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

Alternative cosmologies, based on extensions of General Relativity, predictmodified thermal histories in the Early Universe during the pre Big BangNucleosynthesis (BBN) era, epoch which is not directly constrained bycosmological observations. When the expansion rate is enhanced with respect tothe standard case, thermal relics typically decouple with larger relicabundances. The correct value of the relic abundance is therefore obtained forlarger annihilation cross--sections, as compared to standard cosmology. Adirect consequence is that indirect detection rates are enhanced. Extendingprevious analyses of ours, we derive updated astrophysical bounds on the darkmatter annihilation cross sections and use them to constrain alternativecosmologies in the pre--BBN era. We also determine the characteristics of thesealternative cosmologies in order to provide the correct value of relicabundance for a thermal relic for the (large) annihilation cross--sectionrequired to explain the PAMELA results on the positron fraction, thereforeproviding a "cosmological boost" solution to the dark matter interpretation ofthe PAMELA data.

Thermal Relics in Modified Cosmologies: Bounds on Evolution Histories of the Early Universe and Cosmological Boosts for PAMELA