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 Tools annual

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 monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

There has been considerable interest in recent years in cosmological modelsin which we inhabit a very large, underdense void as an alternative to darkenergy. A longstanding objection to this proposal is that observations limitour position to be very close to the void centre. By selecting from a family ofvoid profiles that fit supernova luminosity data, we carefully determine howfar from the centre we could be. To do so, we use the observed dipole componentof the cosmic microwave background, as well as an additional stochasticpeculiar velocity arising from primordial perturbations. We find that we areconstrained to live within 80 Mpc of the centre of a void--a somewhat weakerconstraint than found in previous studies, but nevertheless a strong violationof the Copernican principle. By considering how such a Gpc-scale void wouldappear on the microwave sky, we also show that there can be a maximum of one ofthese voids within our Hubble radius. Hence, the constraint on our positioncorresponds to a fraction of the Hubble volume of order 10^{-8}. Finally, weuse the fact that void models only look temporarily similar to acosmological-constant-dominated universe to argue that these models are notfree of temporal fine-tuning.

Spatial and temporal tuning in void models for acceleration