PT-symmetric Rabi model: Perturbation theory

We study a non-Hermitian version of the Rabi model, where a two-level system is periodically driven with an imaginary-valued drive strength, leading to alternating gain and loss. In the Floquet picture, the model exhibits PT symmetry, which can be broken when the drive is sufficiently strong. We derive the boundaries of the PT phase diagram for the different resonances by doing perturbation theory beyond the rotating-wave approximation. For the main resonance, we show that the non-Hermitian analog of the Bloch-Siegert shift corresponds to maximal PT-breaking. For the higher-order resonances, we capture the boundaries to lowest order. We also solve the regime of high frequency by mapping to the Wannier-Stark ladder. Our model can be experimentally realized in waveguides with spatially-modulated loss or in atoms with time-modulated spontaneous decay.Comment: 8 pages, 6 figure

The chinese business negotiation process: a socio-cultural analysis

Hoogovens Steel (HS) is a vertically integrated steel company, which until 1995 was functionally structured. During the eighties the steel market became saturated and more heterogeneous. In order to remain a flexible, market-oriented company, HS changed its organizational structure, by introducing business units responsible for their own financial results. Nevertheless, it remained a vertically integrated steel producer. With the functional structure HS had used cost-based transfer prices. But following the introduction of the business units the question was raised as to whether the transfer pricing system should be changed. A business unit structure implies a decentralization of authority and the delegation of certain activities to the units, but vertically integrated production requires close relations between the various stages. This paper discusses the extent to which the tensions between decentralization and integration can be resolved through the coordination of internal transactions. After introducing the relevant theoretical concepts, the issues which emerged in discussions about the coordination of internal transactions at HS are discussed. Some possible solutions are evaluated on the basis of criteria derived from the theoretical concepts, and the choice made within HS is described. Finally, some conclusions are drawn regarding the significance of the theoretical concepts.

String order via Floquet interactions in atomic systems

We study the transverse-field Ising model with interactions that are modulated in time. In a rotating frame, the system is described by a time-independent Hamiltonian with many-body interactions, similar to the cluster Hamiltonians of measurement-based quantum computing. In one dimension, there is a three-body interaction, which leads to string order instead of conventional magnetic order. We show that the string order is robust to power-law interactions that decay with the cube of distance. In two and three dimensions, there are five- and seven-body interactions. We discuss adiabatic preparation of the ground state as well as experimental implementation with trapped ions, Rydberg atoms, and polar molecules.Comment: 8 pages, 6 figure

Institutional Quality, Reforms and Integration in the Maghreb

institutions, Maghreb, economic reform

Minimal Noise-Induced Stabilization of One-Dimensional Diffusions

The phenomenon of noise-induced stabilization occurs when an unstable deterministic system of ordinary differential equations is stabilized by the addition of randomness into the system. In this paper, we investigate under what conditions one-dimensional, autonomous stochastic differential equations are stable, where we take the notion of stability to be that of global stochastic boundedness. Specifically, we find the minimum amount of noise necessary for noise-induced stabilization to occur when the drift and noise coefficients are power, polynomial, exponential, or logarithmic functions

PT\mathcal{PT}-breaking threshold in spatially asymmetric Aubry-Andre Harper models: hidden symmetry and topological states

Aubry-Andre Harper (AAH) lattice models, characterized by reflection-asymmetric, sinusoidally varying nearest-neighbor tunneling profile, are well-known for their topological properties. We consider the fate of such models in the presence of balanced gain and loss potentials $\pm i\gamma$ located at reflection-symmetric sites. We predict that these models have a finite $\mathcal{PT}$ breaking threshold only for {\it specific locations} of the gain-loss potential, and uncover a hidden symmetry that is instrumental to the finite threshold strength. We also show that the topological edge-states remain robust in the $\mathcal{PT}$-symmetry broken phase. Our predictions substantially broaden the possible realizations of a $\mathcal{PT}$-symmetric system.Comment: 8 pages, 5 figure

Local control of entanglement in a spin chain

In a ferromagnetic spin chain, the control of the local effective magnetic field allows to manipulate the static and dynamical properties of entanglement. In particular, the propagation of quantum correlations can be driven to a great extent so as to achieve an entanglement transfer on demand toward a selected site

Estimating the costs and benefits of providing free public transit passes to students in Los Angeles County: lessons learned in applying a health lens to decision-making.

In spite of increased focus by public health to engage and work with non-health sector partners to improve the health of the general as well as special populations, only a paucity of studies have described and disseminated emerging lessons and promising practices that can be used to undertake this work. This article describes the process used to conduct a Health Impact Assessment of a proposal to provide free public transportation passes to students in Los Angeles County. This illustrative case example describes opportunities and challenges encountered in working with an array of cross-sector partners and highlights four important lessons learned: (1) the benefits and challenges associated with broad conceptualization of public issues; (2) the need for more comprehensive, longitudinal data systems and dynamic simulation models to inform decision-making; (3) the importance of having a comprehensive policy assessment strategy that considers health impacts as well as costs and feasibility; and (4) the need for additional efforts to delineate the interconnectivity between health and other agency priorities. As public health advances cross-sector work in the community, further development of these priorities will help advance meaningful collaboration among all partners

Working through Possibilities: A Scientist Reviews When Did Sin Begin?

... [Haarsma] lays out the challenges of reconciling an evolutionary history with a biblical understanding of original sin. Posting about ­­­­­­­­the book When Did Sin Begin? from In All Things - an online journal for critical reflection on faith, culture, art, and every ordinary-yet-graced square inch of God’s creation. https://inallthings.org/from-a-scientist-a-review-of-when-did-sin-begin