1,938 research outputs found

    QCD condensates and holographic Wilson loops for asymptotically AdS spaces

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    The minimization of the Nambu-Goto action for a surface whose contour defines a circular Wilson loop of radius a placed at a finite value of the coordinate orthogonal to the boundary is considered. This is done for asymptotically AdS spaces. The condensates of even dimension n=2n=2 through 1010 are calculated in terms of the coefficient of ana^{n} in the expansion of the on-shell subtracted Nambu-Goto action for small aa The subtraction employed is such that it presents no conflict with conformal invariance in the AdS case and need not introduce an additional infrared scale for the case of confining geometries. It is shown that the UV value of the condensates is universal in the sense that they only depends on the first coefficients of the difference with the AdS case.Comment: 11 pages, 1 figur

    Normal Coordinates and Primitive Elements in the Hopf Algebra of Renormalization

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    We introduce normal coordinates on the infinite dimensional group GG introduced by Connes and Kreimer in their analysis of the Hopf algebra of rooted trees. We study the primitive elements of the algebra and show that they are generated by a simple application of the inverse Poincar\'e lemma, given a closed left invariant 1-form on GG. For the special case of the ladder primitives, we find a second description that relates them to the Hopf algebra of functionals on power series with the usual product. Either approach shows that the ladder primitives are given by the Schur polynomials. The relevance of the lower central series of the dual Lie algebra in the process of renormalization is also discussed, leading to a natural concept of kk-primitiveness, which is shown to be equivalent to the one already in the literature.Comment: Latex, 24 pages. Submitted to Commun. Math. Phy

    Comment on "Geometrothermodynamics of a Charged Black Hole of String Theory"

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    We comment on the conclusions found by Larra\~naga and Mojica regarding the consistency of the Geoemtrothermodynamics programme to describe the critical behaviour of a Gibbons-Maeda-Garfinkle-Horowitz-Strominger charged black hole. We argue that making the appropriate choice of metric for the thermodynamic phase space and, most importantly, considering the homogeneity of the thermodynamic potential we obtain consistent results for such a black hole.Comment: Comment on arXiv:1012.207

    Prolapso de hemipene y hemipenectomía en un gecko leopardo (Eublepharis macularius)

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    Copulatory organ prolapse is a condition more frequently observed in chelonians and ophidians than in lizards. Most common causes are infections, forced separation during mating and inflammation associated to the use of probes for sex determination. Moreover, many other predisposing factors are described (hypocalcaemia, urolithiasis, etc.), but etiological diagnosis is rarely achieved. A four years old leopard gecko (Eublepharis macularius) was received presenting unilateral hemipenile prolapse. Medical therapy was performed using 50 % dextrose baths and prednisone (2 mg/kg) during 24 hours, but it was unsuccessful. Due to the fact that the prolapsed hemipenis showed signs of necrosis, surgical resection was performed. The patient was anesthetized using the combination ketamine (5 mg/kg), dexmedetomidine (0.1 mg/kg), and midazolam (1 mg/kg); also, lidocaine (4 mg/ kg) was administered for local block, whereas atipamezole (0.5 mg/kg) was used for antagonizing dexmedetomidine. The used anesthetic protocol allowed an adequate surgical management. Hemipenectomy solved the problem without any observed complication.El prolapso del órgano copulatorio es una afección más frecuentemente observada en quelonios y ofidios que en saurios. Las causas más comunes son infecciones, separación forzada durante la cópula e inflamación asociada al uso de sondas para determinación del sexo. Además, se han descrito muchas otros factores asociados (hipocalcemia, urolitiasis), pero rara vez se logra llegar al diagnóstico etiológico. Un gecko leopardo (Eublepharis macularius) de cuatro años de edad fue recibido presentando prolapso unilateral de hemipene. Se realizó tratamiento médico usando baños en dextrosa 50 % y prednisona (2 mg/kg) durante 24 horas, pero éste no fue exitoso. Debido a que el hemipene prolapsado presentó signos de necrosis, se realizó la resección quirúrgica. El paciente fue anestesiado empleando la combinación ketamina (5 mg/kg), dexmedetomidina (0,1 mg/kg) y midazolam (1 mg/kg). Además, se administró lidocaína (4 mg/kg) como bloqueo local y se usó atipamezol para antagonizar la dexmedetomidina. El protocolo anestésico empleado permitió el manejo quirúrgico adecuado. La hemipenectomía resolvió el problema sin observarse complicación alguna.Facultad de Ciencias Veterinaria
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