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

Two independent criteria are presented that together guarantee exponentialsuppression of the two-loop cosmological constant in non-supersymmetricheterotic strings. They are derived by performing calculations in both the fullstring theory and in its underlying effective field theory, and comerespectively from contributions that involve only physical untwisted states,and contributions that include orbifold twisted states. The criteria dependpurely on the spectrum and charges, so a model that satisfies them will do sowith no fine-tuning. An additional consistency condition (emerging from theso-called separating degeneration limit of the two-loop diagram) is that theone-loop cosmological constant must also be suppressed, by Bose-Fermidegeneracy in the massless spectrum. We remark that theories of this kind, thathave continued exponential suppression to higher orders, can form the basis fora string implementation of the "naturalness without supersymmetry" idea.

On exponential suppression of the cosmological constant in non-SUSY strings at two loops and beyond