9,261 research outputs found
Compactified String Theories -- Generic Predictions for Particle Physics
In recent years it has been realized that in string/ theories compactified
to four dimensions which satisfy cosmological constraints, it is possible to
make some generic predictions for particle physics and dark matter: a
non-thermal cosmological history before primordial nucleosynthesis, a scale of
supersymmetry breaking which is "high" as in gravity mediation, scalar
superpartners too heavy to be produced at the LHC (although gluino production
is expected in many cases), and a significant fraction of dark matter in the
form of axions. When the matter and gauge spectrum below the compactification
scale is that of the MSSM, a robust prediction of about 125 GeV for the Higgs
boson mass, predictions for various aspects of dark matter physics, as well as
predictions for future precision measurements, can be made. As a prototypical
example, theory compactified on a manifold of holonomy leads to a
good candidate for our "string vacuum", with the TeV scale emerging from the
Planck scale, a de Sitter vacuum, robust electroweak symmetry breaking, and
solutions of the weak and strong CP problems. In this article we review how
these and other results were derived, from the key theoretical ideas to the
final phenomenological predictions.Comment: 30 pages, 1 figure. Invited Review for International Journal of
Modern Physics
On Mirror Symmetry for Manifolds of Exceptional Holonomy
We consider Type II string theories on Joyce
orbifolds. This class contains orbifolds which can be desingularised to give
manifolds of and holonomy .
In the holonomy case we present two types of -duality transformation
which are clearly generalisations of the -duality/mirror transformation in
Calabi-Yau spaces. The first maps Type IIA theory on one such space from this
class to Type IIB theory on another such space. The second maps Type IIA (IIB)
to Type IIA (IIB). In the case of holonomy we present a -duality
transformation which maps Type IIA (IIB) theory on one such space to Type IIA
(IIB) on another such space. As orbifold conformal field theories these
-dual target spaces are related via the inclusion/exclusion of discrete
torsion and the -duality is proven to genus in string perturbation
theory. We then apply a Strominger, Yau, Zaslow type argument which suggests
that manifolds of holonomy which have a ``mirror'' of the first (second)
type admit supersymmetric () fibrations and that
manifolds of holonomy for which a mirror exists admit fibration by
supersymmetric -tori. Further evidence for this suggestion is given by
examining the moduli space structure of wrapped D-branes.Comment: 20 Pages, Late
A Non-thermal WIMP Miracle
Light scalar fields with only gravitational strength couplings are typically
present in UV complete theories of physics beyond the Standard Model. In the
early universe it is natural for these fields to dominate the energy density,
and their subsequent decay, if prior to BBN, will typically yield some dark
matter particles in their decay products. In this paper we make the observation
that a Non-thermal WIMP `Miracle' may result: that is, in the simplest solution
to the cosmological moduli problem, non-thermally produced WIMPs can naturally
account for the observed dark matter relic density. Such a solution may be
generic in string theory compactifications.Comment: 6 pages, no figures, References added, minor errors correcte
Characteristics of Youth Dating Violence and Risk Factors in Mexico: An Analysis From a National Sample
Dating violence is a significant issue affecting today’s youth and can affect anyone regardless of age, gender, ethnicity, socioeconomic, racial, and religious backgrounds, and it occurs in heterosexual, gay, and lesbian relationships. This study examines and identifies the different types of dating violence, and their associated risk factors in Mexico considering the data from a national sample. In 2007, the National Institute of Statistics, Geography and Information (INEGI) conducted a nationwide survey of youth (15-24 years old), to address the problem of dating violence among these demographic group. The survey was conducted in all 32 states of Mexico, which included 4,147 males and 3,807 females. Results indicate that young females in Mexico suffered different types of dating violence from their counterpart. It also found that dating violence has a greater impact on the health status of girls. In addition, this study shows that dating violence has led many young females toward substance abuse
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