Infinite Tension Limit Research Articles

Coupling the precursor of the most general theory of electromagnetism invariant under duality and conformal invariance with scalars, and BIon-type solutions

Recently, the most general theory of electromagnetism invariant under duality and conformal invariance was written, and dubbed ModMax. It arises from a generalization of Born-Infeld (BI) theory by taking the infinite tension limit, $T\ensuremath{\rightarrow}\ensuremath{\infty}$. In this paper we show that this generalization can be obtained from a branelike construction, just like BI, and can thus be coupled to scalars in the same way to obtain a Dirac-Born-Infeld (DBI)-like action. All the BIon and catenoid solutions, and their interpolations, are still solutions of the generalized DBI-like action, suggesting that an interpretation within string theory could be possible. We also show that Ra\~nada's knotted solutions (with nonzero helicities) are still valid, both in the ModMax theory, and in its precursor.

From QCD Strings to WZW

According to the Axionic String Ansatz (ASA) confining flux tubes in pure gluodynamics are in the same equivalence class as a new family of integrable non-critical strings, called axionic strings. In addition to translational modes, axionic strings carry a set of worldsheet axions transforming as an antisymmetric tensor under the group of transverse rotations. We initiate a study of integrable axionic strings at general number of space-time dimensions D. We show that in the infinite tension limit worldsheet axions should be described by a peculiar “pseudofree” theory — their S-matrix is trivial, but the corresponding action cannot be brought into a free form by a local field redefinition. This requirement fixes the axionic action to take a form of the O(D − 2) Wess-Zumino-Witten (WZW) model.

Scattering equations, supergravity integrands, and pure spinors

The tree-level S-matrix of type II supergravity can be computed in scattering equation form by correlators in a worldsheet theory analogous to a chiral, infinite tension limit of the pure spinor formalism. By defining a non-minimal version of this theory, we give a prescription for computing correlators on higher genus worldsheets which manifest spacetime supersymmetry. These correlators are conjectured to provide the loop integrands of supergravity scattering amplitudes, supported on the scattering equations. We give nontrivial evidence in support of this conjecture at genus one and two with four external states. Throughout, we find a close correspondence with the pure spinor formalism of superstring theory, particularly regarding regulators and zero-mode counting.

Long string dynamics in pure gravity on AdS3

We study the classical dynamics of a completion of pure AdS gravity in 3D, whose only degrees of freedom are boundary gravitons and long strings. We argue that the best regime for describing pure gravity is that of "heavy" strings, for which back-reaction effects on the metric must be taken into account. We show that once back-reaction is properly accounted for, regular finite-energy states are produced by heavy strings even in the infinite-tension limit. Such a process is similar to, but different from, nucleation of space out of a "bubble of nothing."

Twistor/ambitwistor strings and null-superstrings in spacetime of D=4, 10 and 11 dimensions

We show that, at the classical level, the recently proposed `ambitwistor string' model is equivalent to the spinor moving frame formulation of null-supersting, which in its turn is equivalent to Siegel's formulation of closed twistor string or to its higher dimensional generalizations. Although the null-(super)string is usually considered as describing the tensionless limit of (super)string, we show that its action can be derived from the spinor moving frame formulation of superstring also in the infinite tension limit. This observation allows us to argue on the absence of critical dimensions and suggests that the (ambi)twistor string based technique(s) to calculate field theory amplitudes can be developed not only in D=10 or 26, but also in D=11 and other dimensions. The D=11 and D=10 twistor strings are described in some details.

Infinite tension limit of the pure spinor superstring

Mason and Skinner recently constructed a chiral infinite tension limit of the Ramond-Neveu-Schwarz superstring which was shown to compute the Cachazo-He-Yuan formulae for tree-level d=10 Yang-Mills amplitudes and the NS-NS sector of tree-level d=10 supergravity amplitudes. In this letter, their chiral infinite tension limit is generalized to the pure spinor superstring which computes a d=10 superspace version of the Cachazo-He-Yuan formulae for tree-level d=10 super-Yang-Mills and supergravity amplitudes.

Light-cone M5 and multiple M2-branes

We present the light-cone gauge fixed Lagrangian for the M5-brane; it has a residual ‘exotic’ gauge invariance with the group of 5-volume preserving diffeomorphisms, SDiff5, as gauge group. For an M5-brane of topology , for closed 3-manifold M3, we find an infinite tension limit that yields an SO(8)-invariant (1 + 2)-dimensional field theory with ‘exotic’ SDiff3 gauge invariance. We show that this field theory is the Carrollian limit of the Nambu bracket realization of the ‘BLG’ model for multiple M2-branes.

Penrose limits, worldvolume fluxes, and supersymmetry

It is noted that a finite Penrose limit for brane probes with non-zero worldvolume fluxes does not generically exist; this is closely related to the observation by Blau et al that for a brane probe the Penrose limit is equivalent to an infinite-tension limit. It is shown that when the limit exists, however, the number of supersymmetries preserved by the probe does not decrease.

Scalar field theory limits of bosonic string amplitudes

We describe in detail the techniques needed to compute scattering amplitudes for colored scalars from the infinite tension limit of bosonic string theory, up to two loops. These techniques apply both to cubic and quartic interactions, and to planar as well as non-planar diagrams. The resulting field theories are naturally defined in the space-time dimension in which they are renormalizable. With a careful analysis of string moduli space in the Schottky representation we determine the region of integration for the moduli, which plays a crucial role in the derivation of the correct combinatorial and color factors for all diagrams.

Ultraviolet and infrared freedom from string amplitudes

The infinite tension limit of string amplitudes is examined with some care, identifying the part responsible of diamagnetic behaviour as well as a peculiar paramagnetic {\em tachyon magnifying} responsible of asymptotic freedom. The way string theory represents abelian gauge theories is connected with the non-planar reggeon/pomeron amplitude and a nontrivial beta function is found in the low energy limit of a single D-brane.

Consistent off-shell string amplitudes

Based on the covariant loop calculus developed by Di Vecchia et al. and by Petersen et al., we construct consistent, modular-invariant, off-shell closed string amplitudes. Our prescription resolves improper non-localities in the would-be off-shell amplitudes of the covariant loop calculus, thereby eliminating on-shell ambiguities in corners of punctured moduli space and deriving consistent renormalization constant in the infinite-tension limit. We also show that, contrary to expectations, the on-shell limit of the amplitudes in general string models depends on the fixing of the projective freedom inherent in the covariant loop calculus.

New approach to one-loop calculations in gauge theories.

We propose using the technology of four-dimensional string theories to calculate amplitudes in gauge theories. Strings make such calculations much more efficient by summing a large number of Feynman diagrams all at once. We check the idea by constructing a string model reducing to a pure non-Abelian gauge theory in the infinite-tension limit and computing its \ensuremath{\beta} function with these techniques.