单光子卫星量子通信噪声和干扰分析

卫星量子通信是建立全球量子通信网络的最佳选择之一。针对采用偏振编码的卫星量子通信中的偏振保持问题,研究了大气散射和卫星与地面站间相对运动等因素对量子偏振态相位和对准的影响以及相位延迟和对准误差对系统量子误码率的影响,分析了背景噪声和系统硬件噪声对通信产生的影响以及单光子通信过程中可能受到的光子分离攻击干扰,为量子信号认知设计提供借鉴意义。     

Portfolio constraints,differences in beliefs and bubbles

I propose an arbitrage-based theory of bubbles in economies with general portfolio constraints and differences in beliefs. I find that, in general, bubbles cannot exist unless the constraints restrict the demand for credit sufficiently to induce low interest rates. Speculation due to heterogeneous beliefs does not cause bubbles. Ruling out bubbles under asymmetric information requires stronger assumptions: the presence of some uninformed agents and mild portfolio restrictions (debt or borrowing constraints), or alternatively, the existence of some impatient and fully informed agents.     

The new exchange rate policy in the Asian emerging economies – goodbye trouble,hello comfort?

In this paper, we discuss new aspects of exchange rate policy that can be observed in the Asian emerging economies. In the first place, we show the alternative regimes they may choose and their respective pros and cons. Secondly, we concentrate on the recent strategy of systematic undervaluation of one's currency – figuring prominently among ‘big’ Asian players such as China and India – and the most likely implications of such a strategy for domestic allocation, distribution and stabilization goals. With the background of Germany's experiences in 1969, almost on the eve of the Bretton Woods' system collapse, we model a speculative attack on an undervalued currency in the vein of the Flood–Garber seminal paper from 1984. Now, however, the country in concern (just like India and China) possesses strong rather than weak fundamentals. The continuous accumulation of international reserves, in addition, leads to the question of an ‘optimal management’ of foreign exchange reserves in Asian emerging economies with regard to size and composition. We finally propose a sequence of reforms/policies that should be implemented in those Asian emerging economies on their still long journey to a regime featured by autonomous monetary policy, flexible exchange rate and capital mobility. A brief summary and an outlook for future research close the paper.     

中国式卖空机制与高管减持——基于融资融券分步扩容的准自然实验

本文以我国的融资融券制度为背景,结合双重差分模型,研究卖空机制对上市公司高管减持行为的影响。研究发现,相对于非融券标的,可融券标的公司高管的月减持比例在允许卖空后下降22%,这种抑制作用在小规模、高盈余平滑度以及非国有公司中体现得更为明显。其次,成为可融券标的后,股价定价效率提高,高管减持收益显著下降。进一步地,本文将高管的减持行为分为定期性与投机性两类,发现卖空机制显著抑制了高管基于信息优势和股价偏差的投机性减持行为。     

Do terror attacks affect the dollar-pound exchange rate? A nonparametric causality-in-quantiles analysis

While much significant research has been done to study the effects of terror attacks on stock markets, less is known about the response of exchange rates to terror attacks. We suggest a non-parametric causality-in-quantiles test to study whether (relative) terror attacks affect exchange-rate returns and volatility. Using data on the dollar-pound exchange rate to illustrate the test, we show that terror attacks mainly affect the lower and upper quantiles of the conditional distribution of exchange-rate returns, while misspecified (due to nonlinearity and structural breaks) linear Granger causality test show no evidence of predictability. Terror attacks also affect almost all quantiles of the conditional distribution of exchange-rate volatility (except the extreme upper-end), with the significance of the effect being particularly strong for the lower quantiles. The importance of terror attacks is shown to hold also under an alternative measure of volatility and for an important emerging-market exchange rate as well.     

Bancarization and violent attacks from guerrilla and other illegal groups in Colombia

Income shocks affect violence through the opportunity cost and rapacity effects. Existing studies focus on the impact of transitory shocks, especially commodity price innovations. This paper builds on this literature and studies the causal effect of permanent income shocks on armed conflict in Colombia. Using a rich dataset reporting all guerrilla and other armed groups' attacks by municipality between 2009 and 2014 and information on the provision of banking services, it shows that increasing bancarization leads to reductions in violence. These results have important implications for public policy in countries with a long history of violence. They suggest that promoting financial inclusion is useful for reducing conflict.     

User costs and bubbles in land markets

In asset markets with speculative behavior, the long-run equilibrium relationship between asset prices and the discounted flow of future rents may become invalid. We distinguish short-term user costs and longer-term user costs with variables that reflect fundamentals. We show how to work around the empirical problem of measuring speculative expectations about asset price changes and derive a simple user cost formula where the asset price change in the short-term relationship comes out as the long-run change in the overall price level.     

Speculative attacks to currency target zones: A market microstructure approach

This paper develops a simple optimization model to characterize the behaviour of market participants during currency attacks and tests it empirically. Specifically, we test for the determinants of the timing, magnitude and chance of success of an attack. The empirical part is carried out using Mexican data, as this market provides us with an appropriate target zone framework and with a very rich dataset. We find empirical support for a set of microeconomic determinants which include: daily order flow, inventory management, intra-day price volatility, and the forward intervention-price differential. Finally, we test for the role of central bank reserves in speculative attack dynamics.     

EMPIRICAL ANALYSIS OF SPECULATIVE ATTACKS WITH CONTRACTIONARY REAL EFFECTS

The effects of a currency crisis on a country's economy depend on nonlinear relations among several variables that characterize the economic, financial, legal and socio‐political structure of the country at the onset of the crisis. Those effects can be associated with contractions or expansions in output. Historically, contractionary speculative attacks are more frequent. This paper uses a parametric censored heteroscedastic TOBIT model to empirically analyse how different economic and financial variables determine the real effects of a contractionary speculative attack. Variables describing the banking sector, the international trade, the severity of the crisis and foreign interest rates are found to be significant in explaining the size of currency crises' contractionary real effects. The TOBIT's results are compared with alternative modelling strategies. Copyright © 2012 John Wiley & Sons, Ltd.     

不完全信息下外汇市场上的投机攻击博弈

伴随着经济全球化和金融自由化的发展,外汇市场上的游戏规则产生了显而易见的变化,投机资本规模迅速膨胀,羊群效应也愈发严重,对一国汇率的稳定形成严重挑战。文章从博弈论的角度出发,构造不完全信息下投机资本攻击一国汇率的博弈模型,揭示投机者进行投机攻击决策的依据和博弈中货币当局败北的原因,创造性地提出“抗投机攻击指数”概念,用以判断一国外汇市场的稳定。