Cosmic age, Statefinder and OmOm diagnostics in the decaying vacuum cosmology

As an extension of $\Lambda$CDM, the decaying vacuum model (DV) describes the dark energy as a varying vacuum whose energy density decays linearly with the Hubble parameter in the late-times, $\rho_\Lambda(t) \propto H(t)$, and produces the matter component. We examine the high-$z$ cosmic age problem in the DV model, and compare it with $\Lambda$CDM and the Yang-Mills condensate (YMC) dark energy model. Without employing a dynamical scalar field for dark energy, these three models share a similar behavior of late-time evolution. It is found that the DV model, like YMC, can accommodate the high-$z$ quasar APM 08279+5255, thus greatly alleviates the high-$z$ cosmic age problem. We also calculate the Statefinder $(r,s)$ and the {\it Om} diagnostics in the model. It is found that the evolutionary trajectories of $r(z)$ and $s(z)$ in the DV model are similar to those in the kinessence model, but are distinguished from those in $\Lambda$CDM and YMC. The ${\it Om}(z)$ in DV has a negative slope and its height depends on the matter fraction, while YMC has a rather flat ${\it Om}(z)$, whose magnitude depends sensitively on the coupling.Comment: 12 pages, 4 figures, with some correction

STUDENTS AT THE NEXUS BETWEEN THE CHINESE DIASPORA AND INTERNATIONALISATION OF HIGHER EDUCATION: THE ROLE OF OVERSEAS STUDENTS IN CHINA’S STRATEGY OF SOFT POWER

In recent years, an increasingly assertive People’s Republic of China (PRC) leadership has sought to extend the PRC’s influence globally. To this end, it has developed diverse strategies ranging from soft power to more coercive means. The more visible strategies include the Belt and Road Initiative, the Chinese Dream, and ‘wolf warrior’ diplomacy. At the soft power end of the spectrum, Chinese overseas students are at the nexus between two strategies of soft power – the Chinese diaspora and the internationalisation of higher education. While there is an established literature analysing China’s soft power worldwide, relatively little has been done on the role of higher education, particularly where this concerns overseas Chinese students. The article will examine China’s use of overseas students to project its soft power. It then identifies the strategies that support this, viz. ideological and political education to prepare young people for this role and, once overseas, an appeal to a conception of the Chinese diaspora, as well as the organisations (e.g. embassies and student associations) that form potential channels to students and monitor and support them in their role

Diffusion in a continuum model of self-propelled particles with alignment interaction

In this paper, we provide the $O(\epsilon)$ corrections to the hydrodynamic model derived by Degond and Motsch from a kinetic version of the model by Vicsek & coauthors describing flocking biological agents. The parameter $\epsilon$ stands for the ratio of the microscopic to the macroscopic scales. The $O(\epsilon)$ corrected model involves diffusion terms in both the mass and velocity equations as well as terms which are quadratic functions of the first order derivatives of the density and velocity. The derivation method is based on the standard Chapman-Enskog theory, but is significantly more complex than usual due to both the non-isotropy of the fluid and the lack of momentum conservation

Geometric vs. Dynamical Gates in Quantum Computing Implementations Using Zeeman and Heisenberg Hamiltonians

Quantum computing in terms of geometric phases, i.e. Berry or Aharonov-Anandan phases, is fault-tolerant to a certain degree. We examine its implementation based on Zeeman coupling with a rotating field and isotropic Heisenberg interaction, which describe NMR and can also be realized in quantum dots and cold atoms. Using a novel physical representation of the qubit basis states, we construct $\pi/8$ and Hadamard gates based on Berry and Aharonov-Anandan phases. For two interacting qubits in a rotating field, we find that it is always impossible to construct a two-qubit gate based on Berry phases, or based on Aharonov-Anandan phases when the gyromagnetic ratios of the two qubits are equal. In implementing a universal set of quantum gates, one may combine geometric $\pi/8$ and Hadamard gates and dynamical $\sqrt{\rm SWAP}$ gate.Comment: published version, 5 page

Berry phase in a composite system

The Berry phase in a composite system with only one subsystem being driven has been studied in this Letter. We choose two spin-$\frac 1 2$ systems with spin-spin couplings as the composite system, one of the subsystems is driven by a time-dependent magnetic field. We show how the Berry phases depend on the coupling between the two subsystems, and what is the relation between these Berry phases of the whole system and those of the subsystems.Comment: 4 pages, 6 figure

The Utilization of Heat Exchangers for Energy Conservation in Air Conditioning

This paper investigates the characteristics of heat exchanger (HPHE) as an efficient coolness recovery unit in air conditioning through experimental studies. It was conducted under a multiple-nozzle code tester based on the ASHRAE standards. The wind tunnel was subjected to airflow with considerable variation in its inlet air temperature. Among the factors being investigated are the air velocity, inlet and outlet air temperatures, overall efficiency and the number of rows in longitudinal direction. The data obtained were compared with the results predicted by previous theoretical studies. Good agreement was observed