Effects of D-instantons in string amplitudes (original) (raw)

An ansatz for a non-perturbative four-graviton amplitude in type IIB superstring theory

Physics Letters B, 1998

A natural SL(2, Z)-invariant generalization of the Veneziano amplitude in type IIB superstring theory is investigated. It includes certain perturbative and non-perturbative (D-instanton) contributions, and it reduces to the correct expressions in different limits. The singularities are poles in the s-tu channels, corresponding to the exchange of particles with a mass spectrum coinciding with that of (p, q) string states. We describe the general structure of the associated perturbative corrections to the effective action.

Instantons in supersymmetric Yang-Mills and D-instantons in IIB superstring theory

Journal of High Energy …, 1998

The one-instanton contributions to various correlation functions of superconformal currents in four-dimensional N = 4 supersymmetric SU(2) Yang-Mills theory are evaluated to the lowest order in perturbation theory. Expressions of the same form are obtained from the leading effects of a single D-instanton extracted from the IIB superstring effective action around the AdS 5 × S 5 background. This is in line with the suggested AdS/Yang-Mills correspondence. The relation between Yang-Mills instantons and Dinstantons is further confirmed by the explicit form of the classical D-instanton solution in the AdS 5 × S 5 background and its associated supermultiplet of zero modes. Speculations are made concerning instanton effects in the large-N c limit of the SU(N c) Yang-Mills theory.

Non-renormalization conditions for four-gluon scattering in supersymmetric string and field theory

Journal of High Energy Physics, 2009

The constraints imposed by maximal supersymmetry on multi-loop contributions to the scattering of four open superstrings in the U (N) theory are examined by use of the pure spinor formalism. The double-trace term k 2 t 8 (trF 2) 2 (where k represents an external momentum and F the Yang-Mills field strength) only receives contributions from L ≤ 2 (where L is the loop number) while the single-trace term k 2 t 8 (trF 4) receives contributions from all L. These statements are verified up to L = 5, but arguments based on supersymmetry suggest they extend to all L. This explains why the single-trace contributions to low energy maximally supersymmetric Yang-Mills field theory are more divergent in the ultraviolet than the double-trace contributions. We also comment further on the constraints on closed string amplitudes and their implications for ultraviolet divergences in N = 8 supergravity.

Quantization and scattering in the IIB SL(2,Bbb Z) covariant superstring

Journal of High Energy Physics, 1999

We rewrite the SL(2, Z) covariant worldsheet action for the IIB string proposed by Townsend in a Polyakov form. In a flat background the formalism yields separate (p, q) sectors. In each one the action is that of the IIB string action with the string slope parameter α ′ replaced by its SL(2, Z) analogue α ′ pq. SL(2, Z) invariant graviton scattering amplitudes are obtained from those of the fundamental (1, 0) string by summing over the different sectors. The tree-level four-graviton amplitude in this formalism differs from a previously conjectured non-perturbative form; both yield the same expansion in order α ′3 .

On the perturbative corrections around D-string instantons

Journal of High Energy Physics, 1999

We study F 4-threshold corrections in an eight dimensional S-dual pair of string theories, as a prototype of dual string vacua with sixteen supercharges. We show that the orbifold CFT description of D-string instantons gives rise to a perturbative expansion similar to the one appearing on the fundamental string side. By an explicit calculation, using the Nambu-Goto action in the static gauge, we show that the first subleading term agrees precisely on the two sides. We then give a general argument to show that the agreement extends to all orders.

Remarks on Non-BPS String Amplitudes and Their All Order α′ Contact Interactions in IIB, IIA

JHEP 1703 (2017) 019, 2017

We explore the entire form of S-Matrix elements of a potential Cn−1 Ramond-Ramond (RR) form field, a tachyon and two transverse scalar fields on both world volume and transverse directions of type IIB and IIA superstring theories. Apart from <VC−2Vϕ0Vϕ0VT0> the other scattering amplitude, namely <VC−1Vϕ−1Vϕ0VT0> is also revealed. We then start to compare all singularity structures of symmetric and asymmetric analysis, generating all infinite singularity structures as well as all order α′ contact interactions on the whole directions. This leads to deriving various new contact terms and several new restricted Bianchi identities in both type IIB and IIA. It is also shown that just some of the new couplings of type IIB (IIA) string theory can be re-verified in an Effective Field Theory (EFT) by pull-back of branes. To construct the rest of S-matrix elements one needs to first derive restricted world volume (or bulk) Bianchi identities and then discover new EFT couplings in both type IIB and IIA. Finally, the presence of commutator of scalar fields inside the exponential of Wess-Zumino action for non-BPS branes has been confirmed as well.

Calculation of graviton scattering amplitudes using string-based methods

Nuclear Physics B, 1995

Techniques based upon the string organisation of amplitudes may be used to simplify eld theory calculations. We apply these techniques to perturbative gravity and calculate all one-loop amplitudes for four-graviton scattering with arbitrary internal particle content. Decomposing the amplitudes into contributions arising from supersymmetric multiplets greatly simplies these calculations. We also discuss how unitarity m a y be used to constrain the amplitudes.

ALE instantons in string effective theory

Nuclear Physics B, 1995

We show that the classical equations of motion of the low-energy effective field theory describing the massless modes of the heterotic (or type I) string admit two classes of supersymmetric self-dual backgrounds. The first class, which was already considered in the literature, consists of solutions with a (conformally) flat metric coupled to axionic instantons. The second includes Asymptotically Locally Euclidean (ALE) gravitational instantonic backgrounds coupled to gauge instantons through the so-called "standard embedding". We show that some elements of these two classes of solutions are dual to each other in the sense of Buscher's duality. We give a world-sheet interpretation of the heterotic ALE istanton solutions in terms of superconformal N = (4, 4) σ-models and argue for their validity to all orders in α ′ . Specializing the gravitational background to the Eguchi-Hanson instanton, we compute the indices of the fermionic operators and give the explicit form of all the relevant fermionic and bosonic zero-modes.

Superstring scattering from D-branes

Nuclear Physics B, 1996

We derive fully covariant expressions for all two-point scattering amplitudes of two massless closed strings from a Dirichlet p-brane This construction relies on the observation that there is a simple relation between these D-brane amplitudes in type II superstring theory and four-point scattering amplitudes for type I open superstrings. From the two-point amplitudes, we derive the long range background fields for the D-branes, and verify that as expected they correspond to those of extremally charged p-brane solutions of the low energy effective action.