3,191 research outputs found
Analysis on Heavy Quarkonia Transitions with Pion Emission in Terms of the QCD Multipole Expansion and Determination of Mass Spectra of Hybrids
One of the most important tasks in high energy physics is search for the
exotic states, such as glueball, hybrid and multi-quark states. The transitions
and attract
great attentions because they may reveal characteristics of hybrids. In this
work, we analyze those transition modes in terms of the theoretical framework
established by Yan and Kuang. It is interesting to notice that the intermediate
states between the two gluon-emissions are hybrids, therefore by fitting the
data, we are able to determine the mass spectra of hybrids. The ground hybrid
states are predicted as 4.23 GeV (for charmonium) and 10.79 GeV (for bottonium)
which do not correspond to any states measured in recent experiments, thus it
may imply that very possibly, hybrids mix with regular quarkonia to constitute
physical states. Comprehensive comparisons of the potentials for hybrids whose
parameters are obtained in this scenario with the lattice results are
presented.Comment: 16 pages, 2 figur
Exact quantum dynamics of XXZ central spin problems
We obtain analytically close forms of benchmark quantum dynamics of the
collapse and revival (CR), reduced density matrix, Von Neumann entropy, and
fidelity for the XXZ central spin problem. These quantities characterize the
quantum decoherence and entanglement of the system with few to many bath spins,
and for a short to infinitely long time evolution. For the homogeneous central
spin problem, the effective magnetic field , coupling constant and
longitudinal interaction significantly influence the time scales of
the quantum dynamics of the central spin and the bath, providing a tunable
resource for quantum metrology. Under the resonance condition , the
location of the -th revival peak in time reaches a simple relation for a large . For , and a
small polarization in the initial spin coherent state, our analytical result
for the CR recovers the known expression found in the Jaynes-Cummings model,
thus building up an exact dynamical connection between the central spin
problems and the light-matter interacting systems in quantum nonlinear optics.
In addition, the CR dynamics is robust to a moderate inhomogeneity of the
coupling amplitudes, while disappearing at strong inhomogeneity.Comment: added new result on inhomogeneous central spin problem and added new
references and supplementary material, 6 pages + 15 pages; 4 figures + 14
figure
Spin transfer in a ferromagnet-quantum dot and tunnel barrier coupled Aharonov-Bohm ring system with Rashba spin-orbit interactions
The spin transfer effect in ferromagnet-quantum dot (insulator)-ferromagnet
Aharonov-Bohm (AB) ring system with Rashba spin-orbit (SO) interactions is
investigated by means of Keldysh nonequilibrium Green function method. It is
found that both the magnitude and direction of the spin transfer torque (STT)
acting on the right ferromagnet electrode can be effectively controlled by
changing the magnetic flux threading the AB ring or the gate voltage on the
quantum dot. The STT can be greatly augmented by matching a proper magnetic
flux and an SO interaction at a cost of low electrical current. The STT,
electrical current, and spin current are uncovered to oscillate with the
magnetic flux. The present results are expected to be useful for information
storage in nanospintronics.Comment: 17pages, 7figure
Transverse electric current induced by optically injected spin current in cross-shaped InGaAs/InAlAs system
We examine electric response of a linearly polarized light normally shed on a
cross-shaped quasi 2-dimensional InGaAs/InAlAs system with structure inversion
asymmetry. The photo-excited conduction electrons carry a pure spin current
with in-plane spin polarization due to the Rashba spin-orbit interaction. We
use Landauer-B\"{u}ttiker formalism to show that this spin current induces two
inward or outward transverse charge currents, which are observable in
experiments. This effect may serve as an experimental probe of certain types of
spin current.Comment: 5 pages, 3 figure
The System Dynamics Model in Electronic Products Closed-Loop Supply Chain Distribution Network with Three-Way Recovery and the Old-for-New Policy
With the technological developments and rapid changes in demand pattern, diverse varieties of electronic products are entering into the market with reduced lifecycle which leads to the environmental problems. The awareness of electronic products take-back and recovery has been increasing in electronic products supply chains. In this paper, we build a system dynamics model for electronic products closed-loop supply chain distribution network with the old-for-new policy and three electronic products recovery ways, namely, electronic products remanufacturing, electronic component reuse and remanufacturing, and electronic raw material recovery. In the simulation study, we investigate the significance of various factors including the old-for-new policy, collection and remanufacturing, their interactions and the type of their impact on bullwhip, and profitability through sensitivity analysis. Our results instruct that the old-for-new policy and three electronic products recovery ways can reduce the bullwhip effect in the retailers and the distributors and increases the profitability in the closed-loop supply chain distribution network
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