FI: SPONTANEOUS CP BREAKING AND THE AXION POTENTIAL: AN EFFECTIVE LAGRANGIAN APPROACH 
 ELENCO COMPLETO 

DATA: 14-09-2017

SEZIONE DI FIRENZE
Seminario Gabriele Veneziano (CERN): Using the well-known low-energy effective Lagrangian of QCD --- valid for small (non-vanishing) quark masses and a large number of colors --- we study in detail the regions of parameter space where CP is spontaneously broken/unbroken for a vacuum angle Ξ = ?. In the CP-broken region there are first order phase transitions as one crosses Ξ = ? , while on the (hyper)surface separating the two regions, there are second order phase transitions signaled by the vanishing of the mass of a pseudo Nambu-Goldstone boson and by a divergent QCD topological susceptibility. The second order point sits at the end of a first order line associated with the CP spontaneous breaking, in the appropriate complex parameter plane. When the effective Lagrangian is extended by the inclusion of an axion these features of QCD imply that standard calculations of the axion potential have to be revised when the QCD parameters fall in the above mentioned CP-broken region, in spite of the fact that the axion solves the strong-CP problem. These latter results could be of interest for axionic dark matter calculations if the topological susceptibility of pure Yang-Mills theory falls off sufficiently fast when temperature is increased towards the QCD deconfining transition.


 SITO COLLEGATO 

 EVENTI RECENTI 
12-12-2019: The charm and beauty of the Little Bang
12-12-2019: Circuit complexity and 2D bosonisation - Dongsheng Ge
12-12-2019: M. Tobar - Precision low energy experiments to test fundamental physics and search for dark matter
12-12-2019: MisuraCC3M@LNL: materiali superconduttivi
11-12-2019: Multiplicity and energy dependence of light charged particle production in ALICE at the LHC
11-12-2019: Double-Logarithmic contribution to Pomeron and application to the photon-photon scattering - Boris Ermolaev
10-12-2019: Dai spazio al tempo
10-12-2019: Machine Learning in High Energy Physics - Tommaso Boccali
09-12-2019: Visita ai laboratori della Sezione INFN di Trieste da parte di studenti del Liceo Scientifico dell' IIS Cattaneo-Dall'Aglio di Castelnovo ne' Monti (RE)
09-12-2019: Properties of nuclei in the N=Z=50 region investigated via multi-nucleon transfer reactions and lifetime measurements - Marco Siciliano

[Back]

 

 

 

Istituto Nazionale di Fisica Nucleare - Piazza dei Caprettari, 70 - 00186 Roma
tel. +39 066840031 - fax +39 0668307924 - email: presidenza@presid.infn.it

F.M. F.E.