Cover's universal portfolio,stochastic portfolio theory,and the numéraire portfolio

Cover's celebrated theorem states that the long‐run yield of a properly chosen “universal” portfolio is almost as good as that of the best retrospectively chosen constant rebalanced portfolio. The “universality” refers to the fact that this result is model‐free, that is, not dependent on an underlying stochastic process. We extend Cover's theorem to the setting of stochastic portfolio theory: the market portfolio is taken as the numéraire, and the rebalancing rule need not be constant anymore but may depend on the current state of the stock market. By fixing a stochastic model of the stock market this model‐free result is complemented by a comparison with the numéraire portfolio. Roughly speaking, under appropriate assumptions the asymptotic growth rate coincides for the three approaches mentioned in the title of this paper. We present results in both discrete and continuous time.     

Discussions on the spurious hyperbolic memory in the conditional variance and a new model

This paper studies the spurious hyperbolic memory in the conditional variance caused by the Markov Regime-Switching GARCH (MRS-GARCH) process. We firstly propose an illustrative cause of this spuriousness and provide simulation evidence. An MRS Hyperbolic GARCH (MRS-HGARCH) model is then developed to successfully address it. Related statistical properties including the stationarity conditions and asymptotic behaviours of the maximum likelihood estimators of the MRS-HGARCH process are also investigated. An empirical study of the S&P 500 and TOPIX indexes returns is then conducted which demonstrates that our MRS-HGARCH model can provide a more reliable estimator of the hyperbolic-memory parameter and outperform both the HGARCH and MRS-GARCH models.     

Hamburg's Spaces of Danger: Race,Violence and Memory in a Contemporary Global City

Germany today is experiencing the strongest upsurge of right‐wing populism since the second world war, most notably with the rise of Pegida and Alternative für Deutschland. Yet wealthy global cities like Hamburg continue to present themselves as the gatekeepers of liberal progress and cosmopolitan openness. This article argues that Hamburg's urban boosterism relies on, while simultaneously obscuring, the same structures of racial violence that embolden reactionary movements. Drawing on the work of Walter Benjamin and Allan Pred, we present an archaeology of Hamburg's landscape, uncovering some of its ‘spaces of danger’—sites layered with histories of violence, many of which lie buried and forgotten. We find that these spaces, when they become visible, threaten to undermine Hamburg's cosmopolitan narrative. They must, as a result, be continually erased or downplayed in order to secure the city as an attractive site for capital investment. To illustrate this argument, we give three historical examples: Hamburg's role in the Hanseatic League during the medieval and early modern period; the city under the Nazi regime; and the recent treatment of Black African refugees. The article's main contribution is to better situate issues of historical landscape, collective memory and racialized violence within the political economy of today's global city.     

Value at risk and return in Chinese and the US stock markets: Double long memory and fractional cointegration

Given that the United States is an engine of global stock market while China is the largest emerging market with a cornucopia of anomalies in particular, it is vital to investigate the risk-return relationship in the two markets. This paper brings new insights not only into risk-return tradeoff, but also to the leverage effect, with the application of the fractionally co-integrated vector auto-regression (FCVAR) model capturing the fractional cointegrated relationship and long memory property. Results show that China stock markets own the property of double long memory but the US markets don’t. Most of all, in the US market, a positive risk-return tradeoff exists for the whole sample while after the crisis, even we find the negative relation, it’s not a volatility feedback effect but low risk and high returns. However, there is only a volatility feedback effect in China stock markets. Besides, there is a leverage effect in the US market, while Chinese market exhibits a reverse one, another anomaly, indicating significant difference in the two markets again.     

A fractional cointegration var analysis of exchange rate dynamics

In their seminal work, Baillie and Bollerslev (1994) carried out an analysis of deviations from the cointegrating relationship of seven important exchange rates. They suggested that the exchange rate series possess long memory and therefore such processes could be well described as fractionally integrated processes. Hence, the influence of shocks to the equilibrium exchange rates may only vanish at very long horizons. In this work we analyze the cointegrating structure of five exchange rates to the US dollar, namely the British pound, the Euro, the Swedish Krona, the Canadian Dollar and the Swiss Franc. The series possess long memory and we show that they can be modeled through fractional integration. In fact, standard cointegration is rejected with the more traditional Johansen CVAR methodology. By using the recently introduced Fractionally Cointegrated VAR by Johansen and Nielsen (2012) we provide a cointegrating relationship taking into account fractional integration.     

Volatility of volatility is (also) rough

Using high-frequency data for major volatility indexes, we compute the volatility of volatility and show that its logarithm follows a fractional Brownian motion with Hurst parameter smaller than 1/2 thereby extending to the volatility asset class the recent findings obtained for the equity index markets. The results confirm that the volatility of volatility is a rough process and it possesses the long memory property. We also show that the correlation between the volatility and the volatility of volatility is positive, consistent with observations in the volatility option market. Lastly, a robustness check using volatility futures confirms the findings.     

浅谈长螺旋钻孔灌注桩技术在水利工程中的应用

长螺旋钻孔灌注桩施工是工业民用建筑基础处理中经常采用的一种施工技术。文章通过对其在围堤湖分洪闸闸室段基础处理工程中成功应用的阐析,提出它在某些水利工程的基础处理施工中同样可以占据一席之地,并有其独特的优势。     

Measuring the persistence of deviations from purchasing power parity with a fractionally integrated STAR model

Empirically, elements of both fractional long memory and threshold non-linearity are present in the real exchange rates of the G-7 countries against the US, notably in the EU countries. Estimated half lives of deviations from PPP using median unbiased corrections to conventional linear autoregressive models corroborate existing evidence related to the PPP paradox as half lives range from at least four years to an infinite number of years. In contrast, for each EU country, accounting for threshold non-linearity results in estimated half lives that can be less than three years even with the allowance for fractional long memory.     

Exploring the predictability of range‐based volatility estimators using recurrent neural networks

We investigate the predictability of several range‐based stock volatility estimates and compare them with the standard close‐to‐close estimate, which is most commonly acknowledged as the volatility. The patterns of volatility changes are analysed using long short‐term memory recurrent neural networks, which are a state‐of‐the‐art method of sequence learning. We implement the analysis on all current constituents of the Dow Jones Industrial Average index and report averaged evaluation results. We find that the direction of changes in the values of range‐based estimates are more predictable than that of the estimate from daily closing values only.     

‘Who Knows What?’ in New Venture Teams: Transactive Memory Systems as a Micro‐Foundation of Entrepreneurial Orientation

The increasing importance of entrepreneurial behaviour has led scholars to embrace the idea that an entrepreneurial orientation (EO) is an important predictor of firm performance. While EO occupies a central position in strategic entrepreneurship research, scholars have yet to explore its origins in new ventures. Drawing on the knowledge‐based and cognitive views, we theorize that a new venture team's transactive memory system is a cognitive mechanism that spurs the development of an EO. In a field study of high‐tech new ventures in China, we examined the relationship between venture teams’ transactive memory systems (representing the distribution, integration, and utilization of the teams’ knowledge) and EO and the moderating influence of team‐, firm‐, and environment‐level factors. We found that the transactive memory system of a new venture team enhanced their EO and that this relationship was positively influenced by intra‐team trust, the structural organicity of a venture, and environmental dynamism. Our findings provide novel insights into the micro‐foundations of TMS in developing an EO in new ventures.