Popper's Experiment and Superluminal Communication

We comment on Tabesh Qureshi, "Understanding Popper's Experiment," AJP 73, 541 (June 2005), in particular on the implications of its section IV. We show, in the situation envisaged by Popper, that analysis solely with conventional non-relativistic quantum mechanics suffices to exclude the possibility of superluminal communication.Comment: Submitted to American Journal of Physic

Ascertaining the spin for new resonances decaying into tau+ tau- at Hadron Colliders

Evidence of a new particle with mass ~125 GeV decaying into a pair of tau leptons at the Large Hadron Collider spurs interest in ascertaining its spin in this channel. Here we present a comparative study between spin-0 and spin-2 nature of this new particle, using spin correlations and decay product directions. The TauSpinner algorithm is used to re-weight distributions from qqbar -> gamma/Z -> tau+ tau- sample to simulate a spin-2 state exchange. The method is based on supplementing the Standard Model matrix elements with those arising from presence of a new interaction. Studies with simulated samples demonstrate the discrimination power between these spin hypotheses based on data collected at the Large Hadron Collider.Comment: 17 pages, 16 encapsulated postscript figure

Is Quantum Field Theory ontologically interpretable? On localization, particles and fields in relativistic Quantum Theory

In this paper, I provide a formal set of assumptions and give a natural criterion for a quantum field theory to admit particles. I construct a na\"ive approach to localization for a free bosonic quantum field theory and show how this localization scheme, as a consequence of the Reeh-Schlieder theorem, fails to satisfy this criterion. I then examine the Newton-Wigner concept of localization and show that it fails to obey strong microcausality and thus is subject to a more general version of the Reeh-Schlieder theorem. I review approaches to quantum field theoretic explanations of particle detection events and explain how particles can be regarded as emergent phenomena of a relativistic field theory. In particular, I show that effective localization of Hilbert space vectors is equivalent to an approximate locality of observable algebras.Comment: 33 page

An internal model approach to (optimal) frequency regulation in power grids with time-varying voltages

This paper studies the problem of frequency regulation in power grids under unknown and possible time-varying load changes, while minimizing the generation costs. We formulate this problem as an output agreement problem for distribution networks and address it using incremental passivity and distributed internal-model-based controllers. Incremental passivity enables a systematic approach to study convergence to the steady state with zero frequency deviation and to design the controller in the presence of time-varying voltages, whereas the internal-model principle is applied to tackle the uncertain nature of the loads.Comment: 16 pages. Abridged version appeared in the Proceedings of the 21st International Symposium on Mathematical Theory of Networks and Systems, MTNS 2014, Groningen, the Netherlands. Submitted in December 201

Domestic Tax Policy and Foreign Investment: Some Evidence

Investment abroad has come to play a major role in the total investment undertaken by U.S. firms. Despite this development, very little attention has been paid to the impacts of domestic tax policy on foreign investment. One reason has been the presumption that, since changes in domestic tax rules ordinarily also apply to foreign-source income, policy changes should affect foreign and domestic investment similarly. However, the fact that the tax on foreign-source income is deferred until the income is repatriated represents a crucial difference in the treatment of foreign and domestic income. So long as the U.S. tax is deferred, the effective U.S. tax rate on foreign-source income can be shown to be irrelevant to a firm's optimal foreign reinvestment decision. Foreign investment is now largely accomplished by firms reinvesting earnings abroad, so the reinvestment decision is of primary importance. Thus, a decrease in the effective U.S. tax rate which applies to both domestic and foreign investment income can be thought of as a cut in the tax on domestic investment income, which is encouraging to domestic investment (perhaps at the expense of foreign investment), combined with a cut in the tax on foreign investment income, which has no effect on the optimal foreign reinvestment decision. Consequently, the impacts on foreign and domestic investment of an apparently neutral policy could be very different . Another reason that the response of foreign investment has been neglected in domestic policy discussions is the lack of evidence on the magnitude of that response. This paper utilizes the theory just described to confirm that foreign investment is influenced negatively and quite strongly by the after-tax rate of return to domestic investment. A further test, in which a "gross domestic rate of return" term and a "domestic tax" term are included separately, produces coefficients virtually equal in absolute value, confirming that the net domestic rate of return is the appropriate variable. The results indicate that a tax incentive which has been found to raise net domestic investment by a dollar reduces net foreign investment by at least twenty cents. This conclusion is further reinforced by results from a forward-looking (Tobin's q) mod el. While these results do not point to the primary outcome of a domestic policy change being a domestic-foreign reallocation of the capital stock, they indicate that a significant reallocation does take place. With open economy tax analysis still in its infancy, the question of how this evidence alters the usual conclusions is largely an open one.