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Full-Text Articles in Physics

Superspace Ward Identities In Supersymmetric Gauge Theories, Asim Gangopadhyaya, Darwin Chang Nov 1984

Superspace Ward Identities In Supersymmetric Gauge Theories, Asim Gangopadhyaya, Darwin Chang

Physics: Faculty Publications and Other Works

In superspace formulation of supersymmetric gauge theories, gauge invariance requires an infinite set of identities between the infinite set of renormalization constants. Using Ward identities in superspace, the same is derived. These identities at one loop level are also demonstrated.


Critical Behavior Of The One-Dimensional S = 1 Xy Model With Single-Ion Anisotropy, O. F. De Alcantara Bonfim, T. Schneider Aug 1984

Critical Behavior Of The One-Dimensional S = 1 Xy Model With Single-Ion Anisotropy, O. F. De Alcantara Bonfim, T. Schneider

Physics Faculty Publications and Presentations

We study the quantum critical behavior of the one-dimensional, S = 1 XY model in the presence of a single-ion anisotropy. Using a path-integral approach, we obtain, at T = 0 and for a positive anisotropy constant, a classical free-energy functional that allows discussion of the critical properties. The rescaling of frequencies is governed by the critical exponent z = 1. Renormalization-group arguments reveal that at criticality the system belongs to the same universality class as the isotropic 2-d XY model.


1/Σ Expansion For Quantum Percolation, A. Brooks Harris Mar 1984

1/Σ Expansion For Quantum Percolation, A. Brooks Harris

Department of Physics Papers

A method for obtaining a 1/σ expansion for certain statistical models is presented, where σ+1 is the coordination number of the lattice. The method depends on being able to generate exact recursion relations for the Cayley tree. By perturbing the recursion relation to take account of the dominant loops in a hypercubic lattice for large σ, we obtain corrections of order σ−2 to the recursion relations. For the tight-binding model on random bond clusters (the quantum-percolation problem) we obtain corrections to this order for the critical concentration p* at which the transition between localized and extended zero-energy ...


Scaling Approach To Spin-Glass Phenomena, S. E. Barnes, A. P. Malozemoff, B. Barbara Jan 1984

Scaling Approach To Spin-Glass Phenomena, S. E. Barnes, A. P. Malozemoff, B. Barbara

Physics Articles and Papers

The scaling model of spin-glass phenomena is extended to consider both longitudinal and transverse order parameters q1 and qt. The lowest-order coupling in the free energy goes as ql2qt2. The field (h) dependence of the reduced temperature t for transverse freezing is found to be t∼h4/δ where δ is the conventional nonlinear susceptibility field exponent (χ∼h2/δ). While the transverse correlation length diverges at t=0, the longitudinal correlation length remains finite.


Esr And Magnetization Of The Spin-Glass Cumn At Low Concentrations, F. R. Hoekstra, G. J. Nieuwenhuys, K. Baberschke, S. E. Barnes Jan 1984

Esr And Magnetization Of The Spin-Glass Cumn At Low Concentrations, F. R. Hoekstra, G. J. Nieuwenhuys, K. Baberschke, S. E. Barnes

Physics Articles and Papers

We have determined the resonance frequency ω versus resonant field H diagram for CuMn with Mn concentrations 2, 3.5, and 5 at.%, both when H⃗ is parallel and antiparallel to the cooling field H⃗c. From the parallel measurements we find anisotropy energy density constants K that are in agreement with K values determined from transverse susceptibility and torque measurements. However, the K values determined from the remanence reversal of dc magnetization are smaller by a factor of approximately 2. We suggest that this is caused by a breakdown of rigid-body spin rotations. By combining the parallel data with ...


Esr In Situ With A Josephson Tunnel Junction, K. Baberschke, K. D. Bures, S. E. Barnes Jan 1984

Esr In Situ With A Josephson Tunnel Junction, K. Baberschke, K. D. Bures, S. E. Barnes

Physics Articles and Papers

The in situ electron-spin resonance of a voltage-biased NbAuNb Josephson junction is reported. The Au barrier is doped with Gd or 167Er ions. Sharp resonances appear in the I-V curves at frequencies equivalent to the crystal-field splitting of AuGd (1.0 and 1.7 GHz) and to the hyperfine splitting of Au167Er (2.87 GHz). The principle of this new type of ESR-Josephson-junction spectrometer, as well as its application, is discussed.


Esr Relaxation In Spin Glasses, S. E. Barnes Jan 1984

Esr Relaxation In Spin Glasses, S. E. Barnes

Physics Articles and Papers

The Bloch-Hasegawa theory for the ESR of magnetic alloys is adapted and extended to spin glasses in the paramagnetic regime, that is, for temperatures T>TG, the cusp temperature. Negative residual widths, reduced thermal broadening, and a possible critical divergence of the residual width are all explained in terms of minor extensions of the standard theory.