What is e-folding?

E-folding is a mathematical concept used to describe the rate at which a quantity decreases over time. This concept is often used in many fields of science, including physics, biology, and economics.

In physics, e-folding is used to describe the decay rate of certain particles or events. For example, in cosmology, it is used to describe the expansion of the universe. The universe is said to have expanded by a factor of e (approximately 2.718) every e-folding time. This means that if the universe were to expand for three e-folding times, its size would have increased by a factor of e^3 (approximately 20).

In biology, e-folding is used to describe the rate at which a population of organisms decreases. For example, if a population of bacteria is decreasing by a factor of e every hour, it would be said to have an e-folding time of one hour. This concept is also used to describe the decay rate of radioactive isotopes, which can be important for dating fossils and rocks.

In economics, e-folding is used to describe the rate at which the value of an investment decreases over time. For example, if the value of an investment decreases by a factor of e every year, it would be said to have an e-folding time of one year. This concept is also used to describe the rate at which the value of a currency depreciates over time.