Excitonic structure and pumping power dependent emission blue-shift of type-II quantum dots

In this work we study theoretically and experimentally the multi-particle structure of the so-called type-II quantum dots with spatially separated electrons and holes. Our calculations based on customarily developed full configuration interaction approach reveal that exciton complexes containing holes interacting with two or more electrons exhibit fairly large antibinding energies. This effect is found to be the hallmark of the type-II confinement. In addition, an approximate self-consistent solution of the multi-exciton problem allows us to explain two pronounced phenomena: the blue-shift of the emission with pumping and the large inhomogenous spectral broadening, both of those eluding explanation so far. The results are confirmed by detailed intensity and polarization resolved photoluminescence measurements on a number of type-II samples.Comment: 11 pages, 5 figure

The subpower membership problem for semigroups

Fix a finite semigroup $S$ and let $a_1,\ldots,a_k, b$ be tuples in a direct power $S^n$. The subpower membership problem (SMP) asks whether $b$ can be generated by $a_1,\ldots,a_k$. If $S$ is a finite group, then there is a folklore algorithm that decides this problem in time polynomial in $nk$. For semigroups this problem always lies in PSPACE. We show that the SMP for a full transformation semigroup on 3 letters or more is actually PSPACE-complete, while on 2 letters it is in P. For commutative semigroups, we provide a dichotomy result: if a commutative semigroup $S$ embeds into a direct product of a Clifford semigroup and a nilpotent semigroup, then SMP(S) is in P; otherwise it is NP-complete

Use of the booklet category test to assess abstract concept formation in schizophrenic disorders

The relationship of concept formation abilities to the presence or absence of delusions in schizophrenic disorders was investigated. Twenty-six schizophrenic patients and 14 normal individuals were administered a short form of the Booklet Category Test (BCT). Patients were grouped into those with and without delusions. It was hypothesized that the delusional group would perform significantly better on the BCT (obtain lower error scores) than the nondelusional group. Normal and delusional groups obtained significantly lower BCT error scores than the nondelusional group, even when differences in IQ scores were statistically partialled out. The two schizophrenic groups also differed significantly on BCT error scores with the delusional group performing better than the nondelusional group

On the Change in the Austrian Business Cycle

This paper analyses the change in the Austrian business cycle over time using data back to 1954. The change in the cyclical pattern is captured using a nonlinear univariate structural time series model where the time of the break point is estimated. Results for GDP series suggest a break in the frequency of the cycle and in the parameter covering the variance of the disturbances of the cycle taking place in the mid 1970s and early 1980s, respectively. Using data for GDP components a break in these variables is found, too, but the timing of the break differs among the series. In a further step the paper assesses the relevance of these findings for forecasting purposes. It is shown that during certain periods the out-of-sample forecasting performance of GDP does improve when a break in one of the two parameters is explicitly modelled

Business Cycles and Growth: A Survey

The paper surveys the evolution of modern macroeconomic models with the focus on the interrelations between endogenous growth and cyclical fluctuations. After reviewing models of the business cycle and endogenous growth, the paper discusses literature combining elements of both of them