Dynamical solutions of a quantum Heisenberg spin glass model

We consider quantum-dynamical phenomena in the $\mathrm{SU}(2)$, $S=1/2$ infinite-range quantum Heisenberg spin glass. For a fermionic generalization of the model we formulate generic dynamical self-consistency equations. Using the Popov-Fedotov trick to eliminate contributions of the non-magnetic fermionic states we study in particular the isotropic model variant on the spin space. Two complementary approximation schemes are applied: one restricts the quantum spin dynamics to a manageable number of Matsubara frequencies while the other employs an expansion in terms of the dynamical local spin susceptibility. We accurately determine the critical temperature $T_c$ of the spin glass to paramagnet transition. We find that the dynamical correlations cause an increase of $T_c$ by 2% compared to the result obtained in the spin-static approximation. The specific heat $C(T)$ exhibits a pronounced cusp at $T_c$. Contradictory to other reports we do not observe a maximum in the $C(T)$-curve above $T_c$.Comment: 8 pages, 7 figure

Arabidopsis thaliana POLYOL/MONOSACCHARIDE TRANSPORTERS 1 and 2: fructose and xylitol/H+ symporters in pollen and young xylem cells

The genome of Arabidopsis thaliana contains six genes, AtPMT1 to AtPMT6 (Arabidopsis thaliana POLYOL/MONOSACCHARIDE TRANSPORTER 1–6), which form a distinct subfamily within the large family of more than 50 monosaccharide transporter-like (MST-like) genes. So far, only AtPMT5 [formerly named AtPLT5 (At3g18830)] has been characterized and was shown to be a plasma membrane-localized H+-symporter with broad substrate specificity. The characterization of AtPMT1 (At2g16120) and AtPMT2 (At2g16130), two other, almost identical, members of this transporter subfamily, are presented here. Expression of the AtPMT1 and AtPMT2 cDNAs in baker's yeast (Saccharomyces cerevisiae) revealed that these proteins catalyse the energy-dependent, high-capacity transport of fructose and xylitol, and the transport of several other compounds with lower rates. Expression of their cRNAs in Xenopus laevis oocytes showed that both proteins are voltage-dependent and catalyse the symport of their substrates with protons. Fusions of AtPMT1 or AtPMT2 with the green fluorescent protein (GFP) localized to Arabidopsis plasma membranes. Analyses of reporter genes performed with AtPMT1 or AtPMT2 promoter sequences showed expression in mature (AtPMT2) or germinating (AtPMT1) pollen grains, as well as in growing pollen tubes, hydathodes, and young xylem cells (both genes). The expression was confirmed with an anti-AtPMT1/AtPMT2 antiserum (αAtPMT1/2) raised against peptides conserved in AtPMT1 and AtPMT2. The physiological roles of the proteins are discussed and related to plant cell wall modifications

Aggregate Unemployment Decreases Individual Returns to Education

On the basis of a theoretical model, we argue that higher aggregate unemployment affects individual returns to education. We therefore include aggregate unemployment and an interaction term between unemployment and the individual education level in a standard Mincer equation. Our results show that an increase in regional unemployment by 1% decreases the returns to education by 0.005 percentage points. This implies that higher skilled employees are better sheltered from labour market changes with respect to their jobs but encounter larger wage changes than less skilled employees. Differences in regional unemployment can in addition almost fully explain the observed large differences in regional returns to education. We use representative individual data and regional panel variation in unemployment between different German regions and for different employee groups. We demonstrate that our results are robust with respect to aggregation bias, time lags and potential endogeneity of the unemployment variable

Do higher corporate taxes reduce wages? : Micro evidence from Germany

Because of endogeneity problems very few studies have been able to identify the incidence of corporate taxes on wages. We circumvent these problems by using an 11-year panel of data on 11,441 German municipalities' tax rates, 8 percent of which change each year, linked to administrative matched employer-employee data. Consistent with our theoretical model, we find a negative effect of corporate taxation on wages: a 1 euro increase in tax liabilities yields a 77 cent decrease in the wage bill. The direct wage effect, arising in a collective bargaining context, dominates, while the conventional indirect wage effect through reduced investment is empirically small due to regional labor mobility. High and medium-skilled workers, who arguably extract higher rents in collective agreements, bear a larger share of the corporate tax burden

Yardstick Competition in German Municipalities

Does increasing transparency improve fiscal policy behavior of local governments? One way this could take place is via Yardstick Competition between incumbents of neighboring municipalities. This paper contributes to the literature by introducing a simple model which employs probabilistic voting to show the effect of Yardstick Competition on the amount of political rents diverted from the tax revenue. Since additional rents lower the probability of being reelected, the incumbent will reduce equilibrium rents if voters use information on fiscal performance in similar municipalities to evaluate the incumbent's quality. I test this hypothesis on a panel dataset of municipal budget and electoral data in the german state of Northrine-Westphalia. I show evidence for Yardstick Competition in the local business and property tax rates.Kann zunehmende Transparenz im kommunalen Budgetprozess die fiskalpolitische Disziplin der politischen Entscheidungsträger verbessern? In dieser Arbeit wird ein positiver Modellrahmen entwickelt, anhand dessen die Wirkungsweise von steigen - der Transparenz auf das Entscheidungsverhalten von Kommunalpolitikern durch den Yardstick Competition Effekt dargestellt werden kann. Politiker reduzieren die Veruntreuung finanzieller Mittel, wenn ihr Verhalten von den Wählern relativ zur Leistung von Politikern in benachbarten Kommunen bewertet wird. Unter Anwendung von Methoden der räumlichen Ökonometrie auf kommunale Haushalts- und Wahldaten der Jahre 1989 bis 2004 wird gezeigt, dass die räumliche Korrelation in den Gewerbe- und Grundsteuerhebesätzen in Nordrhein-Westfalen auf die Existenz von Yardstick Competition zurückzuführen ist

The prosurvival IKK-related kinase IKKϵ integrates LPS and IL17A signaling cascades to promote Wnt-dependent tumor development in the intestine

Constitutive Wnt signaling promotes intestinal cell proliferation, but signals from the tumor microenvironment are also required to support cancer development. The role that signaling proteins play to establish a tumor microenvironment has not been extensively studied. Therefore, we assessed the role of the proinflammatory Ikk-related kinase Ikkϵ in Wnt-driven tumor development. We found that Ikkϵ was activated in intestinal tumors forming upon loss of the tumor suppressor Apc. Genetic ablation of Ikkϵ in b-catenin-driven models of intestinal cancer reduced tumor incidence and consequently extended survival. Mechanistically, we attributed the tumor-promoting effects of Ikkϵ to limited TNF-dependent apoptosis in transformed intestinal epithelial cells. In addition, Ikkϵ was also required for lipopolysaccharide (LPS) and IL17A-induced activation of Akt, Mek1/2, Erk1/2, and Msk1. Accordingly, genes encoding proinflammatory cytokines, chemokines, and anti-microbial peptides were downregulated in Ikkϵ-deficient tissues, subsequently affecting the recruitment of tumor-associated macrophages and IL17A synthesis. Further studies revealed that IL17A synergized with commensal bacteria to trigger Ikkϵ phosphorylation in transformed intestinal epithelial cells, establishing a positive feedback loop to support tumor development. Therefore, TNF, LPS, and IL17A-dependent signaling pathways converge on Ikkϵ to promote cell survival and to establish an inflammatory tumor microenvironment in the intestine upon constitutive Wnt activation. � 2016 American Association for Cancer Research

The Revenue and Base Effects of Local Tax Hikes: Evidence from a Quasi-Experiment

This paper studies the revenue and base effects of local property and business tax hikes using a natural experiment in the German state of North Rhine-Westphalia (NRW). Due to a reform of the local equalization scheme in 2003, a set of municipalities in NRW increased their local tax rates by one to two percentage points while the remaining municipalities kept their rates constant. Using this variation across municipalities and over time to implement a difference-in-differences design covering the period 1995-2010, I find that property tax hikes have a revenue elasticity of unity and no adverse base effects. Business tax hikes have no discernible base effects but also no statistically significant effect on revenues. Furthermore, the results suggest that the tax hikes have no effect on broader economic outcomes such as local employment, firms´ wage bill, and property prices. Overall, increasing local tax rates by one to two percentage points does not seem to affect the local economy adversely

Designing Institutions for Diversity

This paper analyzes the design of innovation contests when the quality of an innovation depends on the research approach of the supplier, but the best approach is unknown. Diversity of approaches is desirable because it generates an option value. In our main model with two suppliers, the buyer optimally uses a bonus tournament, where suppliers can choose between a low bid and a high bid. This allows the buyer to implement any level of diversity with the lowest revenue for the suppliers. We also compare other common contests, in particular, fixed-prize tournaments and auctions. Like bonus tournaments, auctions implement the socially optimal diversity, but usually with higher rents for the suppliers. Fixed-prize tournaments implement insufficient diversity, but may nevertheless be preferred by the buyer to auctions because of lower supplier rents

Tax Mimicking in the Short- and the Long-Run: Evidence from German Reunification

This paper uses the quasi-experiment of Germany's reunification to identify local tax mimicking by municipalities in Eastern-Germany. After reunification, East-German municipalities were allowed to independently set, for the first time in decades, local business and property tax rates. I explore whether the tax rates chosen by East-German border municipalities were influenced by the tax rates of adjacent West-German municipalities. To obtain causal estimates, I rely on instrumental variables regressions within the spatial lag framework, using West-German border municipalities' tax rates in 1989 as instruments for their post-reunification tax rates. The results suggest that East-German municipalities mimicked business tax rates immediately after reunification, but not in later years. I find no evidence of mimicking for property taxes. These results indicate that mimicking is not an important determinant of local tax policy