Toy models for gravitational and scalar QED decoherence

We investigate the dynamics of two quantum mechanical oscillator system-bath toy models obtained by dimensionally truncating linearized gravity coupled to a massive scalar field and scalar QED. The scalar-gravity toy model maps onto the phase damped oscillator, while the scalar QED toy model approximately maps onto an oscillator system subject to two-photon damping. The toy models provide potentially useful insights into solving for open system quantum dynamics relevant to the full scalar QED and weak gravitational field systems, in particular the decoherence of initial scalar field system superposition states

ASPECTS ON THE QUANTUM DYNAMICS OF A SYSTEM COUPLED TO A BOSONIC ENVIRONMENT

In this work we study various aspects of the quantum dynamics for a system coupled to a Bosonic environment, which is described by a collection of quantum harmonic oscillators or a quantum field. We first consider two quantum mechanical oscillator system-bath models obtained by dimensionally truncating linearized gravity coupled to a massive scalar field and scalar QED, and we show that they separately map onto the phase damped oscillator model and the oscillator system subject to two-photon damping. The phase damped oscillator model also corresponds to the optomechanical system with an acoustic field environment, and we study the acoustic environment induced cavity modes dephasing dynamics as well as the possible infrared and ultraviolet divergence dependence on the spatial dimension of the environment with potential experimental realizations. Next, we show that the acoustic phonon field can not only induce the depahsing effects for the system, but also serves as an entanglement channel for two initially separable systems, which bears similarities with the weak, quantum gravitational fields as mediators of quantum entanglement. We then shift our focus to another system-bath model: Unruh-Dewitt (UDW) detectors coupled to a scalar field. We consider two scenarios here; one includes two UWD detectors coupled to a massless scalar field in a gravitational wave spacetime and we show that the entanglement harvested by two detectors depends sensitively on the frequency of the gravitational wave. The resonance effects can be observed when the energy gap of the detectors matches the frequency of the gravitational wave. The other one consists of a UWD detector initially in the ground state coupled to a nonrelativistic particle state of a massive scalar field, and it is found that the transition probability of the detector (which can be interpreted as the probability of detecting the particle at the location of the UWD detector) is qualitatively similar to the non-relativistic probability density of the particle

Persistent powers: party politics, commercialisation, and the transformation of China s state publishing industry

China's media have undergone significant commercialisation since the introduction of the economic reforms initiated three decades ago. But how this process is unfolding is still not well discussed. Book publishing, the oldest media sector but the one least studied, has been in the forefront of media commercialisation and provides a useful vantage point for the investigation of this transformation. This thesis will examine the role of the party-state and the market during the commercialisation of state publishing, paying particular attention to the core processes of conglomeration and corporatisation and, since the party-state has also been decentralised, to the role of regional government. Drawing on original documentary research and primary data generated in an internship in a provincial publishing group, this thesis advances three main arguments. Firstly, that the process of commercialisation in publishing cannot be fully understood outside of the transformation of the wider economic and political context, especially the shift in the general organisation of industry and the evolution of party ideology. Secondly, that this process has been marked by persistent tensions and contradictions. And thirdly, that despite the ongoing commercialisation the publishing industry remains controlled predominantly by the party-state and is far from being a market-driven business. Decentralisation may have enabled local governments to gain strong control over the economics of local publishers, but the central party-state remains dominant on political issues

First-Principles Modeling of Equilibration Dynamics of Hyperthermal Products of Surface Reactions Using Scalable Neural Network Potential

Equilibration dynamics of hot oxygen atoms following O2 dissociation on Pd(100) and Pd(111) surfaces are investigated by molecular dynamics simulations based on a scalable neural network potential enabling first-principles description of O2 and O interacting with variable Pd supercells. We find that to accurately describe the equilibration dynamics after dissociation, the simulation cell length necessarily exceeds twice the maximum distance of equilibrated oxygen adsorbates. By analyzing hundreds of trajectories with appropriate initial sampling, the measured distance distribution of equilibrated atom pairs on Pd(111) is well reproduced. However, our results on Pd(100) suggest that the ballistic motion of hot atoms predicted previously is a rare event under ideal conditions, while initial molecular orientation and surface thermal fluctuation could significantly affect the overall post-dissociation dynamics. On both surfaces, dissociated oxygen atoms remain primarily locate their nascent positions and then randomly cross bridge sites nearby

High-fugacity expansion and crystallization in non-sliding hard-core lattice particle models without a tiling constraint

In this paper, we prove the existence of a crystallization transition for a family of hard-core particle models on periodic graphs in arbitrary dimensions. We establish a criterion under which crystallization occurs at sufficiently high densities. The criterion is more general than that in [Jauslin, Lebowitz, Comm. Math. Phys. 364:2, 2018], as it allows models in which particles do not tile the space in the close-packing configurations, such as discrete hard-disk models. To prove crystallization, we prove that the pressure is analytic in the inverse of the fugacity for large enough complex fugacities, using Pirogov-Sinai theory. One of the main tools used for this result is the definition of a local density, based on a discrete generalization of Voronoi cells. We illustrate the criterion by proving that it applies to two examples: staircase models and the radius 2.5 hard-disk model on the square lattice.Comment: 41 pages, 12 figure

Factors influencing teachers’ level of digital citizenship in underdeveloped regions of China

In digital times, new demands for higher levels of digital citizenship (DC) have aroused concern. Based on the study reported on here, we propose that 4 predictive factors, i.e., internet self-efficacy, internet attitudes, internet use behaviour and demographic characteristics affect teachers’ level of DC in underdeveloped regions of China. From 21 different provinces, 240 primary teachers in underdeveloped regions in China participated in this quantitative research. The description, significance, correlation, and structural equation modelling (SEM) were statistically performed and analysed. We concluded the following: 1) The average score for DC is low and its 5 dimensions score differently with the highest being the ethical element and the lowest being networking agency and critical perspective; no statistically-significant differences exist for gender, school types, teaching subject and professional rank in predicting DC, but do exist for birth-era, suggesting that young teachers have a higher level of DC. 2) Internet self-efficacy, internet attitudes and internet use behaviour are positively correlated with DC. 3) In the SEM test, internet use behaviour acts as a mediator in the research model; internet self-efficacy is the major determinant of DC, followed by internet use behaviour and internet attitudes. The results were analysed and recommendations to promote teachers’ high-level DC in underdeveloped regions are proposed

Truncation technique for variational quantum eigensolver for Molecular Hamiltonians

The variational quantum eigensolver (VQE) is one of the most promising quantum algorithms for the near-term noisy intermediate-scale quantum (NISQ) devices. The VQE typically involves finding the minimum energy of a quantum Hamiltonian through classical optimization of a parametrized quantum ansatz. One of the bottlenecks in VQEs is the number of quantum circuits to be measured. In this work, we propose a physically intuitive truncation technique that starts the optimization procedure with a truncated Hamiltonian and then gradually transitions to the optimization for the original Hamiltonian via an operator classification method. This strategy allows us to reduce the required number of evaluations for the expectation value of Hamiltonian on a quantum computer. The reduction in required quantum resources for our strategy is substantial and likely scales with the system size. With numerical simulations, we demonstrate our method for various molecular systems