Vortex images on Ba{1-x}KxFe2As2 observed directly by the magnetic force microscopy

The vortex states on optimally doped Ba0.6K0.4Fe2As2 and underdoped Ba0.77K0.23Fe2As2 single crystals are imaged by magnetic force microscopy at various magnetic fields below 100 Oe. Local triangular vortex clusters are observed in optimally doped samples. The vortices are more ordered than those in Ba(Fe{1-x}Co{x})2As2, and the calculated pinning force per unit length is about 1 order of magnitude weaker than that in optimally Co-doped 122 at the same magnetic field, indicating that the Co doping at the Fe sites induces stronger pinning. The proportion of six-neighbored vortices to the total amount increases quickly with increasing magnetic field, and the estimated value reaches 100% at several tesla. Vortex chains are also found in some local regions, which enhance the pinning force as well as the critical current density. Lines of vortex chains are observed in underdoped samples, and they may have originated from the strong pinning near the twin boundaries arising from the structural transition.Comment: 7 pages, 8 figure

Large deviation principle for multi-scale distribution dependent stochastic differential equations driven by fractional Brownian motions

In this paper, we are concerned with multi-scale distribution dependent stochastic differential equations driven by fractional Brownian motion (with Hurst index $H>\frac12$ and standard Brownian motion, simultaneously. Our aim is to establish a large deviation principle for the multi-scale distribution dependent stochastic differential equations. This is done via the weak convergence approach and our proof is based heavily on the fractional calculus.Comment: 28 pages ,0 figure

Renormalization group improved pQCD prediction for Υ(1S)\Upsilon(1S) leptonic decay

The complete next-to-next-to-next-to-leading order short-distance and bound-state QCD corrections to $\Upsilon(1S)$ leptonic decay rate $\Gamma(\Upsilon(1S)\to \ell^+\ell^-)$ has been finished by Beneke {\it et al.} \cite{Beneke:2014qea}. Based on those improvements, we present a renormalization group (RG) improved pQCD prediction for $\Gamma(\Upsilon(1S)\to \ell^+\ell^-)$ by applying the principle of maximum conformality (PMC). The PMC is based on RG-invariance and is designed to solve the pQCD renormalization scheme and scale ambiguities. After applying the PMC, all known-type of $\beta$-terms at all orders, which are controlled by the RG-equation, are resummed to determine optimal renormalization scale for its strong running coupling at each order. We then achieve a more convergent pQCD series, a scheme- independent and more accurate pQCD prediction for $\Upsilon(1S)$ leptonic decay, i.e. $\Gamma_{\Upsilon(1S) \to e^+ e^-}|_{\rm PMC} = 1.270^{+0.137}_{-0.187}$ keV, where the uncertainty is the squared average of the mentioned pQCD errors. This RG-improved pQCD prediction agrees with the experimental measurement within errors.Comment: 11 pages, 4 figures. Numerical results and discussions improved, references updated, to be published in JHE

China and the Fifth Estate: Net Delusion or Democratic Potential?

Arguably, liberal democratic societies are seeing the emergence of a ‘Fifth Estate’ that is being enabled by the Internet. This new organizational form is comparable to, but potentially more powerful than, the Fourth Estate, which developed as a significant force in an earlier period with an independent press and other mass media. While the significance of the press and the Internet to democratic governance is questioned in all societies, there is particular skepticism of their relevance outside the most liberal democratic regimes, which have a relatively free press and more pluralistic political systems, such as in North America and West Europe. Nevertheless, there have been vivid examples of where networked individuals have appeared to assert greater communicative power in the politics of governance, the media and everyday life, even in non-liberal democratic regimes, such as Hong Kong, and in some cases, China. This potential points to the need for more systematic empirical research in a wider variety of economic and political settings worldwide, particularly in states in which the Internet might offer a potential for more democratic governance and greater accountability of government controlled media. This paper examines cases in which networked individuals in China used the Internet to hold governmental and press institutions more accountable. The cases provide support for the relevance of the Fifth Estate concept in China, and also illuminates the process – showing how the Internet can be used to empower networked individuals in more autocratic regimes