44 research outputs found
Phenomenological Aspects of F-theory
Stabilizing a heterotic string vacuum with a large expectation value of the
dilaton and simultaneously breaking low-energy supersymmetry is a long-standing
problem of string phenomenology. We reconsider these issues in light of the
recent developments in F-theory.Comment: 11 pages, phyzzx macro
Aspects of Duality in N=2 String Vacua
We collect further evidence for the proposed duality between heterotic
and type II string vacua in a specific model suggested by Kachru and Vafa. In
the gauge sector the previous analysis is extended; it is further shown that
the duality also holds for the one--loop gravitational couplings to the vector
multiplets
Large-Volume String Compactifications, Revisited
We reconsider the issue of large-volume compactifications of the heterotic
string in light of the recent discoveries about strongly-coupled string
theories. Our conclusion remains firmly negative with respect to classical
compactifications of the ten-dimensional field theory, albeit for a new reason:
When the internal sixfold becomes large in heterotic units, the theory acquires
an additional threshold at energies much less then the naive Kaluza-Klein
scale. It is this additional threshold that imposes the ultimate limit on the
compactification scale: Any compactification must have M_{Kaluza Klein} >
4*10^7 Gev; for most compactifications, the actual limit is much higher.
(Generically, M_{Kaluza Klein} > alpha_{GUT} M_{Planck} in either SO(32) or
E_8*E_8 heterotic string.)Comment: 46 pages, uses phyzzx.tex macros, no figure