Dynamical Casimir effect in a periodically changing domain: A dynamical systems approach

We study the problem of the behavior of a quantum massless scalar field in the space between two parallel infinite perfectly conducting plates, one of them stationary, the other moving periodically. We reformulate the physical problem into a problem about the asymptotic behavior of the iterates of a map of the circle, and then apply results from theory of dynamical systems to study the properties of the map. Many of the general mathematical properties of maps of the circle translate into properties of the field in the cavity. For example, we give a complete classification of the possible resonances in the system, and show that small enough perturbations do not destroy the resonances. We use some mathematical identities to give transparent physical interpretation of the processes of creation and amplification of the quantum field due to the motion of the boundary and to elucidate the similarities and the differences between the classical and quantum fields in domains with moving boundaries.Comment: 19 pages, 7 figure

On Charmonia Survival Above Deconfinement

We study charmonium correlators and spectral functions at zero and finite temperature using anisotropic lattices at several different lattice spacings. We find evidence for survival of 1S charmonia states at leas till $1.5T_c$ and dissolution of 1P states at $1.16T_c$.Comment: contribution to the 29th Johns Hopkins Workshop in Theoretical Physics, Budapest, Hungary, 1-3 August 200

Periodic radial velocity variations in RU Lupi

Context. RU Lup is a Classical T Tauri star with unusually strong emission lines, which has been interpreted as manifestations of accretion. Recently, evidence has accumulated that this star might have a variable radial velocity. Aims. We intended to investigate in more detail the possible variability in radial velocity using a set of 68 high-resolution spectra taken at the VLT (UVES), the AAT (UCLES) and the CTIO (echelle). Methods. Using standard cross-correlation techniques, we determined the radial velocity of RU Lup. We analysed these results with Phasedispersion minimization and the Lomb-Scargle periodogram and searched for possible periodicities in the obtained radial velocities. We also analysed changes in the absorption line shapes and the photometric variability of RU Lup. Results. Our analysis indicated that RU Lup exhibits variations in radial velocity with a periodicity of 3.71 days and an amplitude of 2.17 km/s. These variations can be explained by the presence of large spots, or groups of spots, on the surface of RU Lup. We also considered a low-mass companion and stellar pulsations as alternative sources for these variations but found these to be unlikely.Comment: 8 pages, 4 figures, Accepted by A&