501 research outputs found
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
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