A kind of analogue of lattice gauge theory for worldsheet computations in perturbative string theory/string scattering amplitudes.
From the point of view of AdS/CFT-duality, string bit observables are the incarnation of single trace observables on the CFT-side Berenstein-Maldacena-Nastase 02, p. 13.
More in detail:
The single trace operators/observables in conformal field theories such as super Yang-Mills theories play a special role in the AdS-CFT correspondence: They correspond to single string excitations on the AdS-supergravity side of the correspondence, where, curiously, the “string of characters/letters” in the argument of the trace gets literally mapped to a superstring in spacetime (see the references below).
From Polyakov 02, referring to gauge fields and their single trace operators as letter and words, respectively:
The picture which slowly arises from the above considerations is that of the space-time gradually disappearing in the regions of large curvature. The natural description in this case is provided by a gauge theory in which the basic objects are the texts formed from the gauge-invariant words. The theory provides us with the expectation values assigned to the various texts, words and sentences.
These expectation values can be calculated either from the gauge theory or from the strongly coupled 2d sigma model. The coupling in this model is proportional to the target space curvature. This target space can be interpreted as a usual continuous space-time only when the curvature is small. As we increase the coupling, this interpretation becomes more and more fuzzy and finally completely meaningless.
From Berenstein-Maldacena-Nastase 02, who write $Z$ for the elementary field observables (“letters”) $\mathbf{\Phi}$ above:
In summary, the “string of $Z$s” becomes the physical string and that each $Z$ carries one unit of $J$ which is one unit of $p_+$. Locality along the worldsheet of the string comes from the fact that planar diagrams allow only contractions of neighboring operators. So the Yang Mills theory gives a string bit model where each bit is a $Z$ operator.
On the CFT side these BMN operators of fixed length (of “letters”) are usefully identified as spin chains which, with the dilatation operator regarded as their Hamiltonian, are integrable systems (Minahan-Zarembo 02, Beisert-Staudacher 03).
This integrability allows a detailed matching between
single trace operators/BMN operators in D=4 N=4 super Yang-Mills theory
the classical Green-Schwarz superstring on AdS5 $\times$ S5
under AdS/CFT duality (Beisert-Frolov-Staudacher-Tseytlin 03, …). For review see BBGK 04, Beisert et al. 10.
The idea originates with
Roscoe Giles, Charles Thorn, Lattice approach to string theory, Phys. Rev. D 16, 366 – Published 15 July 1977 (doi:10.1103/PhysRevD.16.366)
Igor Klebanov, Leonard Susskind, Continuum strings from discrete field theories, Nuclear Physics B Volume 309, Issue 1, 31 October 1988, Pages 175-187 (doi:10.1016/0550-3213(88)90237-4)
Charles Thorn, Reformulating String Theory with the $1/N$ Expansion, in: L. V. Keldysh and V. Ya. Fainberg (eds.), Sakharov Memorial Lectures in Physics, Nova Science Publishers Inc., Commack, New York,
1992 (arXiv:hep-th/9405069)
It is made explicit in
Review includes
Further developments include the following:
Charles Thorn, Space from String Bits, J. High Energ. Phys. (2014) 2014: 110 (arXiv:1407.8144)
Charles Thorn, String Bits at Finite Temperature and the Hagedorn Phase, Phys. Rev. D 92, 066007 (2015) (arXiv:1507.03036)
Charles Thorn, $1/N$ Perturbations in Superstring Bit Models, Phys. Rev. D 93, 066003 (2016) (arXiv:1512.08439)
Matteo Beccaria, Thermal properties of a string bit model at large $N$, J. High Energ. Phys. (2017) 2017: 200. (arXiv:1709.01801)
Last revised on December 8, 2019 at 18:07:20. See the history of this page for a list of all contributions to it.