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# Topic: String theory

###### In the News (Tue 16 Jul 19)

 What is string theory? In a similar manner, in string theory, the elementary particles we observe in particle accelerators could be thought of as the "musical notes" or excitation modes of elementary strings. The string tension in string theory is denoted by the quantity 1/(2 p a'), where a' is pronounced "alpha prime"and is equal to the square of the string length scale. String theories are classified according to whether or not the strings are required to be closed loops, and whether or not the particle spectrum includes fermions. superstringtheory.com /basics/basic4.html   (436 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. String theory as a whole has not yet made falsifiable predictions that would allow it to be experimentally tested, though various planned observations and experiments could confirm some essential aspects of the theory, such as supersymmetry and extra dimensions. String theory was originally invented and explored, during the late 1960s and early 1970s, to explain some peculiarities of the behavior of hadrons (subatomic particles such as the proton and neutron which experience the strong nuclear force). en.wikipedia.org /wiki/String_theory   (6108 words)

 AllRefer.com - string theory (Physics) - Encyclopedia string theory, description of elementary particles based on one-dimensional curves, or "strings," instead of point particles. Superstring theory, which is string theory that contains a kind of symmetry known as supersymmetry, shows promise as a way of unifying the four known fundamental forces of nature. The strings are embedded in a space-time having as many as 10 dimensions : the three ordinary dimensions plus time and seven compactified dimensions. reference.allrefer.com /encyclopedia/S/stringth.html   (208 words)

 String theory - Facts, Information, and Encyclopedia Reference article Investigating how a string theory may include fermions in its spectrum led to supersymmetry, a mathematical relation between bosons and fermions which is now an independent area of study. String theories which include fermionic vibrations are now known as superstring theories; several different kinds have been described. 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. www.startsurfing.com /encyclopedia/s/t/r/String_theory.html   (2690 words)

 string theory An important theory in modern physics in which the fundamental particles in nature are thought of as the "musical notes" or excitation modes of elementary strings. String theories are classified according to whether or not the strings are required to be closed loops, and whether or not the particle spectrum includes fermions. In order to include fermions in string theory, there must be a special kind of symmetry called supersymmetry, which means that for every boson (a particle, of integral spin, that transmits a force) there is a corresponding fermion (a particle, of half-integral spin, that makes up matter). www.daviddarling.info /encyclopedia/S/stringtheory.html   (415 words)

 String theory - Iridis Encyclopedia   (Site not responding. Last check: 2007-11-03) A 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. The second problem is that, like quantum field theory, much of string theory is still only formulated perturbatively (as a series of approximations rather than as an exact solution). www.iridis.com /String_theory   (1279 words)

 String Theory - Uncyclopedia String theory is the theory of strings panties. String theory is also related to rope science that covers the practice of tying exceedingly complicated knots in them for research purposes. String Theory is a very, very vast and complex subject, and only monks who spend their whole life on it can reach the mysteries of knots, which lies beyond the Tao. uncyclopedia.org /wiki/String_Theory   (1229 words)

 Understanding String Theory But according to string theory, atomic particles and subatomic particles are not pointlike, but instead consists of a tiny one-dimensional filaments somewhat like infinitely thin rubber bands, vibrating oscillating, dancing filament that physicists have named a string. String theory proclaims that the observed particle properties (mass, charge, spin) are a reflection of the various ways in which a string can vibrate. String theorists have shown that all string theories are different aspects of a string theory that has not 10 but 11 spatial dimensions. www.irfi.org /articles/articles_1_50/understanding_string_theory.htm   (1649 words)

 Introduction to "Introduction" Strings were originally intended to describe hadrons directly, since the observed spectrum and high-energy behavior of hadrons (linearly rising Regge trajectories, which in a perturbative framework implies the property of hadronic duality) seems realizable only in a string framework. Thus, strings may be important for hadronic physics as well as for gravity and unified theories; however, the presently known string models seem to apply only to the latter, since they contain massless particles and have (maximum) spacetime dimension D = 10 (whereas confinement in QCD occurs for D ≤ 4). String theory can be considered a particular kind of particle theory, in that its modes of excitation correspond to different particles. insti.physics.sunysb.edu /~siegel/string.html   (2187 words)

 Universal Theory - String Theory   (Site not responding. Last check: 2007-11-03) String Theory is proposed to resolve the inconsistencies between GTR and Quantum Mechanics. In 1995 in order to explain why there are five different models of string theory which are contradicting each other and at the same time claiming to be the theory of everything, they introduced M-theory and took the liberty to add the 7th extra dimension. To me the assumption of one dimensional string particle (extension of mass proper to unseen extra dimensions) and suggesting the existence of a superspace (still a spacelike entity) beyond the familiar space-time is the frantic attempt of cliff settlers to keep their ground and not to pass the edge. www.universaltheory.org /string_theory.htm   (2216 words)

 Introduction to String Theory String theory is the umbrella name for a set of several theories now being studied by physicists as candidates for the long-sought "theory of everything" (TOE). String theory, as stated above, postulates the existence of tiny vibrating strings that correspond to the observed elementary particles. Strings' minimum energies are actually whole-number multiples of the Planck energy (roughly 1000 kilowatt-hours), which, translated into mass, yields the Planck mass (ten billion billion times that of a proton; roughly 1/100 of 1/000 of a gram; about the mass of a grain of sand). library.thinkquest.org /27930/stringtheory1.htm   (1326 words)

 NOVA | The Elegant Universe | Watch the Program | PBS String theory is radically changing our ideas about the nature of space, opening up the possibility that extra dimensions, rips in the fabric of space, and parallel universes actually exist. Strings provide a unified framework for viewing the universe, but for a while, confusingly, there were five different versions of string theory. By the mid-1980s physicists had developed five different versions of string theory, raising the question of whether it would prove to be a theory of everything or a theory of nothing. www.pbs.org /wgbh/nova/elegant/program.html   (715 words)

 Reference.com/Encyclopedia/String theory String theory was originally invented to explain certain peculiarities of hadron behavior. The concepts which resulted became one component of bosonic string theory, which is still the first version taught to many students. 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 is accepted or falisfied. www.reference.com /browse/wiki/String_theory   (2032 words)

 USATODAY.com - String theory: Hanging on by a thread?   (Site not responding. Last check: 2007-11-03) The appeal of string theory, says physicist Sean Carroll of the California Institute of Technology, is that these little energy loops appear to mathematically explain not only the interactions of atomic particles but also where gravity comes from. String theory describes a vibrating string that acts like a "graviton," which produces the force of gravity, much in the same way that the standard model's particles produce forces. String theory is physics' great hope for uniting the physics of galaxies (shown left) with the phyiscs of sub-atomic particles. www.usatoday.com /tech/science/2006-09-18-string-theory_x.htm   (997 words)

 What is superstring theory? - a definition from Whatis.com - see also: string theory, theory of everything According to string theory, at the most microscopic level, everything in the universe is made up of loops of vibrating strings, and apparent particle differences can be attributed to variations of vibration. Superstring theory came to the forefront in the 1980s, when Michael Green at Queen Mary College and John Schwarz at the California Institute of Technology demonstrated that it had the potential to be the unifying theory that Einstein sought: one that could be used to describe gravity as well as electromagnetic forces. String theorists are currently examining the possibility that the strings themselves have multiple dimensions, and are not, as was originally thought, massless (possessing only length, and no width). searchsmb.techtarget.com /sDefinition/0,,sid44_gci341514,00.html   (592 words)

 String Theory The goal of research in string theory is to restrict the structure of spacetime and its matter content by combining gravity with the principles of quantum mechanics. It turns out that there is a surprising connection between gauge theories, such as those that appear in particle theory, and the string theoretic description of such singularities. String theory predicts the existence of consistent quantum field theories in spacetime dimensions higher than four. www-theory.lbl.gov /~origa/develop/Front.html   (887 words)

 Home Page String Theory replaces the point particle with something that does not inscribe a point and as such avoids the singularity problem that normally generates infinities as an answer. The subject of string theory arose in the late 1960's in an attempt to describe strong nuclear forces. Another important development during this period (in 1971) was the discovery that to incorporate a class of elementary particles called fermions (electrons and quarks are examples) string theory requires a two-dimensional version of supersymmetry. www.superstringtheory.fanspace.com   (1019 words)

 'Theory of everything' tying researchers up in knots But he said that so far, string theorists have promised far more than they have delivered and have fostered the false impression that string theory is the only feasible way to explain cosmic mysteries. String theorists fire back that no one else predicted it, either, and besides, "string theory is the only approach that has the potential for explaining dark energy" based on pure theory, says John Schwarz, a pioneering string theorist at Caltech. That's because string theory is the only existing hypothesis that holds serious promise of merging the two grandest branches of physics -- the theory of gravity, the basis of cosmological theory; and quantum mechanics, the science of the subatomic realm, Schwarz says. www.sfgate.com /cgi-bin/article.cgi?f=/c/a/2005/03/14/MNGRMBOURE1.DTL   (1503 words)

 String Theory? Knot! Ever since string theory was first proposed by Leonard Susskind in 1969 it has been plagued by ridicule and controversy, but the theory still continues to attract serious attention from prominent scientists. The initial motivation behind introducing string theory was to amend the Standard Model so that its fundamental units would become one-dimensional, elongated objects, rather than zero-dimensional particles. With such a model, string theorists hoped that a cogent and more consistent quantum theory of gravity would be revealed, in addition to a number of other fantastic consequences that would also follow. www.scienceagogo.com /news/string_theory.shtml   (1237 words)

 What is String Theory ?   (Site not responding. Last check: 2007-11-03) String theory is our most recent attempt to answer the last (and part of the second) question. Strings '00 Pictures: Photos of some of the world's leading string theorists, at the most important yearly conference on the subject (see also the ITP M Theory Program and Strings 96 pictures). String Theory and the Unification of Forces: An explanation of the ambitious goal of string theory, by Prof. www.nuclecu.unam.mx /~alberto/physics/string.html   (1282 words)

 Testing String Theory - - science news articles online technology magazine articles Testing String Theory   (Site not responding. Last check: 2007-11-03) According to one formulation of string theory, quantum gravity is contained within the closed strings, while matter is described by both open and closed strings. String theory thus promises to merge the equations describing the action of the tiny world we cannot see—that of subatomic particles—with the equations describing gravity and the large-scale world we experience every day. Finally, the math behind string theory is extremely sophisticated and beautiful, and the equations have survived every mathematical challenge. www.discover.com /issues/aug-05/cover   (861 words)

 Superstrings While quantum theory, the theory of the infinitesimally small, was being tested with accuracy never attained before, he refused to accept that it was the ultimate theory. In string theory, there are no elementary particles (like electrons or quarks), but pieces of vibrating strings. It is a testimony to the power and the beauty of string theory that physicists would rather give up the very notion of space and time-- and admit a 10-dimension world--than question the path on which the quest for a unified theory has led them. imagine.gsfc.nasa.gov /docs/science/mysteries_l2/superstring.html   (1010 words)

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