Abstract
It is widely believed that anisotropy in the expansion of the universe will decay exponentially fast during inflation. This is often referred to as the cosmic no-hair conjecture. However, we find a counter example to the cosmic no-hair conjecture in the context of supergravity. As a demonstration, we present an exact anisotropic power-law inflationary solution which is an attractor in the phase space. We emphasize that anisotropic inflation is quite generic in the presence of anisotropic sources which couple with an inflaton.
Highlights
As is well known, the event horizon of black holes hides the initial conditions of the collapsed matter other than mass, charge, and angular momenta, which is named the black hole no-hair theorem [1]
We have examined a supergravity model with a gauge kinetic function
It turned out that exact anisotropic power-law inflationary solutions exist when both the potential function for an inflaton and the gauge kinetic function are exponential type
Summary
The event horizon of black holes hides the initial conditions of the collapsed matter other than mass, charge, and angular momenta, which is named the black hole no-hair theorem [1]. Even for a general accelerating universe driven by a scalar field, it is legitimate to expect that the anisotropy decays exponentially first in the presence of the cosmological event horizon. This prejudice is often referred to as the cosmic no-hair conjecture. We have shown that, in the presence of a gauge field coupled with an inflaton, there could be small anisotropy in the expansion rate which never decays during inflation.
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