When do weak-coupling approaches accurately capture the dynamics of complex quantum systems?

Understanding the dynamics of higher-dimensional quantum systems embedded in a complex environment remains a significant theoretical challenge. While several approaches yielding numerically converged solutions exist, these are computationally expensive and often provide only limited physical insight. Here we address the question when more intuitive and simpler to compute weak-coupling approaches still provide adequate accuracy. We develop a simple analytical criterion and verify its validity for the case of the much-studied FMO dynamics as well as the canonical spin-boson model.Comment: 10 pages, 5 figures, comments are very welcome

Determinants of Productivity of Ukrainian Firms

This paper examines the determinants of total factor productivity (TFP) of Ukrainian firms in manufacturing and services, using micro-level data for the years 2005 and 2013. We first estimate regressions for the pooled dataset for the manufacturing and service sectors jointly, and then separately for each sector. Our empirical results show a positive link between the total factor productivity, intangible assets, capital intensity, firm size, competition in the industry, ownership status, and firm internationalization (exports and imports). In addition, we find that the determinants of productivity differ among the sectors and years of our sample