(abbreviated) We study quantized solutions of WdW equation describing a closed FRW universe with a $Lambda $ term and a set of massless scalar fields. We show that when $Lambda ll 1$ in the natural units and the standard $in$-vacuum state is consider
ed, either wavefunction of the universe, $Psi$, or its derivative with respect to the scale factor, $a$, behave as random quasi-classical fields at sufficiently large values of $a$, when $1 ll a ll e^{{2over 3Lambda}}$ or $a gg e^{{2over 3Lambda}}$, respectively. Statistical r.m.s value of the wavefunction is proportional to the Hartle-Hawking wavefunction for a closed universe with a $Lambda $ term. Alternatively, the behaviour of our system at large values of $a$ can be described in terms of a density matrix corresponding to a mixed state, which is directly determined by statistical properties of $Psi$. It gives a non-trivial probability distribution over field velocities. We suppose that a similar behaviour of $Psi$ can be found in all models exhibiting copious production of excitations with respect to $out$-vacuum state associated with classical trajectories at large values of $a$. Thus, the third quantization procedure may provide a boundary condition for classical solutions of WdW equation.
In many models, stability of dark matter particles is protected by a conserved Z_2 quantum number. However dark matter can be stabilized by other discrete symmetry groups, and examples of such models with custom-tailored field content have been propo
sed. Here we show that electroweak symmetry breaking models with N Higgs doublets can readily accommodate scalar dark matter candidates stabilized by groups Z_p with any $p le 2^{N-1}$, leading to a variety of kinds of microscopic dynamics in the dark sector. We give examples in which semi-annihilation or multiple semi-annihilation processes are allowed or forbidden, which can be especially interesting in the case of asymmetric dark matter.
N-Higgs doublet models (NHDM) are a popular framework to construct electroweak symmetry breaking mechanisms beyond the Standard model. Usually, one builds an NHDM scalar sector which is invariant under a certain symmetry group. Although several such
groups have been used, no general analysis of symmetries possible in the NHDM scalar sector exists. Here, we make the first step towards this goal by classifying the elementary building blocks, namely the abelian symmetry groups, with a special emphasis on finite groups. We describe a strategy that identifies all abelian groups which are realizable as symmetry groups of the NHDM Higgs potential. We consider both the groups of Higgs-family transformations only and the groups which also contain generalized CP transformations. We illustrate this strategy with the examples of 3HDM and 4HDM and prove several statements for arbitrary N.
We critically re-examine the calculation of central production of dijets in quasi-elastic hadronic collisions. We find that the process is not dominated by the perturbative contribution, and discuss several sources of uncertainties in the calculation.
The idea of the vector dominance is still in use in various analyses of experimental data of photon-hadron reactions. It makes sense, therefore, to recast results of microscopic calculations of such reactions in this language. Here we present the dif
fractive DIS $rho_3$ production as a specific correction to the generalized vector dominance. We perform a coupled channel analysis of spin-orbital excitations in diffractive photoproduction and reiterate the point that rho_3 in diffractive DIS will be sensitive to a novel aspect of diffraction.
