Dynamical recovery of SU(2) symmetry in the mass-quenched Hubbard model

We use non-equilibrium dynamical mean-field theory with iterative perturbation theory as an impurity solver to study the recovery of $SU(2)$ symmetry in real-time following a hopping integral parameter quench from a mass-imbalanced to a mass-balanced single-band Hubbard model at half-filling. A dynamical order parameter $\gamma(t)$ is defined to characterize the evolution of the system towards $SU(2)$ symmetry. By comparing the momentum dependent occupation from an equilibrium calculation (with the $SU(2)$ symmetric Hamiltonian after the quench at an effective temperature) with the data from our non-equilibrium calculation, we conclude that the $SU(2)$ symmetry recovered state is a thermalized state. Further evidence from the evolution of the density of states supports this conclusion. At the same time, we find the order parameter in the weak Coulomb interaction regime undergoes an approximate exponential decay. We numerically investigate the interplay of the relevant parameters (initial temperature, Coulomb interaction strength, initial mass-imbalance ratio) and their combined effect on the thermalization behavior. Finally, we study evolution of the order parameter as the hopping parameter is changed with either a linear ramp or a pulse. Our results can be useful in strategies to engineer the relaxation behavior of interacting, quantum many-particle systems.Comment: 8 pages, 6 figure

The hydrostatic equilibrium and Tsallis equilibrium for self-gravitating systems

Self-gravitating systems are generally thought to behavior non-extensively due to the long-range nature of gravitational forces. We obtain a relation between the nonextensive parameter q of Tsallis statistics, the temperature gradient and the gravitational potential based on the equation of hydrostatic equilibrium of self-gravitating systems. It is suggested that the nonextensive parameter in Tsallis statistics has a clear physical meaning with regard to the non-isothermal nature of the systems with long-range interactions and Tsallis equilibrium distribution for the self-gravitating systems describes the property of hydrostatic equilibrium of the systems.Comment: 7 pages, 9 Reference

Floquet band structure of a semi-Dirac system

In this work we use Floquet-Bloch theory to study the influence of circularly and linearly polarized light on two-dimensional band structures with semi-Dirac band touching points, taking the anisotropic nearest neighbor hopping model on the honeycomb lattice as an example. We find circularly polarized light opens a gap and induces a band inversion to create a finite Chern number in the two-band model. By contrast, linearly polarized light can either open up a gap (polarized in the quadratically dispersing direction) or split the semi-Dirac band touching point into two Dirac points (polarized in the linearly dispersing direction) by an amount that depends on the amplitude of the light. Motivated by recent pump-probe experiments, we investigated the non-equilibrium spectral properties and momentum-dependent spin-texture of our model in the Floquet state following a quench in absence of phonons, and in the presence of phonon dissipation that leads to a steady-state independent of the pump protocol. Finally, we make connections to optical measurements by computing the frequency dependence of the longitudinal and transverse optical conductivity for this two-band model. We analyze the various contributions from inter-band transitions and different Floquet modes. Our results suggest strategies for optically controlling band structures and experimentally measuring topological Floquet systems.Comment: 17 pages, 8 figure

Quantum games of asymmetric information

We investigate quantum games in which the information is asymmetrically distributed among the players, and find the possibility of the quantum game outperforming its classical counterpart depends strongly on not only the entanglement, but also the informational asymmetry. What is more interesting, when the information distribution is asymmetric, the contradictive impact of the quantum entanglement on the profits is observed, which is not reported in quantum games of symmetric information.Comment: 5 pages, 3 figure

Local Geography of Row-Crop Quality Land and Cropland Cash Rental Rates

While farmland rental markets are likely to be spatially differentiated, the fine spatial structure of row-crop quality land should have a significant effect on cash rent determination. This study provides a rigorous empirical understanding of the effect of land spatial heterogeneity on cash rental rates. The lacunarity index is employed to measure spatial heterogeneity of land quality, which is built directly upon a soil quality measure, the land parcel’s corn suitability rating index (CSR). A panel data random effect model is applied on annual survey data of farmland cash rental rates of Iowa for 1987-2009. As expected, land spatial heterogeneity has a statistically significant and negative effect on local cash rent rates. The effect’s origin warrants further research.land spatial heterogeneity, rental market, Agricultural Finance, C5, G1, Q1,

Caring for people living with AIDS

This paper discusses the concept of care and its implementation with reference to caring for people living with AIDS (PLWA) as 'a labour of love'. The first part of the paper elaborates on care as love, an emotion, and care as labour, an activity, followed by a discussion on four interconnected phases of care, namely 'caring about', 'taking care of', 'care-giving' and 'care-receiving' and the requirements for 'good' care. The gendered nature of care and the resources required for adequate quality care are also discussed. The emphasis in this paper is on the arrangement of care for PLWA, at the micro-level of the household as provided by family and community members, while recognising the role of the state and the market in care provision. This framework is applied to cases from non-urban KwaZulu-Natal in South Africa. The cases, presented according to the four phases of care, not only illustrate care for PLWA as emotion and hard work, but also reveal the gendered nature of care and the resources required to provide quality care. The discussion, the last part of the paper, reflects on care as emotion and care as work and what it entails for different gender groups in this cultural setting characterised by limited access to especially economic resources, where social capital proved to be a crucial resource for the PLWA to access care. It also goes beyond the four phases of care by incorporating the experiences of the caregiver and her/his response to the feedback received from the care receiver