Assisted dark energy

Understand

Cosmological scaling solutions, which give rise to a scalar-field density proportional to a background fluid density during radiation and matter eras, are attractive to alleviate the energy scale problem of dark energy.

• In the presence of multiple scalar fields the scaling solution can exit to the epoch of cosmic acceleration through the so-called assisted inflation mechanism.
• We study cosmological dynamics of a multi-field system in details with a general Lagrangian density p=sum_{i=1}^n X_i g(X_i e^{lambda_i phi_i}), where X_i=-(nabla phi_i)^2/2 is the kinetic energy of the i-th field phi_i, lambda_i is a constant, and g is an arbitrary function in terms of Y_i=X_i e^{lambda_i phi_i}.
• This covers most of the scalar-field models of dark energy proposed in literature that possess scaling solutions.