Stationarity without Degeneracy in a Model of Commodity Money

We develop a model of macroeconomic heterogeneity inspired by the Kiyotaki-Wright (1989) formulation of commodity money, with the addition of linear utility and idiosyncratic shocks to savings. We consider two environments. In the benchmark case, the consumer in a meeting is chosen randomly. In the auctions case, the individual holding more money can be selected to be the consumer. We show that in both environments socially optimal trading decisions (that are individually acceptable) are stationary and solve a tractable static op- timization problem. Savings decisions in the benchmark case are re- markably invariant to mean-preserving changes in the distribution of shocks. This result is overturned in the auctions case.Macroeconomics with heterogeneous savings; commodity money with linear adjustments; mechanism design; auctions

Some benefits of cyclical monetary policy

In this paper, we present a simple random-matching model in which different seasons translate into different propensities to consume and produce. We find that the cyclical creation and destruction of money is beneficial for welfare under a wide variety of circumstances. Our model of seasons can be interpreted as providing support for the creation of the Federal Reserve System, with its mandate of supplying an elastic currency for the nation.Monetary policy ; Money supply

Charging a Double Kerr Solution in 5D Einstein--Maxwell--Kalb--Ramond Theory

We consider the low-energy effective action of the 5D Einstein-Maxwell-Kalb-Ramond theory. After compactifying this truncated model on a two-torus and switching off the U(1) vector fields of this theory, we recall a formulation of the resulting three-dimensional action as a double Ernst system coupled to gravity. Further, by applying the so-called normalized Harrison transformation on a generic solution of this double Ernst system we recover the U(1) vector field sector of the theory. Afterward, we compute the field content of the generated charged configuration for the special case when the starting Ernst potentials correspond to a pair of interacting Kerr black holes, obtaining in this way an exact field configuration of the 5D Einstein-Maxwell-Kalb-Ramond theory endowed with effective Coulomb and dipole terms with momenta. Some physical properties of this object are analyzed as well as the effect of the normalized Harrison transformation on the double Kerr seed solution.Comment: 15 pages in latex, revised versio

Electron - positron cascades in multiple-laser optical traps

We present an analytical and numerical study of multiple-laser QED cascades induced with linearly polarised laser pulses. We analyse different polarisation orientations and propose a configuration that maximises the cascade multiplicity and favours the laser absorption. We generalise the analytical estimate for the cascade growth rate previously calculated in the field of two colliding linearly polarised laser pulses and account for multiple laser interaction. The estimate is verified by a comprehensive numerical study of four-laser QED cascades across a range of different laser intensities with QED PIC module of OSIRIS. We show that by using four linearly polarised 30 fs laser pulses, one can convert more than 50 % of the total energy to gamma-rays already at laser intensity $I\simeq10^{24}\ \mathrm{W/cm^2}$. In this configuration, the laser conversion efficiency is higher compared with the case with two colliding lasers

Liquidity, money creation and destruction, and the returns to banking

We build on our earlier model of money in which bank liabilities circulate as medium of exchange, and investigate the provision of liquidity for a range of central-bank regulations dealing with the potential of bank failure. In our model, banks issue inside money under fractional reserves, facing the event of excess redemptions. They monitor the float of their money issue and make reserve-management decisions which affect aggregate liquidity conditions. Numerical examples demonstrate bank failure when returns to banking are low. Central-bank interventions, injecting more funds or making interest payments proportional to holdings of reserves, may improve banks’ returns and society’s welfare, followed by a reduction in bank failure. JEL Classification: E4, E5liquidity, private money creation