18,512 research outputs found
Multi-Step Knowledge-Aided Iterative ESPRIT for Direction Finding
In this work, we propose a subspace-based algorithm for DOA estimation which
iteratively reduces the disturbance factors of the estimated data covariance
matrix and incorporates prior knowledge which is gradually obtained on line. An
analysis of the MSE of the reshaped data covariance matrix is carried out along
with comparisons between computational complexities of the proposed and
existing algorithms. Simulations focusing on closely-spaced sources, where they
are uncorrelated and correlated, illustrate the improvements achieved.Comment: 7 figures. arXiv admin note: text overlap with arXiv:1703.1052
Evidence for entanglement at high temperatures in an engineered molecular magnet
The molecular compound
[Fe(-oxo)(CHN)(CO)]
was designed and synthesized for the first time and its structure was
determined using single-crystal X-ray diffraction. The magnetic susceptibility
of this compound was measured from 2 to 300 K. The analysis of the
susceptibility data using protocols developed for other spin singlet
ground-state systems indicates that the quantum entanglement would remain at
temperatures up to 732 K, significantly above the highest entanglement
temperature reported to date. The large gap between the ground state and the
first-excited state (282 K) suggests that the spin system may be somewhat
immune to decohering mechanisms. Our measurements strongly suggest that
molecular magnets are promising candidate platforms for quantum information
processing
Adaptação do modelo Century de simulação da dinâmica da MOS aos ecossistemas tropical e subtropical.
Effective action in DSR1 quantum field theory
We present the one-loop effective action of a quantum scalar field with DSR1
space-time symmetry as a sum over field modes. The effective action has real
and imaginary parts and manifest charge conjugation asymmetry, which provides
an alternative theoretical setting to the study of the particle-antiparticle
asymmetry in nature.Comment: 8 page
Experimental Determination of Thermal Entanglement in Spin Clusters using Magnetic Susceptibility Measurements
The present work reports an experimental observation of thermal entanglement
in a clusterized spin chain formed in the compound NaCuSiO.
The presence of entanglement was investigated through two measured quantities,
an Entanglement Witness and the Entanglement of Formation, both derived from
the magnetic susceptibility. It was found that pairwise entanglement exists
below K. Tripartite entanglement was also observed below K. A theoretical study of entanglement evolution as a function of applied
field and temperature is also presented.Comment: Submited to Phys. Rev.
Chemical Evolution of the Galaxy Based on the Oscillatory Star Formation History
We model the star formation history (SFH) and the chemical evolution of the
Galactic disk by combining an infall model and a limit-cycle model of the
interstellar medium (ISM). Recent observations have shown that the SFH of the
Galactic disk violently variates or oscillates. We model the oscillatory SFH
based on the limit-cycle behavior of the fractional masses of three components
of the ISM. The observed period of the oscillation ( Gyr) is reproduced
within the natural parameter range. This means that we can interpret the
oscillatory SFH as the limit-cycle behavior of the ISM. We then test the
chemical evolution of stars and gas in the framework of the limit-cycle model,
since the oscillatory behavior of the SFH may cause an oscillatory evolution of
the metallicity. We find however that the oscillatory behavior of metallicity
is not prominent because the metallicity reflects the past integrated SFH. This
indicates that the metallicity cannot be used to distinguish an oscillatory SFH
from one without oscillations.Comment: 21 pages LaTeX, to appear in Ap
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