404,598 research outputs found
Harmonic maps, SU (N) skyrme models and yang-mills theories
No full textThis thesis examines the construction of static solutions of (3+l)-dimensional SU{N) Skyrme models, usual and alternative, and pure massive SU(N) Yang-Mills theories. In particular, the application of harmonic maps from S(^2) into the subspace of fields configuration space M. Here, the harmonic maps are used as an ansatz to factoring out the angular dependence part of the solutions from the field equations. In this thesis, we consider the harmonic maps S(^2) → Gr(n, N), where Gr(n, N) is the Grassmann manifold of n-dimensional planes passing through the origin in C(^N). Using the harmonic map ansatz of S(^2) → Gr(2, N) to study the usual SU(N) Skyrme models, we have found that our approximate solutions have marginally higher energies in comparison to the corresponding results previously obtained using CP(^N-1) as target space M. For exact spherically symmetric solutions, we present arguments which suggest that the only solutions obtained this way are embeddings. For the alternative SU(N) Skyrme models, using the harmonic map ansatz of S(^2) → CP(^N-1), we have found that our results for the energies of the exact spherically symmetric solutions are higher than in the usual models. When considering the pure massive SU(N) Yang-Mills theories, we have shown that by choosing the gauge potential to be of almost pure gauge form, the theories reduce to the usual SU(N) Skyrme models. This observation has suggested to us to consider the harmonic map ansatz of S(^2) → CP(^N-1) previously applied to monopole theories. Using this ansatz, we have constructed some bounded spherically symmetric solutions of the theories having finite energies
Integrability and maximally helicity violating diagrams in n=4 supersymmetric yang-mills theory.
No full textWe apply maximally helicity violating (MHV) diagrams to the derivation of the one-loop dilatation operator of N=4 supersymmetric Yang-Mills theory in the SO(6) sector. We find that in this approach the calculation reduces to the evaluation of a single MHV diagram in dimensional regularization. This provides the first application of MHV diagrams to an off-shell quantity. We also discuss other applications of the method and future directions
Infinite Dimensional Symmetries of Self-Dual Yang-Mills Theories.
No full textWe construct infinite dimensional symmetries of the Chalmers-Siegel action describing the self-dual sector of non-supersymmetric Yang-Mills. The symmetries are derived by virtue of a canonical transformation between the Yang-Mills fields and new fields that map the Chalmers-Siegel action to a free theory which has been used to construct a Lagrangian approach to the MHV rules. We describe the symmetries of the free theory in a quite general way which are an infinite dimensional algebra in the group algebra of isometries.
We dimensionally reduce the symmetries of the action to write down symmetries of the Hitchin system and further, we extend the construction to the supersymmetric, self-dual theory.
We review recent developments in the approach to calculating N=4 Yang-Mills scattering amplitudes using symmetry arguments. Super-conformal symmetry and the recently discovered dual super-conformal symmetry have been shown to be related as a Yangian algebra and moreover, anomalous terms appearing in their action on amplitudes lead to deformations of the generators which gives rise to recursive relationships between amplitudes
On super form factors of half-BPS operators in N=4 super Yang-Mills
No full textOpen Access, (c) The Authors. Article funded by SCOAP3. This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credited
Scattering Amplitudes of Massive N=2 Gauge Theories in Three Dimensions
No full textWe study the scattering amplitudes of mass-deformed Chern-Simons theories and Yang-Mills-Chern-Simons theories with N=2 supersymmetry in three dimensions. In particular, we derive the on-shell supersymmetry algebras which underlie the scattering matrices of these theories. We then compute various 3 and 4-point on-shell tree-level amplitudes in these theories. For the mass-deformed Chern-Simons theory, odd-point amplitudes vanish and we find that all of the 4-point amplitudes can be encoded elegantly in superamplitudes. For the Yang-Mills-Chern-Simons theory, we obtain all of the 4-point tree-level amplitudes using a combination of perturbative techniques and algebraic constraints and we comment on difficulties related to computing amplitudes with external gauge fields using Feynman diagrams. Finally, we propose a BCFW recursion relation for mass-deformed theories in three dimensions and discuss the applicability of this proposal to mass-deformed N=2 theories
Einstein-Yang-Mills black holes in anti de-Sitter space
No full textIn this thesis we consider Einstein-Yang-Mills black holes in asymptotically anti-de Sitter space, in the presence of an su(N) gauge �eld. For a purely magnetic gauge �eld we de�ne a set of charges, namely the mass and N - 1 gauge invariant magnetic charges, and show that they characterize stable black holes.
We then go on to consider dyonic black holes which carry both electric and magnetic charge. We investigate spherically symmetric black holes and solitons, and �nd equations of motion for solutions with su(N) gauge �elds. These equations are solved numerically to �nd black hole and soliton solutions with su(2) and su(3) gauge groups.
We then turn to dyonic black holes with planar event horizons and investigate their suitability as gravitational analogues to high temperature superconductors under the AdS/CFT correspondence. We generalise a previously known ansatz for su(2) gauge groups to su(N), and show that there is a critical temperature above which non-abelian solutions do not exist. Below this critical temperature, we show that they are thermodynamically favoured over equivalent Reissner-Nordstr�om solutions, and have in�nite D.C. conductivity
Analytic two-loop form factors in N=4 SYM
No full textThe original publication is available at www.springerlink.co
One-loop N=8 supergravity coefficients from N=4 super Yang-Mills
No full textArXiv ePrint: 0906.0521This work was supported by the STFC under a Rolling
Grant ST/G000565/1. GT is supported by an EPSRC Advanced Research Fellowship
EP/C544242/1 and by an EPSRC Standard Research Grant EP/C544250/1
Distributed human computation framework for linked data co-reference resolution
No full textDistributed Human Computation (DHC) is a technique used to solve computational problems by incorporating the collaborative effort of a large number of humans. It is also a solution to AI-complete problems such as natural language processing. The Semantic Web with its root in AI is envisioned to be a decentralised world-wide information space for sharing machine-readable data with minimal integration costs. There are many research problems in the Semantic Web that are considered as AI-complete problems. An example is co-reference resolution, which involves determining whether different URIs refer to the same entity. This is considered to be a significant hurdle to overcome in the realisation of large-scale Semantic Web applications. In this paper, we propose a framework for building a DHC system on top of the Linked Data Cloud to solve various computational problems. To demonstrate the concept, we are focusing on handling the co-reference resolution in the Semantic Web when integrating distributed datasets. The traditional way to solve this problem is to design machine-learning algorithms. However, they are often computationally expensive, error-prone and do not scale. We designed a DHC system named iamResearcher, which solves the scientific publication author identity co-reference problem when integrating distributed bibliographic datasets. In our system, we aggregated 6 million bibliographic data from various publication repositories. Users can sign up to the system to audit and align their own publications, thus solving the co-reference problem in a distributed manner. The aggregated results are published to the Linked Data Cloud
A Multi-Language Comparison of Influences on Author Verification using Character N-Grams
No full textWe create a new multi-language corpus for author verification based on Wikipedia talkpages, and evaluate the influence that differences in topic and time have on character n-gram author profiles. Topic alignment between two texts is found to increase author verification precision, and an authors writing style is found to change over time, but not more significantly after 3 years than after 1 year.Information ArchitectureWISElectrical Engineering, Mathematics and Computer Scienc
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