Testing Oscillating Primordial Spectrum and Oscillating Dark Energy with Astronomical Observations

📝 Abstract

In this paper we revisit the issue of determining the oscillating primordial scalar power spectrum and oscillating equation of state of dark energy from the astronomical observations. By performing a global analysis with the Markov Chain Monte Carlo method, we find that the current observations from five-year WMAP and SDSS-LRG matter power spectrum, as well as the “union” supernovae sample, constrain the oscillating index of primordial spectrum and oscillating equation of state of dark energy with the amplitude less than $|n_{\rm amp}|<0.116$ and $|w_{\rm amp}|<0.232$ at 95% confidence level, respectively. This result shows that the oscillatory structures on the primordial scalar spectrum and the equation of state of dark energy are still allowed by the current data. Furthermore, we point out that these kinds of modulation effects will be detectable (or gotten a stronger constraint) in the near future astronomical observations, such as the PLANCK satellite, LAMOST telescope and the currently ongoing supernovae projects SNLS.

💡 Analysis

In this paper we revisit the issue of determining the oscillating primordial scalar power spectrum and oscillating equation of state of dark energy from the astronomical observations. By performing a global analysis with the Markov Chain Monte Carlo method, we find that the current observations from five-year WMAP and SDSS-LRG matter power spectrum, as well as the “union” supernovae sample, constrain the oscillating index of primordial spectrum and oscillating equation of state of dark energy with the amplitude less than $|n_{\rm amp}|<0.116$ and $|w_{\rm amp}|<0.232$ at 95% confidence level, respectively. This result shows that the oscillatory structures on the primordial scalar spectrum and the equation of state of dark energy are still allowed by the current data. Furthermore, we point out that these kinds of modulation effects will be detectable (or gotten a stronger constraint) in the near future astronomical observations, such as the PLANCK satellite, LAMOST telescope and the currently ongoing supernovae projects SNLS.

📄 Content

arXiv:0901.2033v1 [astro-ph.CO] 14 Jan 2009 Testing Oscillating Primordial Spectrum and Oscillating Dark Energy with Astronomical Observations Jie Liua, Hong Lia,b, Jun-Qing Xiac, and Xinmin Zhanga,b aInstitute of High Energy Physics, Chinese Academy of Science, P.O. Box 918-4, Beijing 100049, P. R. China bTheoretical Physics Center for Science Facilities (TPCSF), Chinese Academy of Science, P.R.China and cScuola Internazionale Superiore di Studi Avanzati, Via Beirut 2-4, I-34014 Trieste, Italy In this paper we revisit the issue of determining the oscillating primordial scalar power spectrum and oscillating equation of state of dark energy from the astronomical observations. By performing a global analysis with the Markov Chain Monte Carlo method, we find that the current observations from five-year WMAP and SDSS-LRG matter power spectrum, as well as the “union” supernovae sample, constrain the oscillating index of primordial spectrum and oscillating equation of state of dark energy with the amplitude less than |namp| < 0.116 and |wamp| < 0.232 at 95% confidence level, respectively. This result shows that the oscillatory structures on the primordial scalar spectrum and the equation of state of dark energy are still allowed by the current data. Furthermore, we point out that these kinds of modulation effects will be detectable (or gotten a stronger constraint) in the near future astronomical observations, such as the PLANCK satellite, LAMOST telescope and the currently ongoing supernovae projects SNLS. I. INTRODUCTION Recent advances in observational cosmology have revealed that our universe has experienced at least two different stages of accelerated expansion. One is the inflation in the very early universe when its tiny patch was superluminally stretched to become our observable Universe today. This can naturally explain why the universe is flat, homogeneous and isotropic. Inflation is driven by a potential energy of a scalar (or multi-scalar) called inflaton and its quantum fluctuations turn out to be the primordial density fluctuations which seed the observed large-scale structures (LSS) and anisotropy of cosmic microwave background radiation (CMB). The other one is accelerating expansion driven by dark energy (DE) which dominates the energy density of the universe currently. Understanding the nature of dark energy is among the biggest problems in modern physics and has been studied actively in the literature. At present, the high quality observational data, CMB[1, 2, 3], LSS[4] and type Ia supernovae (SN Ia)[5] and so on, have provided the stringent constraints on cosmological parameters. For example, current data can constrain the primordial scalar power spectrum index ns and the energy density of dark energy component Ωde to 1% level [6]. Besides the current observations, there are many ongoing projects, such as PLANCK[7], LAMOST[8] and SNLS[9]. These projects will provide more accurate measurements on CMB temperature anisotropies and polarization, LSS matter power spectrum and the luminosity distance, which will be helpful for studies of inflation and dark energy and determinations of cosmological parameters. Generally, the current data analysis bases on the simple parameterizations of the primordial power spectrum and the equation of state (EoS) of DE. However, we note that some inflation models can generate the power spectrum with some modulated wiggles. This picture can be realized by the inflaton field with a step function of the potential [10, 11]or oscillating potential[12]. The effects from the Trans-Planckian initial condition can also lead to oscillations which do imprint directly on the primordial scalar power spectrum[13, 14, 15]. The bouncing model driven by the Quintom[16] matter can also give rise to some wiggles in the primordial scale-invariant power spectrum, because in this model the universe initially experiences a contracting stage, after the contracting phase it bounces to an inflationary phase, therefore the primordial fluctuations in sub-hubble region would deviate from that generated in Bunch-Davies vacuum[17]. The Quintom bounce provide a solution to initial singularity problem, and in this scenario there’s no Trans-Planckian problem since we can choose the initial condition via contracting phase. The featured primordial scalar perturbation spectrum with local bumps are studied in Ref.[18]. In some sense, the study for DE is similar to inflation, either in model building or data fitting. The featured EoS of DE, especially the oscillatory behavior EoS can provide us an unconventional evolution of universe. Observationally, these kinds of modulated EoS will leave clew on the hubble diagram or the matter power spectrum as well as the temperature power spectrum of CMB, which give us some hints to test such a scenario. The periodic oscillatory EoS can be realized by the two scalar field Quintom matter[19]. And in Ref.[20], a class of Quintom models with an oscillating equation of state have been st

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