A new covariant foliation-based construction of scalar-tensor theories up to four derivatives of the scalar field that extends DHOST and U-DHOST without unitary gauge and propagates three degrees of freedom.
"Shadowy" modes in Higher-Order Scalar-Tensor theories
4 Pith papers cite this work. Polarity classification is still indexing.
4
Pith papers citing it
abstract
We consider Higher-Order Scalar-Tensor theories which appear degenerate when restricted to the unitary gauge but are not degenerate in an arbitrary gauge. We dub them U-degenerate theories. We provide a full classification of theories that are either DHOST or U-degenerate and that are quadratic in second derivatives of the scalar field, and discuss its extension to cubic and higher order theories. Working with a simple example of U-degenerate theory, we find that, for configurations in which the scalar field gradient is time-like, the apparent extra mode in such a theory can be understood as a generalized instantaneous, or "shadowy" mode, which does not propagate. Appropriate boundary conditions, required by the elliptic nature of part of the equations of motion, lead to the elimination of the apparent instability associated with this extra mode.
citation-role summary
background 1
citation-polarity summary
roles
background 1polarities
background 1representative citing papers
Extends the stochastic inflation formalism to a wide class of scalar-tensor theories by mapping EFT of dark energy coefficients to stochastic equations of motion.
Requiring stealth Schwarzschild and de Sitter solutions in quadratic/cubic scalar-tensor theories eliminates odd-parity deviations from GR when all solutions are required, while allowing some deviations and non-trivial GW speeds in less restrictive cases.
Reconstruction of EFT background functions from cosmic chronometer Hubble data allows model-independent tests of dark energy evolution in scalar-tensor theories.
citing papers explorer
-
Covariant scalar-tensor theories beyond second derivatives
A new covariant foliation-based construction of scalar-tensor theories up to four derivatives of the scalar field that extends DHOST and U-DHOST without unitary gauge and propagates three degrees of freedom.
-
Stochastic scalar-tensor inflation and beyond
Extends the stochastic inflation formalism to a wide class of scalar-tensor theories by mapping EFT of dark energy coefficients to stochastic equations of motion.
-
Inverting no-hair theorems: How requiring General Relativity solutions restricts scalar-tensor theories
Requiring stealth Schwarzschild and de Sitter solutions in quadratic/cubic scalar-tensor theories eliminates odd-parity deviations from GR when all solutions are required, while allowing some deviations and non-trivial GW speeds in less restrictive cases.
-
EFT of Dark Energy with Cosmic Chronometers: Reconstructing Background EFT Functions
Reconstruction of EFT background functions from cosmic chronometer Hubble data allows model-independent tests of dark energy evolution in scalar-tensor theories.