Probing scalar effective field theories with the soft limits of scattering amplitudes

Self Cite

In contrast to internal symmetries, there is no general proof that the coset construction for spontaneously broken spacetime symmetries leads to universal dynamics. One key difference lies in the role of Goldstone bosons, which for spacetime symmetries includes a subset which are inessential for the non-linear realisation and hence can be eliminated. In this paper we address two important issues that arise when eliminating inessential Goldstones.The first concerns the elimination itself, which is often performed by imposing socalled inverse Higgs constraints. Contrary to claims in the literature, there are a series of conditions on the structure constants which must be satisfied to employ the inverse Higgs phenomenon, and we discuss which parametrisation of the coset element is the most effective in this regard. We also consider generalisations of the standard inverse Higgs constraints, which can include integrating out inessential Goldstones at low energies, and prove that under certain assumptions these give rise to identical effective field theories for the essential Goldstones.Secondly, we consider mappings between non-linear realisations that differ both in the coset element and the algebra basis. While these can always be related to each other by a point transformation, remarkably, the inverse Higgs constraints are not necessarily mapped onto each other under this transformation. We discuss the physical implications of this non-mapping, with a particular emphasis on the coset space corresponding to the spontaneous breaking of the Anti-De Sitter isometries by a Minkowski probe brane.

Section: Jhep10(2017)051mentioning

confidence: 99%

Spontaneously broken spacetime symmetries and the role of inessential Goldstones

Klein

Roest

Stefanyszyn

2017

Self Cite

“…3 In the single field case, these are so-called DBI galileons [33] which have interesting behaviour in their soft amplitudes due to the non-linearly realised symmetry [2,5], as mentioned before. 4 Note that we have set the AdS radius L = 1/ √ 2 but will reintroduce it later on.…”

Section: )mentioning

confidence: 85%

“…The AdS basis is useful since the resulting kinetic sector matches the one from embedding Minkowski 3-branes in (4 + n)-dimensional anti-de Sitter space. 5 Again given the discussion in [30], we parametrise the coset element as…”

Section: Jhep06(2018)006mentioning

confidence: 99%

“…4 Note that we have set the AdS radius L = 1/ √ 2 but will reintroduce it later on. 5 We refer the reader to [30,35] for discussions on the physical equivalence of the resulting non-linear realisations with the conformal group defined in these two different bases.…”

Section: )mentioning

confidence: 99%

“…Moreover, there is a unique scalar EFT with a p 3 scaling which consists of a specific combination of scalar Galileons [2,3]. The interplay between symmetries and soft limits therefore enables one to perform an interesting classification of special EFTs, see [4,5].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Symmetry breaking patterns for inflation

Klein

Roest

Stefanyszyn

2018

Self Cite

Abstract:We study inflationary models where the kinetic sector of the theory has a nonlinearly realised symmetry which is broken by the inflationary potential. We distinguish between kinetic symmetries which non-linearly realise an internal or space-time group, and which yield a flat or curved scalar manifold. This classification leads to well-known inflationary models such as monomial inflation and α-attractors, as well as a new model based on fixed couplings between a dilaton and many axions which non-linearly realises higher-dimensional conformal symmetries. In this model, inflation can be realised along the dilatonic direction, leading to a tensor-to-scalar ratio r ∼ 0.01 and a spectral index n s ∼ 0.975. We refer to the new model as ambient inflation since inflation proceeds along an isometry of an anti-de Sitter ambient space-time, which fully determines the kinetic sector.

Soft bootstrap and supersymmetry

Elvang

Hadjiantonis

Jones

et al. 2019

116

174

The soft bootstrap is an on-shell method to constrain the landscape of effective field theories (EFTs) of massless particles via the consistency of the low-energy Smatrix. Given assumptions on the on-shell data (particle spectra, linear symmetries, and low-energy theorems), the soft bootstrap is an efficient algorithm for determining the possible consistency of an EFT with those properties. The implementation of the soft bootstrap uses the recently discovered method of soft subtracted recursion. We derive a precise criterion for the validity of these recursion relations and show that they fail exactly when the assumed symmetries can be trivially realized by independent operators in the effective action. We use this to show that the possible pure (real and complex) scalar, fermion, and vector exceptional EFTs are highly constrained. Next, we prove how the soft behavior of states in a supermultiplet must be related and illustrate the results in extended supergravity. We demonstrate the power of the soft bootstrap in two applications. First, for the N = 1 and N = 2 CP 1 nonlinear sigma models, we show that on-shell constructibility establishes the emergence of accidental IR symmetries. This includes a new on-shell perspective on the interplay between N = 2 supersymmetry, low-energy theorems, and electromagnetic duality. We also show that N = 2 supersymmetry requires 3-point interactions with the photon that make the soft behavior of the scalar O(1) instead of vanishing, despite the underlying symmetric coset. Second, we study Galileon theories, including aspects of supersymmetrization, the possibility of a vector-scalar Galileon EFT, and the existence of higher-derivative corrections preserving the enhanced special Galileon symmetry. The latter is addressed both by soft bootstrap and by application of double-copy/KLT relations applied to higher-derivative corrections of chiral perturbation theory. arXiv:1806.06079v2 [hep-th]