# Aktuelle Publikationen

• D. Choi, S. Lim, T. Mühlenbruch, W. Raji: Series expansion of the period function and representations of Hecke operators (pdf, 499804) [externer Link]

Abstract: The period polynomial of a cusp form of an integral weight plays an important role in the number theory. In this paper, we study the period function of a cusp form of real weight. We obtain a series expansion of the period function of a cusp form of real weight for SL(2;Z) by using the binomial expansion. Furthermore, we study two kinds of Hecke operators acting on cusp forms and period functions, respectively. With these Hecke operators we show that there is a Hecke-equivariant isomorphism between the space of cusp forms and the space of period functions. As an application, we obtain a formula for a certain L-value of a Hecke eigenform by using the series expansion of its period function.

(Erscheint in Jorunal of Number Theory; externe Links: doi:10.1016/j.jnt.2016.07.020, preprint http://staff.aub.edu.lb/~wr07/Papers/CMRL.pdf)

• J. Kerner and T. Mühlenbruch: Two interacting particles on the half-line [externer Link]

Abstract: In the case of general compact quantum graphs, many-particle models with singular two-particle interactions were introduced by Bolte and Kerner [J. Phys. A: Math. Theor. 46, 045206 (2013); 46, 045207 (2013)] in order to provide a paradigm for further studies on many-particle quantum chaos. In this note, we discuss various aspects of such singular interactions in a two-particle system restricted to the half-line ℝ+. Among others, we give a description of the spectrum of the two-particle Hamiltonian and obtain upper bounds on the number of eigenstates below the essential spectrum. We also specify conditions under which there is exactly one such eigenstate. As a final result, it is shown that the ground state is unique and decays exponentially as sqrt{x^2+y^2} → ∞.

(externe Links: doi:10.1063/1.4940698, arXiv:1504.08283 )

• W. Kirsch and M. Krishna: Lifshitz tails for the Interband Light Absorption Coefficient (pdf)

Abstract. In this paper we consider the Interband Light Absorption Coefficient for various models. We show that at the lower and upper edges of the spectrum the Lifshitz tails behaviour of the density of states implies similar behaviour for the ILAC at appropriate energies. The Lifshitz tails property is also exhibited at some points corresponding to the internal band edges of the density of states.

• W. Kirsch and H. Najar: Lifshitz tails for continuous Laplacian in the site percolation case (pdf)

Abstract. In this paper we study Lifshitz tails for continuous Laplacian in a continuous site percolation situation. By this we mean that we delete a random set $\Gamma_{\omega}$ from $\mathbb{R}^{d}$ and consider the Dirichlet or Neumann Laplacian on $D=\mathbb{R}^{d} \backslash \Gamma_{\omega}$. We prove that the integrated density of states exhibits Lifshitz behavior at the bottom of the spectrum when we consider Dirichlet boundary conditions, while when we consider Neumann boundary conditions, it is bounded from below by a van Hove behavior. The Lifshitz tails are proven independently of the percolation probability, whereas for the van Hove case we need some assumption on the volume of the sets taken out as well as on the percolation probability.

Lehrgebiet Stochastik | 12.09.2016
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