New ambitwistor string theories

Abstract:We re-examine a closed-string model defined by altering the boundary conditions for one handedness of two-dimensional propagators in otherwise-standard string theory. We evaluate the amplitudes using Kawai-Lewellen-Tye factorization into openstring amplitudes. The only modification to standard string theory is effectively that the spacetime Minkowski metric changes overall sign in one open-string factor. This cancels all but a finite number of states: as found in earlier approaches, with enough supersymmetry (e.g., type II) the tree amplitudes reproduce those of the massless truncation of ordinary string theory. However, we now find for the other cases that additional fields, formerly thought to be auxiliary, describe new spin-2 states at the two adjacent mass levels (tachyonic and tardyonic). The tachyon is always a ghost, but can be avoided in the heterotic case.

Section: Derivationmentioning

confidence: 99%

“…String-like theories were proposed that reproduced these amplitudes, at least in the cases where Yang-Mills factors (in spectrum/vertices) were supersymmetric [6][7][8][9]. There the delta-functions arose from related delta-functions inserted explicitly into the vertex operators.…”

Section: Introductionmentioning

confidence: 99%

Factorization of chiral string amplitudes

Huang

Siegel

Yuan

2016

“…To make this point clearer, consider the following state: One can show that the tree-level n-point correlation function of these photon states gives 22) where M A,n is an n by n matrix identical to one of the submatrices of the bigger matrix M n defined in (3.5). From this discussion, it is evident that one more row can be added to the table above [5]:…”

Section: Jhep11(2017)052mentioning

confidence: 99%

Ambitwistor formulations of R2 gravity and (DF)2 gauge theories

Azevedo

Engelund

2017

We consider D-dimensional amplitudes in R 2 gravities (conformal gravity in D = 4) and in the recently introduced (DF ) 2 gauge theory, from the perspective of the CHY formulae and ambitwistor string theory. These theories are related through the BCJ double-copy construction, and the (DF ) 2 gauge theory obeys color-kinematics duality. We work out the worldsheet details of these theories and show that they admit a formulation as integrals on the support of the scattering equations, or alternatively, as ambitwistor string theories. For gravity, this generalizes the work done by Berkovits and Witten on conformal gravity to D dimensions. The ambitwistor is also interpreted as a D-dimensional generalization of Witten's twistor string (SYM + conformal supergravity). As part of our ambitwistor investigation, we discover another (DF ) 2 gauge theory containing a photon that couples to Einstein gravity. This theory can provide an alternative KLT description of Einstein gravity compared to the usual Yang-Mills squared.

“…A proof of this formula for arbitrary n was given by Dolan and Goddard [8]. The CHY proposal for the calculation of tree-level scattering amplitudes has an interpretation in terms of ambitwistor strings [9][10][11][12][13] defined on a Riemann surface at genus zero. At loop level, supergravity integrands of four-point amplitudes at one and two loops have been obtained when introducing higher genus [11,[14][15][16].…”

Section: Introductionmentioning

confidence: 99%

Sudakov representation of the Cachazo-He-Yuan scattering equations formalism

Chachamis¹,

Jiménez²,

Vera³

et al. 2018

Abstract:We show that the use of Sudakov variables greatly simplifies the study of the solutions to the scattering equations in the Cachazo-He-Yuan formalism. We work in the center-of-mass frame for the two incoming particles, which partially fixes the SL(2, C) redundancy in the integrand defining the scattering amplitudes, the remaining freedom translates into a global shift in the azimuthal angle of the outgoing particles. Studying four-and five-particle amplitudes, we see how an appropriate choice of this phase allows for algebraic simplifications when finding solutions to the scattering equations, as well as in the expression of the scattering amplitudes in terms of the locations of the punctures in the sphere. These punctures themselves are remarkably simple functions of the Sudakov parameters.