Collective decision making in cohesive flocks

Most of us must have been fascinated by the eye catching displays of collectively moving animals. Schools of fish can move in a rather orderly fashion and then change direction amazingly abruptly. There are a huge number of further examples both from the living and the non-living world for phenomena during which the many interacting, permanently moving units seem to arrive at a common behavioural pattern taking place in a short time. As a paradigm of this type of phenomena we consider the problem of how birds arrive at a decision resulting in their synchronized landing. We introduce a simple model to interpret this process. Collective motion prior to landing is modelled using a simple self-propelled particle (SPP) system with a new kind of boundary condition, while the tendency and the sudden propagation of the intention of landing is introduced through rules analogous to the random field Ising model in an external field. We show that our approach is capable of capturing the most relevant features of collective decision making in a system of units with a variance of individual intentions and being under an increasing level of pressure to switch states. We find that as a function of the few parameters of our model the collective switching from the flying to the landing state is indeed much sharper than the distribution of the individual landing intentions. The transition is accompanied by a number of interesting features discussed in this report

Jaynes Cummings treatment of superconducting resonators with dielectric loss due to two-level systems

We perform a quantum mechanical analysis of superconducting resonators subject to dielectric loss arising from charged two-level systems. We present numerical and analytical descriptions of the dynamics of energy decay from the resonator within the Jaynes-Cummings model. Our analysis allows us to distinguish the strong and weak coupling regimes of the model and to describe within each regime cases where the two-level system is unsaturated or saturated. We find that the quantum theory agrees with the classical model for weak coupling. However, for strong coupling the quantum theory predicts lower loss than the classical theory in the unsaturated regime. Also, in contrast to the classical theory, the photon number at which saturation occurs in the strong coupling quantum theory is independent of the coupling between the resonator and the two-level system.Comment: 9 pages, 8 figure

Tripartite entanglement detection through tripartite quantum steering in one-sided and two-sided device-independent scenarios

In the present work, we study tripartite quantum steering of quantum correlations arising from two local dichotomic measurements on each side in the two types of partially device-independent scenarios: $1$-sided device-independent scenario where one of the parties performs untrusted measurements while the other two parties perform trusted measurements and $2$-sided device-independent scenario where one of the parties performs trusted measurements while the other two parties perform untrusted measurements. We demonstrate that tripartite steering in the $2$-sided device-independent scenario is weaker than tripartite steering in the $1$-sided device-independent scenario by using two families of quantum correlations. That is these two families of quantum correlations in the $2$-sided device-independent framework detect tripartite entanglement through tripartite steering for a larger region than that in the $1$-sided device-independent framework. It is shown that tripartite steering in the $2$-sided device-independent scenario implies the presence of genuine tripartite entanglement of $2\times 2 \times 2$ quantum system, even if the correlation does not exhibit genuine nonlocality or genuine steering.Comment: 14 pages, 4 figures, accepted for publication in Physical Review

Patience Cycles

Evidence supports the notion that those who grow up to be patient dobetter than those who do not. Parents can inculcate the virtue of delayedgratiÂ…cation in their children by taking the right actions. We study a modelin which parents, for selÂ…sh reasons, invest resources to raise patient chil-dren. In the model, patience raises the marginal return to human capitalacquisition giving the patient young an incentive to spend more on theirown education at the expense of investment in their own progenyÂ’s patience.This dynamic generates intergenerational patience cycles.patience; delayed gratification; human capital

Choosing to Keep Up with the Joneses and Income Inequality

We study a variant of the conventional keeping-up-with-the-Joneses setup in which heterogeneous-ability agents care both about consumption and leisure and receive an utility premium if their consumption exceeds that of the Joneses'. Unlike the conventional setup in which all agents are assumed to want to participate in the rat race of staying ahead of the Joneses, our formulation explicitly permits the option to drop out. Mean-preserving changes in the spread of the underlying ability distribution, via its effect on the economy-wide composition of rat-race participants and drop-outs, have important consequences for induced distributions of leisure and income, consequences that are unobtainable using conventional keeping-up preferences.keeping up with the Joneses; consumption externalities; leisure; labor supply