Quantum cosmology
[501.04899Quantum cosmology: a review">][412.4362Loop Quantum Gravity">] is the attempt in
theoretical physics
Theoretical physics is a branch of physics that employs mathematical models and abstractions of physical objects and systems to rationalize, explain and predict natural phenomena. This is in contrast to experimental physics, which uses experi ...
to develop a
quantum theory of the
universe
The universe is all of space and time and their contents, including planets, stars, galaxies, and all other forms of matter and energy. The Big Bang theory is the prevailing cosmological description of the development of the universe. A ...
. This approach attempts to answer open questions of classical
physical cosmology
Physical cosmology is a branch of cosmology concerned with the study of cosmological models. A cosmological model, or simply cosmology, provides a description of the largest-scale structures and dynamics of the universe and allows study of f ...
, particularly those related to the first phases of the universe.
Classical cosmology is based on
Albert Einstein
Albert Einstein ( ; ; 14 March 1879 – 18 April 1955) was a German-born theoretical physicist, widely acknowledged to be one of the greatest and most influential physicists of all time. Einstein is best known for developing the theor ...
's
general theory of relativity (GTR or simply GR) which describes the evolution of the universe very well, as long as you do not approach the
Big Bang
The Big Bang event is a physical theory that describes how the universe expanded from an initial state of high density and temperature. Various cosmological models of the Big Bang explain the evolution of the observable universe from t ...
. It is the
gravitational singularity and the
Planck time where relativity theory fails to provide what must be demanded of a final theory of space and time. Therefore, a theory is needed that integrates relativity theory and quantum theory. Such an approach is attempted for instance with
loop quantum cosmology
Loop quantum cosmology (LQC) is a finite, symmetry-reduced model of loop quantum gravity ( LQG) that predicts a "quantum bridge" between contracting and expanding cosmological branches.
The distinguishing feature of LQC is the prominent role ...
,
loop quantum gravity
Loop quantum gravity (LQG) is a theory of quantum gravity, which aims to merge quantum mechanics and general relativity, incorporating matter of the Standard Model into the framework established for the pure quantum gravity case. It is an attem ...
,
string theory and
causal set theory.
In quantum cosmology, the universe is treated as a
wave function
A wave function in quantum physics is a mathematical description of the quantum state of an isolated quantum system. The wave function is a complex-valued probability amplitude, and the probabilities for the possible results of measurements m ...
instead of classical
spacetime
In physics, spacetime is a mathematical model that combines the three dimensions of space and one dimension of time into a single four-dimensional manifold. Spacetime diagrams can be used to visualize relativistic effects, such as why diffe ...
.
See also
*
String cosmology
String cosmology is a relatively new field that tries to apply equations of string theory to solve the questions of early cosmology. A related area of study is brane cosmology.
Overview
This approach can be dated back to a paper by Gabriele V ...
*
Brane cosmology
Brane cosmology refers to several theories in particle physics and cosmology related to string theory, superstring theory and M-theory.
Brane and bulk
The central idea is that the visible, three-dimensional universe is restricted to a brane in ...
*
Loop quantum cosmology
Loop quantum cosmology (LQC) is a finite, symmetry-reduced model of loop quantum gravity ( LQG) that predicts a "quantum bridge" between contracting and expanding cosmological branches.
The distinguishing feature of LQC is the prominent role ...
*
Top-down cosmology
*
Non-standard cosmology
*
Loop quantum gravity
Loop quantum gravity (LQG) is a theory of quantum gravity, which aims to merge quantum mechanics and general relativity, incorporating matter of the Standard Model into the framework established for the pure quantum gravity case. It is an attem ...
*
Canonical quantum gravity
*
Dark energy
In physical cosmology and astronomy, dark energy is an unknown form of energy that affects the universe on the largest scales. The first observational evidence for its existence came from measurements of supernovas, which showed that the unive ...
*
Minisuperspace
*
Hamilton–Jacobi–Einstein equation
*
Theory of everything
A theory of everything (TOE or TOE/ToE), final theory, ultimate theory, unified field theory or master theory is a hypothetical, singular, all-encompassing, coherent theoretical framework of physics that fully explains and links together all asp ...
References
*
Notes
External links
A Layman's Explanation of Quantum CosmologyLectures on Quantum Cosmology by J.J. Halliwell
{{Quantum mechanics topics
Quantum gravity
Physical cosmology