Abstract:
We demonstrate a model-independent method of estimating qualitative dynamics of an accelerating universe from observations of distant type Ia supernovae. Our method is based on the luminosity-distance function, optimized to fit observed distances of supernovae, and the Hamiltonian representation of dynamics for the quintessential universe with a general form of equation of state $p=w(a(z))\rho$. Because of the Hamiltonian structure of FRW dynamics with the equation of state $p = w(a(z)) \rho$, the dynamics is uniquelly determined by the potential function $V(a)$ of the system. The effectiveness of this method in discrimination of model parameters of Cardassian evolution scenario is also given. Our main result is the following, restricting to the flat model with the current value of $\Omega_{m,0}=0.3$, the constraints at $2\sigma$ confidence level to the presence of $\rho^{n}$ modification of the FRW models are $-0.50 \lesssim n \lesssim 0.36$. |
