The Cosmological Phonon: Symmetries and Amplitudes on Sub-Horizon Scales
arXiv:2005.12937 · doi:10.1007/JHEP11(2020)097
Abstract
In contrast to massless spinning particles, scalars are not heavily constrained by unitarity and locality. Off-shell, no gauge symmetries are required to write down manifestly local theories, while on-shell consistent factorisation is trivial. Instead a useful classification scheme for scalars is based on the symmetries they can non-linearly realise. Motivated by the breaking of Lorentz boosts in cosmology, in this paper we classify the possible symmetries of a shift-symmetric scalar that is assumed to non-linearly realise Lorentz boosts as, for example, in the EFT of inflation. Our classification method is algebraic; guided by the coset construction and inverse Higgs constraints. We rediscover some known phonon theories within the superfluid and galileid classes, and discover a new galileid theory which we call the . Generic galileids correspond to the broken phase of galileon scalar EFTs and our extended galileids correspond to special subsets where each galileon coupling is fixed by an additional symmetry. We discuss the broken phase of theories that also admit a perturbation theory around Poincaré invariant vacua and we show that the so-called exceptional EFTs, the DBI scalar and special galileon, do not admit such a broken phase. Concentrating on DBI we provide a detailed account of this showing that the scattering amplitudes are secretly Poincaré invariant when the theory is expanded around the superfluid background used in the EFT of inflation. We point out that DBI is an exception to the common lore that the residue of the total energy pole of cosmological correlators is proportional to the amplitude. We also discuss the inevitability of poles in scattering amplitudes when boost are spontaneously broken meaning that such theories do not admit Adler zeros and generalisations even in the presence of a shift symmetry.
arXiv comment45 pages, 6 Figures, 3 Tables
References in corpus (63)
- The galileon as a local modification of gravity
- Resummation of Massive Gravity
- The Effective Field Theory of Inflation
- Theoretical Aspects of Massive Gravity
- DBI in the Sky
- Ghost Condensation and a Consistent Infrared Modification of Gravity
- G-inflation: inflation driven by the Galileon field
- Classical and Quantum Consistency of the DGP Model
- On graviton non-Gaussianities during inflation
- Galilean Genesis: an alternative to inflation
- Galileon inflation
- Solid Inflation
- DBI and the Galileon reunited
- Cuscuton: A Causal Field Theory with an Infinite Speed of Sound
- Effective Field Theories from Soft Limits
- Conformal consistency relations for single-field inflation
- Equilateral Non-Gaussianity and New Physics on the Horizon
- On-Shell Recursion Relations for Effective Field Theories
- New Recursion Relations and a Flat Space Limit for AdS/CFT Correlators
- A Periodic Table of Effective Field Theories
- Relativistic Fluids, Superfluids, Solids and Supersolids from a Coset Construction
- A formal introduction to Horndeski and Galileon theories and their generalizations
- Consistency Conditions on the S-Matrix of Massless Particles
- An Infinite Set of Ward Identities for Adiabatic Modes in Cosmology
- Semiclassics, Goldstone Bosons and CFT data
- Signs of Analyticity in Single-Field Inflation
- Galileons as Wess-Zumino Terms
- A Hidden Symmetry of the Galileon
- Soft Bootstrap and Supersymmetry
- Low-Energy Quantum Effective Action for Relativistic Superfluids
- Weakly Broken Galileon Symmetry
- Higher-spin massless S-matrices in four-dimensions
- On the CFT Operator Spectrum at Large Global Charge
- Galileon Duality
- (Re-)Inventing the Relativistic Wheel: Gravity, Cosets, and Spinning Objects
- Soft Theorems For Shift-Symmetric Cosmologies
- Spontaneous Symmetry Probing
- Shift Symmetries in (Anti) de Sitter Space
- On the Symmetries of Cosmological Perturbations
- Aspects of Galileon Non-Renormalization
- Massive Higher Spins: Effective Theory and Consistency
- A Model Independent Ultraviolet Cutoff for Theories with Charged Massive Higher Spin Fields
- Low-energy effective field theory for finite-temperature relativistic superfluids
- The Effective Theory of Shift-Symmetric Cosmologies
- Inflation at the Tip
- Nonlinear realizations of symmetries and unphysical Goldstone bosons
- Unification of Galileon Dualities
- Goldstones with Extended Shift Symmetries
- Rotating superfluids and spinning charged operators in conformal field theory
- Inflation in Motion: Unitarity Constraints in Effective Field Theories with Broken Lorentz Symmetry
- Lie-algebraic classification of effective theories with enhanced soft limits
- Symmetric Superfluids
- Probing Scalar Effective Field Theories with the Soft Limits of Scattering Amplitudes
- New structures in scattering amplitudes: a review
- An Algebraic Classification of Exceptional EFTs
- Spontaneously Broken Spacetime Symmetries and the Role of Inessential Goldstones
- Solid Soft Theorems
- Symmetric Scalars
- Weinberg Soft Theorems from Weinberg Adiabatic Modes
- UV Constraints on Massive Spinning Particles: Lessons from the Gravitino
- First Sound in Holographic Superfluids at Zero Temperature
- An Algebraic Classification of Exceptional EFTs Part II: Supersymmetry
- ISO(4,1) Symmetry in the EFT of Inflation
Cited by in corpus (19)
- Building a Boostless Bootstrap for the Bispectrum
- Linking the Singularities of Cosmological Correlators
- From Locality and Unitarity to Cosmological Correlators
- The Boostless Bootstrap: Amplitudes without Lorentz boosts
- Cosmological Bootstrap in Slow Motion
- Bootstrapping Large Graviton non-Gaussianities
- Amplitudes meet Cosmology: A (Scalar) Primer
- Steinmann Relations and the Wavefunction of the Universe
- Positivity Bounds without Boosts
- Cosmological Correlators Through the Looking Glass: Reality, Parity, and Factorisation
- On Graviton non-Gaussianities in the Effective Field Theory of Inflation
- Enhanced Soft Limits in de Sitter Space
- Soft limits of the wavefunction in exceptional scalar theories
- Perturbative unitarity bounds from momentum-space entanglement
- Inflationary Adler Conditions
- Soft theorems for boosts and other time symmetries
- Soft Phonon Theorems
- Fractional soft limits
- Bispectrum Islands