# Inflationary epoch

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In physical cosmology, the inflationary epoch was the period in the evolution of the early universe when, according to inflation theory, the universe underwent an extremely rapid exponential expansion. This rapid expansion increased the linear dimensions of the early universe by a factor of at least 10$^{26}$ (and possibly a much larger factor), and so increased its volume by a factor of at least 10$^{78}$. Expansion by a factor of 10$^{26}$ is equivalent to expanding an object 1 nanometer (10$^{−9}$ m, about half the width of a molecule of DNA) in length to one approximately 10.6 light years (about 62 trillion miles).

## Description

Vacuum state is a configuration of quantum fields representing a local minimum (but not necessarily a global minimum) of energy.
Inflationary models propose that at approximately 10$^{−36}$ seconds after the Big Bang, the vacuum state of the Universe was different from the one seen at the present time: the inflationary vacuum had a much higher energy density.
According to general relativity, any vacuum state with non-zero energy density generates a repulsive force that leads to an expansion of space. In inflationary models, early high-energy vacuum state causes a very rapid expansion. This expansion explains various properties of the current universe that are difficult to account for without such an inflationary epoch.
Most inflationary models propose a scalar field called the inflaton field, with properties necessary for having (at least) two vacuum states.
It is not known exactly when the inflationary epoch ended, but it is thought to have been between 10$^{−33}$ and 10$^{−32}$ seconds after the Big Bang. The rapid expansion of space meant that any potential elementary particles (or other "unwanted" artifacts, such as topological defects) remaining from the time before inflation were now distributed very thinly across the universe.
When the inflaton field reconfigured itself into the low-energy vacuum state we currently observe, the huge difference in potential energy was released in the form of a dense, hot mixture of quarks, anti-quarks and gluons as it entered the electroweak epoch.