagnet.Comment: 22 pages + 4 figures (figures not included, postscript files
available upon request
The Effective Lagrangian of Three Dimensional Quantum Chromodynamics
We consider the low energy limit of three dimensional Quantum Chromodynamics
with an even number of flavors. We show that Parity is not spontaneously
broken, but the global (flavor) symmetry is spontaneously broken. The low
energy effective lagrangian is a nonlinear sigma model on the Grassmannian.
Some Chern--Simons terms are necessary in the lagrangian to realize the
discrete symmetries correctly. We consider also another parametrization of the
low energy sector which leads to a three dimensional analogue of the
Wess--Zumino--Witten--Novikov model. Since three dimensional QCD is believed to
be a model for quantum anti--ferromagnetism, our effective lagrangian can
describe their long wavelength excitations (spin waves).Comment: 18 page
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