| 日時: |
2008-02-15 13:30 - 15:30 |
| 場所: |
研究本館2階220室 |
| 会議名: |
Twistor Strings, Gauge Theory and Gravity (1) : (2) on 18th Feb. |
| 連絡先: |
津田 |
| 講演者: |
Dr. Mohab Abou-zeid (IHES) |
| 講演言語: |
英語 |
| アブストラクト: |
Twistor string theory offers a new and very promising approach to the understanding of perturbative Yang-Mills scattering amplitudes and to their efficient computation.
ﾊ
At tree level in string perturbation theory, both the open string sector of Witten's topological B-model on the supertwistor space CP^3/4, and the alternative theory of open twistor strings due to Berkovits, yield the correct perturbative tree amplitudes in N=4 super Yang-Mills. However, in computations of gauge theory loop scattering amplitudes, conformal supergravity modes are unavoidably mixed in with the gauge theory ones. This suggests that the original twistor string models of these authors may be inconsistent quantum mechanically and it also limits their usefulness for the purpose of computing amplitudes, as there appears to be no decoupling limit giving pure super-Yang-Mills amplitudes.?
ﾊ
The aim of my talks will be to present a modification of the Berkovits string which gives Einstein supergravity (with second order field equations for the graviton) coupled to Yang-Mills theory, and has a limit in which the gravity modes can be decoupled to give pure gauge theory amplitudes.
ﾊ
I will first review some remarkable properties of perturbative Yang-Mills scattering amplitudes, in particular the holomorphy of the maximally helicity violating (MHV) amplitudes. These properties are most apparent in the description via spinors, which I will recall.
ﾊ
I will then survey a number of relevant aspects of twistor theory, including the special features associated with different space-time signatures; the supertwistor space; the Penrose transform; the? infinity twistor; and the non-linear graviton construction of Penrose.
ﾊ
I will then survey the Witten and Berkovits strings, with emphasis on the latter. The world-sheet formulation of the Berkovits model involves so-called beta-gamma systems; I will describe the symmetries of such systems and their gauging, and explain how the analysis can be applied to the construction of a family of new gauged Berkovits twistor strings which are free from world-sheet anomalies. I will also describe the corresponding spectra in space-time, and show that they give Einstein supergravities instead of the higher derivative conformal supergravities arising in the original twistor string models. The new theories include one with the spectrum of N=8 supergravity, two theories with the spectrum of N=4 supergravity coupled to N=4 Yang-Mills, a family of N>0 models with the spectra of self-dual supergravity coupled to self-dual super-Yang-Mills, and a non-supersymmetric string with the spectrum of self-dual gravity coupled to self-dual Yang-Mills and a scalar. |
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