Competition for access; spectrum rights and downstream access in wireless telecommunications

We analyse downstream access and capacity choice in the market for wireless telecommunications, where spectrum rights are owned by vertically integrated duopolists and may be traded. In the market for wireless telecommunications, radio spectrum is an essential input. Prior to network construction, the incumbents may offer contracts for capacity to an entrant, granting service-based access on the network they will construct. Alternatively, when spectrum trading is allowed, they may sell part of their license, allowing the entrant to build its own network and enter as an infrastructure player. We find that in this Cournot setting, access is generally provided, as incumbents compete to appropriate the profits of serving a differentiated market through the entrant. Although selling spectrum rights instead of network capacity leads to a loss of economies of scale in infrastructure construction, infrastructure-based entry may dominate as a result of a strategic effect. By delegating capacity choice to the entrant, the access providing incumbent can commit to compete more aggressively, causing its rival incumbent to reduce capacity. A lower aggregate capacity will increase prices and thereby profits.

Renormalization Group Theory of the Three-Dimensional Dilute Bose Gas

We study the three-dimensional atomic Bose gas using renormalization group techniques. Using our knowledge of the microscopic details of the interatomic interaction, we determine the correct initial values of our renormalization group equations and thus obtain also information on nonuniversal properties. As a result, we can predict for instance the critical temperature of the gas and the superfluid and condensate density of the Bose-Einstein condensed phase in the regime $na\Lambda_{th}^2\ll 1$.Comment: 48 pages of ReVTeX and 13 postscript figures. Submitted for publication in Physical Review

Systemic risk across sectors; Are banks different?

This research compares systemic risk in the banking sector, the insurance sector, the construction sector, and the food sector. To measure systemic risk, we use extreme negative returns in stock market data for a time-varying panel of the 20 largest U.S. firms in each sector. We find that systemic risk is significantly larger in the banking sector relative to the other three sectors. This result is robust to separating out correlations with an economy-wide stock market index. For the non-banking sectors, the ordering from high to low systemic risk is: insurance sector, construction sector, and food sector. The difference between the insurance sector and the construction sector is no longer significant after correcting for correlations with the economy as a whole. The correction has a large effect for the banking sector and the insurance sector, and a smaller effect for the other two sectors.

Dynamics of Fluctuating Bose-Einstein Condensates

We present a generalized Gross-Pitaevskii equation that describes also the dissipative dynamics of a trapped partially Bose condensed gas. It takes the form of a complex nonlinear Schr\"odinger equation with noise. We consider an approximation to this Langevin field equation that preserves the correct equilibrium for both the condensed and the noncondensed parts of the gas. We then use this formalism to describe the reversible formation of a one-dimensional Bose condensate, and compare with recent experiments. In addition, we determine the frequencies and the damping of collective modes in this case.Comment: 4 pages of REVTeX, including 4 figure

Opportunistic competition law enforcement

We analyse the interplay between investigation policies, deterrence and desistance in a model where a competition authority monitors multiple sectors and faces a budget constraint that prevents it from deterring cartels in all sectors simultaneously. Most studies of competition law enforcement treat competition authorities as all-knowing, unwavering and benevolent. They do not behave opportunistically, do not face asymmetric information and choose their actions to optimize social welfare. In this paper, we drop one of these assumptions, and study a competition authority that can not commit to a particular investigation strategy. As a consequence, a competition authority’s decisions to investigate will be driven by the (ex-post) desistance effect instead of the (ex ante) deterrence effect of an investigation policy. The resulting opportunistic behaviour may lead to a suboptimal investigation strategy. We find that, in the absence of commitment, developing a sector specific reward scheme based on the number of captured cartels can improve welfare.

Omphale: Streamlining the Communication for Jobs in a Multi Processor System on Chip

Our Multi Processor System on Chip (MPSoC) template provides processing tiles that are connected via a network on chip. A processing tile contains a processing unit and a Scratch Pad Memory (SPM). This paper presents the Omphale tool that performs the first step in mapping a job, represented by a task graph, to such an MPSoC, given the SPM sizes as constraints. Furthermore a memory tile is introduced. The result of Omphale is a Cyclo Static DataFlow (CSDF) model and a task graph where tasks communicate via sliding windows that are located in circular buffers. The CSDF model is used to determine the size of the buffers and the communication pattern of the data. A buffer must fit in the SPM of the processing unit that is reading from it, such that low latency access is realized with a minimized number of stall cycles. If a task and its buffer exceed the size of the SPM, the task is examined for additional parallelism or the circular buffer is partly located in a memory tile. This results in an extended task graph that satisfies the SPM size constraints

Efficient Inter-Task Communication for Nested Loop Programs on a Multiprocessor System

In modern multiprocessor systems, processors can be stalled by inter-task communication when reading from a remote buffer. This paper presents a solution for the inter-task communication, that has a minimal impact on the performance of the system, hides the inter-task communication latency without requiring additional hardware. The solution applies to jobs, represented as task graphs, where the tasks are nested loop programs. Buffers are allocated in scratch-pad memories of the consuming tasks to provide low latency read access. For the nested loop programs, minimal buffer sizes can be determined to cover all possible communication patterns. The added computational complexity is low, as the solution adds only a few operations to the nested loop programs