Hydrodynamics Beyond the Gradient Expansion: Resurgence and Resummation

Consistent formulations of relativistic viscous hydrodynamics involve short lived modes, leading to asymptotic rather than convergent gradient expansions. In this Letter we consider the Mueller-Israel-Stewart theory applied to a longitudinally expanding quark-gluon plasma system and identify hydrodynamics as a universal attractor without invoking the gradient expansion. We give strong evidence for the existence of this attractor and then show that it can be recovered from the divergent gradient expansion by Borel summation. This requires careful accounting for the short-lived modes which leads to an intricate mathematical structure known from the theory of resurgence.Comment: Presentation improved, typos fixed; roughly matches the published versio

Macro-prudential regulation of credit booms and busts -- the case of Poland

The last several years before the global downturn of 2008-2009 saw rapid credit growth in Poland. The credit-to-gross domestic product ratio rose from about 25 percent in 2004 to close to 50 percent in 2009. Such an expansionitself might potentially be a source of risks to financial stability, but it was also coupled with relatively new phenomena, such as massive foreign currency lending. Thanks to the pro-active attitude of the Polish authorities and sound economic fundamentals, the risks largely have not materialized. Since 2006 the financial supervisor has addressed in its recommendations for banks the problem of foreign exchange lending, which contributed to the high quality of the portfolio. Before the economy slowed down, the Polish Financial Supervisory Authority persuaded banks to accumulate an additional capital buffer that helped protect them from the negative consequences of the downturn. Some regulatory concepts that had been put into place in Poland in the previous years, including quantitative liquidity requirements, are now being implemented globally. The Polish Financial Supervisory Authority participates in international debates on a new regulatory regime for the financial system. The major message the authority intends to convey is that all new regulations must be tailored carefully. Regulators should make an effort to ensure that the benefits of enhanced quality of the capital base or the countercyclical buffer are not compromised by international overregulation that could undermine national authorities'ability to pursue effective country-specific policies.Banks&Banking Reform,Debt Markets,Access to Finance,Bankruptcy and Resolution of Financial Distress,Emerging Markets

Risk Attitudes and Measures of Value for Risky Lotteries.

The topic of this thesis is decision-making under risk. I focus my analysis on expected utility theory by von Neumann and Morgenstern. I am especially interested in modeling risk attitudes represented by Bernoulli utility functions that belong to the following classes: Constant Absolute Risk Aversion, Decreasing Absolute Risk Aversion (understood as strictly decreasing) and in particular a subset thereof - Constant Relative Risk Aversion. I build a theory of buying and selling price for a lottery, the concepts defined by Raiffa, since such theory proves useful in analyzing a number of interesting issues pertaining to risk attitudes' characteristics within expected utility model. In particular, I analyze the following: - Chapter 2 - expected utility without consequentialism, buying/selling price gap, preference reversal, Rabin paradox - Chapter 3 - characterization results for CARA, DARA, CRRA, simple strategies and an extension of Pratt result on comparative risk aversion - Chapter 4 - riskiness measure and its intuition, extended riskiness measure and its existence, uniqueness and propertiesdecision-making under risk; lottery; gamble; expected utility theory; risk attitudes; CARA; DARA; CRRA; buying and selling price for a lottery; D81; D03; C91;Decision making; Strategic planning; Risk-taking (Psychology);