Axion quality problem and nonminimal gravitational coupling in the Palatini formulation

Palatini formulation of modified gravity with a nonminimal curvature-matter coupling

BROWN HET-1070 Origin of Magnetic Fields in the Universe Due to Nonminimal Gravitational-Electromagnetic Coupling

Basically the only existing theories for the creation of a magnetic field (B) in the Universe are the creation of a seed field ∼ 10 G in spiral galaxy which is subsequently supposedly amplified up to the observed 10—10 G by a dynamo process or a seed intergalactic field of ∼ 10—10 G which is amplified by collapse and differential rotation. No satisfactory dynamo theory, however, exists today. W...

Inflation and quintessence with nonminimal coupling

The nonminimal coupling (NMC) of the scalar field to the Ricci curvature is unavoidable in many cosmological scenarios. Inflation and quintessence models based on nonminimally coupled scalar fields are studied, with particular attention to the balance between the scalar potential and the NMC term ξRφ2/2 in the action. NMC makes acceleration of the universe harder to achieve for the usual potent...

On a Theory for Nonminimal Gravitational-electromagnetic Coupling Consistent with Observational Data

The idea that the seed primordial magnetic fields can be explained by the nonminimal coupling between gravitational and electromagnetic fields is discussed. The predicted values of the magnetic field of the spiral galaxies are in agreement with the observations.

String compactification, QCD axion and axion-photon-photon coupling

It is pointed out that there exist a few problems to be overcome toward an observable sub-meV QCD axion in superstring compactification. We give a general expression for the axion decay constant. For a large domain wall number NDW , the axion decay constant can be substantially lowered from a generic value of a scalar singlet VEV. The Yukawa coupling structure in the recent Z12−I model is studi...