Orientifolds

For example, one of the simplest ways around the old “no go” arguments for de Sitter space is to take into account the positive term in the moduli potential that arises in supercritical dimensionality (combined with other ingredients such as orientifolds and RR fluxes). ❋ Sean (2006)

There was a no-go theorem (Maldacena-Nunez) showing that starting with higher dimensional theory, one cannot obtain deSitter vacua without invoking elements unique to string theory (e.g orientifolds). ❋ Sean (2007)

F-theoretical flux vacua i.e. type IIB vacua with non-trivial axion-dilaton fields, orientifolds, and D-branes. ❋ Unknown (2010)

Ibáňez reviewed the MSSM landscape, Weigand included orientifolds, Donagi looked at the High ❋ Unknown (2010)

Now, yes, topological strings also exhibit tadpole cancellation: A-model and B-model can only be decoupled from one another if the total charge is canceled between the D-branes and orientifolds. ❋ Unknown (2010)

He will look at top. strings on compact Calabi-Yaus with both D-branes and orientifolds. ❋ Unknown (2010)

By now, we've included D-branes but orientifolds are needed to cancel the tadpoles. ❋ Unknown (2010)

The expansion coefficients are integers iff you cancel the tadpoles between orientifolds and crosscaps (not an obvious relationship). ❋ Unknown (2010)

If we could look at the universe through a super-powerful microscope, we would see that it is composed of "Tinkertoy" elements called fluxes, branes, moduli, orientifolds (and more) all arranged on a tiny knot of higher-dimensional space called a Calabi-Yau manifold. ❋ Unknown (2009)