Voting on income-contingent loans for higher education

We consider risk-averse individuals who differ in two characteristics - ability to benefit from education and inherited wealth - and analyze higher education participation under two alternative financing schemes - tax subsidy and (risk-sharing) income-contingent loans. With decreasing absolute risk aversion, wealthier individuals are more likely to undertake higher education despite the fact that, according to the stylized financing schemes we consider, individuals do not pay any up-front financial cost of education. We then determine which financing scheme arises when individuals are allowed to vote between schemes. We show that the degree of risk aversion plays a crucial role in determining which financing scheme obtains a majority, and that the composition of the support group for each financing scheme can be of two different types.

An efficiency argument for affirmative action in higher education

In a dynamic framework in which generations are linked by educational background, we identify an intergenerational externality that is larger for disadvantaged groups. This provides an argument for affirmative action in higher education based on efficiency alone.

Financing schemes for higher education

Most industrial countries have traditionally subsidized the provision of higher education. Several alternative financing schemes, which rely on larger contributions from students, are being increasingly adopted. Schemes such as income contingent loans, like the Australian Higher Education Contribution Scheme (HECS), provide insurance against uncertain educational outcomes. This paper analyses alternative financing schemes for higher education, with particular emphasis on the insurance role and its effect on higher education participation.

Strong correlations in quantum vortex nucleation of ultracold atomic gases

We review some recent developments in the theory of rotating atomic gases. These studies have thrown light on the process of nucleation of vortices in regimes where mean-field methods are inadequate. In our review we shall describe and compare quantum vortex nucleation of a dilute ultracold bosonic gas trapped in three different configurations: a one-dimensional ring lattice, a one-dimensional ring superlattice and a two-dimensional asymmetric harmonic trap. In all of them there is a critical rotation frequency, at which the particles in the ground state exhibit strong quantum correlations. However, the entanglement properties vary significantly from case to case. We explain these differences by characterizing the intermediate states that participate in the vortex nucleation process. Finally, we show that noise correlations are sensitive to these differences. These new studies have, therefore, shown how novel quantum states may be produced and probed in future experiments with rotating neutral atom systems.Comment: 17 pages, 5 figure

A generalized phase space approach for solving quantum spin dynamics

Numerical techniques to efficiently model out-of-equilibrium dynamics in interacting quantum many-body systems are key for advancing our capability to harness and understand complex quantum matter. Here we propose a new numerical approach which we refer to as GDTWA. It is based on a discrete semi-classical phase-space sampling and allows to investigate quantum dynamics in lattice spin systems with arbitrary $S\geq 1/2$. We show that the GDTWA can accurately simulate dynamics of large ensembles in arbitrary dimensions. We apply it for $S>1/2$ spin-models with dipolar long-range interactions, a scenario arising in recent experiments with magnetic atoms. We show that the method can capture beyond mean-field effects, not only at short times, but it also correctly reproduces long time quantum-thermalization dynamics. We benchmark the method with exact diagonalization in small systems, with perturbation theory for short times, and with analytical predictions made for closed system which feature quantum-thermalization at long times. By computing the Renyi entropy, currently an experimentally accessible quantifier of entanglement, we reveal that large $S$ systems can feature larger entanglement than corresponding $S=1/2$ systems. Our analyses demonstrate that the GDTWA can be a powerful tool for modeling complex spin dynamics in regimes where other state-of-the art numerical methods fail

Many-Body Quantum Spin Dynamics with Monte Carlo Trajectories on a Discrete Phase Space

Interacting spin systems are of fundamental relevance in different areas of physics, as well as in quantum information science, and biology. These spin models represent the simplest, yet not fully understood, manifestation of quantum many-body systems. An important outstanding problem is the efficient numerical computation of dynamics in large spin systems. Here we propose a new semiclassical method to study many-body spin dynamics in generic spin lattice models. The method is based on a discrete Monte Carlo sampling in phase-space in the framework of the so-called truncated Wigner approximation. Comparisons with analytical and numerically exact calculations demonstrate the power of the technique. They show that it correctly reproduces the dynamics of one- and two-point correlations and spin squeezing at short times, thus capturing entanglement. Our results open the possibility to study the quantum dynamics accessible to recent experiments in regimes where other numerical methods are inapplicable.Comment: 8 pages, 6 figure