Holographic QCD with Topologically Charged Domain-Wall/Membranes

We study the thermodynamical phase structures of holographic QCD with nontrivial topologically charged domain-wall/membranes which are originally related to the multiple $\theta$-vacua in the large $N_c$ limit. We realize the topologically charged membranes as the holographic D6-brane fluxes in the Sakai-Sugimoto model. The D6-brane fluxes couple to the probe D8-anti-D8 via Chern-Simon term, and act as the source for the baryonic current density of QCD. We find rich phase structures of the dual meson system by varying asymptotic separation of D8 and anti-D8. Especially, there can be a thermodynamically favored and stable phase of finite baryonic current density. This provides the supporting evidence for the discovery of the topologically charged membranes found in the lattice QCD calculations. We also find a crossover phase with the limiting baryonic current density and temperature which suggest a Hagedorn-like phase transition of meson dissociation.Comment: 23 pages, 19 figures;v2 typos corrected;v3 text improve

Andreev reflection through a quantum dot coupled with two ferromagnets and a superconductor

We study the Andreev reflection (AR) in a three terminal mesoscopic hybrid system, in which two ferromagnets (F$_1$ and F$_2$) are coupled to a superconductor (S) through a quantum dot (QD). By using non-equilibrium Green function, we derive a general current formula which allows arbitrary spin polarizations, magnetization orientations and bias voltages in F$_1$ and F$_2$. The formula is applied to study both zero bias conductance and finite bias current. The current conducted by crossed AR involving F$_1$, F$_2$ and S is particularly unusual, in which an electron with spin $\sigma$ incident from one of the ferromagnets picks up another electron with spin $\bar{\sigma}$ from the other one, both enter S and form a Cooper pair. Several special cases are investigated to reveal the properties of AR in this system.Comment: 15 pages, 7 figures, LaTe

Probing Spin States of Coupled Quantum Dots by dc Josephson Current

We propose an idea for probing spin states of two coupled quantum dots (CQD), by the dc Josephson current flowing through them. This theory requires weak coupling between CQD and electrodes, but allows arbitrary inter-dot tunnel coupling, intra- and inter- dot Coulomb interactions. We find that the Coulomb blockade peaks exhibit a non-monotonous dependence on the Zeeman splitting of CQD, which can be understood in terms of the Andreev bound states. More importantly, the supercurrent in the Coulomb blockade valleys may provide the information of the spin states of CQD: for CQD with total electron number N=1,3 (odd), the supercurrent will reverse its sign if CQD becomes a magnetic molecule; for CQD with N=2 (even), the supercurrent will decrease sharply around the transition between the spin singlet and triplet ground states of CQD.Comment: 10 pages, 3 figure

Theory of Nonequilibrium Coherent Transport through an Interacting Mesoscopic Region Weakly Coupled to Electrodes

We develop a theory for the nonequilibrium coherent transport through a mesoscopic region, based on the nonequilibrium Green function technique. The theory requires the weak coupling between the central mesoscopic region and the multiple electrodes connected to it, but allows arbitrary hopping and interaction in the central region. An equation determining the nonequilibrium distribution in the central interacting region is derived and plays an important role in the theory. The theory is applied to two special cases for demonstrations, revealing the novel effects associated with the combination of phase coherence, Coulomb interaction, and nonequilibrium distribution.Comment: 10 Pages, 5 figure

When Google Meets Xiaomi: Comparative Case Study in Western and Eastern Corporate Management

Google Inc. of the West and Xiaomi Inc. of the East are recognized as ‘flat organizations’. They exercise ‘flat management’ in their corporate culture, wherein mid-level management is abridged, leaving the corporate structure less-bureaucratic, top-down-and-less-hierarchical, and more laissez-faire. Using the Confucian criteria of Wu Yu, namely morality (or, virtue), intellectual (or, wisdom), physical ability (or, sportsmanship), groupism (or, cooperation), and aesthetics (or, elegance), this paper assesses managerial philosophy and corporate practice of Google and Xiaomi. It is found that under flat management, although each company nevertheless reveals its corporate idiosyncrasy, they achieve business success and sustainability through adopting small-team orientation, vision of integrating innovation with business, effective communication, work liberty and flexibility, working with best talents, and cultivating collegiate workplace, of which these administrative components may suggest new managerial standards to modern corporate management