Phenomenology of nonstandard embedding and five-branes in M theory - art. no. 016001

We study the phenomenology of the strong-coupling limit of E-8 x E-8 hetero tic string obtained from M theory, using Calabi-Yau compactification. After summarizing the standard embedding results, we concentrate on nonstandard embedding vacua as well as vacua when nonperturbative objects such as five- branes are present. We analyze in detail the different scales of the theory , 11-dimensional Planck mass, compactification scale, and orbifold scale, a nd how they are related taking into account higher-order corrections. To ob tain the phenomenologically favored GUT scale is easier than in standard em bedding vacua. To lower this scale to intermediate (approximate to 10(11) G eV) or 1 TeV values or to obtain the radius of the orbifold as large as a m illimeter is possible. However, we point out that these special limits are unnatural. Finally, we perform a systematic analysis of the soft supersymme try-breaking terms. We point out that scalar masses larger than gaugino mas ses can easily be obtained unlike the standard embedding case and weakly co upled heterotic string.