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

From the "top-down" approach we investigate physics implications of the classof D- and F- flat directions formed from non-Abelian singlets which are provenflat to all orders in the nonrenormalizable superpotential, for a prototypequasi-realistic free fermionic string model with the standard model gauge groupand three families (CHL5). These flat directions have at least an additionalU(1)' unbroken at the string scale. For each flat direction, the complete setof effective mass terms and effective trilinear superpotential terms in theobservable sector are computed to all orders in the VEV's of the fields in theflat direction. The "string selection-rules" disallow a large number ofcouplings allowed by gauge invariance, resulting in a massless spectrum with alarge number of exotics, in most cases excluded by experiment, thus signifyinga generic flaw of these models. Nevertheless, the resulting trilinear couplingsof the massless spectrum possess a number of interesting features which weanalyse for two representative flat directions: for the fermion texture;baryon- and lepton-number violating couplings; R-parity breaking; non-canonicalmu terms; and the possibility of electroweak and intermediate scale symmetrybreaking scenarios for U(1)'. The gauge coupling predictions are obtained inthe electroweak scale case. Fermion masses possess t-b and tau-mu universality,with the string scale Yukawa couplings g and $g/\sqrt{2}$, respectively.Fermion textures are present for certain flat directions, but only in thedown-quark sector. Baryon- and lepton- number violating couplings can triggerproton-decay, $N-{\bar N}$ oscillations, leptoquark interactions and R-parityviolation, leading to the absence of a stable LSP.Comment: 36 pages, 5 tables, 4 figures, RevTeX, minor change

Physics implications of flat directions in free fermionic superstring models. I. Mass spectrum and couplings