3,972 research outputs found
Instantons and Holomorphic Couplings in Intersecting D-brane Models
We clarify certain aspects and discuss extensions of the recently introduced
string D-instanton calculus (hep-th/0609191). The one-loop determinants are
related to one-loop open string threshold corrections in intersecting D6-brane
models. Utilising a non-renormalisation theorem for the holomorphic Wilsonian
gauge kinetic functions, we derive a number of constraints for the moduli
dependence of the matter field Kaehler potentials of intersecting D6-brane
models on the torus. Moreover, we compute string one-loop corrections to the
Fayet-Iliopoulos terms on the D6-branes finding that they are proportional to
the gauge threshold corrections. Employing these results, we discuss the issue
of holomorphy for E2-instanton corrections to the superpotential. Eventually,
we discuss E2-instanton corrections to the gauge kinetic functions and the
FI-terms.Comment: 28 pages, 5 figure
Direct Imaging of Extra-Solar Planets – Homogeneous Comparison of Detected Planets and Candidates
Searching the literature, we found 25 stars with directly imaged planets and
candidates. We gathered photometric and spectral information for all these
objects to derive their luminosities in a homogeneous way, taking a bolometric
correction into account. Using theoretical evolutionary models, one can then
estimate the mass from luminosity, temperature, and age. According to our mass
estimates, all of them can have a mass below 25 Jup masses, so that they are
considered as planets.Comment: Invited review, accepted by InTech for the Book "Topics in Adaptive
Optics", 28 pages, 5 figures, in pres
Power Towers of String Instantons for N=1 Vacua
We provide arguments for the existence of novel hereinafter called
poly-instanton corrections to holomorphic couplings in four-dimensional N=1
supersymmetric string compactifications. After refining quantitatively the
D-brane instanton calculus for corrections to the gauge kinetic function, we
explicitly apply it to the Type I toroidal orbifold defined in arXiv:0710.3080
and compare the results to the proposed heterotic S-dual model. This leads us
to the intriguing conclusion that N=1 string vacua feature a power tower like
proliferation of instanton corrections.Comment: 34 pages, 8 figure
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