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The q-deformed harmonic oscillator is studied in the light of q-deformed phase space variables. This allows a formulation of the corresponding Hamiltonian in terms of the ordinary canonical variables x and p. The spectrum shows unexpected features such as degeneracy and an additional part that cannot be reached from the ground state by creation operators.… (More)

- Andreas Ruffing, Thomas Deck, Martin Schlichenmaier
- 1992

The propagation differential for bosonic strings on a complex torus with three symmetric punctures is investigated. We study deformation aspects between two point and three point differentials as well as the behaviour of the corresponding Krichever-Novikov algebras. The structure constants are calculated and from this we derive a central extension of the… (More)

- Andreas Ruffing, Moritz Simon
- 2006

Throughout the paper we discuss results related to the class of entire functions ϕ N (z) ≡ ϕ N (z; λ, q) for N ∈ N, defined by ϕN (0) = 1 and ϕ N (z) = λN z N −1 ϕN (qz) for all z ∈ C, where λ = 0 and while the basic parameter q ∈ (0, 1) assigns a fixed delay. In that sense the functions ϕ N may be regarded as q-delayed analogs of the standard exponentials… (More)

- S Mathias, M Wiesenmayer, F Deicke, A Ruffing, L Miaja-Avila, M M Murnane +3 others
- 2008

The angle resolved photoelectron spectroscopy (ARPES) has emerged as a leading technique in identifying static key properties of complex systems such as the electronic band structure of adsorbed molecules, ultrathin quantum-well films or high temperature superconductors. We efficiently combined ARPES by using a two-dimensional analyzer for parallel energy… (More)

- Monika Blanke, Andreas Ruffing, Moritz And, Simon
- 2005

A generalization of the ladder operator formalism for the harmonic oscillator in one-dimensional Schrödinger theory to time scales T shall be considered. Stemming from a fundamental decomposition of the Hamiltonian H into ladder operators A and A † , this can be achieved at least on unitary lattices — characterized by a constant growth of graininess. In… (More)

- S Mathias, S Eich, J Urbancic, S Michael, A V Carr, S Emmerich +16 others
- Nature communications
- 2016

Capturing the dynamic electronic band structure of a correlated material presents a powerful capability for uncovering the complex couplings between the electronic and structural degrees of freedom. When combined with ultrafast laser excitation, new phases of matter can result, since far-from-equilibrium excited states are instantaneously populated. Here,… (More)

- Jerico B. Bacani, Gunther Peichl, Andreas Ruffing
- 2014

- Maria Meiler, Andreas Ruffing
- 2008

In this article, discrete versions of diffusion equations are presented on basic adap-tive grids. These equations stem from originally considering discrete versions of exponential functions which have zeros on the negative axis. As a main result, similarity solutions to these difference equations are developed which reduce in the transition to the real axis… (More)

- Andreas Ruffing, Moritz Simon
- 2007

Mixed linear birth–and–death processes with killing are investigated in view of their spectral representation. Having discussed the relations of linear/q-linear rate structures to Meixner/Al-Salam–Chihara polynomials, six special types of such mixed rate structures shall be encountered. Half of them can be understood as perturbations of pure birth–and–death… (More)

The orthogonal polynomials with recurrence relation (λ n + µ n − z) F n (z) = µ n+1 F n+1 (z) + λ n−1 F n−1 (z) with two kinds of cubic transition rates λ n and µ n , corresponding to indeterminate Stieltjes moment problems, are analyzed. We derive generating functions for these two classes of polynomials, which enable us to compute their Nevanlinna… (More)