94,271 research outputs found
Evolutionary computation in dynamic and uncertain environments
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Harmonic maps, SU (N) skyrme models and yang-mills theories
Full text linkThis 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
Quench characteristics of a Cu-Stabilized 2G HTS conductor
No full textThe prospect of medium/high field superconducting magnets using 2G HTS tapes is approaching to reality with continued enhancement in the performance of these conductors. Direct measurements of 1d adiabatic quench initiation and propagation of a Cu-stabilized 2G conductor have been carried out with spatial-temporal recording of temperature and voltage following the deposition of various local heat pulses to the conductor at different temperatures between 40K and 64K carrying different transport currents. It was found that the stabilizer-free 2G tape maintains the unique characteristics previously measured in non-stabilized tape of increasing MPZ with transport current and higher quench energy at lower temperatures. The minimum quench energy, minimum propagation zone (MPZ) length are determined as a function of temperature and transport current. The change in MPZ size is investigated with measured temperature dependent E-J characteristics. The results add more detail to help understand the unique characteristics of increasing MPZ with transport current and lower temperatures
On super form factors of half-BPS operators in N=4 super Yang-Mills
Full text linkOpen 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
Infinite Dimensional Symmetries of Self-Dual Yang-Mills Theories.
Full text linkWe 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
Abstraction Refinement Guided by a Learnt Probabilistic Model
Full text linkThe core challenge in designing an effective static program analysis is to find a good program abstraction -- one that retains only details relevant to a given query. In this paper, we present a new approach for automatically finding such an abstraction. Our approach uses a pessimistic strategy, which can optionally use guidance from a probabilistic model. Our approach applies to parametric static analyses implemented in Datalog, and is based on counterexample-guided abstraction refinement. For each untried abstraction, our probabilistic model provides a probability of success, while the size of the abstraction provides an estimate of its cost in terms of analysis time. Combining these two metrics, probability and cost, our refinement algorithm picks an optimal abstraction. Our probabilistic model is a variant of the Erdos-Renyi random graph model, and it is tunable by what we call hyperparameters. We present a method to learn good values for these hyperparameters, by observing past runs of the analysis on an existing codebase. We evaluate our approach on an object sensitive pointer analysis for Java programs, with two client analyses (PolySite and Downcast)
A bilinear approach to a Pfaffian self-dual Yang-Mills equation
Full text linkBy using the bilinear technique of soliton theory, a pfaffian version of the SU(2) self-dual Yang-Mills equation and its solution is constructed
Scattering Amplitudes of Massive N=2 Gauge Theories in Three Dimensions
Full text linkWe 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
Application of local fractional series expansion method to solve Klein-Gordon equations on cantor sets
No full textWe use the local fractional series expansion method to solve the Klein-Gordon equations on Cantor sets within the local fractional derivatives. The analytical solutions within the nondifferential terms are discussed. The obtained results show the simplicity and efficiency of the present technique with application to the problems of the liner differential equations on Cantor sets. © 2014 Ai-Min Yang et al
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