Large variations in stock prices happen with sufficient frequency to raise doubts about existing models, which all fail to account for non-Gaussian statistics. We construct simple models of a stock market, and argue that the large variations may be due to a crowd effect, where agents imitate...

Large variations in stock prices happen with sufficient frequency to raise doubts about existing models, which all fail to account for non-Gaussian statistics. We construct simple models of a stock market, and argue that the large variations may be due to a crowd effect, where agents imitate...

Why is 'worthless' fiat money generally accepted as payment for goods and services? In equilibrium theory, the value of money is generally not determined: the number of equations is one less than the number of unknowns, so only relative prices are determined. In the language of mathematics, the...

An overlapping generations model of an exchange economy is considered, with individials having a fininte expected life-span. As the model is designed to be a fully playable game, conditions concerning birth, death, inheritance and bequests are fully specified.

Modeling problems for a monetary economy are discussed and some examples are presented in the context of an infinite-horizon economy with one or two types of traders, who use fiat money to buy a single perishable consumption good. Three instances are considered, all with transactions in fiat...

We construct stationary Markov equilibria for an economy with fiat money, one nondurable commodity, countably-many time periods, and a continuum of agents. The total production of commodity remains constant, but individual agents' endowments fluctuate in a random fashion from period to period....

The sun provides an explosive, heavenly example of self-organized criticality. Sudden bursts of intense radiation emanate from rapid rearrangements of the magnetic field network in the corona. Avalanches are triggered by loops of flux that reconnect or snap into lower-energy configurations when...

Sea ice breaks up and regenerates rapidly during winter conditions in the Arctic. Analyzing satellite data from the Kara Sea, we find that the average ice floe size depends on weather conditions. Nevertheless, the frequency of floes of size A is a power law, N∼A−τ, where τ=1.6±0.2, for A...