Mode stability on the real axis

A generalization of the mode stability result of Whiting (1989) for the Teukolsky equation is proved for the case of real frequencies. The main result of the paper states that a separated solution of the Teukolsky equation governing massless test fields on the Kerr spacetime, which is purely outgoing at infinity, and purely ingoing at the horizon, must vanish. This has the consequence, that for real frequencies, there are linearly independent fundamental solutions of the radial Teukolsky equation which are purely ingoing at the horizon, and purely outgoing at infinity, respectively. This fact yields a representation formula for solutions of the inhomogenous Teukolsky equation.Comment: 20 pages, 4 figures. Reference added, revtex4-1 forma

Cavity state preparation using adiabatic transfer

We show how to prepare a variety of cavity field states for multiple cavities. The state preparation technique used is related to the method of stimulated adiabatic Raman passage or STIRAP. The cavity modes are coupled by atoms, making it possible to transfer an arbitrary cavity field state from one cavity to another, and also to prepare non-trivial cavity field states. In particular, we show how to prepare entangled states of two or more cavities, such as an EPR state and a W state, as well as various entangled superpositions of coherent states in different cavities, including Schrodinger cat states. The theoretical considerations are supported by numerical simulations.Comment: 11 pages, 9 figures. Accepted in Phys. Rev.

Electoral systems help explain why left-wing governments (sometimes) tax the poor

Using novel historical data, Per F. Andersson demonstrates that left-wing governments tax more regressively in proportional representation systems and more progressively in majoritarian ones. He illustrates how political risk shapes the strategies of key actors and helps explain the divergence in tax policy using the examples of Swedish and British tax policy after 1945

Essays on the Politics of Taxation

Taxation is a key activity of any state and a constant point of political struggle. The structure of taxation is continuously changing and evolving, and its size has grown dramatically during the last two hundred years. Many of the cross-national patterns we observe today are the result of centuries old conflicts and challenges, hence we need to take history into account if we want to understand contemporary tax systems. This dissertation is concerned with the evolution of taxation in the last two centuries. During this period modern parliamentary democracy developed and spread, and it is during this period that the contemporary party systems crystallized and the broad lines of conflict between the left and the right emerged. Thus, this period is crucial for our understanding of the effects of political institutions and ideology on policy making.Because of a lack of comparative information on taxation with a long time scale, previous research has been constrained to a small number of mostly European countries. In this dissertation I present a novel dataset (a collaboration with Thomas Brambor) over government tax revenues covering 31 countries from 1800 to 2012. The dataset is unprecedented in both temporal and geographic scope and includes countries from Europe, North America, South America, as well as Australia, New Zealand, and Japan.The first paper is concerned with the notion that democracy itself has an impact on taxation by extending influence to previously excluded groups of poor citizens. I present evidence for the argument that the effects of democracy depend on urbanization. Democratization in an urbanized state leads to higher taxes on income and lower taxes on consumption. In contrast, democratization in rural countries is associated with lower taxes on property.The second paper investigates the influence of ideology on taxation. A puzzle in the literature is why left-wing parties are associated with regressive taxation (e.g., on consumption). I argue that how left-wing governments tax depend on the institutional environment. In countries using majoritarian/plurality electoral systems the left relies more on income tax, and in countries using proportional representation systems the left relies more on consumption tax.In the third paper I investigate the mechanism behind left-wing tax strategy in more detail by studying reforms of consumption taxation in post- war United Kingdom and Sweden. I find that strategic considerations related to how the political system concentrates power in the United Kingdom affected the Labour Party’s attitude towards the value-added tax and its decision not to adopt the tax. The left-wing government in Sweden on the other hand, operating in a different institutional context, decided to introduce a similar tax.The fourth paper, which is coauthored with Johannes Lindvall, contrasts political investments, of which taxation is one example, with short- term crisis management. We present a game theoretic model in which institutions that concentrate power are better at handling sudden crises but worse at making policy with short-run costs and long-term gains. Power-sharing institutions, on the other hand, are better at resolving inter- temporal dilemmas, but perform worse when faced with sudden crises

Quantum algorithms for testing Boolean functions

We discuss quantum algorithms, based on the Bernstein-Vazirani algorithm, for finding which variables a Boolean function depends on. There are 2^n possible linear Boolean functions of n variables; given a linear Boolean function, the Bernstein-Vazirani quantum algorithm can deterministically identify which one of these Boolean functions we are given using just one single function query. The same quantum algorithm can also be used to learn which input variables other types of Boolean functions depend on, with a success probability that depends on the form of the Boolean function that is tested, but does not depend on the total number of input variables. We also outline a procedure to futher amplify the success probability, based on another quantum algorithm, the Grover search

Chaotic sources and Percolation of strings

It is shown that different ways of interacting strings formed in high energy nucleus-nucleus collisions cause a different strength of the chaoticity parameter lambda of Bose-Einstein correlations. In particular, in the case of percolation of strings, lambda shows a peculiar dependence on the string density, very similar to the dependence of the fractional average cluster size. In both, the derivative on the string density is maximum at the critical point. The reasonable agreement with the existing experimental data indicates that percolation of strings can actually occurs.Comment: 11 pages, LaTeX, 3 eps figure