COSMIC CONSTRAINTS ON DECELERATION PARAMETER WITH Sne Ia AND CMB

2009 ◽  
Vol 24 (05) ◽  
pp. 369-376 ◽  
Author(s):  
LIXIN XU ◽  
JIANBO LU
Keyword(s):  
Cosmic Microwave Background ◽  
Observational Data ◽  
Deceleration Parameter ◽  
Background Radiation ◽  
Cosmic Microwave Background Radiation ◽  
Accelerated Expansion ◽  
Microwave Background ◽  
Strong Constraint ◽  
Microwave Background Radiation ◽  
Type Ia

In this paper, a parametrized deceleration parameter q(a) = q0+q1(1-a) is constrained by using the current cosmic observational data from type Ia Supernova (Sne Ia) and Cosmic Microwave Background Radiation (CMB). When the CMB dataset is added as a strong constraint, it is found that the 1σ error is largely reduced. The values of transition redshift zT from decelerated expansion to accelerated expansion and current deceleration parameter q0 are larger than that obtained from the case where Sne Ia dataset is used alone. With comparison to the case of Sne Ia 182 dataset used,15 it is found that the value of transition redshift is smaller than that in Sne 192 dataset case. This is the so-called dataset dependence.

Statistics of Cosmic Microwave Background Radiation with the Cosmic String Model

1997 ◽  
Vol 06 (05) ◽  
pp. 535-544
Author(s):  
Petri Mähönen ◽  
Tetsuya Hara ◽  
Toivo Voll ◽  
Shigeru Miyoshi
Keyword(s):  
Cosmic Microwave Background ◽  
Cosmic String ◽  
Large Scale ◽  
Background Radiation ◽  
Unit Length ◽  
Angular Size ◽  
Cosmic Microwave Background Radiation ◽  
Density Parameter ◽  
Microwave Background ◽  
Microwave Background Radiation

We have studied the cosmic microwave background radiation by simulating the cosmic string network induced anisotropies on the sky. The large-angular size simulations are based on the Kaiser–Stebbins effect calculated from full cosmic-string network simulation. The small-angular size simulations are done by Monte-Carlo simulation of perturbations from a time-discretized toy model. We use these results to find the normalization of μ, the string mass per unit length, and compare this result with one needed for large-scale structure formation. We show that the cosmic string scenario is in good agreement with COBE, SK94, and MSAM94 microwave background radiation experiments with reasonable string network parameters. The predicted rms-temperature fluctuations for SK94 and MSAM94 experiments are Δ T/T=1.57×10-5 and Δ T/T=1.62×10-5, respectively, when the string mass density parameter is chosen to be Gμ=1.4×10-6. The possibility of detecting non-Gaussian signals using the present day experiments is also discussed.

scholarly journals Cosmological Applications of Hα Surveys

1998 ◽  
Vol 15 (1) ◽  
pp. 111-117 ◽  
Author(s):  
David Valls–Gabaud
Keyword(s):  
Cosmic Microwave Background ◽  
Background Radiation ◽  
Massive Stars ◽  
High Redshift ◽  
Formation Rate ◽  
Cosmic Microwave Background Radiation ◽  
Microwave Background ◽  
Microwave Background Radiation

AbstractWe briefly review three main applications of Hα surveys in cosmology, namely: (1) the diffuse Hα emission as a tracer of the free–free foreground that contaminates the fluctuations in the cosmic microwave background radiation; (2) the Hα emission from galaxies as a measure of the formation rate of massive stars, both at low and high redshift; and (3) the diffuse Hα emission from ionised clouds as a constraint on the local ionising background radiation.

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