26,420 research outputs found
On the Finite-Time Blowup of a 1D Model for the 3D Incompressible Euler Equations
We study a 1D model for the 3D incompressible Euler equations in axisymmetric
geometries, which can be viewed as a local approximation to the Euler equations
near the solid boundary of a cylindrical domain. We prove the local
well-posedness of the model in spaces of zero-mean functions, and study the
potential formation of a finite-time singularity under certain convexity
conditions for the velocity field. It is hoped that the results obtained on the
1D model will be useful in the analysis of the full 3D problem, whose loss of
regularity in finite time has been observed in a recent numerical study (Luo
and Hou, 2013).Comment: 23 page
Relationship Between the Kinetic Power and Bolometric Luminosity of Jets: limitation from black hole X-ray binaries, active galactic nuclei, and gamma-ray bursts
The correlation between the kinetic power and intrinsic
bolometric luminosity of jets may reveal the underlying jet
physics in various black hole systems. Based on the recent work by Nemmen et
al. (2012), we re-investigate this correlation with additional sources of
black-hole X-ray binaries (BXBs) in hard/quiescent states and low-luminosity
active galactic nuclei (LLAGNs). The new sample includes 29 sets of data from 7
BXBs and 20 LLAGNs, with and being derived from
spectral modeling of the quasi-simultaneous multi-band spectra under the
accretion-jet scenario. Compared to previous works, the range of luminosity is
now enlarged to more than decades, i.e. from to
, which allows for better constraining of the correlation.
One notable result is that the jets in BXBs and LLAGNs almost follow the same
correlation that was obtained from blazars and
gamma-ray bursts (GRBs). The slope indices we derived are for the
whole sample, for BXB subsample, for LLAGN
subsample, and for the LLAGN-blazar subsample, respectively. The
correlation index around unit implies the independence of jet efficiency on the
luminosity or kinetic power. Our results may further support the hypothesis
that similar physical processes exist in the jets of various black hole
systems.Comment: 5 pages, 3 figures, to appear in ApJL, updated versio
Achieving quantum precision limit in adaptive qubit state tomography
The precision limit in quantum state tomography is of great interest not only
to practical applications but also to foundational studies. However, little is
known about this subject in the multiparameter setting even theoretically due
to the subtle information tradeoff among incompatible observables. In the case
of a qubit, the theoretic precision limit was determined by Hayashi as well as
Gill and Massar, but attaining the precision limit in experiments has remained
a challenging task. Here we report the first experiment which achieves this
precision limit in adaptive quantum state tomography on optical polarization
qubits. The two-step adaptive strategy employed in our experiment is very easy
to implement in practice. Yet it is surprisingly powerful in optimizing most
figures of merit of practical interest. Our study may have significant
implications for multiparameter quantum estimation problems, such as quantum
metrology. Meanwhile, it may promote our understanding about the
complementarity principle and uncertainty relations from the information
theoretic perspective.Comment: 9 pages, 4 figures; titles changed and structure reorganise
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