the basic six-parameter model in the limit that the additional parameter(s) approach the default values. For example, possible extensions of the simplest ΛCDM model allow for spatial curvature ( may be different from 1); or quintessence rather than a cosmological constant where the equation of state of dark energy is allowed to differ from −1. Cosmic inflation predicts tensor fluctuations (gravitational waves). Their amplitude is parameterized by the tensor-to-scalar ratio (denoted ), which is determined by the unknown energy scale of inflation. Other modifications allow hot dark matter in the form of neutrinos more massive than the minimal value, or a running spectral index; the latter is generally not favoured by simple cosmic inflation models. Allowing additional variable parameter(s) will generally increase the uncertainties in the standard six parameters quoted above, and may also shift the central values slightly. The Table below shows results for each of the possible "6+1" scenarios with one additional variable parameter; this indicates that, as of 2015, there is no convincing evidence that any additional parameter is different from its default value. Some researchers have suggested that there is a running spectral index, but no statistically significant study has revealed one. Theoretical expectations suggest that the tensor-to-scalar ratio should be between 0 and 0.3, and the latest results are now within those limits. See also Bolshoi Cosmological Simulation Galaxy formation and evolution Illustris project List of cosmological computation software Millennium Run Weakly interacting massive particles (WIMPs) The ΛCDM model is also known as the standard model of cosmology, but is not related to the Standard Model of particle physics. References Further reading External links Cosmology tutorial/NedWright Millennium Simulation WMAP estimated cosmological parameters/Latest Summary Physical cosmology Dark matter Dark energy Concepts in astronomy Scientific models