Continuous Time Quantum Monte Carlo Method for Fermions: Beyond Auxiliary Field Framework

Numerically exact continuous-time Quantum Monte Carlo algorithm for finite fermionic systems with non-local interactions is proposed. The scheme is particularly applicable for general multi-band time-dependent correlations since it does not invoke Hubbard-Stratonovich transformation. The present determinantal grand-canonical method is based on a stochastic series expansion for the partition function in the interaction representation. The results for the Green function and for the time-dependent susceptibility of multi-orbital super-symmetric impurity model with a spin-flip interaction are presented

Multi-Orbital Hubbard Model in Infinite Dimensions: Quantum Monte Carlo Calculation

Using Quantum Monte Carlo we compute thermodynamics and spectra for the orbitally degenerate Hubbard model in infinite spatial dimensions. With increasing orbital degeneracy we find in the one-particle spectra: broader Hubbard bands (consistent with increased kinetic energy), a narrowing Mott gap, and increasing quasi-particle spectral weight. In opposition, Hund's rule exchange coupling decreases the critical on-site Coulomb energy for the Mott transition. The metallic regime resistivity for two-fold degeneracy is quadratic-in-temperature at low temperatures.Comment: 4 pages, 4 figures, to be published in PR

Income-Related Minimum Taxation Concepts and Their Impact on Corporate Investment Decisions

In this paper we analyze the impact of various minimum taxation concepts on corporate investment decisions. These investments can be realized in the form of either a real or a financial investment. In a quantitative analysis we refer to the future values of the investments as an indicator of tax-favored and tax-discriminated projects. Varying the concept-specific loss-offset parameters and cash flow time structure and performing a Monte Carlo simulation reveals the impact of the particular minimum taxation concept. For the first time a comprehensive set of equations has been deduced to integrate different minimum tax concepts in a unique model. The resulting equations can be used as a basis for further analyses of group taxation, wealth taxation and asymmetric taxation and allows us to gain first insights into the direction and magnitude of tax distortions of possible competing concepts. Depending on the set of parameters, complex and ambiguous tax effects can be identified. The effect of minimum taxation depends on the existence and magnitude of a depreciation effect. Both effects run contrary to each other, and the depreciation effect is always greater. We find that all concepts distort in the same direction and that real investments with increasing cash flows are more likely to be discriminated by minimum taxation than financial investments or real investments with constant cash flows. However, in comparison to real investments with decreasing cash flows financial investments suffer more from income-related minimum taxation concepts. These results provide interesting information for corporate investors having to decide on the location of an investment, and for tax reform discussions

Cross-Border Group-Taxation and Loss-Offset in the EU - An Analysis for CCCTB (Common Consolidated Corporate Tax Base) and Etas (European Tax Allocation System)

The European Commission proposed to replace the currently existing Separate Accounting by an EU-wide tax system based on a Common Consolidated Corporate Tax Base (CCCTB). Besides the CCCTB, there is an alternative tax reform proposal, the European Tax Allocation System (ETAS). In a dynamic capital budgeting model we analyze the impacts of selected loss-offset limitations currently existing in the EU under both concepts on corporate crossborder real investments of MNE. The analyses show that replacing Separate Accounting by either concept can lead to increasing profitability due to cross-border loss compensation. However, if the profitability increases, the study indicates that the main criteria of decisions on location are the tax rate divergences within the EU Member States. High tax rate differentials in the Member States imply significant redistribution of tax payments under CCCTB and ETAS. The results clarify that in both reform proposals tax payment reallocations occur in favor of the holding. National loss-offset limitations and minimum taxation concepts in tendency lose their impact on the profitability under both proposals. However, we found scenarios in which national minimum taxation can encroach upon the group level, although in our model the minimum taxation's impacts seem to be slight. Moreover, we identify harmful paradoxes in ETAS due to the tax credit mechanism. Our results can contribute to the current discussion on corporate group tax harmonization within the EU and other economic zones, e.g. the US, and help to anticipate the tax effects of lossoffset restrictions under the respective tax systems

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