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SUMMARY:On the null origin of the ambitwistor string - Eduardo Casali - Ox
 ford
DTSTART:20161117T130000Z
DTEND:20161117T140000Z
UID:TALK67921@talks.cam.ac.uk
CONTACT:Kenny Wong
DESCRIPTION:The Cachazo-He-Yuan (CHY) formulas are a remarkable representa
 tion of tree-level massless scattering amplitudes. Similarly to the Twisto
 r String formulas\, the CHY formula presents amplitudes as an integrals ov
 er the moduli space of Riemann surfaces constrained to the solutions of a 
 set of algebraic equations called the scattering equations. Contrary to th
 e Twistor String formulas\, they can be written in any dimension and for a
  variety of massless theories. The CHY formula and the scattering equation
 s can be derived using a 2D chiral CFT called the Ambitwistor String. The 
 Ambitwistor string possesses peculiar characteristics when viewed as a str
 ing theory. Its low energy effective action is the same as Type II closed 
 strings but the appearance of the scattering equations suggests a high-ene
 rgy limit a la Gross and Mende. Also\, its genus one correlation functions
  are modular invariant but UV divergent\, they correspond to 10D SUGRA amp
 litudes. In this talk I'll talk about a program started with P. Tourkine i
 n which the Ambitwistor String is interpreted as a gauge fixing of the ten
 sionless limit of the classical action of string theory. These are known a
 s null strings and have a long history in the literature. I'll review the 
 null string and its supersymmetric extensions and show how the Ambitwistor
  String can be obtained from a particular gauge fixing of the null string.
  In doing so\, I'll address the issue of possible inequivalent quantizatio
 ns of the null string\, compare it to the case of the usual string and she
 d some light on its relation to the Ambitwistor String.
LOCATION:Potter Room (first floor\, Pav. B)
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