## Cosmology

The Inflationary Universe Standard Model Cosmic Inflation Cosmological Constant Cosmic Microwave Background

The Inflationary Universe Standard Model Cosmic Inflation Cosmological Constant Cosmic Microwave Background

source The Inflationary Universe: A Possible Solution To The Horizon And Flatness Problems (Guth, 1980) Questions I still have # DONEWHY#1: why is that approximation unstable? # See Flatness Problem Abstract # The initial conditions defined in the Standard Model present two problems: The early universe is defined to be homogeneous despite the massive distances between regions (causal disconnect) The Hubble constant must be set very finely to produce a flat universe (like ours) These problems could disappear if the universe (in its early stages) cooled to temperatures twenty-eight or more orders of magnitude below the critical temperature for “some phase transition”. ...

This refers to the Cosmological “Standard Model”, i.e. the \(\Lambda\)CDM. This is not the same as the Standard Model of Particle Physics Lambda-CDM # The lambda-cdm or, lambda cold-dark-matter, is a three-parameter description of the Big Bang Cosmological model parametrized by: the Cosmological Constant \(\Lambda\) dark matter normal matter Of the cosmological models, this presents the simplest one in terms of describing the universe as we see it observationally. ...

The Cosmological Principle states that at large enough scales (>100Mpc) the universe’s matter distribution is isotropic and homogeneous and should not produce irregularities in the large-scale structure of the universe over the course of its evolution.

TODO

TODO

A manifold is a topological space that locally resembles Euclidean space near each point. As defined in Physics # An N-dimensional manifold of points is one for which N independent real coordinates \((x^{1}, x^{2},…,x^{N})\) are required to specify a point completely. These N coordinates are denoted collectively by \(x^{a}\), where it is understood that \(a\,=\,1,2,…,N\). As an example, in \(\mathbb{R}^{2}\) we have a 2-dimensional manifold of points descrived by the real coordinates \((x^{1}, x^{2})\). ...

Open/Closed/Flat # TODO #

The Principle of Relativity states that: The laws of physics take the same form in every intertial frame. No exception has been found to this principle, and it holds equally well in both Newtonian theory and Special Relativity.

The Problem # People used to believe that the Universe was infinite (in age and size) and static. If this were true Why is the night sky not as bright as day? That is to say, if the universe is infinite as are the stars, and the universe is not undergoing any sort of evolution, we should expect every point of the night sky to be filled with the light from any one of its inifnite stars. ...