Summarizing Cosmology and Particle Physics

Cosmology and Particle Physics Summary

• Cosmology is the study of the character and evolution of the universe.
• The two most important features of the universe are the cosmological red shifts of its galaxies being proportional to distance and its cosmic microwave background (CMBR). Both support the notion that there was a gigantic explosion, known as the Big Bang that created the universe.
• Galaxies farther away than our local group have, on an average, a recessional velocity given by

  \(v={H}_{0}d\text{,}\)

  where \(d\) is the distance to the galaxy and \({H}_{0}\) is the Hubble constant, taken to have the average value \({H}_{0}=20\text{km/s}\cdot \text{Mly}\text{.}\)

• Explanations of the large-scale characteristics of the universe are intimately tied to particle physics.
• The dominance of matter over antimatter and the smoothness of the CMBR are two characteristics that are tied to particle physics.
• The epochs of the universe are known back to very shortly after the Big Bang, based on known laws of physics.
• The earliest epochs are tied to the unification of forces, with the electroweak epoch being partially understood, the GUT epoch being speculative, and the TOE epoch being highly speculative since it involves an unknown single superforce.
• The transition from GUT to electroweak is called spontaneous symmetry breaking. It released energy that caused the inflationary scenario, which in turn explains the smoothness of the CMBR.

Glossary

Big Bang

a gigantic explosion that threw out matter a few billion years ago

cosmic microwave background

the spectrum of microwave radiation of cosmic origin

cosmological red shift

the photon wavelength is stretched in transit from the source to the observer because of the expansion of space itself

cosmology

the study of the character and evolution of the universe

electroweak epoch

the stage before 10⁻¹¹ back to 10⁻³⁴ after the Big Bang

GUT epoch

the time period from 10⁻⁴³ to 10⁻³⁴ after the Big Bang, when Grand Unification Theory, in which all forces except gravity are identical, governed the universe

Hubble constant

a central concept in cosmology whose value is determined by taking the slope of a graph of velocity versus distance, obtained from red shift measurements

inflationary scenario

the rapid expansion of the universe by an incredible factor of 10⁻⁵⁰ for the brief time from 10⁻³⁵ to about 10⁻³²s

spontaneous symmetry breaking

the transition from GUT to electroweak where the forces were no longer unified

superforce

hypothetical unified force in TOE epoch

TOE epoch

before 10⁻⁴³ after the Big Bang