English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Gravitational Wave (GW) astronomy severely narrowed down the theoreticalspace for scalar-tensor theories. We propose a new class of attractor modelsfor Horndeski action in which GWs propagate at the speed of light in the nearbyuniverse but not in the past. To do so we derive new solutions to theinteracting dark sector in which the ratio of dark energy and dark matterremains constant, which we refer to as doppelg\"anger dark energy (DDE). Wethen remove the interaction between dark matter and dark energy by a suitablechange of variables. The accelerated expansion that (we) baryons observe is dueto a conformal coupling to the dark energy scalar field. We show how in thiscontext it is possible to find a non trivial subset of solutions in which GWspropagate at the speed of light only at low red-shifts. The model is anattractor, thus reaching the limit $c_{T}\to1$ relatively fast. However, theeffect of baryons turns out to be non-negligible and severely constrains theform of the Lagrangian. In passing, we found that in the simplest DDE modelsthe no-ghost conditions for perturbations require a non-universal coupling togravity. In the end, we comment on possible ways to solve the lack of matterdomination stage for DDE models.

Doppelg\"anger dark energy: modified gravity with non-universal couplings after GW170817