3,941 research outputs found

### Branes at angles and calibrated geometry

In a recent paper, Ohta and Townsend studied the conditions which must be
satisfied for a configuration of two intersecting M5-branes at angles to be
supersymmetric. In this paper we extend this result to any number of M5-branes
or any number of M2-branes. This is accomplished by interpreting their results
in terms of calibrated geometry, which is of independent interest.Comment: 16 pages, LaTeX2e (Minor correction in next to last paragraph of
section 5.2

### Planes, branes and automorphisms: I. Static branes

This is the first of a series of papers devoted to the group-theoretical
analysis of the conditions which must be satisfied for a configuration of
intersecting M5-branes to be supersymmetric. In this paper we treat the case of
static branes. We start by associating (a maximal torus of) a different
subgroup of Spin(10) with each of the equivalence classes of supersymmetric
configurations of two M5-branes at angles found by Ohta & Townsend. We then
consider configurations of more than two intersecting branes. Such a
configuration will be supersymmetric if and only if the branes are G-related,
where G is a subgroup of Spin(10) contained in the isotropy of a spinor. For
each such group we determine (a lower bound for) the fraction of the
supersymmetry which is preserved. We give examples of configurations consisting
of an arbitrary number of non-coincident intersecting fivebranes with
fractions: 1/32, 1/16, 3/32, 1/8, 5/32, 3/16 and 1/4, and we determine the
resulting (calibrated) geometry.Comment: 26 pages (Added a reference and modified one table slightly.

### Kahler Independence of the G2-MSSM

The G2-MSSM is a model of particle physics coupled to moduli fields with
interesting phenomenology both for colliders and astrophysical experiments. In
this paper we consider a more general model - whose moduli Kahler potential is
a completely arbitrary G2-holonomy Kahler potential and whose matter Kahler
potential is also more general. We prove that the vacuum structure and spectrum
of BSM particles is largely unchanged in this much more general class of
theories. In particular, gaugino masses are still supressed relative to the
gravitino mass and moduli masses. We also consider the effects of higher order
corrections to the matter Kahler potential and find a connection between the
nature of the LSP and flavor effects.Comment: Final version, matches the version published in JHE

### Heterotic strings on G_2 orbifolds

We study compactification of heterotic strings to three dimensions on
orbifolds of G_2 holonomy. We consider the standard embedding and show that the
gauge group is broken from E_8 x E_8 or SO(32) to F_4 x E_8 or SO(25)
respectively. We also compute the spectrum of massless states and compare with
the results obtained from reduction of the 10-dimensional fields. Non-standard
embeddings are discussed briefly. For type II compactifications we verify that
IIB and IIA have equal massless spectrum.Comment: LaTex, 21 page

### New G2-conifolds in M-theory and their field theory interpretation

A recent theorem of Foscolo-Haskins-Nordström [1] which constructs complete G -holonomy orbifolds from circle bundles over Calabi-Yau cones can be utilised to construct and investigate a large class of generalisations of the M-theory flop transition. We see that in many cases a UV perturbative gauge theory appears to have an infrared dual described by a smooth G -holonomy background in M-theory. Various physical checks of this proposal are carried out affirmatively. 2

### Branes at conical singularities and holography

For supergavrity solutions which are the product of an anti-de Sitter space
with an Einstein space X, we study the relation between the amount of
supersymmetry preserved and the geometry of X. Depending on the dimension and
the amount of supersymmetry, the following geometries for X are possible, in
addition to the maximally supersymmetric spherical geometry: Einstein-Sasaki in
dimension 2k+1, 3-Sasaki in dimension 4k+3, 7-dimensional manifolds of weak G_2
holonomy and 6-dimensional nearly Kaehler manifolds. Many new examples of such
manifolds are presented which are not homogeneous and have escaped earlier
classification efforts. String or M theory in these vacua are conjectured to be
dual to superconformal field theories. The brane solutions interpolating
between these anti-de Sitter near-horizon geometries and the product of
Minkowski space with a cone over X lead to an interpretation of the dual
superconformal field theory as the world-volume theory for branes at a conical
singularity (cone branes). We propose a description of those field theories
whose associated cones are obtained by (hyper-)Kaehler quotients.Comment: 38 pages (published version

### A Comparison of Supersymmetry Breaking and Mediation Mechanisms

We give a unified treatment of different models of supersymmetry breaking and
mediation from a four dimensional effective field theory standpoint. In
particular a comparison between GMSB and various gravity mediated versions of
SUSY breaking shows that, once the former is embedded within a SUGRA framework,
there is no particular advantage to that mechanism from the point of view of
FCNC suppression. We point out the difficulties of all these scenarios - in
particular the cosmological modulus problem. We end with a discussion of
possible string theory realizations.Comment: Added clarifications and references, 20 page

### Stabilizing All Kahler Moduli in Type IIB Orientifolds

We describe a simple and robust mechanism that stabilizes all Kahler moduli
in Type IIB orientifold compactifications. This is shown to be possible with
just one non-perturbative contribution to the superpotential coming from either
a D3-instanton or D7-branes wrapped on an ample divisor. This
moduli-stabilization mechanism is similar to and motivated by the one used in
the fluxless G_2 compactifications of M-theory. After explaining the general
idea, explicit examples of Calabi-Yau orientifolds with one and three Kahler
moduli are worked out. We find that the stabilized volumes of all two- and
four-cycles as well as the volume of the Calabi-Yau manifold are controlled by
a single parameter, namely, the volume of the ample divisor. This feature would
dramatically constrain any realistic models of particle physics embedded into
such compactifications. Broad consequences for phenomenology are discussed, in
particular the dynamical solution to the strong CP-problem within the
framework.Comment: RevTeX, 24 pages, 2 tables, 1 figure

### Theory and Phenomenology of mu in M theory

We consider a solution to the mu-problem within M theory on a G2-manifold.
Our study is based upon the discrete symmetry proposed by Witten that forbids
the mu-term and solves the doublet-triplet splitting problem. We point out that
the symmetry must be broken by moduli stabilization, describing in detail how
this can occur. The mu-term is generated via Kahler interactions after strong
dynamics in the hidden sector generate a potential which stabilizes all moduli
and breaks supersymmetry with m_{3/2} ~ 20 - 30 TeV. We show that mu is
suppressed relative to the gravitino mass, by higher dimensional operators, mu
~ 0.1 m_{3/2} ~ 2-3 TeV. This necessarily gives a Higgsino component to the
(mostly Wino) LSP, and a small but non-negligible LSP-nucleon scattering
cross-section. The maximum, spin-independent cross-sections are not within
reach of the current XENON100 experiment, but are within reach of upcoming runs
and upgrades.Comment: 34 pages, 3 figure

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