The Tolman "Antitelephone" Paradox: Its Solution by Tachyon Mechanics

Some recent experiments led to the claim that something can travel faster than light in vacuum. However, such results do not seem to place relativistic causality in jeopardy. Actually, it is possible to solve also the known causal paradoxes, devised for "faster than $c$" motion: even if this is not widely recognized. Here we want to show, in detail and rigorously, how to solve the oldest causal paradox, originally proposed by Tolman, which is the kernel of so many further tachyon paradoxes. The key to the solution is a careful application of {\em tachyon mechanics}, that can be unambiguously derived from special relativity

The index of a geodesic in a Randers space and some remarks about the lack of regularity of the energy functional of a Finsler metric

In some recent papers, the relations existing between the metric properties of Randers spaces and the conformal geometry of stationary Lorentzian manifolds were discovered and investigated. In this note, we focus on the equality between the index of a geodesic in a Randers space and that of its lightlike lift in the associated conformal stationary spacetime. Moreover we make some remarks about regularity of the energy functional of a Finsler metric on the infinite dimensional manifold of $H^1$ curves between two points, in connection with infinite dimensional techniques in Morse Theory.Comment: Contribution to the proceedings of "Workshop on Finsler geometry and its applications", Debrecen, 24--29 May, 2009. 8 pages, AMSLaTex. v2 minor revision: typos fixed, references update

The Long-run Effects of Household Liquidity Constraints and Taxation on Fertility, Education, Saving, and Growth

This paper investigates economic growth under liquidity constraints by taking into account the choices of fertility, human capital and saving. In a model of four overlapping generations, parents are altruistic towards their offspring and finance their education investment. The government provides education subsidies to young adult parents and levies taxes on income of the adult generation. Sensitivity analysis on borrowing limits and tax parameters highlights effects with opposite sign on the main endogenous variables at steady state. A lift in liquidity constraints decreases savings and capital accumulation and this effect is responsible for the ambiguous sign of comparative statics on the rate of fertility and on human capital investment. From model simulation, we derive an inverted U-shaped curve relating the borrowing limit with fertility, education and growth, meaning that financial reforms in the less developed countries have positive effects on the economy in the long-run, even if they raise fertility and reduce savings. Greater government subsidies to human capital investments and lower income taxes have positive effects on savings and fertility. The same parameters present ambiguous effects on education investments and growth. Numerical simulations show that a) human capital investment has an inverted U-shaped relation with income taxes and education subsidies; b) economic growth decreases with greater income taxes and increases with higher education subsidies.-

The Long-run Effects of Household Liquidity Constraints and Taxation on Fertility, Education, Saving and Growth

This paper investigates economic growth under liquidity constraints by taking into account the choices of fertility, human capital and saving. In a model of four overlapping generations, parents are altruistic towards their offspring and finance their education investment. The government provides education subsidies to young adult parents and levies taxes on income of the adult generation. Sensitivity analysis on borrowing limits and tax parameters highlights effects with opposite sign on the main endogenous variables at steady state. A lift in liquidity constraints decreases savings and capital accumulation and this effect is responsible for the ambiguous sign of comparative statics on the rate of fertility and on human capital investment. From model simulation, we derive an inverted U-shaped curve relating the borrowing limit with fertility, education and growth, meaning that financial reforms in the less developed countries have positive effects on the economy in the long-run, even if they raise fertility and reduce savings. Greater government subsidies to human capital investments and lower income taxes have positive effects on savings and fertility. The same parameters present ambiguous effects on education investments and growth. Numerical simulations show that a) human capital investment has an inverted U-shaped relation with income taxes and education subsidies ; b) economic growth decreases with greater income taxes and increases with higher education subsidies. Jel codes: O40, O16, J13, D91.Borrowing constraints, taxation, endogenous population, economic growth

On the Phenomenology of Tachyon Radiation

We present a brief overview of the different kinds of electromagnetic radiations expected to come from (or to be induced by) space-like sources (tachyons). New domains of radiation are here considered; and the possibility of experimental observation of tachyons via electromagnetic radiation is discussed