Nonequilibrium transitions induced by multiplicative noise

A new simple model exhibiting a noise-induced ordering transition (NIOT) and a noise-induced disordering transition (NIDT), in which the noise is purely multiplicative, is presented. Both transitions are found in two as well as in one dimension (where they had not been previously reported). We show analytically and numerically that the critical behavior of these two transitions is described by the so called multiplicative noise(MN) universality class. A computation of the set of critical exponents is presented in both $d=1$, and $d=2$ (where they have not been previously measured).Comment: 4 pages, 2 figures, Late

Reseñas

Obra ressenyada: Myles W. JACKSON, The Genealogy of a Gene: Patents, HIV/AIDS, and Race. Cambridge: MIT Press, 2015

Three essays on the comovement of financial assets

In this thesis I study the effects of institutional trading on the comovementof financial assets. In the first chapter, joint work with Christopher Polk, we connect stocks through common active mutual fund ownership, and use these connections to forecast cross-sectional variation in return covariance, controlling for similarity in style and other pair characteristics. We argue this covariance is due to contagion based on return decomposition evidence, cross-sectional heterogeneity in the extent of the effect, and the magnitude of average abnormal returns to a cross-stock reversal trading strategy exploiting information in these connections. We show that the typical long/short hedge fund covaries negatively with this strategy suggesting that hedge funds may potentially exacerbate the price dislocation we document. In the second chapter I study the sources of change in the systematic risks of stocks added to the S&P 500 index. Firstly, using vector autoregressions (VARs) and a two-beta decomposition, I find that I cannot reject the hypothesis that all of the well-known change in beta comes from the cash-flow news component of a firm's return. Secondly, I study fundamentals of included firms directly to reduce any concerns that the VAR-based results are sensitive to my particular speciffcation. As ownership structure cannot directly influence fundamentals, these results challenge previous findings, as they are consistent with the change in beta being due to a selection effect. In the third chapter, joint work with Daniel Bergstresser, we explore index-based comovement in the market for Credit Default Swaps (CDS). We exploit the additions of individual CDS contracts in the Markit CDX Index, a major credit derivative benchmark. We find that for single name CDS contracts, comovement increases after inclusion in the index. Comparing movements in the CDS spreads to movements of the bonds of the same issuers, the CDS spread comovement increases significantly more than the bond spread comovement. This pattern of evidence is consistent with the excess comovement in equity markets documented by Barberis et al (2005) and others

Academic and Molecular Matrices:A Study of the Transformations of Connective Tissue Research at the University of Manchester (1947–1996)

This paper explores the different identities adopted by connective tissue research at the University of Manchester during the second half of the 20th century. By looking at the long-term redefinition of a research programme, it sheds new light on the interactions between different and conflicting levels in the study of biomedicine, such as the local and the global, or the medical and the biological. It also addresses the gap in the literature between the first biomedical complexes after World War II and the emergence of biotechnology. Connective tissue research in Manchester emerged as a field focused on new treatments for rheumatic diseases. During the 1950s and 60s, it absorbed a number of laboratory techniques from biology, namely cell culture and electron microscopy. The transformations in scientific policy during the late 70s and the migration of Manchester researchers to the US led them to adopt recombinant DNA methods, which were borrowed from human genetics. This resulted in the emergence of cell matrix biology, a new field which had one of its reference centres in Manchester. The Manchester story shows the potential of detailed and chronologically wide local studies of patterns of work to understand the mechanisms by which new biomedical tools and institutions interact with long-standing problems and existing affiliations

Dietrich I von Mörs (1226-1262). Paradigmatic example of the new medieval german nobility after the era of Innocent III

Uno de los aspectos más importantes de la política exterior del papa Inocencio III fue su relación con el Imperio; como gran jurista y experto en teología, comenzó un movimiento por el cual se consideraba guardián y defensor de las almas de toda la Cristiandad, mientras que los príncipes laicos eran solamente los defensores físicos de sus vasallos. Se reservaba así el derecho a intervenir en política dentro de los territorios cristianos, y respetando la capacidad de los Electores (tres de los cuales eran a su vez príncipes eclesiásticos) se afirmó en su derecho de ratificar esa elección (o no), pues el mismo Imperio procedía en principio y por su propia motivación a la Iglesia. Así, tras la muerte de Enrique VI en 1197, Inocencio III impuso su gran autoridad para erigirse en árbitro y juez de los pretendientes al trono. El posterior conflicto entre el ya usurpador Otón IV y Felipe Augusto de Francia (batalla del Domingo de Bouvines, en 1214), transformó definitivamente las relaciones entre papado e Imperio, dejando profundas huellas en las tierras alemanas y una configuración política e institucional que nos proponemos demarcar con el ilustrativo ejemplo de los condes de Mörs.One of the most important aspects of the foreign policy concerning Pope Innocent III was his relationship with the Empire; as great jurist and expert in theology himself, he began a movement by which he was considered guardian and defender of the souls of all Christendom, while the lay princes were only the way of physical defense of his subjects. He reserved the right to intervene in politics in Christian lands, and respecting the capacity of Electors (three of which were in turn princes of the Church) he stated his right to ratify that choice (or not), as the Empire itself came in principle and by their own motivation, from the Church. Thus, after the death of Henry VI in 1197, Innocent III imposed his great authority to establish himself as referee and judge of the pretenders to the throne. The subsequent conflict between the already usurper Otto IV and Philip Augustus of France (Battle of Bouvines, 1214), definitely transformed the relations between Papacy and Empire, leaving deep footprints in the German lands and a political and institutional setting that we propose to demarcate with the illustrative example of the counts of Mörs.Ciencias ReligiosasDerech

El prefecto del pretorio: una figura dominante de la política romana en el siglo III

El artículo analiza el desarrollo de la figura del Prefecto del Pretorio, que desde sus comienzos fue una de las más importantes dentro de las instituciones de estado romanas, pero que con la llegada de los cambios políticos después de la muerte de Marco Aurelio, aumentó su protagonismo hasta el punto de gozar de más poder en ocasiones que el mismo emperador. La coyuntura inestable y las fuertes prerrogativas de las que gozaba convirtieron a ese alto funcionario, mitad militar y mitad burócrata, en un personaje clave dentro de las intrigas políticas romanas, que desde su posición inigualable fue capaz a menudo de eliminar al emperador mediante una conspiración para ocupar su lugar. La situación se hizo tan grave llegado el siglo IV que Constantino decidió retirarle el mando de tropas y las funciones militares, convirtiendo al Prefecto del Pretorio en un juez supremo y organizador del suministro.«The Praetorian Prefect: a Commanding Figure of the Roman Politics in the Third Century (199-284)» analyzes the developing of the Praetorian Prefect character, who was from the beginning one of the most important in the roman state institutions, but with the arrival of the political changes after the death of Marcus Aurelius, enhanced his leading role to the point of sometimes exceeding the power of the emperor himself. The instable circumstances and his strong prerogatives turned that high functionary, half bureaucrat half military, into a key figure inside the roman political intrigues, and from his position he was quite often able to eliminate the emperor with a conspiracy, and then take his place. The situation was so serious with the rising of the Fourth Century that the emperor Constantine decided to remove the military functions and the troop leading of the Praetorian Prefects, making them supreme judges and high offi cials of supply organization

Rebel legions and their premeditated destruction: the case of Tetricus, Gallic emperor, compared in the sources

En este artículo se presenta el caso de las legiones romanas en el Imperio Gálico, el estado paralelo occidental durante la Anarquía Militar del siglo III ; tras asesinar a varios altos funcionarios y emperadores estas tropas habían llegado a un punto de indisciplina tal que el propio Tétrico decidió traicionar a su ejército para que fuese destruido y rendirse, buscando su salvación en la clemencia de Aureliano. Se analiza aquí ese episodio histórico y es comparado con otros dos casos similares, relacionados con la usurpación de Magnencio en Occidente y la conquista bizantina de África en tiempos de Justiniano.This article discusses the situation of the Roman legions in the Gallic Empire, the parallel western State that existed during the Military Anarchy of the Third Century. After killing some senior bureaucrats and emperors, these troops had become so undisciplined that Tetricus himself decided to betray his army so that it would be destroyed and surrender, seeking his own salvation in the mercy of Aurelian. This historical episode is analyzed and compared with two similar situations, the usurpation of Magnentius in the West and the Byzantine conquest of Africa in the time of Justinian