Acquiring foreign firms far away might be hazardous to your share price: evidence from Germany

This paper examines shareholder wealth effects of cross-border acquisitions. In a sample of 155 large acquisitions by German corporations from 1985–2006 international transactions in total do not lead to significant announcement returns. Geography, however, makes a difference: Shareholders of acquiring firms gain 6.5% in cross-border transactions into countries that have a common border with Germany but lose 4.4% in other international transactions. We find proximity to be one of the most important success factors in cross-border mergers and acquisitions, even when we control for firm, deal and country characteristics

Spin-orbit coupling and anisotropic exchange in two-electron double quantum dots

The influence of the spin-orbit interactions on the energy spectrum of two-electron laterally coupled quantum dots is investigated. The effective Hamiltonian for a spin qubit pair proposed in F. Baruffa et al., Phys. Rev. Lett. 104, 126401 (2010) is confronted with exact numerical results in single and double quantum dots in zero and finite magnetic field. The anisotropic exchange Hamiltonian is found quantitatively reliable in double dots in general. There are two findings of particular practical importance: i) The model stays valid even for maximal possible interdot coupling (a single dot), due to the absence of a coupling to the nearest excited level, a fact following from the dot symmetry. ii) In a weak coupling regime, the Heitler-London approximation gives quantitatively correct anisotropic exchange parameters even in a finite magnetic field, although this method is known to fail for the isotropic exchange. The small discrepancy between the analytical model (which employes the linear Dresselhaus and Bychkov-Rashba spin-orbit terms) and the numerical data for GaAs quantum dots is found to be mostly due to the cubic Dresselhaus term.Comment: 15 pages, 11 figure

Dynamics in the Ising field theory after a quantum quench

We study the real-time dynamics of the order parameter $$in the Ising field theory after a quench in the fermion mass, which corresponds to a quench in the transverse field of the corresponding transverse field Ising chain. We focus on quenches within the ordered phase. The long-time behaviour is obtained analytically by a resummation of the leading divergent terms in a form-factor expansion for$$. Our main result is the development of a method for treating divergences associated with working directly in the field theory limit. We recover the scaling limit of the corresponding result by Calabrese et al. [Phys. Rev. Lett. \textbf{106}, 227203 (2011)], which was obtained for the lattice model. Our formalism generalizes to integrable quantum quenches in other integrable models

Spectrum of Low-Lying Excitations in a Supersymmetric Extended Hubbard Model

We continue the study of the $u(2|2)$-supersymmetric extension of the Hubbard model in one dimension. We determine the excitation spectrum at zero temperature even in the sectors where the ground states are $u(2|2)$-descendants of Bethe states. The excitations include spinons, holons, electrons, localons (local electrons pairs, moving coherently through the lattice) and their bound states. The spectra are found to be very different for repulsive and attractive on-site interaction. We also study the thermodynamics of the model.Comment: 37 pages, uuencoded compressed postscript fil

Applications of Massive Integrable Quantum Field Theories to Problems in Condensed Matter Physics

We review applications of the sine-Gordon model, the O(3) non-linear sigma model, the U(1) Thirring model, and the O(N) Gross--Neveu model to quasi one-dimensional quantum magnets, Mott insulators, and carbon nanotubes. We focus upon the determination of dynamical response functions for these problems. These quantities are computed by means of form factor expansions of quantum correlation functions in integrable quantum field theories. This approach is reviewed here in some detail.Comment: 150 pages, 35 figures, published in the I. Kogan Memorial Volume by World Scientifi

Dynamical Magnetic Susceptibilities in Cu Benzoate

Recent experiments on the quasi 1-D antiferromagnet Cu Benzoate revealed a magentic field induced gap coexisting with (ferro)magnetic order. A theory explaining these findings has been proposed by Oshikawa and Affleck. In the present work we discuss consequences of this theory for inelastic neutron scattering experiments by calculating the dynamical magnetic susceptibilities close to the antiferromagnetic wave vector by the formfactor method.Comment: 6 pages of revtex, 9 figures, extended comparison with experimen

Time evolution of local observables after quenching to an integrable model

We consider quantum quenches in integrable models. We argue that the behaviour of local observables at late times after the quench is given by their expectation values with respect to a single representative Hamiltonian eigenstate. This can be viewed as a generalization of the eigenstate thermalization hypothesis to quantum integrable models. We present a method for constructing this representative state by means of a generalized Thermodynamic Bethe Ansatz (GTBA). Going further, we introduce a framework for calculating the time dependence of local observables as they evolve towards their stationary values. As an explicit example we consider quantum quenches in the transverse-field Ising chain and show that previously derived results are recovered efficiently within our framework.Comment: 7 page