Effects of Cosmic Strings on Free Streaming

We study the effect of free streaming in a universe with cosmic strings with time-varying tension as well as with constant tension. Although current cosmological observations suggest that fluctuation seeded by cosmic strings cannot be the primary source of cosmic density fluctuation, some contributions from them are still allowed. Since cosmic strings actively produce isocurvature fluctuation, the damping of small scale structure via free streaming by dark matter particles with large velocity dispersion at the epoch of radiation-matter equality is less efficient than that in models with conventional adiabatic fluctuation. We discuss its implications to the constraints on the properties of particles such as massive neutrinos and warm dark matter.Comment: 14 pages, 9 figure

Large amplitude coherent state superposition generated by a time-separated two-photon subtraction from a continuous wave squeezed vacuum

Theoretical analysis is given for a two-photon subtraction from a continuous wave (CW) squeezed vacuum with finite time separation between two detection events. In the CW photon subtraction process, the generated states are inevitably described by temporal mutimode states. Our approach is based on Schr\"{o}dinger picture which provides mathematically simple forms and an intuitive understanding of its multimode structure. We show that, in our process, the photon subtracted squeezed vacuum is generated in two temporal modes and one of these modes acts as an ancillary mode to make the other one a large amplitude coherent state superposition.Comment: 9 pages, 8 figure

Temporally multiplexed superposition states of continuous variables

We study non-Gaussian states generated by two-photon subtraction from a cw squeezed light source. In a cw scheme one can subtract two photons from the source with a designated time separation and can genarate temporally multiplexed superposition states of continuous variables. We numerically study the properties of these states in the light of bosonic interference in the time domain. In an appropriate temporal mode amplified kittens are produced in a region where the time separation is comparable with the correlation time of squeezed packets.Comment: 12 pages, 10 figure