cmb temperature bispectrum from a cosmic string network keitaro takahashi (kumamoto u) based on the...
TRANSCRIPT
CMB temperature bispectrum from a cosmic string network
Keitaro Takahashi(Kumamoto U)
Based on the collaboration with
Yamauchi (U Tokyo), Sendouda (Hirosaki U), Yoo (Nagoya), Hiramatsu (Kyoto)
Line-like topological defects
Formed in the early universe through the spontaneous symmetry breaking
F-strings, D-strings, and their bound states which appear in string theory
Formed though the brane collision at the end of the stringy inflation
Cosmic strings Cosmic superstrings
P=1 P~10-3<<1
Intercommuting probability P
String gravity : conical structureThe spacetime around a straight cosmic string is locally flat.
An angular wedge of width Δ=8πGμ is removed from the space and the remaining edges identified.
String-induced integrated Sachs-Wolfe effect
[Planck 25 (2013)]
(δT/T)/Gμ
Cosmic strings create line-like discontinuities in the CMB signal.
Gott-Kaiser-Stebbins (GKS) effect[Kaiser+Stebbins(1984), Gott III(1985)]
CMB temp. power spectrum induced by a cosmic string network
An analytic model including the probabilistic nature of the intercomuting process [Yamauchi, KT, et al. (2011)]
[Atacama Cosmology Telescope (ACT), 2010]
For ACT,
For Planck satellite,
geodesic
potential
CMB lensing Deflection of CMB photons
Unlensed CMB map
[Hu+Okamoto(2002)]
z=zCMB
z=zL
z=0Lensed CMB map
Lensing contribution
“αβ-type” lensing bispectrum
The anisotropy is assumed to be decomposed into
(α,β : contributions from each components)
“αβ-type” lensing bispectrum
Various types of CMB lensing : contributions from cosmic strings
SP-type
PP-type (standard) PS-type
SS-type
Standard density pert.
Standard density pert.
Standard density pert.
Cosmic strings
Cosmic strings
Cosmic strings
Cosmic strings
Standard density pert.
“P” : primordial density perturbations, “S” : string contributions
Equilateral-shaped bispectra induced by a cosmic string network
Silk damping
At small scale, the standard ISW-L (PP-type) and SP-type bispectra are damped due to the Silk damping, and only the (GKS)3, PS-type bispectra are relevant.
(Gμ,P)(10-7,1)(10-8,10-3)(10-9,10-6)
[Yamauchi, KT, et al., in prep.]
SS-type ∝ Cl
ΘsφsClΘsΘs
∝(Gμ)4
(GKS)3
∝(Gμ)3
PreliminarySP-type
∝ ClΘsφsCl
ΘpΘp
∝(Gμ)2
PS-type ∝ Cl
ΘpφpClΘsΘs
∝ (Gμ)2
Cumulative signal-to-noise ratio
(GKS)3
∝(Gμ)3
SS-type ∝(Gμ)4
PS-type ∝ (Gμ)2
SP-type ∝(Gμ)2
PA : Planck+ACTPol–like noise, P : Planck-like noise
[Yamauchi, KT, et al., in prep.]
Preliminary
Constraint in Gμ-P plane ((S/N)<5000=1)
For small P, the PS-type GKS-L bispectrum C∝ lΘpφpCl
ΘsΘs (Gμ)∝ 2 gives the tighter constraint on Gμ than the (GKS)3 bispectrum (Gμ)∝ 3.
(GKS)3
PS-type ∝ Cl
ΘpφpClΘsΘs
SP-type ∝ Cl
ΘsφsClΘpΘp
[Yamauchi, KT, et al., in prep.]
PreliminarySS-type
∝ ClΘsφsCl
ΘsΘs
Summary
We study the effect of weak lensing by cosmic strings on the anisotropies of cosmic microwave background.
In developing a method to evaluate the lensing contribution due to strings, we calculate the analytic expression for the various-type, namely αβ-type, lensing bispectra.
For smaller tension, the lensing bispectrum have window to constrain the string parameters even tighter than the bispectrum induced by GKS.