16,036 research outputs found

    Conformal correlators of mixed-symmetry tensors

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    We generalize the embedding formalism for conformal field theories to the case of general operators with mixed symmetry. The index-free notation encoding symmetric tensors as polynomials in an auxiliary polarization vector is extended to mixed-symmetry tensors by introducing a new commuting or anticommuting polarization vector for each row or column in the Young diagram that describes the index symmetries of the tensor. We determine the tensor structures that are allowed in n-point conformal correlation functions and give an algorithm for counting them in terms of tensor product coefficients. A simple derivation of the unitarity bound for arbitrary mixed-symmetry tensors is obtained by considering the conservation condition in embedding space. We show, with an example, how the new formalism can be used to compute conformal blocks of arbitrary external fields for the exchange of any conformal primary and its descendants. The matching between the number of tensor structures in conformal field theory correlators of operators in d dimensions and massive scattering amplitudes in d+1 dimensions is also seen to carry over to mixed-symmetry tensors.Comment: 46 pages, many figures, v2: Reformulated the counting of tensor structures, new section on conserved operators, v3: fixed typo

    Coaxial cable stripping device facilitates RF cabling fabrication

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    Coaxial cable stripping device assures clean, right angled shoulder for RF cable connector fabrication. This method requires minimal skill and creates a low voltage standing wave ratio and mechanical stability in the interconnecting RF Cables

    Magnetic excitations in a bond-centered stripe phase: Spin waves far from the semi-classical limit

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    Using a spin-only model, we compute spin excitation spectra in a bond-centered stripe state with long-range magnetic order. We employ a bond operator formalism, which naturally captures both dimerization and broken spin symmetry in a unified framework. At low energies, the spin excitations resemble spin waves, but at higher energies they are very similar to spin-1 excitations of isolated spin ladders. Our theory does well describe neutron scattering data [J. M. Tranquada et al., Nature 429, 534 (2004)] on LaBaCuO, pointing towards bond order in this material.Comment: 4 pages, 3 figs, of possible relevance to experiments reported in cond-mat/0401621; (v2) final version as publishe

    Beyond Rainbow-Ladder in bound state equations

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    In this work we devise a new method to study quark anti-quark interactions beyond simple ladder-exchange that yield massless pions in the chiral limit. The method is based on the requirement to have a representation of the quark-gluon vertex that is explicitly given in terms of quark dressings functions. We outline a general procedure to generate the Bethe-Salpeter kernel for a given vertex representation. Our method allows not only the identification of the mesons' masses but also the extraction of their Bethe-Salpeter wave functions exposing their internal structure. We exemplify our method with vertex models that are of phenomenological interest.Comment: 13 pages, 6 figures; v2: typos corrected, colors improve

    Other-regarding behaviour: Testing guilt- and reciprocity-based models

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    We analyse two types of belief-dependant models of social preferences: guilt aversion and reciprocity. In particular, we test the relevance of their input variables (second-order beliefs and general dispositions for guilt/reciprocity). The data confirm the predictions of belief-dependant models. Both second-order beliefs and a participant's sensitivity to guilt/reciprocity are relevant for the decisions taken. Second-order beliefs appear to have an inverse U-shaped effect on the extent of kind behaviour.social preferences, other-regarding behaviour, belief-dependent models, experiments, trust game, guilt aversion, beliefs, psychological game theory, emotions, reciprocity
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