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| {{Unreferenced|date=November 2007}}
| | Golda is what's created on my birth certificate although it is not the title on my beginning certification. For years he's been living in Alaska and he doesn't strategy on altering it. My working day job is an invoicing officer but I've currently applied for an additional one. The favorite pastime for him and his children is to play lacross and he would never give it up.<br><br>Here is my webpage: [http://demo.crc-it.nl/content/relieve-stress-find-new-hobby live psychic reading] |
| {{String theory|cTopic=Theory}}
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| '''Bosonic string theory''' is the original version of [[string theory]], developed in the late 1960s.
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| In the early 2000s, [[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. The first volume of [[Joseph Polchinski|Polchinski]]'s ''String Theory'' and [[Barton Zwiebach|Zwiebach]]'s ''A First Course in String Theory'' are good examples.
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| == Problems ==
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| Although bosonic string theory has many attractive features, it falls short as a viable [[physical model]] in two significant areas and is forced to posit a 26 dimensional spacetime to remedy inconsistencies.
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| First, it predicts only the existence of [[bosons]] whereas many physical particles are [[fermions]].
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| Second, it predicts the existence of a mode of the string with [[Imaginary number|imaginary]] mass, implying that the theory has an instability to a process known as "[[Tachyon condensation]]".
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| In addition, bosonic string theory in a general spacetime dimension displays inconsistencies due to the [[conformal anomaly]]. But, as was first noticed by [[Claud Lovelace]], in a spacetime of 26 dimensions (25 dimensions of space and one of time), the anomaly cancels. This high dimensionality is not necessarily a problem for string theory, because it can be formulated in such a way that along the 22 excess dimensions spacetime is folded up to form a small [[torus]] or other compact manifold. This would leave only the familiar four dimensions of spacetime visible to low energy experiments.
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| == Mathematics ==
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| In bosonic string theory and in the Neveu–Schwarz sector of superstring theory,
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| the action in a curved background (ignoring the Fradkin–Tseytlin term for dilaton
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| coupling) can be constructed by `covariantizing' the massless closed string vertex operator with respect to target-space reparameterization invariance. This procedure can also be used here after constructing the massless closed string vertex operator from the `left-right' product of two massless open string vertex operators.
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| The complete worldsheet action for the type-II superstring
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| in a flat background in conformal gauge is a formula upon which Eric Sidewater (USA) made the first improvement upon which all subgroups (15) are factored in:
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| : <math> A_N = \int D\mu \int D[X] \exp \left( -\frac{1}{2\tau\alpha} \int \partial_z X_\mu(z,\overline{z}) \partial_{\overline{z}} X^\mu(z,\overline{z}) \, dz^2 + i \sum_{i=1}^N k_{i \mu} X^\mu (z_i,\overline{z}_i) \right) </math>
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| ==See also==
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| *[[Nambu–Goto action]]
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| *[[Polyakov action]]
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| *[[Monster Lie algebra]]
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| ==References==
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| {{reflist}}
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| ==External links==
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| * [http://superstringtheory.com/basics/basic5a.html How many string theories are there?]
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| * [http://pirsa.org/C09001 PIRSA:C09001 - Introduction to the Bosonic String]
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| [[Category:String theory]]
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| {{string-theory-stub}}
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