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String Theory in Electromagnetic Fields

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 Added by Richard Szabo
 Publication date 2000
  fields Physics
and research's language is English




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A review of various aspects of superstrings in background electromagnetic fields is presented. Topics covered include the Born-Infeld action, spectrum of open strings in background gauge fields, the Schwinger mechanism, finite-temperature formalism and Hagedorn behaviour in external fields, Debye screening, D-brane scattering, thermodynamics of D-branes, and noncommutative field and string theories on D-branes. The electric field instabilities are emphasized throughout and contrasted with the case of magnetic fields. A new derivation of the velocity-dependent potential between moving D-branes is presented, as is a new result for the velocity corrections to the one-loop thermal effective potential.



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125 - E.Dudas 2010
In string models with brane supersymmetry breaking exponential potentials emerge at (closed-string) tree level but are not accompanied by tachyons. Potentials of this type have long been a source of embarrassment in flat space, but can have interesting implications for Cosmology. For instance, in ten dimensions the logarithmic slope |V/V| lies precisely at a critical value where the Lucchin--Matarrese attractor disappears while the scalar field is emph{forced} to climb up the potential when it emerges from the Big Bang. This type of behavior is in principle perturbative in the string coupling, persists after compactification, could have trapped scalar fields inside potential wells as a result of the cosmological evolution and could have also injected the inflationary phase of our Universe.
69 - Shaun Hampton 2019
The strongly coupled dynamics of black hole formation in bulk AdS is conjectured to be dual to the thermalization of a weakly interacting CFT on the boundary for low $N$ which, for $Ntoinfty$, becomes strongly coupled. We search for this thermalization effect by utilizing the D1D5 CFT to compute effective string interactions for $N=2$. This is done by turning on a marginal deformation of the theory which twists together or untwists effective strings. For a system to thermalize, the initial state, which is far from thermal, must redistribute its energy via interactions until a thermal state is achieved. In our case, we consider excited states of the effective strings. We compute splitting amplitudes for 1) one excitation going to three excitations and 2) two excitations going to four excitations using two insertions of the deformation. Scenario 1) corresponds to a single particle moving in AdS. Scenario 2) corresponds to two particles moving and colliding in AdS. We find that the `1 to 3 amplitude has terms which oscillate with time, $t$, where $t$ is the duration of the two deformations. We find that the `2 to 4 amplitude has similar oscillatory terms as well as secular terms which grow like $t^2$. For this case the growth implies that for large $t$ the excitations in the initial state, which carry a given energy, prefer to redistribute themselves amongst lower energy modes in the final state. This is a key feature of thermalization. Albeit in a simplified setting, we therefore argue that we have identified the thermalization vertex in the D1D5 CFT, which after repeated applications, should lead to thermalization. This ultimately maps to two particles colliding and forming a black hole in AdS, which in our case, is a fuzzball.
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