$2,000 in free prizes! piglix.com is giving away ten (10) Meccano Erector sets, retail at $200 each, that build a motorized Ferris Wheel (or one of 22 other models) ... see details
Free Ads! if you are a business with annual revenues of less than $1M  piglix.com will place your ads free of charge for up to one year! ... read more
The ΛCDM (Lambda cold dark matter) or LambdaCDM model is a parametrization of the Big Bang cosmological model in which the universe contains a cosmological constant, denoted by Lambda (Greek Λ), associated with dark energy, and cold dark matter (abbreviated CDM). It is frequently referred to as the standard model of Big Bang cosmology because it is the simplest model that provides a reasonably good account of the following properties of the cosmos:
The model assumes that general relativity is the correct theory of gravity on cosmological scales. It emerged in the late 1990s as a concordance cosmology, after a period of time when disparate observed properties of the universe appeared mutually inconsistent, and there was no consensus on the makeup of the energy density of the universe.
The ΛCDM model can be extended by adding cosmological inflation, quintessence and other elements that are current areas of speculation and research in cosmology.
Some alternative models challenge the assumptions of the ΛCDM model. Examples of these are modified Newtonian dynamics, modified gravity and theories of largescale variations in the matter density of the universe.
Most modern cosmological models are based on the cosmological principle, which states that our observational location in the universe is not unusual or special; on a largeenough scale, the universe looks the same in all directions (isotropy) and from every location (homogeneity).
The model includes an expansion of metric space that is well documented both as the red shift of prominent spectral absorption or emission lines in the light from distant galaxies and as the time dilation in the light decay of supernova luminosity curves. Both effects are attributed to a Doppler shift in electromagnetic radiation as it travels across expanding space. Although this expansion increases the distance between objects that are not under shared gravitational influence, it does not increase the size of the objects (e.g. galaxies) in space. It also allows for distant galaxies to recede from each other at speeds greater than the speed of light; local expansion is less than the speed of light, but expansion summed across great distances can collectively exceed the speed of light.
Description  Symbol  Value  

Independent parameters 
Physical baryon density parameter  Ω_{b}h^{2}  30±0.00014 0.022 
Physical dark matter density parameter  Ω_{c}h^{2}  ±0.0010 0.1188  
Age of the universe  t_{0}  ±0.021 × 10^{9} years 13.799  
Scalar spectral index  n_{s}  ±0.0040 0.9667  
Curvature fluctuation amplitude, k_{0} = 0.002 Mpc^{−1}  Δ2 R 
+0.088 −0.092×10^{−9} 2.441 

Reionization optical depth  τ  ±0.012 0.066  
Fixed parameters 
Total density parameter  Ω_{tot}  1 
Equation of state of dark energy  w  −1  
Sum of three neutrino masses  ∑ m_{ν}  0.06 eV/c^{2}  
Effective number of relativistic degrees of freedom  N_{eff}  3.046  
Tensor/scalar ratio  r  0  
Running of spectral index  dn_{s} / d ln k  0  
Calculated values 
Hubble constant  H_{0}  ±0.46 km s^{−1} 67.74Mpc^{−1} 
Baryon density parameter  Ω_{b}  ±0.0010 0.0486  
Dark matter density parameter  Ω_{c}  ±0.0057 0.2589  
Matter density parameter  Ω_{m}  ±0.0062 0.3089  
Dark energy density parameter  Ω_{Λ}  ±0.0062 0.6911  
Critical density  ρ_{crit}  ±0.12)×10^{−27} kg/m^{3} (8.62  
Fluctuation amplitude at 8h^{−1} Mpc  σ_{8}  ±0.0086 0.8159  
Redshift at decoupling  z_{∗}  089.90±0.23 1  
Age at decoupling  t_{∗}  700±3200 years 377  
Redshift of reionization (with uniform prior)  z_{re}  +1.0 −1.1 8.5 
Description  Symbol  Value 

Total density parameter  Ω_{tot}  +0.0056 −0.0054 1.0023 
Equation of state of dark energy  w  ±0.053 −0.980 
Tensortoscalar ratio  r  < 0.11, k_{0} = 0.002 Mpc^{−1} (2σ) 
Running of the spectral index  dn_{s} / d ln k  ±0.020, k_{0} = 0.002 Mpc^{−1} −0.022 
Physical neutrino density parameter  Ω_{ν}h^{2}  < 0.0062 
Sum of three neutrino masses  ∑ m_{ν}  < 0.58 eV/c^{2} (2σ) 
Don't forget! that as one of our early users, you are eligible to receive the 1,000 point bonus as soon as you have created five (5) acceptable piglix.