Quantum state transfer in the presence of non homogeneous external potentials

Heisenberg-type spin models in the limit of a low number of excitations are useful tools to study basic mechanisms in strongly correlated and magnetic systems. Many of these mechanisms can be experimentally tested using ultracold atoms. Here, we discuss the implementation of a quantum state transfer protocol in a tight-binding chain in the presence of an inhomogeneous external potential. We show that it can be used to extend the parameter range in which high fidelity state transfer can be achieved beyond the well established weak-coupling regime. Among the class of mirror-reflecting potentials that allow for high-fidelity quantum state transfer, the harmonic case is especially relevant because it allows us to formulate a proposal for the experimental implementation of the protocol in the context of optical lattices

Genuine correlations in finite-size spin systems

Genuine multipartite correlations in finite-size XY chains are studied as a function of the applied external magnetic field. We find that, for low temperatures, multipartite correlations are sensitive to the parity change in the Hamiltonian ground state, given that they exhibit a minimum every time that the ground state becomes degenerate. This implies that they can be used to detect the factorizing point, that is, the value of the external field such that, in the termodynamical limit, the ground state becomes the tensor product of single-spin states.Comment: Submitted to Int. J. Mod. Phys. B, special issue "Classical Vs Quantum correlations in composite systems" edited by L. Amico, S. Bose, V. Korepin and V. Vedra

Executive Compensation: Facts

In this paper we describe the important features of executive compensation in the US from 1993 to 2006. Some confirm what has been found for earlier periods and some are novel. Notable facts are that: the compensation distribution is highly skewed; each year, a sizeable fraction of chief executives lose money; the use of security grants has increased over time; the income accruing to CEOs from the sale of stock increased; regardless of the measure we adopt, compensation responds strongly to innovations in shareholder wealth; measured as dollar changes in compensation, incentives have strengthened over time, measured as percentage changes in wealth, they have not changed in any appreciable way.CEO, Pay–Performance Sensitivity, Stock, Options

Executive Compensation: Facts

In this paper we describe the important features of executive compensation in the US from 1993 to 2006. Some confirm what has been found for earlier periods and some are novel. Notable facts are that: the compensation distribution is highly skewed; each year, a sizeable fraction of chief executives lose money; the use of security grants has increased over time; the income accruing to CEOs from the sale of stock increased; regardless of the measure we adopt, compensation responds strongly to innovations in shareholder wealth; measured as dollar changes in compensation, incentives have strengthened over time, measured as percentage changes in wealth, they have not changed in any appreciable way.CEO, Pay–Performance Sensitivity, Stock, Options

Statistical properties of time-reversible triangular maps of the square

Time reversal symmetric triangular maps of the unit square are introduced with the property that the time evolution of one of their two variables is determined by a piecewise expanding map of the unit interval. We study their statistical properties and establish the conditions under which their equilibrium measures have a product structure, i.e. factorises in a symmetric form. When these conditions are not verified, the equilibrium measure does not have a product form and therefore provides additional information on the statistical properties of theses maps. This is the case of anti-symmetric cusp maps, which have an intermittent fixed point and yet have uniform invariant measures on the unit interval. We construct the invariant density of the corresponding two-dimensional triangular map and prove that it exhibits a singularity at the intermittent fixed point.Comment: 15 pages, 3 figure

A Theory of Firm Decline

We study the problem of an investor that buys an equity stake in an entrepreneurial venture, under the assumption that the former cannot monitor the latter’s operations. The dynamics implied by the optimal incentive scheme is rich andquite different from that induced by other models of repeated moral hazard. In particular, our framework generates a rationale for firm decline. As young firms accumulate capital, the claims of both investor (outside equity) and entrepreneur (inside equity) increase. At some juncture, however, even as the latter keeps on growing, capital and firm value start declining and so does the value of outside equity. The reason is that incentive provision becomes costlier as inside equity grows. In turn, this leads to a decline in the constrained–efficient level of effort and therefore to a drop in the return to investment. In the long run, the entrepreneur gains control of all cash–flow rights and the capital stock converges to a constant value.Principal–Agent, Moral Hazard, Hidden Action, Incentives, Firm Dynamics.

A Theory of Firm Decline

We study the problem of an investor that buys an equity stake in an entrepreneurial venture, under the assumption that the former cannot monitor the latter’s operations. The dynamics implied by the optimal incentive scheme is rich and quite different from that induced by other models of repeated moral hazard. In particular, our framework generates a rationale for firm decline. As young firms accumulate capital, the claims of both investor (outside equity) and entrepreneur (inside equity) increase. At some juncture, however, even as the latter keeps on growing, invested capital and firm value start declining and so does the value of outside equity. The reason is that incentive provision is costlier the wealthier the entrepreneur (the greater is inside equity). In turn, this leads to a decline in the constrained–efficient level of effort and therefore to a drop in the return to investment.Principal Agent, Moral Hazard, Hidden Action, Incentives, Survival, Firm Dynamics

TARIFFICATION UNDER THE URUGUAY ROUND OF GATT: THE CASE OF SWISS ASPARAGUS TRADE

International Relations/Trade,