Monopolistic Location Choice in Two-Sided Industries

We analyze the optimal location choice of a monopolistic firm that operates two platforms on a two-sided market. We show that the optimal platform locations are equivalent to the one-sided benchmark if both sides are either restricted to single- or multi-homing. In the mixed case (one side single-homes, the other one multi-homes), the optimal platform locations are determined by the relative profitability of both market sides. Our results indicate that modeling mergers on two-sided markets with fixed locations is often inappropriate

A grand-canonical approach to the disordered Bose gas

We study the problem of disordered interacting bosons within grand-canonical thermodynamics and Bogoliubov theory. We compute the fractions of condensed and non-condensed particles and corrections to the compressibility and the speed of sound due to interaction and disorder. There are two small parameters, the disorder strength compared to the chemical potential and the dilute-gas parameter.Comment: 9 pages, 3 figure

Bogoliubov theory on the disordered lattice

Quantum fluctuations of Bose-Einstein condensates trapped in disordered lattices are studied by inhomogeneous Bogoliubov theory. Weak-disorder perturbation theory is applied to compute the elastic scattering rate as well as the renormalized speed of sound in lattices of arbitrary dimensionality. Furthermore, analytical results for the condensate depletion are presented, which are in good agreement with numerical data.Comment: 10 pages, contributed to Lyon BEC 201

All unital qubit channels are 44-noisy operations

We show that any unital qubit channel can be implemented by letting the input system interact unitarily with a $4$-dimensional environment in the maximally mixed state and then tracing out the environment. We also provide an example where the dimension of such an environment has to be at least $3$.Comment: 8 pages, no picture

A note on the relationship of mainstream and art house movie theaters

We use a set of German micro data to study the relationship between mainstream and art house movie theaters. We find that both types of cinema have a significant price effect within their own group, but there is no significant price effect between the two types. Furthermore, we provide an example for the biased results that occur, if both types of movie theaters are pooled into one regression. Doing so, we demonstrate that it is important, to carefully distinguish mainstream and art house facilities in empirical studies of the movie theater industry.substitutability; complementarity; movie theater industry; Germany

A note on the relationship of mainstream and art house movie theaters

We use a set of German micro data to study the relationship between mainstream and art house movie theaters. We find that both types of cinema have a significant price effect within their own group, but there is no significant price effect between the two types. Furthermore, we provide an example for the biased results that occur, if both types of movie theaters are pooled into one regression. Doing so, we demonstrate that it is important, to carefully distinguish mainstream and art house facilities in empirical studies of the movie theater industry.substitutability; complementarity; movie theater industry; Germany

Searching for the Concentration-Price Effect in the German Movie Theater Industry

This paper investigates whether a price-concentration relationship can be found on local cinema markets in Germany. First, we test a model of monopolistic pricing using a new set of German micro data and find no significant difference in admission prices on monopoly and oligopoly markets. In a next step, we test whether this can be explained by the existence of local monopolies, but find no hint of that. Implicit or explicit collusion among cinema operators might explain our observations.price-concentration study; cinema pricing

A Bramble-Pasciak conjugate gradient method for discrete Stokes equations with random viscosity

We study the iterative solution of linear systems of equations arising from stochastic Galerkin finite element discretizations of saddle point problems. We focus on the Stokes model with random data parametrized by uniformly distributed random variables and discuss well-posedness of the variational formulations. We introduce a Bramble-Pasciak conjugate gradient method as a linear solver. It builds on a non-standard inner product associated with a block triangular preconditioner. The block triangular structure enables more sophisticated preconditioners than the block diagonal structure usually applied in MINRES methods. We show how the existence requirements of a conjugate gradient method can be met in our setting. We analyze the performance of the solvers depending on relevant physical and numerical parameters by means of eigenvalue estimates. For this purpose, we derive bounds for the eigenvalues of the relevant preconditioned sub-matrices. We illustrate our findings using the flow in a driven cavity as a numerical test case, where the viscosity is given by a truncated Karhunen-Lo\`eve expansion of a random field. In this example, a Bramble-Pasciak conjugate gradient method with block triangular preconditioner outperforms a MINRES method with block diagonal preconditioner in terms of iteration numbers.Comment: 19 pages, 1 figure, submitted to SIAM JU