Energy Correlations In Random Transverse Field Ising Spin Chains

The end-to-end energy - energy correlations of random transverse-field quantum Ising spin chains are computed using a generalization of an asymptotically exact real-space renormalization group introduced previously. Away from the critical point, the average energy - energy correlations decay exponentially with a correlation length that is the same as that of the spin - spin correlations. The typical correlations, however, decay exponentially with a characteristic length proportional to the square root of the primary correlation length. At the quantum critical point, the average correlations decay sub-exponentially as $\bar{C_{L}}\sim e^{-const\cdot L^{1/3}}$, whereas the typical correlations decay faster, as $\sim e^{-K\sqrt{L}}$, with $K$ a random variable with a universal distribution. The critical energy-energy correlations behave very similarly to the smallest gap, computed previously; this is explained in terms of the RG flow and the excitation structure of the chain. In order to obtain the energy correlations, an extension of the previously used methods was needed; here this was carried out via RG transformations that involve a sequence of unitary transformations.Comment: Submitted to Phys. Rev.

A Next-to-Minimal Supersymmetric Model of Hybrid Inflation

We propose a model of inflation based on a simple variant of the NMSSM, called $\phi$NMSSM, where the additional singlet $\phi$ plays the role of the inflaton in hybrid (or inverted hybrid) type models. As in the original NMSSM, the $\phi$NMSSM solves the $\mu$ problem of the MSSM via the VEV of a gauge singlet $N$, but unlike the NMSSM does not suffer from domain wall problems since the offending $Z_3$ symmetry is replaced by an approximate Peccei-Quinn symmetry which also solves the strong CP problem, and leads to an invisible axion with interesting cosmological consequences. The PQ symmetry may arise from a superstring model with an exact discrete $Z_3 \times Z_5$ symmetry after compactification. The model predicts a spectral index $n=1$ to one part in $10^{12}$.Comment: 17 pages, Latex; note added, accepted for Phys. Lett.

Political Culture and Monopoly Price Determination

In this paper we study the endogenous determination of monopoly price. Our proposed game of endogenous monopoly-price setting extends the literature on monopoly-price, monopoly rent-seeking contests and monopoly rent-seeking rent-avoidance contests by (i) determining the monopoly price such that it maximizes a composite utility function that depends on two components: expected social welfare and lobbying efforts. The welfare component has a positive or no effect on the utility while the lobbying efforts have a positive, negative or no effect on the utility (ii) introducing the political culture of the government and clarifying its role in the endogenous determination of monopoly price. In the proposed model the single parameter representing political culture is the weight assigned to the enhancement of social welfare. Our main concern is with the study of the relationship between this parameter and the proposed monopoly price and, in turn, the rent-seeking rent-avoidance efforts of the potential monopoly and the consumers and their aggregate expected benefit.

Interactions between Local and Migrant Workers at the Workplace

In this paper we consider the interaction between local workers and migrants in the production process of a firm. Both local workers and migrants can invest effort in assimilation activities in order to increase the assimilation of the migrants into the firm and thereby increase their interaction and production activities. We consider the effect of the relative size (in the firm) of each group and the cost of activities on the migrants’ assimilation process.assimilation, contracts, ethnicity, market structure, networks, harassment

The Why, When and How of Immigration Amnesties

This paper presents some of the many issues involved in the granting of an amnesty to illegal immigrants. Complementing studies by Chau (2001, 2003), Karlson and Katz (2003) and Gang and Yun (2006), we consider government behavior with respect to allocations on limiting infiltration (border control) and apprehending infiltrators (internal control) and with respect to the granting of amnesties, the timing of amnesties, and limitations on eligibility for those amnesties. We demonstrate the effects of government actions on allocations and the flow of immigrants, and how the interactions between these factors combine to yield an optimal amnesty policy. We also consider two extensions – intertemporal transfers of policing funds and “fuzziness” in declarations regarding eligibility for an amnesty aimed at apprehending and deporting undesirables.Amnesty, Immigration, Illegal Immigration, Border Controls, Internal Controls

Strategic Restraint in Contests

Economic policy is modeled as the outcome of a (political) game between two inte rest groups. The possible ex-post (realized) outcomes in the game correspond to the proposed policies. In the literature the policies fought for are exogenous. We extend such games by allowing the endogenous determination of the proposed policies. In a first stage the groups decide which policy to lobby for and then, in a second stage, engage in a contest over the proposed policies. Our main result is that competition over endogenously determined policies induces strategic restraint that reduces polarization and, in turn, wasteful lobbying activities.Interest groups, endogenous lobbying targets, voluntary restraint, polarization, voluntary restraint

The Impact of Worker Effort on Public Sentiment Towards Temporary Migrants

Temporary and circular migration programs have been devised by many destination countries and supported by the European Commission as a policy to reduce welfare and social costs of immigration in destination countries. In this paper we present an additional reason for proposing temporary migration policies based on the characteristics of the foreign labor-effort supply. The level of effort exerted by migrants, which decreases over their duration in the host country, positively affects production, real wages and capital owners' profits. We show that the acceptance of job offers by migrants result in the displacement in employment of national workers. However it increases the workers‟ exertion, decreases prices and thus can counter anti-immigrant voter sentiment. Therefore, the favorable sentiment of the capital owners and the local population towards migrants may rise when temporary migration policies are adopted.Migration, Exertion of effort, Contracted Temporary Migration

A Theory of Immigration Amnesties

This paper presents a first attempt at understanding some of the many issues involved in the granting of an amnesty to illegal immigrants. We consider government behavior with respect to allocations on limiting infiltration (border control) and apprehending infiltrators (internal control) and with respect to the granting of amnesties, the timing of amnesties, and limitations on eligibility for those amnesties. We demonstrate the effects of government actions on allocations and the flow of immigrants, and how the interactions between these factors combine to yield an optimal amnesty policy. We also consider various extensions such as intertemporal transfers of policing funds, risk-aversion, and -fuzziness, in declarations regarding eligibility for an amnesty aimed at apprehending and deporting undesirables.Amnesty, Immigration, Illegal Immigration, Border Controls, Internal Controls.

The Impact of Worker Effort on Public Sentiment Towards Temporary Migrants

Temporary and circular migration programs have been devised by many destination countries and supported by the European Commission as a policy to reduce welfare and social costs of immigration in destination countries. In this paper we present an additional reason for proposing temporary migration policies based on the characteristics of the foreign labor-effort supply. The level of effort exerted by migrants, which decreases over their duration in the host country, positively affects production, real wages and capital owners\' profits. We show that the acceptance of job offers by migrants result in the displacement in employment of national workers. However it increases the workers\' exertion, decreases prices and thus can counter anti-immigrant voter sentiment. Therefore, the favorable sentiment of the capital owners and the local population towards migrants may rise when temporary migration policies are adopted.Migration, Exertion of effort, Contracted Temporary Migration

Politics of Randomness

The main drawback of the public-policy contest is that the notion of contest success function, a crucial component of the contest model, does not have micro-foundations and, therefore, the random behavior of the government seems ad-hoc. In the present paper we propose a partial micro-foundation for the public-policy contest. The possible rationalization of random government behavior is illustrated in the case of the all-pay auction and Tullock's lottery logit functions. We also clarify how stake asymmetry, lobbying-skill asymmetry and return to lobbying effort determine the relative desirability, from the government's point of view, of these CSFsinterest groups, policy makers, lobbying, public-policy contests, contest success function, rationalization of random government's behavior