brane cosmology

In physical cosmology, the Big Bang is the scientific theory that the Universe emerged from an enormously dense and hot state about 13.7 billion years ago. The Big Bang is a consequence of the observed Hubble's law velocities of distant galaxies that when taken together with the cosmological principle imply that space is expanding according to the Friedmann-Lemaître model of general relativity. Extrapolated into the past, these observations show that the Universe has expanded from a primeval state, in which all the matter and energy ...

Including:

• Big Bang - History
• Big Bang - Overview
• Big Bang - Theoretical underpinnings
• Big Bang - Observational evidence
• Big Bang - Hubble's law expansion
• Big Bang - Cosmic microwave background radiation
• Big Bang - Abundance of primordial elements
• Big Bang - Galactic evolution and distribution
• Big Bang - Features issues and problems
• Big Bang - Horizon problem
• Big Bang - Flatness problem
• Big Bang - Magnetic monopoles
• Big Bang - Baryon asymmetry
• Big Bang - Globular cluster age
• Big Bang - Dark matter
• Big Bang - Dark energy
• Big Bang - The future according to the Big Bang theory
• Big Bang - Speculative physics beyond the Big Bang
• Big Bang - Philosophical and religious interpretations

Read more here: » Big Bang: Encyclopedia - Big Bang

edit In cosmology, dark energy is a hypothetical form of energy which permeates all of space and has strong negative pressure. According to the theory of relativity, the effect of such a negative pressure is qualitatively similar to a force acting in opposition to gravity at large scales. Invoking such an effect is currently the most popular method for explaining the observations of an accelerating universe as well as accounting for a significant portion of the missing mass in the universe. Two prop ...

Including:

• Dark energy - Evidence for dark energy
• Dark energy - Nature of dark energy
• Dark energy - Cosmological constant
• Dark energy - Quintessence
• Dark energy - Other ideas
• Dark energy - Implications for the fate of the universe
• Dark energy - History

Read more here: » Dark energy: Encyclopedia - Dark energy

edit A multiverse (or meta-universe) is the hypothetical set of multiple possible universes, including the observable universe, which comprise the absolute whole of physical reality. The structure of the multiverse, the nature of each universe within it and the relationship between the various constituent universes, depend on the specific multiverse hypothesis considered. Multiverses have been hypothesized in physics, philosophy; and fiction, particularly in science fiction. (The specific term "multiverse" ...

Including:

• Multiverse - Multiverse hypotheses in physics
• Multiverse - Classification
• Multiverse - Open multiverse
• Multiverse - Bubble Theory
• Multiverse - Big bounce
• Multiverse - Many world interpretation of quantum physics
• Multiverse - M-theory
• Multiverse - String Landscape
• Multiverse - Arguments against multiverse theories
• Multiverse - Multiverse hypotheses in philosophy
• Multiverse - Anthropic principle
• Multiverse - Modal realism
• Multiverse - Trans-world identity issues
• Multiverse - Fictional multiverses

Read more here: » Multiverse: Encyclopedia - Multiverse

In theoretical physics, D-branes are a special class of p-branes, named for the physicist Johann Dirichlet. Dirichlet boundary conditions have long been used in the study of fluids and potential theory, where they involve specifying some quantity all along a boundary. In fluid dynamics, fixing a Dirichlet boundary condition could mean assigning a known fluid velocity to all points on a surface; when studying electrostatics, one may establish Dirichlet boundary conditions by fixing the voltage to known values at particular locations, l ...

Including:

• D-brane - D-branes in string theory
• D-brane - Theoretical background
• D-brane - Braneworld cosmology
• D-brane - Gauge theories
• D-brane - Black holes

Read more here: » D-brane: Encyclopedia - D-brane

The cyclic model is a brane cosmology model of the creation of the universe, derived from the earlier ekpyrotic model. It was proposed in 2001 by Paul Steinhardt and Neil Turok. Cyclic model - The model. In the cyclic model, two parallel orbifold planes or M-branes collide periodically in a higher dimensional space. The visible four-dimensional universe lies on one of these branes. The collisions correspond to a reversal from contraction to expansion, or a big crunch followed immediately by a big ba ...

Including:

• Cyclic model - The model

Read more here: » Cyclic model: Encyclopedia - Cyclic model

A number of problems have arisen within the Big Bang theory throughout its history. Some of them are mainly of historical interest today, and have been avoided either through modifications to the theory or as the result of better observations. Other issues, such as the cuspy halo problem and the dwarf galaxy problem of cold dark matter, are not considered to be fatal as they can be addressed through refinements of the theory. There are a small number of proponents of non-standard cosmologies who doubt that there was a Big Bang at all. ...

See also:

Big Bang, Big Bang - History, Big Bang - Overview, Big Bang - Theoretical underpinnings, Big Bang - Observational evidence, Big Bang - Hubble's law expansion, Big Bang - Cosmic microwave background radiation, Big Bang - Abundance of primordial elements, Big Bang - Galactic evolution and distribution, Big Bang - Features issues and problems, Big Bang - Horizon problem, Big Bang - Flatness problem, Big Bang - Magnetic monopoles, Big Bang - Baryon asymmetry, Big Bang - Globular cluster age, Big Bang - Dark matter, Big Bang - Dark energy, Big Bang - The future according to the Big Bang theory, Big Bang - Speculative physics beyond the Big Bang, Big Bang - Philosophical and religious interpretations

Read more here: » Big Bang: Encyclopedia II - Big Bang - Features issues and problems

Below, some of the most active areas of inquiry in cosmology are described, in roughly chronological order. This does not include all of the big bang cosmology, which is presented in cosmological timeline. Physical cosmology - The very early universe. While the early, hot universe appears to be well explained by the big bang from roughly 10-33 seconds onwards, there are several problems. One is that there is no compelling reason, using current particle physics, to expect the universe to be flat, ...

See also:

Physical cosmology, Physical cosmology - History of physical cosmology, Physical cosmology - Areas of study, Physical cosmology - The very early universe, Physical cosmology - Big bang nucleosynthesis, Physical cosmology - Cosmic microwave background, Physical cosmology - Formation and evolution of large-scale structure, Physical cosmology - Dark matter, Physical cosmology - Dark energy, Physical cosmology - Other areas of inquiry, Physical cosmology - External references, Physical cosmology - From groups, Physical cosmology - From individuals

Read more here: » Physical cosmology: Encyclopedia II - Physical cosmology - Areas of study

There have been a number of non-standard models which have been proposed. Standard responses to some of the claims made in by the variable mass and plasma cosmology proposals are footnoted to the notes section at the end of the article. Non-standard cosmology - Creationist ideas. Main article: Creationist cosmologies Young Earth Creationists who for various reasons object to standard cosmology have offered a variety of alternatives that have ranged from the idea that the universe ...

See also:

Non-standard cosmology, Non-standard cosmology - Non-standard versus standard, Non-standard cosmology - History, Non-standard cosmology - Non-standard cosmologies, Non-standard cosmology - Creationist ideas, Non-standard cosmology - Quasi-steady state, Non-standard cosmology - Tired light, Non-standard cosmology - Variable mass hypothesis and intrinsic redshifts, Non-standard cosmology - Plasma cosmology, Non-standard cosmology - Self Creation Cosmology, Non-standard cosmology - Nucleosynthesis objections to non-standard cosmologies, Non-standard cosmology - Notes, Non-standard cosmology - Bibliography

Read more here: » Non-standard cosmology: Encyclopedia II - Non-standard cosmology - Non-standard cosmologies

The exact nature of this dark energy is a matter of speculation. It is known to be very homogeneous, not very dense and doesn't interact strongly through any of the fundamental forces other than gravity. Since it is not very dense—roughly 10−29 grams per cubic centimeter—it is hard to imagine experiments to detect it in the laboratory (but see the references for a claimed detection). Dark energy can only have such a profound impact on the universe, making up 70% of all energy, because it uniformly fills otherwise empty space. The two leading models are quintessence and the cosmological constant. ...

See also:

Dark energy, Dark energy - Evidence for dark energy, Dark energy - Nature of dark energy, Dark energy - Cosmological constant, Dark energy - Quintessence, Dark energy - Other ideas, Dark energy - Implications for the fate of the universe, Dark energy - History

Read more here: » Dark energy: Encyclopedia II - Dark energy - Nature of dark energy

List of string theory topics - String dualities. T-duality S-duality U-duality Mysterious duality Montonen-Olive duality Seiberg duality List of string theory topics - Particles and fields. graviton dilaton tachyon Ramond-Ramond field Kalb-Ramond field magnetic monopole List of string theory topics - Branes. p-brane < ...

See also:

List of string theory topics, List of string theory topics - String theory, List of string theory topics - String dualities, List of string theory topics - Particles and fields, List of string theory topics - Branes, List of string theory topics - Supersymmetry, List of string theory topics - Conformal field theory, List of string theory topics - Geometry, List of string theory topics - Holography, List of string theory topics - Gauge theory, List of string theory topics - People

Read more here: » List of string theory topics: Encyclopedia II - List of string theory topics - String theory

There have been a number of non-standard models which have been proposed. Standard responses to some of the claims made in by the variable mass and plasma cosmology proposals are footnoted to the notes section at the end of the article. Non-standard cosmology - Creationist ideas. Young Earth Creationists who for various reasons object to standard cosmology have offered a variety of alternatives that have ranged from the idea that the universe was created as according to Genesis with light from distant obje ...

See also:

Non-standard cosmology, Non-standard cosmology - Non-standard versus standard, Non-standard cosmology - History, Non-standard cosmology - Non-standard cosmologies, Non-standard cosmology - Creationist ideas, Non-standard cosmology - Quasi-steady state, Non-standard cosmology - Tired light, Non-standard cosmology - Variable mass hypothesis and intrinsic redshifts, Non-standard cosmology - Plasma cosmology, Non-standard cosmology - Nucleosynthesis objections to non-standard cosmologies, Non-standard cosmology - Notes, Non-standard cosmology - Bibliography

Read more here: » Non-standard cosmology: Encyclopedia II - Non-standard cosmology - Non-standard cosmologies

Multiverse - Classification. According to Max Tegmark, the existence of other universes are a direct implication of cosmological observations. In an article entitled "Parallel Universes" in the May 2003 issue of Scientific American, he presents a clear and comprehensive picture of the idea of parallel universes. Tegmark describes the set of related concepts which share the notion that there are universes beyond the familiar observable one. He goes on t ...

See also:

Multiverse, Multiverse - Multiverse hypotheses in physics, Multiverse - Classification, Multiverse - Open multiverse, Multiverse - Bubble Theory, Multiverse - Big bounce, Multiverse - Many world interpretation of quantum physics, Multiverse - M-theory, Multiverse - String Landscape, Multiverse - Arguments against multiverse theories, Multiverse - Multiverse hypotheses in philosophy, Multiverse - Anthropic principle, Multiverse - Modal realism, Multiverse - Trans-world identity issues, Multiverse - Fictional multiverses

Read more here: » Multiverse: Encyclopedia II - Multiverse - Multiverse hypotheses in physics

Brane cosmology assumes that the visible universe lies on a four-dimensional brane which moves in higher dimensional space. Our brane may be one of innumerable others moving through these extra dimensions. The ekpyrotic scenario was proposed by Khoury, Ovrut, Steinhardt and Turok in 2001. It suggests that the visible universe was empty and contracting in the distant past. At some time, our brane collided with another, parallel "hidden" brane, which caused the contracting universe to reverse and begin expanding. Hot matter and radiation was c ...

See also:

Ekpyrotic, Ekpyrotic - Introduction, Ekpyrotic - Outstanding problems, Ekpyrotic - Popular reception

Read more here: » Ekpyrotic: Encyclopedia II - Ekpyrotic - Introduction

While the classical theory (i.e. the tree diagrams) and semiclassical corrections (one-loop diagrams) behaved as expected, the Feynman diagrams with two (or more) loops led to ultraviolet divergences - i.e. infinite results that could not be removed because the quantized general relativity was not renormalizable, unlike Quantum electrodynamics. In popular terms, the discreteness of quantum theory is not compatible with the smoothness of Einstein's general relativity. These problems, together with some conceptual puzzles, led many physicists ...

See also:

Graviton, Graviton - Gravitons and models of quantum gravity, Graviton - Gravitons and experiments, Graviton - Problems with the Graviton

Read more here: » Graviton: Encyclopedia II - Graviton - Gravitons and models of quantum gravity

D-brane - Theoretical background. Most versions of string theory involve two, closely related, types of string: open strings with unjoined endpoints and closed strings which connect upon themselves to form closed loops. Exploring the consequences of the Nambu-Goto action, it becomes clear that energy can flow along a string, slipping off the endpoint and vanishing. This poses a problem: conservation of energy dictates that energy should not be able to disappear from the system. Therefore, a consiste ...

See also:

D-brane, D-brane - D-branes in string theory, D-brane - Theoretical background, D-brane - Braneworld cosmology, D-brane - Gauge theories, D-brane - Black holes

Read more here: » D-brane: Encyclopedia II - D-brane - D-branes in string theory

A number of problems have arisen within the Big Bang theory throughout its history. Some of them are mainly of historical interest today, and have been avoided either through modifications to the theory or as the result of better observations. Other issues, such as the cuspy halo problem and the dwarf galaxy problem of cold dark matter, are not considered to be fatal as they can be addressed through refinements of the theory. There are a small number of proponents of non-standard cosmologies who doubt that there was a Big Bang at all. ...

See also:

Big Bang, Big Bang - History, Big Bang - Overview, Big Bang - Theoretical underpinnings, Big Bang - Observational evidence, Big Bang - Hubble's law expansion, Big Bang - Cosmic microwave background radiation, Big Bang - Abundance of primordial elements, Big Bang - Galactic evolution and distribution, Big Bang - Features, issues and problems, Big Bang - Horizon problem, Big Bang - Flatness problem, Big Bang - Magnetic monopoles, Big Bang - Baryon asymmetry, Big Bang - Globular cluster age, Big Bang - Dark matter, Big Bang - Dark energy, Big Bang - The future according to the Big Bang theory, Big Bang - Speculative physics beyond the Big Bang, Big Bang - Philosophical and religious interpretations

Read more here: » Big Bang: Encyclopedia II - Big Bang - Features, issues and problems

Non-standard cosmologies are usually not considered by physicists, because the essentials of the big bang theory have been confirmed by a wide enough range of complementary observations that they believe there is little chance of the theory being replaced in its essentials. A well known letter by advocates of non-standard cosmology has affirmed this: "today, virtually all financial and experimental resources in cosmology are devoted to big bang studies." [ ...

See also:

Non-standard cosmology, Non-standard cosmology - Non-standard versus standard, Non-standard cosmology - History, Non-standard cosmology - Non-standard cosmologies, Non-standard cosmology - Creationist ideas, Non-standard cosmology - Quasi-steady state, Non-standard cosmology - Tired light, Non-standard cosmology - Variable mass hypothesis and intrinsic redshifts, Non-standard cosmology - Plasma cosmology, Non-standard cosmology - Self Creation Cosmology, Non-standard cosmology - Nucleosynthesis objections to non-standard cosmologies, Non-standard cosmology - Notes, Non-standard cosmology - Bibliography

Read more here: » Non-standard cosmology: Encyclopedia II - Non-standard cosmology - Non-standard versus standard

Since the discovery of the cosmic microwave background by Penzias and Robert Wilson in 1965, most cosmologists have concluded that observations are best explained by the big bang model. However, there have been two periods in which interest in non-standard cosmology has increased due to observational data which posed difficulties for the big bang. The first occurred was the late 1970s when there were a number of unsolved problems such as the horizon problem, the flatness problem, and the lack of magnetic monopoles challenged the big bang mod ...

See also:

Non-standard cosmology, Non-standard cosmology - Non-standard versus standard, Non-standard cosmology - History, Non-standard cosmology - Non-standard cosmologies, Non-standard cosmology - Creationist ideas, Non-standard cosmology - Quasi-steady state, Non-standard cosmology - Tired light, Non-standard cosmology - Variable mass hypothesis and intrinsic redshifts, Non-standard cosmology - Plasma cosmology, Non-standard cosmology - Self Creation Cosmology, Non-standard cosmology - Nucleosynthesis objections to non-standard cosmologies, Non-standard cosmology - Notes, Non-standard cosmology - Bibliography

Read more here: » Non-standard cosmology: Encyclopedia II - Non-standard cosmology - History

One of the major successes of the Big Bang theory has been to provide a prediction that corresponds to the observations of the abundance of light elements in the universe. Along with the explanation provided for the Hubble law and for the Cosmic microwave background, this observation has proved very difficult for alternative theories to explain. Theories which assert that the universe has an infinite age, including many of the theories described above, fail to account for the abundance of deuterium in the cosmos, because deuterium eas ...

See also:

Non-standard cosmology, Non-standard cosmology - Non-standard versus standard, Non-standard cosmology - History, Non-standard cosmology - Non-standard cosmologies, Non-standard cosmology - Creationist ideas, Non-standard cosmology - Quasi-steady state, Non-standard cosmology - Tired light, Non-standard cosmology - Variable mass hypothesis and intrinsic redshifts, Non-standard cosmology - Plasma cosmology, Non-standard cosmology - Nucleosynthesis objections to non-standard cosmologies, Non-standard cosmology - Notes, Non-standard cosmology - Bibliography

Read more here: » Non-standard cosmology: Encyclopedia II - Non-standard cosmology - Nucleosynthesis objections to non-standard cosmologies

One of the major successes of the Big Bang theory has been to provide a prediction that corresponds to the observations of the abundance of light elements in the universe. Along with the explanation provided for the Hubble law and for the Cosmic microwave background, this observation has proved very difficult for alternative theories to explain. Theories which assert that the universe has an infinite age, including many of the theories described above, fail to account for the abundance of deuterium in the cosmos, because deuterium eas ...

See also:

Non-standard cosmology, Non-standard cosmology - Non-standard versus standard, Non-standard cosmology - History, Non-standard cosmology - Non-standard cosmologies, Non-standard cosmology - Creationist ideas, Non-standard cosmology - Quasi-steady state, Non-standard cosmology - Tired light, Non-standard cosmology - Variable mass hypothesis and intrinsic redshifts, Non-standard cosmology - Plasma cosmology, Non-standard cosmology - Self Creation Cosmology, Non-standard cosmology - Nucleosynthesis objections to non-standard cosmologies, Non-standard cosmology - Notes, Non-standard cosmology - Bibliography

Read more here: » Non-standard cosmology: Encyclopedia II - Non-standard cosmology - Nucleosynthesis objections to non-standard cosmologies