Positronium collisions with rare-gas atoms

We calculate elastic scattering of positronium (Ps) by the Xe atom using the recently developed pseudopotential method [I. I. Fabrikant and G. F. Gribakin, Phys. Rev. A 90, 052717 (2014)] and review general features of Ps scattering from heavier rare-gas atoms: Ar, Kr, and Xe. The total scattering cross section is dominated by two contributions: elastic scattering and Ps ionization (breakup). To calculate the Ps ionization cross sections we use the binary-encounter method for Ps collisions with an atomic target. Our results for the ionization cross section agree well with previous calculations carried out in the impulse approximation. Our total Ps-Xe cross section, when plotted as a function of the projectile velocity, exhibits similarity with the electron-Xe cross section for the collision velocities higher than 0.8 a.u., and agrees very well with the measurements at Ps velocities above 0.5 a.u.Comment: 7 pages, 7 figures, submitted to J. Phys.

Credibility and Law Enforcement

The precommitment approach to law enforcement is inappropriate as a positive theory of crime and punishment because it is inconsistent with the institutional structure of U.S. law enforcement. We develop a formal model which integrates theories of optimal sanctions, individual criminal behavior and the allocation of effort to apprehension, and imposes credibility constraints on the choice of sanction—i.e., given the severity of a crime and the individual characteristics of the criminal, the sanction imposed must be optimal from society's perspective, after the crime has been committed

Equilibrium Enforcement and Compliance in the Presence of Tax Practitioners

We develop a game-theoretic model in which taxpayers, tax practitioners and a tax agency all interact to determine the extent of tax compliance. The model focuses exclusively on the service aspects of third-party assistance. We characterize four types of equilibria, depending on whether taxpayers prefer to use tax practitioners and whether the tax agency prefers them to use tax practitioners. In the empirically relevant case, which occurs when tax practitioner penalties for noncompliance are sufficiently low and the efficiency gains from using practitioners are sufficiently high, the tax agency prefers taxpayers to prepare their own returns, but taxpayers prefer to use a tax practitioner. In this case, the use of a tax practitioner is associated with lower compliance and higher audit rates

Application of strategic fuzzy games to wage increase negotiation and decision problems

We propose a flexible decision support scheme which could be used in managing the wage negotiation between employers and employees. This scheme uses fuzzy inference systems and game theory concepts in arriving at decisions on future wage increase which could be more mutually agreeable. For example, rather than specifying 5% yearly increase of wages, we propose that the uncertain factors which are mostly difficult to predict and that could affect wage decisions need to be taken into consideration by the wage formula. These include business revenues or (profit), inflation rate, number of competitors, cost of production, and other uncertain factors that may affect business operations. The accuracy of the fuzzy rule base and the game strategies will help to mitigate the adverse effects that a business may suffer from these uncertain factors. Based on our scheme, we propose that employers and employees should calculate their future wage by using a fuzzy rule base and strategies that take into consideration these uncertain variables. The proposed approach is illustrated with a case study and the procedure and methodology may be easily implemented by business organizations in their wage bargaining and decision processes. © 2012 Elsevier Ltd. All rights reserved

Income Tax Compliance in a Principal-Agent Framework

Previous analyses have modeled income tax evasion as a "portfolio problem," deriving the optimal consumption of the "risky asset" (unreported income) under the assumption of a fixed probability of detection, The purpose of this paper is to examine some of these issues in tax compliance starting from a different set of assumptions. In particular, we compare alternative audit policies to the standard random audit policy. We focus on an "audit cutoff" policy, in which an agent triggers an audit if his or her reported income is "too low," and is not audited if reported income is "sufficiently high." This paper establishes two major results. First, random audit rules are weakly dominated by audit cutoff rules. It can be shown, given lump-sum taxes and fines, that these audit cutoff rules are the least-cost policies which induce truthful reporting of income. Second, the dominance of audit cutoff rules over random audit rules holds for "lump-sum" as well as proportional taxation—in fact, the equilibrium consequences of the two are equivalent

Settlement and Litigation Under Alternative Legal Systems

We consider a situation in which one party (the plaintiff) has a legally admissible claim for damages from another party (the defendant). The level of damage is known to the plaintiff; the defendant knows only its distribution, which is assumed to be continuous on some range. Before a trial takes place, the plaintiff makes a settlement demand. If the defendant rejects the demand, the court settles the dispute. We characterize the plaintiff's settlement demand policy and the defendant's probability of rejection policy for both separating and pooling equilibria. In the separating equilibrium, the defendant correctly infers the level of true damage from the settlement demand made by the plaintiff. In this case we show that, under risk neutrality, the equilibrium probability of a trial (as a function of true damages) is independent of the allocation of litigation costs. We also analyze the comparative statics of the equilibrium policies and compare them for specific litigation cost allocation systems