Related papers: A Note on a Standard Embedding on Half-Flat Manifo…
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…
It is shown that many of the conjectured dualities involving orbifold compactification of M-theory follow from the known dualities involving M-theory and string theory in ten dimensions, and the ansatz that orbifolding procedure commutes…
In this paper we consider Type I string theory compactified on a Z_7 orbifold. The model has N=1 supersymmetry, a U(4) \otimes U(4) \otimes U(4) \otimes SO(8) gauge group, and chiral matter. There are only D9-branes (for which we discuss…
We study the minimal supersymmetric standard model derived from the $Z_8$ orbifold models and its hidden sectors. We use a target-space duality anomaly cancellation so as to investigate hidden sectors consistent with the MSSM unification.…
We work in the smooth category. Let $N$ be a closed connected orientable 4-manifold with torsion free $H_1$, where $H_q:=H_q(N;Z)$. Our main result is a complete readily calculable classification of embeddings $N\to R^7$, up to the…
Following a recent suggestion by Randall and Sundrum, we consider string compactification scenarios in which a compact slice of AdS-space arises as a subspace of the compactification manifold. A specific example is provided by the type II…
Recently spatially localized anomalies have been considered in higher dimensional field theories. The question of the quantum consistency and stability of these theories needs further discussion. Here we would like to investigate what…
In this paper we initiate a broad study of some central properties of the string axiverse arising from Calabi-Yau compactifications of the perturbative heterotic $E_8\times E_8$ theory. Along this road toward a heterotic axiverse, we…
Spacetime theories obtained from perturbative string theory constructions are automatically free of perturbative anomalies, but it is not settled whether they are always free of global anomalies. Here we discuss a possible…
We study two phases of a heterotic standard model, obtained from a Calabi-Yau compactification of the E8xE8 heterotic string, in the context of the associated four-dimensional effective theories. In the first phase we have a standard model…
We study quantum effects in five dimensions in heterotic superstring theory compactified on K_3 x S_1 and analyze the conjecture that its dual effective theory is eleven-dimensional supergravity compactified on a Calabi-Yau threefold. This…
At the leading order, M-theory admits minimal supersymmetric compactifications if the internal manifold has exceptional holonomy. The inclusion of non-vanishing fluxes in M-theory and string theory compactifications induce a superpotential…
We consider $G_2$-structures with torsion coupled with $G_2$-instantons, on a compact $7$-dimensional manifold. The coupling is via an equation for $4$-forms which appears in supergravity and generalized geometry, known as the Bianchi…
Seven-manifolds of G_2 holonomy provide a bridge between M-theory and string theory, via Kaluza-Klein reduction to Calabi-Yau six-manifolds. We find first-order equations for a new family of G_2 metrics D_7, with S^3\times S^3 principal…
We construct more dual pairs of type II-heterotic strings in four dimensions with $N=2,1$ spacetime supersymmetry. On the type II side the construction utilizes the various possible choices of K3 automorphisms with fixed points which…
In M-theory on $S^1/Z_2$, we point out that to be consistant, we should keep the scale, gauge couplings and soft terms at next order, and obtain the soft term relations: $M_{1/2} = -A$, $|{{M_{0}}/{M_{1/2}}}| \leq {1/{\sqrt 3}}$ in the…
A review of orbifold geometry is given, followed by a review of the construction of four-dimensional heterotic string models by compactification on a six-dimensional Z_3 orbifold. Particular attention is given to the details of the…
Inequivalent standard-like observable sector embeddings in $Z_3$ orbifolds with two discrete Wilson lines, as determined by Casas, Mondragon and Mu\~noz, are completed by examining all possible ways of embedding the hidden sector. The…
Localization properties of fields in compact extra dimensions are crucial ingredients for string model building, particularly in the framework of orbifold compactifications. Realistic models often require a slight deviation from the…
In this work we provide a self-contained and modern introduction to some of the tools, obstacles and open questions arising in string compactifications. Techniques and current progress are illustrated in the context of smooth heterotic…