5,998 research outputs found
Thermoelectric DC conductivities with momentum dissipation from higher derivative gravity
We present a mechanism of momentum relaxation in higher derivative gravity by
adding linear scalar fields to the Gauss-Bonnet theory. We analytically
computed all of the DC thermoelectric conductivities in this theory by adopting
the method given by Donos and Gauntlett in [arXiv:1406.4742]. The results show
that the DC electric conductivity is not a monotonic function of the effective
impurity parameter : in the small limit, the DC conductivity is
dominated by the coherent phase, while for larger , pair creation
contribution to the conductivity becomes dominant, signaling an incoherent
phase. In addition, the DC heat conductivity is found independent of the
Gauss-Bonnet coupling constant.Comment: 1+19 pages, 2 figures,typos in Eq.(40) correcte
Anisotropic plasma with a chemical potential and scheme-independent instabilities
Generically, the black brane solution with planar horizons is
thermodynamically stable. We find a counter-example to this statement by
demonstrating that an anisotropic black brane is unstable. We present a charged
black brane solution dual to a spatially anisotropic finite temperature
super Yang-Mills plasma at finite chemical potential.
This static and regular solution is obtained both numerically and analytically.
We uncover rich thermodynamic phase structures for this system by considering
the cases when the anisotropy constant "a" takes real and imaginary values,
respectively. In the case , the phase structure of this anisotropic
black brane is similar to that of Schwarzschild-AdS black hole with
horizon topology, yielding a thermodynamical instability at smaller horizon
radii. For the condition , the thermodynamics is dominated by the
black brane phase for all temperatures.Comment: 14pages,14figures, minor changes, PLB in pres
The spin-down accretion regime of Galactic ultra-luminous X-ray pulsar Swift J0243.6+6124
The relative high fluxes of the Galactic ultra-luminous X-ray pulsar Swift
J0243 allow a detailed study of its spin-down regime in quiescence state, for a
first time. After the 2017 giant outburst, its spin frequencies show a linear
decreasing trend with some variations due to minor outbursts. The linear
spin-down rate is Hz/s during the period of lowest
luminosity, from which one can infer a dipole field G.
The relation during the spin-down regime is complex, and the
is close to 0 when the luminosity reaches both the high end
() and the lowest value (). The luminosity of
zero-torque is different for the giant outburst and other minor outbursts. It
is likely due to different accretion flows for different types of outburst, as
evidenced by the differences of the spectra and pulse profiles at a similar
luminosity for different types of outburst (giant or not). The pulse profile
changes from double peaks in the spin-up state to a single broad peak in the
low spin-down regime, indicating the emission beam/region is larger in the low
spin-down regime. These results show that accretion is still ongoing in the low
spin-down regime for which the neutron star is supposed to be in a propeller
state.Comment: 7 pages, 7 figs, to appear in ApJ, comments welcom
Distributed filtering of networked dynamic systems with non-gaussian noises over sensor networks: A survey
summary:Sensor networks are regarded as a promising technology in the field of information perception and processing owing to the ease of deployment, cost-effectiveness, flexibility, as well as reliability. The information exchange among sensors inevitably suffers from various network-induced phenomena caused by the limited resource utilization and complex application scenarios, and thus is required to be governed by suitable resource-saving communication mechanisms. It is also noteworthy that noises in system dynamics and sensor measurements are ubiquitous and in general unknown but can be bounded, rather than follow specific Gaussian distributions as assumed in Kalman-type filtering. Particular attention of this paper is paid to a survey of recent advances in distributed filtering of networked dynamic systems with non-Gaussian noises over sensor networks. First, two types of widely employed structures of distributed filters are reviewed, the corresponding analysis is systematically addressed, and some interesting results are provided. The inherent purpose of adding consensus terms into the distributed filters is profoundly disclosed. Then, some representative models characterizing various network-induced phenomena are reviewed and their corresponding analytical strategies are exhibited in detail. Furthermore, recent results on distributed filtering with non-Gaussian noises are sorted out in accordance with different network-induced phenomena and system models. Another emphasis is laid on recent developments of distributed filtering with various communication scheduling, which are summarized based on the inherent characteristics of their dynamic behavior associated with mathematical models. Finally, the state-of-the-art of distributed filtering and challenging issues, ranging from scalability, security to applications, are raised to guide possible future research
Vanadium(v) phenolate complexes for ring opening homo- and co-polymerisation of ε-caprolactone, L-lactide and rac-lactide
The vanadyl complexes [VO(OtBu)L¹ ] (1) and {[VO(OiPr)]₂ (μ-p-L²ᵖ)} (2) {[VO(OR)]₂ (μ-p-L²ᵐ )} (R = iPr 3, tBu 4) have been prepared from [VO(OR)₃ ] (R = nPr, iPr or tBu) and the respective phenol, namely 2,2′-ethylidenebis(4,6-di-tert-butylphenol) (L¹ H₂ ) or α,α,α′,α′-tetra(3,5-di-tert-butyl-2-hydroxyphenyl–p/m-)xylene-para-tetraphenol (L2p/mH₄). For comparative studies, the known complexes [VO(μ-OnPr)L¹]₂ (I), [VOL³ ]₂ (II) (L³H₃ = 2,6-bis(3,5-di-tert-butyl-2-hydroxybenzyl)-4-tert-butylphenol) were prepared. An imido complex {[VCl(Np-tolyl)(NCMe)]₂(μ-p-L²ᵖ)} (5) has been prepared following work-up from [V(Np-tolyl)Cl₃ ], L²ᵖH₄ and Et₃ N. The molecular structures of complexes 1–5 are reported. Complexes 1–5 and I and II have been screened for their ability to ring open polymerise ε-caprolactone, L-lactide or rac-lactide with and without solvent present. The co-polymerization of ε-caprolactone with L-lactide or rac-lactide afforded co-polymers with low lactide content; the reverse addition was ineffective
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