Classifying spaces of compact Lie groups that are p-compact for all prime numbers

We consider a problem on the conditions of a compact Lie group G that the loop space of the p-completed classifying space be a p-compact group for a set of primes. In particular, we discuss the classifying spaces BG that are p-compact for all primes when the groups are certain subgroups of simple Lie groups. A survey of the p-compactness of BG for a single prime is included.Comment: This is the version published by Geometry & Topology Monographs on 29 January 200

A Large Speculator in Contagious Currency Crises

This paper studies the implications of the presence of a large speculator like George Soros during a contagious currency crisis. The model proposes a new contagion channel and shows how a currency crisis can spread from one country to another even when these countries are totally unrelated in terms of economic fundamentals. This model enables us to distinguish between whether a crisis is a coincidence or due to contagion when it happens in two countries. It finds that the better the economic fundamentals in the originating crisis country, the more severe the contagion under certain conditions. The large speculator is more aggressive in attacking the currency peg than he would be if his size were small. Furthermore, the mere presence of the large speculator makes other small speculators more aggressive in attacking the currency peg, which in turn makes countries more vulnerable to currency crises. But surprisingly, the presence of the large speculator mitigates contagion of crises across countries. The model presents policy implications as to financial disclosure and size regulation of speculators such as hedge funds, which recently have been hot topics among policy makers. First, financial disclosure by speculators eliminates contagion, but may make countries more vulnerable to crises. Second, regulating the size of speculators (e.g., prohibiting hedge funds from high-leverage and thereby limiting the amount of short-selling) makes countries less vulnerable to crises, but makes contagion more severeContagion; Currency Crises; George Soros; Global Game

Contagion of Currency Crises across Unrelated Countries without Common Lender

I construct a micro-model to show that a currency crisis can spread from one country to another even when these countries are unrelated in terms of economic fundamentals and there is no capital linkage across countries through a common lender or an interbank market. The key to explaining contagious currency crises in the model lies in each speculator's private information and learning behavior about other speculators' type. Since the payoff of each speculator depends on other speculators' behavior determined by their types, each speculator's behavior depends on her belief about other speculators' types. If a currency crisis in one country reveals the speculators' types to some degree, it leads to an updating of each speculator's belief about other speculators' types and therefore a change in her optimal behavior, which in turn can cause a currency crisis even in another unrelated country without capital linkage. Although the presence of contagion itself is not new in the literature, there is an important implication difference between the literature and this paper. The model shows that the crisis with better economic fundamentals can be more contagious than that with worse economic fundamentals; this has not been shown in the literature. This is because the former conveys information about types of speculators while the latter does not. Even if country B does not suffer from a contagious crisis due to bad economic fundamentals from country A, it does not necessarily mean that it will never suffer contagion from some other country with better economic fundamentals than country AContagion; Currency Crises; Global Game

Van Lambalgen's Theorem for uniformly relative Schnorr and computable randomness

We correct Miyabe's proof of van Lambalgen's Theorem for truth-table Schnorr randomness (which we will call uniformly relative Schnorr randomness). An immediate corollary is one direction of van Lambalgen's theorem for Schnorr randomness. It has been claimed in the literature that this corollary (and the analogous result for computable randomness) is a "straightforward modification of the proof of van Lambalgen's Theorem." This is not so, and we point out why. We also point out an error in Miyabe's proof of van Lambalgen's Theorem for truth-table reducible randomness (which we will call uniformly relative computable randomness). While we do not fix the error, we do prove a weaker version of van Lambalgen's Theorem where each half is computably random uniformly relative to the other

Derandomization in Game-theoretic Probability

We give a general method for constructing a deterministic strategy of Reality from a randomized strategy in game-theoretic probability. The construction can be seen as derandomization in game-theoretic probability.Comment: 19 page