16,906 research outputs found
Superspace Formulation in a Three-Algebra Approach to D=3, N=4,5 Superconformal Chern-Simons Matter Theories
We present a superspace formulation of the D=3, N=4,5 superconformal
Chern-Simons Matter theories, with matter supermultiplets valued in a
symplectic 3-algebra. We first construct an N=1 superconformal action, and then
generalize a method used by Gaitto and Witten to enhance the supersymmetry from
N=1 to N=5. By decomposing the N=5 supermultiplets and the symplectic 3-algebra
properly and proposing a new super-potential term, we construct the N=4
superconformal Chern-Simons matter theories in terms of two sets of generators
of a (quaternion) symplectic 3-algebra. The N=4 theories can also be derived by
requiring that the supersymmetry transformations are closed on-shell. The
relationship between the 3-algebras, Lie superalgebras, Lie algebras and
embedding tensors (proposed in [E. A. Bergshoeff, O. Hohm, D. Roest, H.
Samtleben, and E. Sezgin, J. High Energy Phys. 09 (2008) 101.]) is also
clarified. The general N=4,5 superconformal Chern-Simons matter theories in
terms of ordinary Lie algebras can be rederived in our 3-algebra approach. All
known N=4,5 superconformal Chern-Simons matter theories can be recovered in the
present superspace formulation for super-Lie-algebra realization of symplectic
3-algebras.Comment: 37 pages, minor changes, published in PR
Entangling two superconducting LC coherent modes via a superconducting flux qubit
Based on a pure solid-state device consisting of two superconducting LC
circuits coupled to a superconducting flux qubit, we propose in this paper that
the maximally entangled coherent states of the two LC modes can be generated
for arbitrary coherent states through flux qubit controls.Comment: 5 pages, 2 figure
Spin and orbital angular momentum in gauge theories (II): QCD and nucleon spin structure
Parallel to the construction of gauge invariant spin and orbital angular
momentum for QED in paper (I) of this series, we present here an analogous but
non-trivial solution for QCD. Explicitly gauge invariant spin and orbital
angular momentum operators of quarks and gluons are obtained. This was
previously thought to be an impossible task, and opens a more promising avenue
towards the understanding of the nucleon spin structure.Comment: 3 pages, no figure; presented by F. Wang at NSTAR200
Search for quantum dimer phases and transitions in a frustrated spin ladder
A two-leg spin-1/2 ladder with diagonal interactions is investigated
numerically. We focus our attention on the possibility of columnar dimer phase,
which was recently predicted based on a reformulated bosonization theory. By
using density matrix renormalization group technique and exact diagonalization
method, we calculate columnar dimer order parameter, spin correlation on a
rung, string order parameters, and scaled excitation gaps. Carefully using
various finite-size scaling techniques, our results show no support for the
existence of columnar dimer phase in the spin ladder under consideration.Comment: 5 pages, 4 figures. To be published in Phys. Rev.
Magnetic field dependence of antiferromagnetic resonance in NiO
We report on measurements of magnetic field and temperature dependence of antiferromagnetic resonances in the prototypical antiferromagnet NiO. The frequencies of the magnetic resonances in the vicinity of 1 THz have been determined in the time-domain via time-resolved Faraday measurements after selective excitation by narrow-band superradiant terahertz (THz) pulses at temperatures down to 3 K and in magnetic fields up to 10 T. The measurements reveal two antiferromagnetic resonance modes, which can be distinguished by their characteristic magnetic field dependencies. The nature of the two modes is discussed by comparison to an eight-sublattice antiferromagnetic model, which includes superexchange between the next-nearest-neighbor Ni spins, magnetic dipolar interactions, cubic magneto-crystalline anisotropy, and Zeeman interaction with the external magnetic field. Our study indicates that a two-sublattice model is insufficient for the description of spin dynamics in NiO, while the magnetic-dipolar interactions and magneto-crystalline anisotropy play important roles
The Tensor Current Divergence Equation in U(1) Gauge Theories is Free of Anomalies
The possible anomaly of the tensor current divergence equation in U(1) gauge
theories is calculated by means of perturbative method. It is found that the
tensor current divergence equation is free of anomalies.Comment: Revtex4, 7 pages, 2 figure
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