13,338 research outputs found
Hessian geometry and the holomorphic anomaly
We present a geometrical framework which incorporates higher derivative
corrections to the action of N = 2 vector multiplets in terms of an enlarged
scalar manifold which includes a complex deformation parameter. This enlarged
space carries a deformed version of special Kahler geometry which we
characterise. The holomorphic anomaly equation arises in this framework from
the integrability condition for the existence of a Hesse potential.Comment: 43 pages. Revised version: minimal changes. Final version, accepted
for publication by JHE
The N=1 effective actions of D-branes in Type IIA and IIB orientifolds
We discuss the four-dimensional N=1 effective actions of single space-time
filling Dp-branes in general Type IIA and Type IIB Calabi-Yau orientifold
compactifications. The effective actions depend on an infinite number of normal
deformations and gauge connection modes. For D6-branes the N=1 Kaehler
potential, the gauge-coupling function, the superpotential and the D-terms are
determined as functions of these fields. They can be expressed as integrals
over chains which end on the D-brane cycle and a reference cycle. The infinite
deformation space will reduce to a finite-dimensional moduli space of special
Lagrangian submanifolds upon imposing F- and D-term supersymmetry conditions.
We show that the Type IIA moduli space geometry is captured by three real
functionals encoding the deformations of special Lagrangian submanifolds,
holomorphic three-forms and Kaehler two-forms of Calabi-Yau manifolds. These
elegantly combine in the N=1 Kaehler potential, which reduces after applying
mirror symmetry to the results previously determined for space-time filling
D3-, D5- and D7-branes. We also propose general chain integral expressions for
the Kaehler potentials of Type IIB D-branes.Comment: 61 pages, v2: typos corrected and refs adde
Duality Symmetries and Supersymmetry Breaking in String Compactifications
We discuss the spontaneous supersymetry breaking within the low-energy
effective supergravity action of four-dimensional superstrings. In particular,
we emphasize the non-universality of the soft supersymmetry breaking
parameters, the -problem and the duality symmetries.Comment: (invited talk to the 27th ICHEP, Glasgow, July 1994), 11 page
Perturbative and non-perturbative monodromies in N=2 heterotic string vacua
In this talk we summarise our recent results on perturbative and
non-perturbative monodromies in four-dimensional heterotic strings with
space-time supersymmetry, and we compare our results with the rigid
Yang-Mills monodromies.Comment: 6 pages, latex using espcrc2. Based on Talks given at the 29th
International Symposium on the Theory of Elementary Particles, Buckow, August
1995 and at the 5th Hellenic School and Workshop on Elementary Particle
Physics, Corfu, September 199
Deviations from the Area Law for Supersymmetric Black Holes
We review modifications of the Bekenstein-Hawking area law for black hole
entropy in the presence of higher-derivative interactions. In four-dimensional
N=2 compactifications of string theory or M-theory these modifications are
crucial for finding agreement between the macroscopic entropy obtained from
supergravity and the microscopic entropy obtained by counting states in string
or M-theory. Our discussion is based on the effective Wilsonian action, which
in the context of N=2 supersymmetric theories is defined in terms of
holomorphic quantities. At the end we briefly indicate how to incorporate
non-holomorphic corrections.Comment: 18 pages, LaTeX, Contribution to the Proceedings of the 32nd
Symposium Ahrenshoop on the Theory of Elementary Particles, Buckow, September
1-5, 1998; a typo correcte
On the Duality between the Heterotic String and F-Theory in 8 Dimensions
In this note we compare the moduli spaces of the heterotic string
compactified on a two-torus and F-Theory compactified on an elliptic K3 surface
for the case of an unbroken E8 x E8 gauge group. The explicit map relating the
deformation parameters alpha and beta of the F-Theory K3 surface to the moduli
T and U of the heterotic torus is found using the close relationship between
the K3 discriminant and the discriminant of the Calabi-Yau-threefold
X(1,1,2,8,12)[24] in the limit of a large base P1.Comment: 10 pages, LaTe
Citizenship education in England 2001-2010 : young people's practices and prospects for the future : the eighth and final report from the Citizenship Education Longitudinal Study (CELS)
On the one hand, there has been a marked and steady increase in young peopleâs civic and political participation and indications that these young people will continue to participate as adult citizens. In contrast, there has been a hardening of attitudes toward equality and society, a weakening of attachment to communities and fluctuating levels of engagement, efficacy and trust in the political arena. The factors that shape young peopleâs citizenship outcomes include age and life-stage, background factors, prior citizenship outcomes, as well as levels of âreceivedâ citizenship education
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