Constraining dark energy with type Ia supernovae and large-scale structure

Measurements of the distances to type Ia supernovae have produced strong evidence that the expansion of the Universe is accelerating, implying the existence of a nearly uniform component of dark energy with negative pressure, We show that constraints to this mysterious component based upon large-scale structure nicely complement the SN Ia data, and that together they require Omega(X) = rho(X)/rho(crit) is an element of (0.6,0.7) and w = rho(X)/rho(X) < -0.6 (95% C.L.), for the favored hat Universe. Other cosmological data support this conclusion. The simplest explanation, a cosmological constant, is consistent with this, while some of the other possibilities are not.