Neutrinoless double-beta decay, which is a very old and yet elusive process, is reviewed. Its
observation will signal that the lepton number is not conserved and that the neutrinos are …

The dark matter in the universe can be in the form of a superheavy matter species
(wimpzilla). Several mechanisms have been proposed for the production of wimpzilla …

We consider the universal extra dimensions scenario of Appelquist, Cheng, and Dobrescu,
in which all of the standard model fields propagate into one extra compact dimension …

It has been suggested recently that self-interacting dark matter (SIDM) fits better the
observational characteristics of galaxy dynamics. We propose that the SIDM is composed …

The first particle physics observable whose origin may be sought in string theory is the triple
replication of the matter generations. The class of Z2× Z2 orbifolds of six-dimensional …

Free fermionic construction of four-dimensional string vacua, are related to the Z2× Z2
orbifolds at special points in the moduli space, and yielded the most realistic three family …

This chapter is an introduction to the Free Fermionic Formulation of string theory, with
emphasis on heterotic model building. After a brief review of bosonization in two …

A bstract Genetic Algorithms are introduced as a search method for finding string vacua with
viable phenomenological properties. It is shown, by testing them against a class of Free …

Recently it was demonstrated that free fermionic heterotic strings can produce models with
solely the minimal supersymmetric standard model states in the low energy spectrum. This …

We continue the classification of the fermionic Z2× Z2 heterotic string vacua with symmetric
internal shifts. The space of models is spanned by working with a fixed set of boundary …