Credit rating and competition

In principle, credit rating agencies are supposed to be impartial observers that bridge the gap between private information of issuers and the information available to the wider pool of investors. However, since the 1970s, rating agencies have relied on an issuer-pay model, creating a conflict of interest - the largest source of income for the rating agencies are the fees paid by the issuers the rating agencies are supposed to impartially rate. In this paper, we explore the trade-off between reputation and fees and find that relative to monopoly, rating agencies are more prone to inflate ratings under competition, resulting in lower expected welfare. Our results suggest that more competition by itself is undesirable under the current issuer-pay model and will do little to resolve the conflict of interest problem

The use of platelet rich plasma enriched with bone marrow aspirate in puddu tibial osteotomy

OBJETIVO: O presente estudo procurou avaliar a aplicação do plasma rico em plaquetas associado ao aspirado de medular óssea como substituto ósseo ao enxerto autólogo do ilíaco nas osteotomias tibiais proximais de cunha de adição medial (OTCAM). MÉTODOS: Foram estudados 25 pacientes submetidos a OTCAM divididos de forma randomizada em dois grupos, grupo ilíaco, 14 pacientes submetidos a OTCAM nos quais se utilizou o enxerto autólogo do ilíaco para preencher o sitio da osteotomia, grupo PRP, 11 pacientes submetidos a OTCAM nos quais se utilizou um composto formado por plasma rico em plaquetas associado ao aspirado de medular ósseo para preencher o sitio da osteotomia. Foram avaliados o sangramento (variação dos níveis de hemoglobina e hematócrito) e a dor (escala visual analógica -EVA), comparando os grupos em relação a essas variáveis. RESULTADOS: Não foram observadas diferenças entre os grupos no que se refere à variação dos níveis de hemoglobina (p = 0,820) e hematócrito (p = 0,323). Os grupos não foram diferentes em relação à intensidade da dor segundo a EVA (p = 0,538). CONCLUSÃO: O uso do PRP associado ao aspirado de medular óssea nas OTCAM não demonstrou vantagem sobre a utilização do enxerto autólogo do ilíaco no que se refere a dor e sangramento.OBJECTIVE: The present study was performed in order to evaluate the use of platelet rich plasma associated to bone marrow aspirate, substituting autologous iliac bone graft in medial opening wedge osteotomy (OWHTO). METHODS: Twenty-five patients were submitted to tibial opening wedge osteotomy, being divided into two groups. Iliac group: 14 patients submitted to OWHTO, using autologous iliac bone graft to fill the gap. PRP group: 11 patients using platelet rich plasma associated to bone marrow aspirate to fill the gap. We evaluated bleeding (hemoglobin and hematocrit levels) and pain (visual analogic scale-VAS), then we compared the groups regarding these variables. RESULTS: Differences between the groups were not found regarding hemoglobin levels (p=0.820) and hematocrit levels (p=0.323). The groups were not different regarding pain measured with VAS (p=0.538). CONCLUSION: The use of platelet rich plasma associated to bone marrow aspirate in medial opening wedge osteotomy did not offer advantages over autologous iliac bone graft regarding bleeding and pain

Holographic c-theorems in arbitrary dimensions

We re-examine holographic versions of the c-theorem and entanglement entropy in the context of higher curvature gravity and the AdS/CFT correspondence. We select the gravity theories by tuning the gravitational couplings to eliminate non-unitary operators in the boundary theory and demonstrate that all of these theories obey a holographic c-theorem. In cases where the dual CFT is even-dimensional, we show that the quantity that flows is the central charge associated with the A-type trace anomaly. Here, unlike in conventional holographic constructions with Einstein gravity, we are able to distinguish this quantity from other central charges or the leading coefficient in the entropy density of a thermal bath. In general, we are also able to identify this quantity with the coefficient of a universal contribution to the entanglement entropy in a particular construction. Our results suggest that these coefficients appearing in entanglement entropy play the role of central charges in odd-dimensional CFT's. We conjecture a new c-theorem on the space of odd-dimensional field theories, which extends Cardy's proposal for even dimensions. Beyond holography, we were able to show that for any even-dimensional CFT, the universal coefficient appearing the entanglement entropy which we calculate is precisely the A-type central charge.Comment: 62 pages, 4 figures, few typo's correcte

Holographic Entanglement Entropy in Lovelock Gravities

We study entanglement entropies of simply connected surfaces in field theories dual to Lovelock gravities. We consider Gauss-Bonnet and cubic Lovelock gravities in detail. In the conformal case the logarithmic terms in the entanglement entropy are governed by the conformal anomalies of the CFT; we verify that the holographic calculations are consistent with this property. We also compute the holographic entanglement entropy of a slab in the Gauss-Bonnet examples dual to relativistic and non-relativistic CFTs and discuss its properties. Finally, we discuss features of the entanglement entropy in the backgrounds dual to renormalization group flows between fixed points and comment on the implications for a possible c-theorem in four spacetime dimensions.Comment: harvmac, 30 pages, 1 figure, References added, typos correcte

Credit Rating and Competition

In principle, credit rating agencies are supposed to be impartial observers that bridge the gap between private information of issuers and the information available to the wider pool of investors. However, since the 1970s, rating agencies have relied on an issuer-pay model, creating a conflict of interest the largest source of income for the rating agencies are the fees paid by the issuers the rating agencies are supposed to impartially rate. In this paper, we explore the trade-off between reputation and fees and find that relative to monopoly, rating agencies are more prone to inflate ratings under competition, resulting in lower expected welfare. Our results suggest that more competition by itself is undesirable under the current issuer-pay model and will do little to resolve the conflict of interest problem.