Eur. Phys. J. C (2010) 66: 307-324
https://doi.org/10.1140/epjc/s10052-009-1229-2

Regular Article - Theoretical Physics

Cosmological constant in a model with superstring-inspired E ₆ unification and shadow θ-particles

¹ Centre for Theoretical Particle Physics, Technical University of Lisbon, Avenida Rovisco Pais, 1, 1049-001, Lisbon, Portugal
² The Institute of Theoretical and Experimental Physics, Bolshaya Cheremushkinskaya, 25, 117218, Moscow, Russia
³ Department of Physics, University of Helsinki and Helsinki Institute of Physics, P.O. Box 64, 00014, Helsinki, Finland

^* e-mail: anca.tureanu@helsinki.fi

Received: 16 September 2009
Revised: 4 November 2009
Published online: 18 December 2009

Abstract

We have developed the concept of parallel existence of the ordinary (O-) and mirror (M-), or shadow (Sh-) worlds. In the first part of the paper we consider a mirror world with broken mirror parity and the breaking E ₆→SU(3)³ in both worlds. We show that in this case the evolutions of coupling constants in the O- and M-worlds are not identical, having different parameters for similar evolutions. E ₆ unification, inspired by superstring theory, restores the broken mirror parity at the scale ∼10¹⁸ GeV. With the aim to explain the tiny cosmological constant, in the second part we consider the breakings: E ₆→SO(10)×U(1) _Z in the O-world, and E′₆→SU(6)′×SU(2)′ _θ in the Sh-world. We assume the existence of shadow θ-particles and the low-energy symmetry group SU(3)′ _C ×SU(2)′ _L ×SU(2)′ _θ ×U(1)′ _Y in the shadow world, instead of the Standard Model. The additional non-Abelian SU(2)′ _θ group with massless gauge fields, “thetons”, has a macroscopic confinement radius 1/Λ′ _θ . The assumption that Λ′ _θ ≈2.3⋅10⁻³ eV explains the tiny cosmological constant given by recent astrophysical measurements. In this way the present work opens the possibility to specify a grand unification group, such as E ₆, from cosmology.