Standard cosmological model
Write an essay describing the current standard cosmological model including aspects of theory and evidence for the model, focusing on the content of the universe (cold dark matter, baryons, etc.) and how galaxies have grown from seed fluctuations in the early universe.
1. Overview.
Give an overview of the current standard model for the context of the essay. Include one
figure for this section.
2. Dark Matter.
Describe two lines of evidence for dark matter. These should be distinct and complementary.
A line of evidence can consist of more than one observational phenomenon that together provide the evidence. Include two figures for this section.
3. Baryons.
Describe one indirect constraint on the baryon density (BBN or CMB), and key direct measurements of various baryonic components. Include two figures for this section.
4. Dark Energy.
Describe two lines of evidence for dark energy. Comment on possible modifications to the
standard model. Include two figures for this section.
5. Growth of structure.
Describe how initial fluctuations from inflation have grown to form galaxies. Consider the
growth rate on various scales, and the different behaviour of dark matter and baryons.
Include two figures for this section.
6. Conclusions.
Providing some concluding remarks and comment on future tests of the standard model.
http://carina.fcaglp.unlp.edu.ar/extragalactica/Bibliografia/Ryden_IntroCosmo.pdf
http://alpha.sinp.msu.ru/~panov/LibBooks/CS/liddle_a_an_introduction_to_modern_cosmology.pdf
Sample Solution
The current standard model of cosmology is based on a range of observations and theories which, when taken together, provide an increasingly accurate picture of the universe. This model postulates that our universe is composed of four main components: dark energy, dark matter, baryonic matter and radiation. These components interact with one another to form structures such as galaxies and other large scale structures in the cosmos (Weinberg 2008). In addition to this, it posits that all these forms of matter arose from tiny quantum fluctuations in space-time during the early universe which eventually grew into star systems due to gravitational attraction (Schwartz 2009).
Dark energy is thought to be responsible for accelerating the expansion of the universe and making up around 70% its total mass-energy content (Barboza & Mota 2010 ). Dark matter accounts for approximately 25 %while baryonic matter such as stars , planets and dust make up just 5%. Radiation including light , X-rays etc., constitute less than 0.1 % although they play an important role in providing clues about how galaxies were formed.(Boehme &Wolff 2011 )
Galaxies are believed to have grown out of seed fluctuations within this primordial soup . Small density variations within these regions then caused by gravity led to clumps forming which gradually consolidated into large stellar systems over time . Recent simulations suggest that supermassive black holes at their centers may also have helped initiate galaxy formation by pulling material towards them through powerful jets created during accretion processes (Hopkins et al., 2012).
