6,040 research outputs found
Non-perturbative gauge couplings from holography
We show how D-instanton corrections modify the dilaton-axion profile emitted
by an O7/D7 system turning it into the non-singular F-theory background which
corresponds to the effective coupling on a D3 probe.Comment: 6 pages. Proceedings of the "XVII European Workshop on String Theory
2011", Padova, Italy, 5-9 September 201
N=2 Instanton Calculus In Closed String Background
In this contribution we describe how to obtain instanton effects in four
dimensional gauge theories by computing string scattering amplitudes in
D3/D(-1) brane systems. In particular we study a system of fractional D3/D(-1)
branes in a Z_2 orbifold and in a Ramond-Ramond closed string background, and
show that it describes the gauge instantons of N=2 super Yang-Mills theory and
their interactions with the graviphoton of N=2. Using string theory methods we
compute the prepotential of the effective gauge theory exploiting the
localization methods of the instanton calculus, showing that this leads to the
same information given by the topological string.Comment: 12 pages, 2 figures; to appear in the proceedings of 21st
Nishinomiya-Yukawa Memorial Symposium on Theoretical Physics: Noncommutative
Geometry and Quantum Spacetime in Physics, Nishinomiya and Kyoto, Japan,
11-15 Nov 200
Instanton Calculus With R-R Background And Topological Strings
The non-perturbative low energy effective action of N=2 SYM is studied within
a microscopic string realization via D3/D-instanton systems. The localization
deformation of instanton moduli space which has allowed the exact computation
of multi-instanton contributions is, in this setting, due to a RR graviphoton
background. The relation of deformed instanton contributions to topological
string amplitudes on CY, argued by Nekrasov, appears quite natural in this
framework. Based on arXiv:hep-th/0606013.Comment: 5 pages, 3 fig.s, Latex, uses w-art class (included). To appear in
the proceedings of the RTN workshop "ForcesUniverse", Naples, October 9-13,
200
Exotic prepotentials from D(-1)D7 dynamics
We compute the partition functions of D(-1)D7 systems describing the
multi-instanton dynamics of SO(N) gauge theories in eight dimensions. This is
the simplest instance of the so called exotic instantons. In analogy with the
Seiberg-Witten theory in four space-time dimensions, the prepotential and
correlators in the chiral ring are derived via localization formulas and found
to satisfy relations of the Matone type. Exotic prepotentials of SO(N) gauge
theories with N=2 supersymmetries in four-dimensions are also discussed.Comment: 19 page
Conceptual Graphs in CAD
This paper elaborates on the use of conceptual graphs in a prototype of a computer based support system for re-design. Re-design support involves the modelling of assemblies and components. The requirements of the components to be modelled are a compromise between the functioning of the assembly and the manufacturability of the individual components. Conceptual graphs provide for an elegant way of representing both functioning and manufacturing aspects. In the prototype system, conceptual graphs are used for representing and defining assemblies, components and features as well as the relations between these entities. Constraints, such as kinematic, tolerance and manufacturing constraints are also represented using conceptual graphs
Stringy instantons and dualities
We discuss non-perturbative corrections to the gauge kinetic functions in a
four-dimensional N=2 gauge theory realized with a system of D7/D3-branes in a
compactification of type I' theory on T_4/Z_2 x Z_2. The non-perturbative
contributions arise when D(-1) branes, corresponding to stringy instantons, are
added to the system; such contributions can be explicitly evaluated using
localization techniques and precisely match the results predicted by the
heterotic/type I' duality. This agreement represents a very non-trivial test of
the stringy multi-instanton calculus.Comment: 6 pages, Contribution to the proceedings of the XVIth European
Workshop on String Theory, Madrid, Spain, June 14-18 201
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