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

We explore the qualitative changes that would occur if the amplitude Q ~10^{-5} of cosmological density fluctuations were different. If is less thanabout 10^{-6}, the cosmological objects that form would have so low virialtemperatures that they may be unable to cool and form stars, and would be soloosely bound that even if they could produce a supernova explosion, they mightbe unable to retain the heavy elements necessary for planetary life. If Q isgreater than about 10^{-4}, dense supermassive galaxies would form, andbiological evolution could be marred by short disruption timescales forplanetary orbits. If Q were still larger, most bound systems would collapsedirectly to supermassive black holes. These constraints on Q can be expressedin terms of fundamental constants alone, and depend only on the electromagneticand gravitational coupling constants, the electron-proton mass ratio and thematter-to-photon ratio. We discuss the implications for inflation and defectmodels, and note that the recent anthropic upper bounds on the cosmologicalconstant Lambda would be invalid if both Q and Lambda could vary and there wereno anthropic constraints on Q. The same applies to anthropic bounds on thecurvature parameter Omega.

Why Is the Cosmic Microwave Background Fluctuation Level 10−5?

Why Is the Cosmic Microwave Background Fluctuation Level 10⁻⁵?