10 research outputs found
The B-L/Electroweak Hierarchy in Smooth Heterotic Compactifications
E8 X E8 heterotic string and M-theory, when appropriately compactified, can
give rise to realistic, N=1 supersymmetric particle physics. In particular, the
exact matter spectrum of the MSSM, including three right-handed neutrino
supermultiplets, one per family, and one pair of Higgs-Higgs conjugate
superfields is obtained by compactifying on Calabi-Yau manifolds admitting
specific SU(4) vector bundles. These "heterotic standard models" have the
SU(3)_{C} X SU(2)_{L} X U(1)_{Y} gauge group of the standard model augmented by
an additional gauged U(1)_{B-L}. Their minimal content requires that the B-L
gauge symmetry be spontaneously broken by a vacuum expectation value of at
least one right-handed sneutrino. In a previous paper, we presented the results
of a renormalization group analysis showing that B-L gauge symmetry is indeed
radiatively broken with a B-L/electroweak hierarchy of O(10) to O(10^{2}). In
this paper, we present the details of that analysis, extending the results to
include higher order terms in tan[beta]^{-1} and the explicit spectrum of all
squarks and sleptons.Comment: 60 pages, 6 figure
Wilson Lines and a Canonical Basis of SU(4) Heterotic Standard Models
The spontaneous breaking of SU(4) heterotic standard models by Z_3 x Z_3
Wilson lines to the MSSM with three right-handed neutrino supermultiplets and
gauge group SU(3)_C x SU(2)_L x U(1) x U(1) is explored. The two-dimensional
subspace of the Spin(10) Lie algebra that commutes with su(3)_C + su(2)_L is
analyzed. It is shown that there is a unique basis for which the initial soft
supersymmetry breaking parameters are uncorrelated and for which the U(1) x
U(1) field strengths have no kinetic mixing at any scale. If the Wilson lines
"turn on" at different scales, there is an intermediate regime with either a
left-right or a Pati-Salam type model. We compute their spectra directly from
string theory, and adjust the associated mass parameter so that all gauge
parameters exactly unify. A detailed analysis of the running gauge couplings
and soft gaugino masses is presented.Comment: 59 pages, 9 figure
Numerical Hermitian Yang-Mills Connections and Vector Bundle Stability in Heterotic Theories
A numerical algorithm is presented for explicitly computing the gauge
connection on slope-stable holomorphic vector bundles on Calabi-Yau manifolds.
To illustrate this algorithm, we calculate the connections on stable monad
bundles defined on the K3 twofold and Quintic threefold. An error measure is
introduced to determine how closely our algorithmic connection approximates a
solution to the Hermitian Yang-Mills equations. We then extend our results by
investigating the behavior of non slope-stable bundles. In a variety of
examples, it is shown that the failure of these bundles to satisfy the
Hermitian Yang-Mills equations, including field-strength singularities, can be
accurately reproduced numerically. These results make it possible to
numerically determine whether or not a vector bundle is slope-stable, thus
providing an important new tool in the exploration of heterotic vacua.Comment: 52 pages, 15 figures. LaTex formatting of figures corrected in
version 2
Higgs Multiplets in Heterotic GUT Models
For supersymmetric GUT models from heterotic string theory, built from a
stable holomorphic SU(n) vector bundle on a Calabi-Yau threefold , the
net amount of chiral matter can be computed by a Chern class computation.
Corresponding computations for the number of Higgses lead for the
phenomenologically relevant cases of GUT group SU(5) or SO(10) to consideration
of the bundle \La^2 V. In a class of bundles where everything can be computed
explicitly (spectral bundles on elliptic ) we find that the computation for
gives a result which is in conflict with expectations. We argue that this
discrepancy has its origin in the subtle geometry of the spectral data for
\La^2 V and that taking this subtlety into account properly should resolve
the problem.Comment: 29 pages; comments and references adde
Moduli restriction and Chiral Matter in Heterotic String Compactifications
Supersymmetric heterotic string models, built from a stable holomorphic
vector bundle on a Calabi-Yau threefold , usually come with many vector
bundle moduli whose stabilisation is a difficult and complex task. It is
therefore of interest to look for bundle constructions which, from the outset,
have as few as possible bundle moduli. One way to reach such a set-up is to
start from a generic construction and to make discrete modifications of it
which are available only over a subset of the bundle moduli space. Turning on
such discrete 'twists' constrains the moduli to the corresponding subset of
their moduli space: the twisted bundle has less parametric freedom. We give an
example of a set-up where this idea can be considered concretely. Such
non-generic twists lead also to new contributions of chiral matter (which
greatly enhances the flexibility in model building); their computation
constitutes the main issue of this note.Comment: 37 pages; comments and references adde
Searching for the Standard Model in the String Landscape : SUSY GUTs
The goal of the present review article is to describe the ingredients
necessary to find the Standard Model in the string landscape.Comment: 70 pages, 20 figures, this review article will be published in
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