Spectral Properties of Tensor Products of Channels

We investigate spectral properties of the tensor products of two quantum channels defined on matrix algebras. This leads to the important question of when an arbitrary subalgebra can split into the tensor product of two subalgebras. We show that for two unital quantum channels $\mathcal{E}_1$ and $\mathcal{E}_2$ the multiplicative domain of $\mathcal{E}_1\otimes\mathcal{E}_2$ splits into the tensor product of the individual multiplicative domains. Consequently, we fully describe the fixed points and peripheral eigen operators of the tensor product of channels. Through a structure theorem of maximal unital proper $^*$-subalgebras (MUPSA) of a matrix algebra we provide a non-trivial upper bound of the 'multiplicative index' of a unital channel which was recently introduced. This bound gives a criteria on when a channel cannot be factored into a product of two different channels. We construct examples of channels which can not be realized as a tensor product of two channels in any way. With these techniques and results, we found some applications in quantum error correction.Comment: Proofs of Section 3 are simplified using a result of Ola Bratteli. Some references have been update

The effect of a collective exchange rate adjustment on East Asian exports

This paper estimates long-run effects of a collective exchange rate adjustment on multilateral exports from China, Japan, South Korea, and Taiwan. The findings show that a 1 percent generalized appreciation of all East Asian exchange rates would reduce East Asian exports by about 3 percent.Global imbalance; exchange rate appreciation; collective adjustment; production networks; East Asia

Impact of economic growth and financial development on exports: Cointegration and causality analysis in Pakistan

The analysis shows cointegration between exports, economic growth and financial development in case of Pakistan. The results that economic growth and financial development stimulate rate of exports growth in Pakistan. The causality analysis reveals bidirectional causal relationship between financial development and economic growth, financial development and exports and exports and economic growth in case of Pakistan.Economic growth, financial development, Cointegration, Pakistan

Stateless Puzzles for Real Time Online Fraud Preemption

The profitability of fraud in online systems such as app markets and social networks marks the failure of existing defense mechanisms. In this paper, we propose FraudSys, a real-time fraud preemption approach that imposes Bitcoin-inspired computational puzzles on the devices that post online system activities, such as reviews and likes. We introduce and leverage several novel concepts that include (i) stateless, verifiable computational puzzles, that impose minimal performance overhead, but enable the efficient verification of their authenticity, (ii) a real-time, graph-based solution to assign fraud scores to user activities, and (iii) mechanisms to dynamically adjust puzzle difficulty levels based on fraud scores and the computational capabilities of devices. FraudSys does not alter the experience of users in online systems, but delays fraudulent actions and consumes significant computational resources of the fraudsters. Using real datasets from Google Play and Facebook, we demonstrate the feasibility of FraudSys by showing that the devices of honest users are minimally impacted, while fraudster controlled devices receive daily computational penalties of up to 3,079 hours. In addition, we show that with FraudSys, fraud does not pay off, as a user equipped with mining hardware (e.g., AntMiner S7) will earn less than half through fraud than from honest Bitcoin mining

Downward Accountability of NGOs in Bangladesh: Theoretical Issues and Empirical Investigation

This article analyses overall NGO accountability and accountability to beneficiaries in particular. It is based on the collection of qualitative data from four NGOs in Bangladesh. The participation of beneficiaries has been disaggregated into three phases for more analytical discussion: decision-making, implementation, and evaluation. The study results reveal that the participation of beneficiaries is much higher in the project/program implementation phase. The condition is alarming for the decision-making and evaluation phase, where participation is more rhetoric and sham rituals than the actual exercise. The study also identified some formal and informal mechanisms of participation