Stars form via the gravitational collapse of molecular clouds during which time the protostellar object contracts by over seven orders of magnitude. If all the angular momentum present in the natal cloud was conserved during collapse, stars would approach rotational velocities rapid enough to tear themselves apart within just a few Myr. In contrast to this, observations of pre-main sequence rotation rates are relatively slow (∼ 1 − 15 days) indicating that significant quantities of angular momentum must be removed from the star. I use observations of fully convective pre-main sequence stars in two well-studied, nearby regions of star formation (namely the Orion Nebula Cluster and Taurus-Auriga) to determine the removal rate of stellar angular momentum. I find the accretion disc-hosting stars to be rotating at a slower rate and contain less specific angular momentum than the disc-less stars. I interpret this as indicating a period of accretion disc-regulated angular momentum evolution followed by near-constant rotational evolution following disc dispersal. Furthermore, assuming that the age spread inferred from the Hertzsprung-Russell diagram constructed for the star forming region is real, I find that the removal rate of angular momentum during the accretion-disc hosting phase to be more rapid than that expected from simple disc-locking theory whereby contraction occurs at a fixed rotation period. This indicates a more efficient process of angular momentum removal must operate, most likely in the form of an accretion-driven stellar wind or outflow emanating from the star-disc interaction. The initial circumstellar envelope that surrounds a protostellar object during the earliest stages of star formation is rotationally flattened into a disc as the star contracts. An effective viscosity, present within the disc, enables the disc to evolve: mass accretes inwards through the disc and onto the star while momentum migrates outwards, forcing the outer regions of the disc to expand. I used spatially resolved submillimetre detections of the dust and gas components of protoplanetary discs, gathered from the literature, to measure the radial extent of discs around low-mass pre-main sequence stars of ∼ 1−10 Myr and probe their viscous evolution. I find no clear observational evidence for the radial expansion of the dust component. However, I find tentative evidence for the expansion ofthe gas component. This suggests that the evolution of the gas and dust components of protoplanetary discs are likely governed by different astrophysical processes. Observations of jets and outflows emanating from protostars and pre-main sequence stars highlight that it may also be possible to remove angular momentum from the circumstellar material. Using the sample of spatially resolved protoplanetary discs, I find no evidence for angular momentum removal during disc evolution. I also use the spatially resolved debris discs from the Submillimetre Common-User Bolometer Array-2 Observations of Nearby Stars survey to constrain the amount of angular momentum retained within planetary systems. This sample is compared to the protoplanetary disc angular momenta and to the angular momentum contained within pre-stellar cores. I find that significant quantities of angular momentum must be removed during disc formation and disc dispersal. This likely occurs via magnetic braking during the formation of the disc, via the launching of a disc or photo-evaporative wind, and/or via ejection of planetary material following dynamical interactions.

Momentum is one of the most robust anomalies in financial markets, there are two main recent explanations for this phenomenon, a behavioral-based explanation through disposition-effect (i.e., the willingness to sell \"winners\" too quickly and to hold \"losers\" for a long time) and a fund-flow based explanation. The disposition-effect explanation is centered in the convergence of the spread between the fundamental value and the observed market price (disposition-effect causes an underreaction to news that generates this spread), and the fund flows-based explanation is due to the persistence of the performance of mutual-funds (which usually keep buying winning positions and selling the losses). This master thesis compares those theories using Brazilian data (which is suitable for the strong presence of momentum). Our empirical analysis was done using Fama-MacBeth regressions with results pointing the disposition-effect explanation as the most significant, with our robustness analysis contributing positively to the main findings. / Uma das anomalias mais robustas presente nos mercados financeiros é a existência de momentum nos preços de ações, existem duas principais explicações recentes para este fenômeno: explicação comportamental através do efeito-disposição (i.e. disposição de vender ativos \"vencedores\" rapidamente e de segurar ativos \"perdedores\" por muito tempo) e explicações de fluxos de fundos de investimento. A explicação através do efeito-disposição é centrada na convergência do spread entre o valor fundamental de um ativo e o preço de mercado observado (o efeito-disposição causa uma reação branda a notícias que gera esse spread), e a explicação baseada em fluxos de fundos que se deve pela persistência da performance de fundos (que usualmente continuam comprando posições vencedoras e vendendo as perdedoras). O objetivo desta dissertação é comparar essas teorias utilizando dados brasileiros (que é adequado pela forte presença de momentum). Nossa análise empírica foi feita através de regressões de Fama-MacBeth com resultados apontando a explicação centrada no efeito-disposição como a mais significativa, com nossa análise de robustez contribuindo positivamente para nossos resultados principais.

Bakgrund: Inom investering förekommer ett flertal tumregler och myter. En myt som cirkulerat bland investerare är att framsidor i branschtidskrifter, benämnt Cover Stories, skulle utgöra en indikator för en contrarian strategi. Våren 2007 presenterade den första studie där det undersöktes om Cover Stories hade utgjort indikatorer för enskilda företag i USA. Vi kommer att undersöka om Cover Stories i Affärsvärlden och Veckans Affärer utgjort en indikator på den svenska marknaden under tidsperioden 1987 till 2006. Utfallen av våra resultat kan eventuellt bidra till att investerare inte fattar beslut utifrån en felaktig myt om samband inte kan påvisas. Finner vi ett samband kan vi fastställa att det funnits fog för myten. Syfte: Vår studie syftar till att undersöka huruvida Cover Stories har kunnat användas som indikator i en contrarian eller momentum strategi under tidsperioden 1987 till 2006. Genomförande: Vår studie har genomförts med den amerikanska studien som utgångspunkt. Affärsvärldens och Veckans Affärers framsidor har undersökts för tidsperioden 1987 till 2006. Under denna tidsperiod fann vi 298 företag som kunde kategoriseras beroende på om Cover Storyn var positiv eller negativ till företaget i fråga. Kategoriseringen som gjorts i ursprungsstudien ansåg vi vara för generell varför en metodutveckling gjordes. Därefter beräknades avkastningen kring publiceringsdagen för olika tidsintervall. Eventuell överavkastning beräknades genom att 1) justera för marknadens avkastning samt 2) justera för respektive bransch avkastning. Detta för att utreda huruvida trender kunde fastställas och om det var möjligt att använda Cover Stories som en indikator. De erhållna resultaten är testade för statistiskt signifikans. Slutsats: Generellt har positiva Cover Stories utgjort en momentum indikator medan negativa Cover Stories utgjort contrarian indikator. Kategorispecifika resultat visar dock på värden som till största del saknar statistisk signifikans. Vidare är spridningen i hur företag avkastar stor. Sammantaget finner vi därför inget stöd för myten och rekommenderar inte en contrarian strategi med Cover Stories som indikator, vilket är i linje med ursprungsstudien. / Background: Myths and rules of thumb are widely spread within finance. One among many others is that Cover Stories of financial magazines are effective contrarian indicators. In spring of 2007 the first study was presented were it had been investigated if Cover Stories could have been used as indicators for companies in the U.S. We will examine whether Cover Stories in the Swedish financial magazines ‘Affärsvärlden’ and ‘Veckans Affärer’ constitute indicators for the Swedish market from 1987 to 2006. The outcome of our study can either prevent investors from making incorrect decisions based on a myth for which we have found no proof or strengthen the myth if we the magazines indeed could have been used as an indicator. Purpose: The purpose of this study is to examine whether Cover Stories could have been used as indicators for either a contrarian or momentum strategy in the period of 1987 to 2006. Realization: The basis of our study has been the study made on the U.S.-market. The Cover Stories of ‘Affärsvärldens’ and ‘Veckans Affärer’ have been categorized for the period of 1987 to 2006, depending on the nature of the Cover Story, i.e. if it is depicting the company in a positive or negative manner. We considered the categorisation which hade been applied in the original study to be too general. Therefore we further developed the methodology regarding the categorisation. Subsequently the change of the stock price, for each company being the object of a cover story, before and after publication was compared. The return was then adjusted for the market return and the return of respective industry, again for each company. This enabled us to determine whether Cover Stories had been useful as an indicator. The results have been tested statistically. Findings: Positive Cover Stories constituted a momentum indicator while negative Cover Stories represented contrarian indicators. The majority of the results in the specific categories lack statistic significance, furthermore are the discrepancy in the returns of the companies considerable. To sum up, our results do not support the myth and we would not recommend a contrarian strategy based solely on Cover Stories as an indicator.

<p>Bakgrund: Inom investering förekommer ett flertal tumregler och myter. En myt som cirkulerat bland investerare är att framsidor i branschtidskrifter, benämnt Cover Stories, skulle utgöra en indikator för en contrarian strategi. Våren 2007 presenterade den första studie där det undersöktes om Cover Stories hade utgjort indikatorer för enskilda företag i USA. Vi kommer att undersöka om Cover Stories i Affärsvärlden och Veckans Affärer utgjort en indikator på den svenska marknaden under tidsperioden 1987 till 2006. Utfallen av våra resultat kan eventuellt bidra till att investerare inte fattar beslut utifrån en felaktig myt om samband inte kan påvisas. Finner vi ett samband kan vi fastställa att det funnits fog för myten.</p><p>Syfte: Vår studie syftar till att undersöka huruvida Cover Stories har kunnat användas som indikator i en contrarian eller momentum strategi under tidsperioden 1987 till 2006.</p><p>Genomförande: Vår studie har genomförts med den amerikanska studien som utgångspunkt. Affärsvärldens och Veckans Affärers framsidor har undersökts för tidsperioden 1987 till 2006. Under denna tidsperiod fann vi 298 företag som kunde kategoriseras beroende på om Cover Storyn var positiv eller negativ till företaget i fråga. Kategoriseringen som gjorts i ursprungsstudien ansåg vi vara för generell varför en metodutveckling gjordes. Därefter beräknades avkastningen kring publiceringsdagen för olika tidsintervall. Eventuell överavkastning beräknades genom att 1) justera för marknadens avkastning samt 2) justera för respektive bransch avkastning. Detta för att utreda huruvida trender kunde fastställas och om det var möjligt att använda Cover Stories som en indikator. De erhållna resultaten är testade för statistiskt signifikans.</p><p>Slutsats: Generellt har positiva Cover Stories utgjort en momentum indikator medan negativa Cover Stories utgjort contrarian indikator. Kategorispecifika resultat visar dock på värden som till största del saknar statistisk signifikans. Vidare är spridningen i hur företag avkastar stor. Sammantaget finner vi därför inget stöd för myten och rekommenderar inte en contrarian strategi med Cover Stories som indikator, vilket är i linje med ursprungsstudien.</p> / <p>Background: Myths and rules of thumb are widely spread within finance. One among many others is that Cover Stories of financial magazines are effective contrarian indicators. In spring of 2007 the first study was presented were it had been investigated if Cover Stories could have been used as indicators for companies in the U.S. We will examine whether Cover Stories in the Swedish financial magazines ‘Affärsvärlden’ and ‘Veckans Affärer’ constitute indicators for the Swedish market from 1987 to 2006. The outcome of our study can either prevent investors from making incorrect decisions based on a myth for which we have found no proof or strengthen the myth if we the magazines indeed could have been used as an indicator.</p><p>Purpose: The purpose of this study is to examine whether Cover Stories could have been used as indicators for either a contrarian or momentum strategy in the period of 1987 to 2006.</p><p>Realization: The basis of our study has been the study made on the U.S.-market. The Cover Stories of ‘Affärsvärldens’ and ‘Veckans Affärer’ have been categorized for the period of 1987 to 2006, depending on the nature of the Cover Story, i.e. if it is depicting the company in a positive or negative manner. We considered the categorisation which hade been applied in the original study to be too general. Therefore we further developed the methodology regarding the categorisation. Subsequently the change of the stock price, for each company being the object of a cover story, before and after publication was compared. The return was then adjusted for the market return and the return of respective industry, again for each company. This enabled us to determine whether Cover Stories had been useful as an indicator. The results have been tested statistically.</p><p>Findings: Positive Cover Stories constituted a momentum indicator while negative Cover Stories represented contrarian indicators. The majority of the results in the specific categories lack statistic significance, furthermore are the discrepancy in the returns of the companies considerable. To sum up, our results do not support the myth and we would not recommend a contrarian strategy based solely on Cover Stories as an indicator.</p>

Cette thèse applique la théorie des prospects et la théorie du regret à l’étude sur la performance des actions et à expliquer une anomalie du marché connue appelé l’effet momentum. Cette thèse propose un modèle théorique qui lie les facteurs comportementaux à la performance des actions et à l’effet momentum, et ensuite réalise des tests empiriques pour examiner le modèle théorique. Dans le chapitre 2, le modèle est établi sur un concept des gains/pertes potentiels, qui indiquent si un investisseur se trouve actuellement dans une situation gagnante ou perdante. Ensuite, le modèle montre que les investisseurs sont très réticents à vendre leurs stocks dans une situation des grands gains ou des grandes pertes. Les chapitres 3 et 4 effectuent des tests empiriques sur le modèle des gains/pertes potentiels. L'échantillon des tests comprend tous les stocks de NYSE et l'AMEX de l’année 1982 à 2012. Les tests sont en mesure de confirmer l'influence des gains/pertes potentiels sur les rendements des actions. En outre, une stratégie de coût nul d’Extrémité moins Moyen (EMM), basée sur le modèle théorique, est documentée pour être rentable après contrôlée pour des risques. Dans le chapitre 5, le modèle des gains/pertes potentiels est développé dans une version dynamique. Il suggère que l'influence des gains/pertes potentiels pourrait persister pendant une période de intermédiaire à long terme, et génère une tendance à la hausse de la performance pour les actions avec un grand gain/perte potentiel. Les tests empiriques dans ce chapitre se concentrent sur l'évolution de série temporelle des rendements. Les tests montrent que les actions avec un grand gain/perte potentiel ont une plus forte tendance à la hausse. Le chapitre 6 applique les résultats du chapitre précédent pour expliquer l'effet momentum. La tendance à la hausse correspond à une auto-corrélation positive des rendements, ce qui est l'une des sources qui contribuent au profit de momentum. Les tests empiriques dans ce chapitre regardent la similitude entre la stratégie de momentum et les gains/pertes potentiels, et examinent également la corrélation entre le profit de momentum et le profit de la stratégie EMM. Les tests montrent que des gains/pertes potentiels pourraient contribuer à l'effet momentum, mais ne sont pas la seule source. L'effet momentum peut être le résultat d'une combinaison de plusieurs facteurs complexes. / This dissertation applies the prospect theory and the regret theory to the study on the stock performance and to explain one well-known market anomaly called the momentum effect. The dissertation proposes a theoretical model that links the behavior factors to stock performance and the momentum effect, and performed empirical test to examine the theoretical model. In chapter 2, the model is established on the concept of the potential gain/loss, which indicates if an investor is currently at a winning or a losing position. The model then shows that the investors are highly reluctant to sell their stocks in a large gain or in a large loss situation. The chapter 3 and 4 perform empirical tests on the model of potential gain/loss. The test sample includes all stocks in NYSE and AMEX from 1982 to 2012. The tests are able to confirm the influence of the potential gain/loss on stock returns. Moreover, a zero-cost Extremity minus Middle (EMM) strategy based on the theoretical model is documented to be profitable after controlling for risks. In chapter 5, the model of potential gain/loss is developed into a dynamic version. It suggests that the influence of a potential gain/loss could persist over an intermediate to long term, and generates an upward trend in performance for stocks with large potential gain/loss. The empirical tests in this chapter focus on the time serial evolution of returns. The tests show that stocks with large potential gain/loss have a stronger upward trend. The chapter 6 applies the results from the previous chapter to explain the momentum effect. The upward trend corresponds to a positive return autocorrelation, which is one of the sources that contribute to the momentum profit. The empirical tests in this chapter look into the similarity between the momentum strategy and the potential gain/loss, and also examine the correlation between the momentum profit and the profit from the EMM strategy. Tests show that the potential gain/loss could contribute to the momentum effect, but is not the only source. The momentum effect could be a result of a combination of many complex factors.

Momentum is one of the most robust anomalies in financial markets, there are two main recent explanations for this phenomenon, a behavioral-based explanation through disposition-effect (i.e., the willingness to sell \"winners\" too quickly and to hold \"losers\" for a long time) and a fund-flow based explanation. The disposition-effect explanation is centered in the convergence of the spread between the fundamental value and the observed market price (disposition-effect causes an underreaction to news that generates this spread), and the fund flows-based explanation is due to the persistence of the performance of mutual-funds (which usually keep buying winning positions and selling the losses). This master thesis compares those theories using Brazilian data (which is suitable for the strong presence of momentum). Our empirical analysis was done using Fama-MacBeth regressions with results pointing the disposition-effect explanation as the most significant, with our robustness analysis contributing positively to the main findings. / Uma das anomalias mais robustas presente nos mercados financeiros é a existência de momentum nos preços de ações, existem duas principais explicações recentes para este fenômeno: explicação comportamental através do efeito-disposição (i.e. disposição de vender ativos \"vencedores\" rapidamente e de segurar ativos \"perdedores\" por muito tempo) e explicações de fluxos de fundos de investimento. A explicação através do efeito-disposição é centrada na convergência do spread entre o valor fundamental de um ativo e o preço de mercado observado (o efeito-disposição causa uma reação branda a notícias que gera esse spread), e a explicação baseada em fluxos de fundos que se deve pela persistência da performance de fundos (que usualmente continuam comprando posições vencedoras e vendendo as perdedoras). O objetivo desta dissertação é comparar essas teorias utilizando dados brasileiros (que é adequado pela forte presença de momentum). Nossa análise empírica foi feita através de regressões de Fama-MacBeth com resultados apontando a explicação centrada no efeito-disposição como a mais significativa, com nossa análise de robustez contribuindo positivamente para nossos resultados principais.

Call number: LD2668 .T4 1985 S54 / Master of Science

Thesis (PhD)--Stellenbosch University, 2015.

The determination of the mechanisms setting the strength and structure of the large scale circulation is a fundamental and long-standing problem in physical oceanography. In this thesis, we seek to explore the mechanisms contributing to the steady state and variability of the large scale flow, with a focus on better understanding the dynamics of the Atlantic meridional overturning circulation (AMOC). In the first part of this thesis, we explore the linear sensitivity of the monthly mean subtropical AMOC to surface fluxes of buoyancy and momentum. Our approach is to use a numerical adjoint. Key insights are provided into the memory of the AMOC to historic atmospheric forcing. We find that significant memory to wind forcing is confined to timescales of less than a year. In contrast, we identify significant memory to surface buoyancy forcing spanning multi-decadal timescales and characterised by a large scale oscillation in the sign of sensitivity between the eastern and western North Atlantic basin. An important result is that to understand the origins of seasonal variability in the modelled AMOC, we must examine the response to a multidecadal history of atmospheric forcing. In the second part of this thesis, a new tool is presented that enables a clean diagnosis of the force balance controlling the circulation regime for a Boussinesq fluid. Specifically, the tool is based on the development of the "rotational momentum" equations and sets of scalar "velocity potentials" and analogous "force functions". The latter allow the projection of all forces onto the acceleration of the vertical shears and external modes of overturning to be visualised in isolation. The rotational momentum decomposition is applied to the modelled circulation in idealised Atlantic and global configurations of the MITgcm, with a focus on elucidating the dynamics of the simulated AMOC. We discuss the key role played by the rotational buoyancy forcing right on the western boundary.

Thesis (MBA)--Stellenbosch University, 2012. / The success of momentum investing has puzzled the investment society for quite some time. Numerous academics have released studies that proved the success of different momentum investing strategies, even after compensating for trading costs. According to the efficient market hypothesis investors can only realise additional returns by taking additional risks. But no real risk factors can be ascribed to momentum investing. This study investigated the success of momentum investing strategies on the Johannesburg Stock Exchange (JSE) during the period January 1997 to March 2012. Three strategies were tested, namely: return momentum, price relative to high price and the crossover ratio. These strategies were tested using different combinations of testing and holding periods and only the more liquid stocks trading on the JSE were used in the study. The study showed that the momentum investing strategies generated statically significant outperformance over the period. The momentum investing strategies were then dissected according to the three risk factors identified by the Fama and French (1992) three-factor model. None of the risk factors were able to explain the outperformance of the momentum strategies. The outperformance of the momentum strategies also showed remarkable resilience after being subjected to trading costs. The success of the three momentum investing strategies is in clear contravention of the efficient market hypothesis and adds to the growing body of evidence against the hypothesis.