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Topic: Bosonic string theories


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In the News (Sat 28 Nov 09)

  
  Superstring theory - Wikipedia, the free encyclopedia
Superstring theory is an attempt to explain all of the particles and fundamental forces of nature in one theory by modeling them as vibrations of tiny supersymmetric strings.
Superstring theory is a shorthand for "supersymmetric string theory" because unlike bosonic string theory, it is the version of string theory that incorporates fermions and supersymmetry.
The graviton (the proposed messenger particle of the gravitational force), for example, is predicted by the theory to be a string with wave amplitude zero.
en.wikipedia.org /wiki/Superstrings   (950 words)

  
 String theory - Wikipedia, the free encyclopedia
String theory is a model of fundamental physics whose building blocks are one-dimensional extended objects (strings) rather than the zero-dimensional points (particles) that are the basis of the Standard Model of particle physics.
Bosonic string theory is formulated in terms of the Nambu-Goto action, a mathematical quantity which can be used to predict how strings move through space and time.
Since string theory may not be tested in the foreseeable future, some scientists have asked if it even deserves to be called a scientific theory: it is not yet a falsifiable theory in the sense of Popper.
en.wikipedia.org /wiki/String_theory   (2656 words)

  
 Bosonic string theory - Wikipedia, the free encyclopedia
Bosonic string theory is the original version of string theory, developed in the late 1960s.
In the early 1970s, supersymmetry was discovered in the context of string theory, and a new version of string theory called superstring theory (supersymmetric string theory) became the real focus.
Nevertheless, bosonic string theory remains a very useful "toy model" to understand many general features of perturbative string theory, and string theory textbooks usually start with the bosonic string.
en.wikipedia.org /wiki/Bosonic_string_theory   (180 words)

  
 String theory - Wikipedia, the free encyclopedia   (Site not responding. Last check: 2007-10-21)
String theory is a physical model whose fundamental building blocks are one-dimensional extended objects (strings) rather than the zero-dimensional points (particles) that were the basis of most earlier physics.
String theory has also led to much insight into supersymmetric gauge theories, a subject which includes possible extensions of the standard model.
String theory was originally invented to explain certain peculiarities of hadron behavior.
lexington-fayette.us /project/wikipedia/index.php/String_theory   (2123 words)

  
 String theory - FreeEncyclopedia   (Site not responding. Last check: 2007-10-21)
String theories are able to avoid problems, such as infinite energy density, associated with the presence of mathematical points in a physical theory.
The term 'string theory' properly refers to both the 26-dimensional bosonic string theories and to the 10-dimensional superstring theories discovered by adding supersymmetry to bosonic string theory.
A central consequence of string theory is that the observed physics of the known universe can be stated as arising from two seemingly incompatible geometries: one being 'as large as we see', and the other being smaller by far than the Planck length.
www.openproxy.ath.cx /st/String_theory.html   (299 words)

  
 D-brane - Indopedia, the Indological knowledgebase
Strings that are constrained by D-branes can be studied by use of renormalizable 2-dimensional quantum field theory.
Because string theory implies that the Universe has more dimensions than we expect—26 for bosonic string theories and 10 for superstring theories—we have to find a reason why the extra dimensions are not apparent.
Interestingly, the force of gravity is not due to open strings; the gravitons which carry gravitational forces are vibrational states of closed strings.
www.indopedia.org /D-brane.html   (770 words)

  
 How many theories?
The bosonic string theories are all unstable because the lowest excitation mode, or the ground state, is a tachyon with M
Scalar tachyon, massless vector boson, antisymmetric tensor, graviton and dilaton
String theorists learned that all of these bad ghost states decouple from the spectrum when two conditions are satisfied: the number of spacetime dimensions is 10, and theory is supersymmetric, so that there are equal numbers of bosons and fermions in the spectrum.
superstringtheory.com /basics/basic5a.html   (1102 words)

  
 D-brane - Wikpedia   (Site not responding. Last check: 2007-10-21)
Because string theories are by nature relativistic, adding energy to a string is equivalent to adding mass, by Einstein's relation E = mc^2.
Examining the consequences of the Nambu-Goto action (and applying the rules of quantum mechanics to quantize the string), one finds that among the spectrum of particles is one resembling the photon, the fundamental quantum of the electromagnetic field.
(The string theory does contain other interactions, but they are only detectable at very high energies.) Gauge theories were not invented starting with bosonic or fermionic strings; they originated from a different area of physics, and have become quite useful in their own right.
www.bostoncoop.net /~tpryor/wiki/index.php?title=D-brane   (1585 words)

  
 String theory   (Site not responding. Last check: 2007-10-21)
The first problem is that, as with any current theory of quantum gravity, it does not yet make any firm predictions that are currently subject to experimental verification (it is not falsifiable, because human beings do not have the technology to observe strings, which are said to be roughly 10
Nonetheless, while these possibilities for confirmation, however remote, do exist, as things now stand string theory cannot be disproven by experiment, which is a serious problem for any theory of physics.
The second problem is that much of theory is still only formulated perturbatively (as a series of approximations rather than as an exact solution).
www.sciencedaily.com /encyclopedia/string_theory   (847 words)

  
 World War 1 and 2 - String theory   (Site not responding. Last check: 2007-10-21)
It is by no means the only theory currently being developed which suffers from this difficulty; any new development can pass through a stage of unverifiability before it becomes conclusively accepted or rejected.
All these possibilities must be checked, which may take a considerable time.) No version of string theory has yet made a prediction which differs from those made by other theories—at least, not in a way that an experiment could check.
In this sense, string theory is still in a "larval stage": it possesses many features of mathematical interest, and it may yet become supremely important in our understanding of the Universe, but it requires further developments before it can become verifiable.
www.worldwardiary.com /history/String_theory   (1975 words)

  
 Search Tuna Report for string theory   (Site not responding. Last check: 2007-10-21)
The most popular version of the theory depends on a mathematical property called supersymmetry, and the theory derived form this principle is properly called {superstring theory}, a term which is often used interchangeably with string theory.
Strings also provide the only known theories of quantum gravity which are too complicated to prove wrong, and therefore provide a convenient method of turning up our noses at all the ordinary particle theorists who haven't even learned general relativity yet....
String duality is the statement that all five diffferent perturbative strings are related in such a fashion and are just expansions of one single unified theory around different backgrounds....
searchtuna.com /ftlive2/4698.html   (2596 words)

  
 String theory - InfoSearchPoint.com   (Site not responding. Last check: 2007-10-21)
String theories are able to avoid problems associated with the presence of pointlike particles in a physical theory.
The different superstring theories were discovered to be different limits of an unknown 11-dimensional theory called M-theory proposed by Edward Witten in the 1990s.
On a more practical level, string theory has led to advances in the mathematics of knots, Calabi-Yau spaces and many other fields.
www.infosearchpoint.com /display/String_theory   (456 words)

  
 M-theory, the theory formerly known as Strings
In String Theory, the myriad of particle types is replaced by a single fundamental building block, a `string'.
Furthermore, the string is free to vibrate, and different vibrational modes of the string represent the different particle types, since different modes are seen as different masses or spins.
Apart from the fact that instead of one there are five different, healthy theories of strings (three superstrings and two heterotic strings) there was another difficulty in studying these theories: we did not have tools to explore the theory over all possible values of the parameters in the theory.
www.damtp.cam.ac.uk /user/gr/public/qg_ss.html   (1344 words)

  
 Physics 7910
The reason why bosonic string theories can only live in 26 dimensions and the spectrum of the bosonic string will be discussed.
The world-sheet quantum field theory that describes the bosonic string is a conformally invariant quantum field theory in two dimensions.
In order to make contact between string theory and the real world six of the dimensions can be small and compact while the four additional dimensions are infinitely extended and represent our world.
www.physics.utah.edu /~katrin/phys7910.html   (525 words)

  
 The Last Free City :: View topic - Has any one heard of the string theory
there is a theory going around that inside the smallest parts ofr atoms there are tiny bits of circular energy and that the difference between the wave lengths is what makes you and me different from everything else
String theory, as with any current theory of quantum gravity, is unverifiable, and therefore it is also unfalsifiable.
Human beings do not have the technology to observe strings (which are said to be roughly 10-35 meters across).
forums.thelastfreecity.com /viewtopic.php?t=25812   (1129 words)

  
 Harvard Physics Department Faculty - Shiraz Minwalla   (Site not responding. Last check: 2007-10-21)
Shiraz Minwalla's research deals with string theory, quantum field theory, and quantum gravity.
His work is motivated by the desire to understand the qualitatively new features of dynamics in string theory.
He has been involved in the study of special limits of string theory (noncommutative field theories, noncommutative open string theory, OM theory), some of which he helped discover.
www.physics.harvard.edu /people/facpages/minwalla.html   (188 words)

  
 How many theories?
A supersymmetric string theory is called a superstring theory.
For bosonic strings, this question is only answered in the affirmative if the spacetime dimensions number 26.
And now the biggest rush in string research is to collapse the table above into one theory, which some people want to call M theory, for it is the Mother of all theories.
superstringtheory.com /basics/basic5.html   (487 words)

  
 String theory   (Site not responding. Last check: 2007-10-21)
The Nth Dimension - A comprehensive insight to String Theory.
Beyond String Theory - An ongoing project, illuminating many aspects of string theory and related topics.
"Cosmic strings reborn?" by Tom Kibble, a talk given in September 2004.
www.firebird.cn /wiki/String_theory   (2544 words)

  
 Citebase - Symmetry Breaking at enhanced Symmetry Points   (Site not responding. Last check: 2007-10-21)
The influence of world-sheet boundary condensates on the toroidal compactification of bosonic string theories is considered.
The quantum corrections to the open-string theory generate a mixing of open and closed strings so that the coset-space pions mix with the closed-string G× G gauge fields, resulting in a Higgs-like breakdown of the symmetry to the diagonal G group.
Equations of motion for the heterotic string from the conformal invariance of the sigma model, Phys.
citebase.eprints.org /cgi-bin/citations?id=oai:arXiv.org:hep-th/9509171   (1631 words)

  
 string theory | TutorGig.co.uk Encyclopedia   (Site not responding. Last check: 2007-10-21)
unsolvedphysicsIs string theory, superstring theory, or M-theory, or some other variant on this theme, a step on the road to a " theory of everything," or just a blind alley?
Popular Music See all 10 results in string theory..
Classical Music See all 1 results in string theory..
www.tutorgig.co.uk /ed/string_theory   (2604 words)

  
 Citebase - D0-branes in SO(32)$\times$SO(32) open type 0 string theory
It has been proposed that this theory is S-dual to bosonic string theory compactified on SO(32) lattice, which has SO(32)×SO(32) spinor states as excited states of fundamental string.
A non-supersymmetric ten-dimensional open string theory is constructed as an orbifold of type I string theory, and as an orientifold of the bosonic type B theory.
It is conjectured that the two closed bosonic string theories, Type 0A and Type 0B, correspond to certain supersymmetry breaking orbifold compactifications of M-theory.
citebase.eprints.org /cgi-bin/citations?id=oai:arXiv.org:hep-th/9907094   (943 words)

  
 Nordic Graduate Program in Physics   (Site not responding. Last check: 2007-10-21)
NORDITA is organizing in Copenhagen a Nordic course in string theory.
The course is addressed to Nordic master and PhD students who have a good knowledge of field theory and some superficial knowledge of string theory and who are strongly motivated to learn in a short time some of the exciting developments occurred recently in string theory.
String on a pp-wave background and properties of N=4 super Yang-Mills.
www.nordita.dk /conference/strings2003   (290 words)

  
 String Theory   (Site not responding. Last check: 2007-10-21)
New Insights Into Open String Theory July 2002 - Science Daily
They are sometimes associated with Angel Hair linked to the presence of spirits or extraterrestrials, who leave a thin opaque spider-like substance behind.
The strings create patterns as if bringing a message.
www.crystalinks.com /stringtheory.html   (344 words)

  
 Quantization of bosonic string   (Site not responding. Last check: 2007-10-21)
1 : An Introduction to the Bosonic String (Cambridge Monogra...
Re: Tachyons, bosonic strings, loop quantization of E&M...
The LQG -- String: Loop Quantum Gravity Quantization of String Theory I. Flat Ta...
www.scienceoxygen.com /phys/268.html   (96 words)

  
 Perturbative String and Superstring Theories
In this section we overview some basic aspects of bosonic and fermionic strings.
We focus mainly in the description of the spectrum of the theory in the light-cone gauge, the effective action, the description of spectra of the five consistent superstring theories and the perturbative Calabi-Yau compactifications (for details, precisions and further developments see for instance [
The energy-momentum tensor of the two-dimensional theory is given by
fisica.usac.edu.gt /public/hugo/courseguate/node2.html   (503 words)

  
 Various String Theories   (Site not responding. Last check: 2007-10-21)
Different string theories may employ different forms of strings for their basic building blocks.
Three of the five string theories are superstring theories, that is, they combine string theory with supersymmetry.
Weak coupling can be understood by expanding in a series, so if two theories are related by S-duality the strong theory can be understood through transformation into the weak theory and subsequently expanding the series.
ffden-2.phys.uaf.edu /212_fall2003.web.dir/erik_johnson/various.html   (198 words)

  
 String theory - Questionz.net , answers to all your questions   (Site not responding. Last check: 2007-10-21)
String theory - Questionz.net, answers to all your questions
Problems with string theory String theory suffers from two major problems.
In other words, it does not make any predictions that may be subject to experimental verification; thus, it can be neither proven nor disproven, which is a serious problem for any theory of physics.
www.questionz.net /Albert_Einstein/String_theory.html   (468 words)

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