25 feb. 2017The Elegant Universe
https://en.wikipedia.org/wiki/Superstring_theory
https://en.wikipedia.org/wiki/The_Elegant_Universe
The Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory is a book by Brian Greene published in 1999, which introduces string and superstring theory, and provides a comprehensive though non-technical assessment of the theory and some of its shortcomings. In 2000, it won the Royal Society Prize for Science Books and was a finalist for the Pulitzer Prize Nonfiction. A new edition was released in 2003, with an updated preface.
"PBS wins eight news and documentary Emmys - 2005 Emmy Awards". MSNBC. 14 September 2004. Retrieved 10 March 2010.
The two are very rarely used together, and the most common case that combines them is in the study of black holes.
Having peak density, or the maximum amount of matter possible in a space, and very small area, the two must be used in synchrony to predict conditions in such places.
Yet, when used together, the equations fall apart, spitting out impossible answers, such as imaginary distances and less than one dimension.
The major problem with their congruence is that, at Planck scale (a fundamental small unit of length) lengths, general relativity predicts a smooth, flowing surface, while quantum mechanics predicts a random, warped surface, neither of which are anywhere near compatible.
Superstring theory resolves this issue, replacing the classical idea of point particles with strings.
These strings have an average diameter of the Planck length, with extremely small variances, which completely ignores the quantum mechanical predictions of Planck-scale length dimensional warping.
Also, these surfaces can be mapped as branes.
These branes can be viewed as objects with a morphism between them.
In this case, the morphism will be the state of a string that stretches between brane A and brane B.
Singularities are avoided because the observed consequences of "Big Crunches" never reach zero size.
In fact, should the universe begin a "big crunch" sort of process, string theory dictates that the universe could never be smaller than the size of one string, at which point it would actually begin expanding.
Greene discusses the essential problem facing modern physics: unification of Albert Einstein's theory of General Relativity and Quantum Mechanics.
Greene suggests that string theory is the solution to these two conflicting approaches.
Greene frequently uses analogies and thought experiments to provide a means for the layman to come to terms with the theory which has the potential to create a unified theory of physics.
All four of the known fundamental forces are mediated by fields, which in the Standard Model of particle physics result from exchange of gauge bosons.
Specifically the four fundamental interactions to be unified are:
In 1820 Hans Christian Ørsted discovered that electric currents exerted forces on magnets, while in 1831, Michael Faraday made the observation that time-varying magnetic fields could induce electric currents.
Until then, electricity and magnetism had been thought of as unrelated phenomena.
In 1864, Maxwell published his famous paper on a dynamical theory of the electromagnetic field.
This was the first example of a theory that was able to encompass previously separate field theories (namely electricity and magnetism) to provide a unifying theory of electromagnetism. By 1905, Albert Einstein had used the constancy of the speed of light in Maxwell's theory to unify our notions of space and time into an entity we now call spacetime and in 1915 he expanded this theory of special relativity to a description of gravity, General Relativity, using a field to describe the curving geometry of four-dimensional spacetime.
In the years following the creation of the general theory, a large number of physicists and mathematicians enthusiastically participated in the attempt to unify the then-known fundamental interactions.[2]
In view of later developments in this domain, of particular interest are the theories of Hermann Weyl of 1919, who introduced the concept of an (electromagnetic) gauge field in a classical field theory[3] and, two years later, that of Theodor Kaluza, who extended General Relativity to five dimensions.[4]
Continuing in this latter direction, Oscar Klein proposed in 1926 that the fourth spatial dimension be curled up into a small, unobserved circle.
In Kaluza–Klein theory, the gravitational curvature of the extra spatial direction behaves as an additional force similar to electromagnetism.
These and other models of electromagnetism and gravity were pursued by Albert Einstein in his attempts at a classical unified field theory.
By 1930 Einstein had already considered the Einstein–Maxwell–Dirac System [Dongen].
This system is (heuristically) the super-classical [Varadarajan] limit of (the not mathematically well-defined) Quantum Electrodynamics.
One can extend this system to include the weak and strong nuclear forces to get the Einstein–Yang–Mills–Dirac System.
The French physicist Marie-Antoinette Tonnelat published a paper in the early 1940s on the standard commutation relations for the quantized spin-2 field.
She continued this work in collaboration with Erwin Schrödinger after the World War II.
In 1965, Tonnelat published a book on the state of research on unified field theories
https://en.wikipedia.org/wiki/Superstring_theory
https://en.wikipedia.org/wiki/The_Elegant_Universe
https://en.wikipedia.org/wiki/Superstring_theory
From Wikipedia, the free encyclopedia
Hardcover edition
|
|
| Author | Brian Greene |
|---|---|
| Cover artist | Sherry Love |
| Country | Australia |
| Language | English |
| Subject | String theory |
| Genre | Non-fiction |
| Publisher | W. W. Norton |
Publication date
|
1999/2003 |
| Media type | Print (hardcover and paperback) |
| Pages | 448 pp. (2003 edition) |
| ISBN | 0-393-05858-1 (2003 edition) |
| Followed by | The Fabric of the Cosmos |
Contents
Table of contents
- Preface (with an additional preface to the 2003 edition)
- Part I: The Edge of Knowledge
- Part II: The Dilemma of Space, Time, and the Quanta
- Part III: The Cosmic Symphony
- Part IV: String Theory and the Fabric of Spacetime
- Part V: Unification in the Twenty-First Century
Contents
Beginning with a brief consideration of classical physics, which concentrates on the major conflicts in physics, Greene establishes a historical context for string theory as a necessary means of integrating the probabilistic world of the standard model of particle physics and the deterministic Newtonian physics of the macroscopic world. Greene discusses the essential problem facing modern physics: unification of Albert Einstein's theory of General Relativity and Quantum Mechanics. Greene suggests that string theory is the solution to these two conflicting approaches. Greene frequently uses analogies and thought experiments to provide a means for the layman to come to terms with the theory which has the potential to create a unified theory of physics.Adaptations
The Elegant Universe was adapted into an Emmy Award-winning[1] three- hour program in three parts for television broadcast in late 2003 on the PBS series NOVA.[2]- Einstein's Dream
- Strings The Thing
- Welcome To The 11th Dimension
See also
Footnotes
- WGBH Educational Foundation (2003). "The Elegant Universe". PBS NOVA. Retrieved 2006-06-04.
References
- Brian Greene, "The Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory", Vintage Series, Random House Inc., February 2000 ISBN 0-375-70811-1
External links
- "SparkNotes: The Elegant Universe". Barnes & Noble. 2004. Retrieved 2006-06-04.
- The Elegant Universe at the Internet Movie Database
- "Science & the City" podcast of Armitage's adaptation, produced by the New York Academy of Sciences
- Perkowitz, Sidney (11 June 1999). "The Seductive Melody of the Strings". Science. 284 (5421): 1780. doi:10.1126/science.284.5421.1780a. JSTOR 2898035.
- Brown, Laurie M. (June 2004). "Reviewed Work: The Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory by Brian Greene". Isis. 95 (2): 327. doi:10.1086/426259. JSTOR 10.1086/426259.
- Santiago, Luis E. Ibáñez (November 2000). "Un viaje hacia la teoría final". Revista de libros de la Fundación Caja Madrid (in Spanish) (47): 28. JSTOR 30229390.
Integrating general relativity and quantum mechanics
General relativity typically deals with situations involving large mass objects in fairly large regions of spacetime whereas quantum mechanics is generally reserved for scenarios at the atomic scale (small spacetime regions).The two are very rarely used together, and the most common case that combines them is in the study of black holes.
Having peak density, or the maximum amount of matter possible in a space, and very small area, the two must be used in synchrony to predict conditions in such places.
Yet, when used together, the equations fall apart, spitting out impossible answers, such as imaginary distances and less than one dimension.
The major problem with their congruence is that, at Planck scale (a fundamental small unit of length) lengths, general relativity predicts a smooth, flowing surface, while quantum mechanics predicts a random, warped surface, neither of which are anywhere near compatible.
Superstring theory resolves this issue, replacing the classical idea of point particles with strings.
These strings have an average diameter of the Planck length, with extremely small variances, which completely ignores the quantum mechanical predictions of Planck-scale length dimensional warping.
Also, these surfaces can be mapped as branes.
These branes can be viewed as objects with a morphism between them.
In this case, the morphism will be the state of a string that stretches between brane A and brane B.
Singularities are avoided because the observed consequences of "Big Crunches" never reach zero size.
In fact, should the universe begin a "big crunch" sort of process, string theory dictates that the universe could never be smaller than the size of one string, at which point it would actually begin expanding.
Contents
Beginning with a brief consideration of classical physics, which concentrates on the major conflicts in physics, Greene establishes a historical context for string theory as a necessary means of integrating the probabilistic world of the standard model of particle physics and the deterministic Newtonian physics of the macroscopic world.Greene discusses the essential problem facing modern physics: unification of Albert Einstein's theory of General Relativity and Quantum Mechanics.
Greene suggests that string theory is the solution to these two conflicting approaches.
Greene frequently uses analogies and thought experiments to provide a means for the layman to come to terms with the theory which has the potential to create a unified theory of physics.
Introduction
According to the modern understanding of physics, forces are not transmitted directly between interacting objects, but instead are described by intermediary entities called fields.All four of the known fundamental forces are mediated by fields, which in the Standard Model of particle physics result from exchange of gauge bosons.
Specifically the four fundamental interactions to be unified are:
- Strong interaction: the interaction responsible for holding quarks together to form hadrons, and holding neutrons and also protons together to form atomic nuclei.
The exchange particle that mediates this force is the gluon. - Electromagnetic interaction: the familiar interaction that acts on electrically charged particles.
The photon is the exchange particle for this force. - Weak interaction: a short-range interaction responsible for some forms of radioactivity, that acts on electrons, neutrinos, and quarks.
It is mediated by the W and Z bosons. - Gravitational interaction: a long-range attractive interaction that acts on all particles. The postulated exchange particle has been named the graviton.
History
The first successful classical unified field theory was developed by James Clerk Maxwell.In 1820 Hans Christian Ørsted discovered that electric currents exerted forces on magnets, while in 1831, Michael Faraday made the observation that time-varying magnetic fields could induce electric currents.
Until then, electricity and magnetism had been thought of as unrelated phenomena.
In 1864, Maxwell published his famous paper on a dynamical theory of the electromagnetic field.
This was the first example of a theory that was able to encompass previously separate field theories (namely electricity and magnetism) to provide a unifying theory of electromagnetism. By 1905, Albert Einstein had used the constancy of the speed of light in Maxwell's theory to unify our notions of space and time into an entity we now call spacetime and in 1915 he expanded this theory of special relativity to a description of gravity, General Relativity, using a field to describe the curving geometry of four-dimensional spacetime.
In the years following the creation of the general theory, a large number of physicists and mathematicians enthusiastically participated in the attempt to unify the then-known fundamental interactions.[2]
In view of later developments in this domain, of particular interest are the theories of Hermann Weyl of 1919, who introduced the concept of an (electromagnetic) gauge field in a classical field theory[3] and, two years later, that of Theodor Kaluza, who extended General Relativity to five dimensions.[4]
Continuing in this latter direction, Oscar Klein proposed in 1926 that the fourth spatial dimension be curled up into a small, unobserved circle.
In Kaluza–Klein theory, the gravitational curvature of the extra spatial direction behaves as an additional force similar to electromagnetism.
These and other models of electromagnetism and gravity were pursued by Albert Einstein in his attempts at a classical unified field theory.
By 1930 Einstein had already considered the Einstein–Maxwell–Dirac System [Dongen].
This system is (heuristically) the super-classical [Varadarajan] limit of (the not mathematically well-defined) Quantum Electrodynamics.
One can extend this system to include the weak and strong nuclear forces to get the Einstein–Yang–Mills–Dirac System.
The French physicist Marie-Antoinette Tonnelat published a paper in the early 1940s on the standard commutation relations for the quantized spin-2 field.
She continued this work in collaboration with Erwin Schrödinger after the World War II.
In 1965, Tonnelat published a book on the state of research on unified field theories
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