scholarly journals Measuring the effects of loop quantum cosmology in the CMB data

2017 ◽  
Vol 26 (12) ◽  
pp. 1743023 ◽  
Author(s):  
Spyros Basilakos ◽  
Vahid Kamali ◽  
Ahmad Mehrabi
Keyword(s):  
Power Spectrum ◽  
Spectral Index ◽  
Excellent Agreement ◽  
Quantum Cosmology ◽  
Loop Quantum Cosmology ◽  
Alternative Scenario ◽  
Slow Roll ◽  
Scalar Spectral Index ◽  
Robust Prediction ◽  
Scalar Fluctuation

In this paper we investigate the observational signatures of Loop Quantum Cosmology (LQC) in the CMB data. First, we concentrate on the dynamics of LQC and we provide the basic cosmological functions. We then obtain the power spectrum of scalar and tensor perturbations in order to study the performance of LQC against the latest CMB data. We find that LQC provides a robust prediction for the main slow-roll parameters, like the scalar spectral index and the tensor-to-scalar fluctuation ratio, which are in excellent agreement within [Formula: see text] with the values recently measured by the Planck collaboration. This result indicates that LQC can be seen as an alternative scenario with respect to that of standard inflation.

Slow-roll inflation in loop quantum cosmology of scalar–tensor theories of gravity

2015 ◽  
Vol 30 (26) ◽  
pp. 1550127
Author(s):  
Yu Han
Keyword(s):  
Quantum Cosmology ◽  
Field Model ◽  
Equations Of Motion ◽  
Index Formula ◽  
Jordan Frame ◽  
Loop Quantum Cosmology ◽  
Slow Roll ◽  
Scalar Spectral Index ◽  
Theories Of Gravity ◽  
Slow Roll Inflation

The slow-roll inflation of scalar–tensor theories (STTs) of gravity in the context of loop quantum cosmology (LQC) is investigated in this paper. After deriving the effective Hamiltonian, we obtain the semiclassical equations of motion for the background variables in both Jordan frame and Einstein frame of STTs. Then we apply these equations in the slow-roll limit and derive the LQC corrections to the scalar spectral index [Formula: see text] and the tensor-to-scalar ratio [Formula: see text] in the two frames of STTs. Finally, we take two special sectors of STTs as specific examples, namely the Starobinsky model and the non-minimally coupled scalar field model (with the coupling function [Formula: see text] and the potential [Formula: see text]). We derive the detailed expressions of the LQC corrections to [Formula: see text] and [Formula: see text] in terms of the [Formula: see text]-folding number for these two models in both frames.

scholarly journals CHAPLYGIN INFLATION IN LOOP QUANTUM COSMOLOGY

2009 ◽  
Vol 24 (22) ◽  
pp. 1763-1773 ◽  
Author(s):  
XIN ZHANG ◽  
JINGFEI ZHANG ◽  
JINGLEI CUI ◽  
LI ZHANG
Keyword(s):  
Equation Of State ◽  
Quantum Cosmology ◽  
Chaplygin Gas ◽  
Effective Theory ◽  
Loop Quantum Cosmology ◽  
Inflationary Universe ◽  
Quadratic Potential ◽  
Inflation Model ◽  
Slow Roll ◽  
Scalar Spectral Index

In this paper we discuss the inflationary universe in the context of a Chaplygin gas equation of state within the framework of the effective theory of loop quantum cosmology. Under the slow-roll approximation, we calculate the primordial perturbations for this model. We give the general expressions of the scalar spectral index, its running, and the tensor-to-scalar ratio, etc. For the chaotic inflation with a quadratic potential, using the WMAP 5-year results, we determine the parameters of the Chaplygin inflation model in loop quantum cosmology. The results are consistent with the WMAP observations.

The evolutionary pictures for phantom field in loop quantum cosmology

2019 ◽  
Vol 28 (15) ◽  
pp. 1950170
Author(s):  
Kui Xiao
Keyword(s):  
Dark Matter ◽  
Quantum Cosmology ◽  
Scalar Fields ◽  
Chaplygin Gas ◽  
Loop Quantum Cosmology ◽  
Phantom Field ◽  
Dynamical Behaviors ◽  
Slow Roll ◽  
The Universe ◽  
Slow Roll Inflation

The evolutionary pictures for phantom field in loop quantum cosmology are discussed in this paper. Comparing the dynamical behaviors of the phantom field with one of the canonical scalar fields in loop quantum cosmology scenario, we found that the [Formula: see text] phase trajectories are the same, but the [Formula: see text] phase-spaces are very different, and the phantom field with considering potentials can drive neither super inflation nor slow-roll inflation in loop quantum cosmology (LQC) scenario. While the universe is filled with multiple dark fluids, to ensure that the condition [Formula: see text] does not violate, the energy density of dark matter [Formula: see text] and the equation-of-state of phantom field [Formula: see text] should satisfy the condition [Formula: see text] at the bounce point. If this constraint condition holds, the universe can enter an inflationary stage, and it is possible to unify the description of phantom field, dark matter and inflation. We introduced a toy model which has the same form of the general Chaplygin gas to unify the dark energy, dark matter and slow-roll inflation, and the slow-roll inflation of the toy model has also been discussed.

scholarly journals Loop quantum cosmology-corrected Gauss–Bonnet singular cosmology

2018 ◽  
Vol 15 (04) ◽  
pp. 1850064 ◽  
Author(s):  
K. Kleidis ◽  
V. K. Oikonomou
Keyword(s):  
Power Spectrum ◽  
Classical Theory ◽  
Quantum Cosmology ◽  
Loop Quantum Cosmology ◽  
Leading Order ◽  
Type Iii ◽  
Type Iv ◽  
Inflation Scenario

In this work we investigate which Loop Quantum Cosmology (LQC)-corrected Gauss–Bonnet [Formula: see text] gravity can realize two singular cosmological scenarios, the intermediate inflation and the singular bounce scenarios. The intermediate inflation scenario has a Type III sudden singularity at [Formula: see text], while the singular bounce has a soft Type IV singularity. By using perturbative techniques, we find the holonomy-corrected [Formula: see text] gravities that generate at leading order the aforementioned cosmologies and we also argue that the effect of the holonomy corrections is minor to the power spectrum of the primordial curvature perturbations of the classical theory.

scholarly journals Dynamics of tachyon fields and inflation - comparison of analytical and numerical results with observation

2016 ◽  
pp. 1-8 ◽  
Author(s):  
M. Milosevic ◽  
D.D. Dimitrijevic ◽  
G.S. Djordjevic ◽  
M.D. Stojanovic
Keyword(s):  
Scalar Field ◽  
String Theory ◽  
Numerical Methods ◽  
Spectral Index ◽  
Early Universe ◽  
Slow Roll ◽  
Scalar Spectral Index ◽  
Homogeneous Universe ◽  
The Given ◽  
Good Agreement

The role tachyon fields may play in evolution of early universe is discussed in this paper. We consider the evolution of a flat and homogeneous universe governed by a tachyon scalar field with the DBI-type action and calculate the slow-roll parameters of inflation, scalar spectral index (n), and tensor-scalar ratio (r) for the given potentials. We pay special attention to the inverse power potential, first of all to V (x) ~ x?4, and compare the available results obtained by analytical and numerical methods with those obtained by observation. It is shown that the computed values of the observational parameters and the observed ones are in a good agreement for the high values of the constant X0. The possibility that influence of the radion field can extend a range of the acceptable values of the constant X0 to the string theory motivated sector of its values is briefly considered.

scholarly journals WHAT IF THE INFLATON IS A SPINOR CONDENSATE?

2009 ◽  
Vol 18 (14) ◽  
pp. 2173-2179 ◽  
Author(s):  
S. SHANKARANARAYANAN
Keyword(s):  
Scalar Field ◽  
Gravitational Wave ◽  
Spectral Index ◽  
Spinor Condensate ◽  
Slow Roll ◽  
Scalar Spectral Index ◽  
The Future ◽  
Wmap Data ◽  
Elementary Field ◽  
Canonical Scalar Field

In the usual cosmological inflationary scenarios, the scalar field — the inflaton — is usually assumed to be an elementary field. In this essay, we ask: What are the observational signatures if the scalar field is a spinor condensate? And is there a way to distinguish between the canonical scalar field and the spinor-condensate-driven models? In the homogeneous and isotropic background, we show that — although the dark-spinor (Elko) condensate leads to an acceleration equation identical to that of the canonical-scalar-field-driven inflation — the dynamics of the two models are different. In the slow-roll limit, we show that the model predicts a running of the scalar spectral index consistent with the WMAP data. We show that the consistency relations between the spinor condensate and the canonical-scalar-field-driven model are different, which we will be able to test using the future CMB and gravitational wave missions.

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