Teleportation Criteria: Form and Significance

Our criteria for continuous variable quantum teleportation [T.C.Ralph and P.K.Lam, Phys.Rev.Lett. {\bf 81}, 5668 (1998)] take the form of sums, rather than products, of conjugate quadrature measurements of the signal transfer coefficients and the covariances between the input and output states. We discuss why they have this form. We also discuss the physical significance of the covariance inequality.Comment: 6 pages, to appear in Lecture Notes in Physics; Dan Walls Memorial Volume (Springer 2000

Unitary Solution to a Quantum Gravity Information Paradox

We consider a toy model of the interaction of a qubit with an exotic space-time containing a time-like curve. Consistency seems to require that the global evolution of the qubit be non-unitary. Given that quantum mechanics is globally unitary, this then is an example of a quantum gravity information paradox. However, we show that a careful analysis of the problem in the Heisenberg picture reveals an underlying unitarity, thus resolving the paradox.Comment: 5 page

Moral Constraints and the Evasion of Income Tax

This paper re-examines the individual income tax evasion decision in the simple framework introduced by Allingham and Sandmo (1972), where the individual taxpayer decides how much of his income is invested in a safe asset (reported income) and in a risky asset (concealed income). These early models could not convincingly reproduce the empirically observed positive influence of higher tax rates and higher gross income on tax evasion simultaneously. We replace the standard assumption that risk aversion is the factor limiting the extent of evasion by assuming risk neutral taxpayers and argue that this is a reasonable approximation. The observation that concealing income is costly leads to the conclusion that, instead of risk aversion, evasion costs (such as concealment expenses and moral cost) might be the factors that limit tax evasion. We reproduce the stylized facts not explained by older models for very general tax and penalty schemes, including those where the standard model definitely fails to do so.tax evasion, risk preferences, moral constraints

Cooperation in Partnerships: The Role of Breakups and Reputation

We investigate experimentally if endogenous partnership formation can improve efficiency in social dilemma situations. Subjects play multiple two-player public goods games, where they can break up with their current partner after every fourth game. Subjects without a partner provide rankings of the available other singles regarding their preferred subject to be matched with. A stable marriage mechanism determines the new matches. We vary the information subjects have when they express their preferences for their future matches and also if staying in a partnership leads to a cost or a bonus. We find that endogenous group formation can increase efficiency. Both the provision of contribution history at the time of re-matching and bonuses for staying in a partnership have positive effects. At least one of the two positive factors has to be present for an efficiency improvement. The presence of both leads to the best results.Social Dilemma, Endogenous Group Formation, Public Goods

A Contest with the Taxman: The Impact of Tax Rates on Tax Evasion and Wastefully Invested Resources

We develop a moral hazard model with auditing where both the principal and the agent can influence the probability that the true state of nature is verified. This setting is widely applicable for situations where fraudulent reporting with costly state verification takes place. However, we use the framework to investigate tax evasion. We model tax evasion as a concealment-detection contest between the taxpayer and the authority. We show that higher tax rates cause more evasion and increase the resources wasted in the contest. Additionally, we find conditions under which a government should enforce incentive compatible auditing in order to reduce wasted resources.tax evasion, auditing rules, contest, moral hazard