Can Cosmological Constant be a Forbidden Zone (GAP) in Quantum Vacuum
  In this work we suggest, without detailed mathematical analysis, a hypothesis on the physical meaning of cosmological constant. It is primarily based on a conceptual analogy with energy characteristics of the crystal lattice structure, i.e. energy zones theory in solid state physics. Namely, according to some theories (holographic principle, emergent gravity etc.) it is supposed that empty space, i.e. quantum vacuum holds a structure like to crystal lattice. It implies a possibility of the existence of totally occupied zones consisting of many levels of the negative energies as well as at least one negative energy forbidden zone, i.e. negative energy gap without any (occupied or empty) level of the negative energy. We suppose that given negative energy forbidden zone in the quantum vacuum represents effectively a positive energy zone without quantum particles that corresponds to cosmological constant. Also we suggest some other (less extravagant) model of the cosmological constant. Here cosmological constant is usually considered as the effect of the quantum vacuum fluctuations where problem of the cut-off can be solved quite simply since here integration over unlimited domain of the quasi-momentums must be changed by integration over one, finite "Brillouin zone". 
Vladan Pankovic, Rade Glavatovic, Simo Ciganovic