A consistent approximation scheme beyond RPA for bosons

In this paper, we develop a consistent extension of RPA for bosonic systems. In order to illustrate the method, we consider the case of the anharmonic oscillator. We compare our results with those obtained in mean-field and standard RPA approaches, with the exact ones and show that they are very close to the exact ones.Comment: 19 pages, Latex, 1 figure, accepted version in EPJ

Measurement of time differences between luminous events Patent

Mechanism for measuring nanosecond time differences between luminous events using streak camer

Fast opening diaphragm Patent

Magnetically opened diaphragm design with camera shutter and expansion tube application

How to preserve symmetries with cut-off regularized integrals?

We present a prescription to calculate the quadratic and logarithmic divergent parts of several integrals employing a cutoff in a coherent way, i.e. in total agreement with symmetry requirements. As examples we consider one-loop Ward identities for QED and a phenomenological chiral model.Comment: 11 pages, 3 graph

Pseudoscalar Goldstone bosons in the color-flavor locked phase at moderate densities

The properties of the pseudoscalar Goldstone bosons in the color-flavor locked phase at moderate densities are studied within a model of the Nambu--Jona-Lasinio type. The Goldstone bosons are constructed explicitly by solving the Bethe-Salpeter equation for quark-quark scattering in random phase approximation. Main focus of our investigations are (i) the weak decay constant in the chiral limit, (ii) the masses of the flavored (pseudo-) Goldstone bosons for non-zero but equal quark masses, (iii) their masses and effective chemical potentials for non-equal quark masses, and (iv) the onset of kaon condensation. We compare our results with the predictions of the low-energy effective field theory. The deviations from results obtained in the weak-coupling limit are discussed in detail.Comment: 18 pages, 12 figure