Secondary multiplication in Tate cohomology of generalized quaternion groups

Let k be a field and let G be a finite group. By a theorem of D.Benson, H.Krause and S.Schwede, there is a canonical element in the Hochschild cohomology of the Tate cohomology HH^{3,-1} H*(G) with the following property: Given any graded H*(G)-module X, the image of the canonical element in Ext^{3,-1}(X,X) is zero if and only if X is isomorphic to a direct summand of H*(G,M) for some kG-module M. In particular, if the canonical element vanishes, then every module is a direct summand of a realizable H*(G)-module. We prove that the converse of that last statement is not true by studying in detail the case of generalized quaternion groups. Suppose that k is a field of characteristic 2 and G is generalized quaternion of order 2^n with n>2. We show that the canonical element is non-trivial for all n, but there is an H*(G)-module detecting this non-triviality if and only if n=3.Comment: 17 page

The Impact of Feedback Frequency on Risk Taking: How general is the Phenomenon?

In a recent QJE-article, Gneezy and Potters (1997) present experimental evidence for the impact of feedback frequency on individual risk taking behavior in repeated investment decisions. They find an increased willingness to invest into a risky asset if less frequent feedback about the outcome of previous investments is provided. The observed decision pattern is explained by myopic loss aversion, a combination of mental accounting and loss aversion. In this note, we argue that the findings of Gneezy and Potters on the relationship between feedback frequency and risk taking are not as general as they might seem. We provide theoretical arguments and experimental evidence to demonstrate that the reported phenomenon is not robust to changes in the risk profiles of the given investment options.

Space-Time Isogeometric Analysis of Parabolic Evolution Equations

We present and analyze a new stable space-time Isogeometric Analysis (IgA) method for the numerical solution of parabolic evolution equations in fixed and moving spatial computational domains. The discrete bilinear form is elliptic on the IgA space with respect to a discrete energy norm. This property together with a corresponding boundedness property, consistency and approximation results for the IgA spaces yields an a priori discretization error estimate with respect to the discrete norm. The theoretical results are confirmed by several numerical experiments with low- and high-order IgA spaces

Overconfidence of Professionals and Lay Men: Individual Differences Within and Between Tasks?

Overconfidence can manifest itself in various forms. For example, people think that their knowledge is more precise than it really is (miscalibration) and they believe that their abilities are above average (better than average effect). The questions whether judgment biases are related or whether stable individual differences in the degree of overconfidence exist, have long been unexplored. In this paper, we present two studies that analyze whether professional traders or investment bankers who work for international banks are prone to judgment biases to the same degree as a population of lay men. We examine whether there are robust individual differences in the degree of overconfidence within various tasks. Furthermore, we analyze whether the degree of judgment biases is correlated across tasks. Based on the answers of 123 professionals, we find that expert judgment is biased. In most tasks, their degrees of overconfidence are significantly higher than the respective scores of a student control group. In line with the literature, we find stable individual differences within tasks (e.g. in the degree of miscalibration). However, we find that correlations across distinct tasks are sometimes insignificant or even negative. We conclude that some manifestations of overconfidence, that are often argued to be related, are actually unrelated.

The Retrospective Evaluation of Payment Sequences: Duration Neglect and Peak-and-End-Effects

In this paper we present experimental research examining the ability of individuals to make good retrospective evaluations of payment sequences. Inspired by the evidence on systematic biases in the retrospective evaluation of affective episodes involving pain and pleasure we designed choice scenarios for payment sequences in which the existence of peak and end effects as well as duration neglect could be examined. There are two main results: We do not observe a systematic impact of payment sequence features (other than its sum) on the choices if subjects merely get delivered the payments without any affection or effort. Subjects, by and large, choose the sequence with the highest total payment. In a second scenario, in which payments were linked to the subjects? effort and performance in strenuous tasks, we observe a strong effect of duration neglect and a weaker, but still significant end effect. We further find that the mere number of peak losses in a sequence strongly influences its attractiveness. In this scenario subjects do not often choose the sequence with the highest total payment.

On the notion of order in the stable module category

The notion of order in triangulated categories, as introduced by Schwede, is investigated in the case of the stable category of kG-modules, where k is a field of characteristic p and G is a finite group. For Tate cohomology classes ζ of even degree, we obtain bounds on the ζ-order which are similar to corresponding results on the p-order in the stable homotopy category. On our way we introduce a power operation P1 on Tate cohomology which serves as an obstruction for the ζ-order to be larger than its minimal possible value. Furthermore, it enables us to compute certain higher Massey products explicitly

The impact of feedback frequency on risk taking : how general ist the phenomenon?

In a recent QJE-article, Gneezy and Potters (1997) present experimental evidence for the impact of feedback frequency on individual risk taking behavior in repeated investment decisions. They find an increased willingness to invest into a risky asset if less frequent feedback about the outcome of previous investments is provided. The observed decision pattern is explained by myopic loss aversion, a combination of mental accounting and loss aversion. In this note, we argue that the findings of Gneezy and Potters on the relationship between feedback frequency and risk taking are not as general as they might seem. We provide theoretical arguments and experimental evidence to demonstrate that the reported phenomenon is not robust to changes in the risk profiles of the given investment options