SEARCHING FOR QUANTUM GRAVITY EFFECTS IN COSMOLOGICAL DATA

1994 ◽  
Vol 03 (01) ◽  
pp. 257-263 ◽  
Author(s):  
D.S. SALOPEK
Keyword(s):  
Quantum Gravity ◽  
Initial Conditions ◽  
Microwave Background ◽  
Nonlinear Quantum ◽  
Gravity Effects ◽  
Cosmological Data ◽  
Clustering Data ◽  
Non Gaussian ◽  
Excess Power ◽  
The Universe

If the inflationary scenario describes our Universe, then it is possible that quantum gravity phenomena could be observed in anisotropy experiments of the microwave background as well as in galaxy clustering data. Primordial gravitational radiation arising from inflation is a consequence of quantum gravity. Moreover, the wavefunction of the Universe is currently being measured by the COBE satellite. A non-Gaussian distribution could be a signature of nonlinear quantum gravity. In fact, the excess power power seen in the APM survey of galaxies can arise from non-Gaussian initial conditions generated during inflation.

scholarly journals GRAVITY HEATS THE UNIVERSE

2009 ◽  
Vol 18 (14) ◽  
pp. 2201-2207
Author(s):  
ADAM MOSS ◽  
DOUGLAS SCOTT
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Energy Conservation ◽  
Cosmic Microwave Background ◽  
Initial Conditions ◽  
Gravitational Instability ◽  
Simplified Model ◽  
Microwave Background ◽  
Average Temperature ◽  
The Universe

Structures in the Universe grew through gravitational instability from very smooth initial conditions. Energy conservation requires that the growing negative potential energy of these structures be balanced by an increase in kinetic energy. A fraction of this is converted into heat in the collisional gas of the intergalactic medium. Using a toy model of gravitational heating, we attempt to link the growth of structure in the Universe with the average temperature of this gas. We find that the gas is rapidly heated from collapsing structures at around z ~ 10, reaching a temperature > 106 K today, depending on some assumptions of our simplified model. Before that there was a cold era from z ~ 100 to ~10 in which the matter temperature was below that of the cosmic microwave background.

scholarly journals Large Scale Anisotropy of the Cosmic Microwave Background

1974 ◽  
Vol 63 ◽  
pp. 157-162 ◽  
Author(s):  
R. B. Partridge
Keyword(s):  
Angular Distribution ◽  
Large Scale ◽  
Background Radiation ◽  
Big Bang ◽  
Microwave Background ◽  
Initial State ◽  
Microwave Background Radiation ◽  
Cosmological Data ◽  
The Big Bang ◽  
The Universe

It is now generally accepted that the microwave background radiation, discovered in 1965 (Penzias and Wilson, 1965; Dicke et al., 1965), is cosmological in origin. Measurements of the spectrum of the radiation, discussed earlier in this volume by Blair, are consistent with the idea that the radiation is in fact a relic of a hot, dense, initial state of the Universe – the Big Bang. If the radiation is cosmological, measurements of both its spectrum and its angular distribution are capable of providing important – and remarkably precise – cosmological data.

OBSERVATIONAL COSMOLOGY 2004: WHAT THE DATA SAY ABOUT DARK ENERGY AND THE CONTENTS OF THE UNIVERSE

2005 ◽  
Vol 20 (14) ◽  
pp. 2931-2942
Author(s):  
JOSEPH FOWLER
Keyword(s):  
Dark Energy ◽  
Background Radiation ◽  
Current Data ◽  
Observational Cosmology ◽  
Microwave Background ◽  
Hubble Expansion ◽  
Microwave Background Radiation ◽  
Expansion Of The Universe ◽  
Cosmological Data ◽  
The Universe

The latest cosmological data point to a model of the universe that is self-consistent but deeply weird. It seems that most matter in our universe is non-baryonic and hidden from direct view. Meanwhile, a repulsive "dark energy" causes the expansion of the universe to proceed at an accelerating rate. Sources of current data include studies of the distribution of matter in the universe, the anisotropies of the cosmic microwave background radiation, and the Hubble expansion law as probed by distant supernovae. In the near future, we can hope that measurements like these will begin to illuminate the nature of dark energy, starting with the question of whether it behaves like a cosmological constant or shows a more complicated evolution.

scholarly journals Primordial Non-Gaussianity and Bispectrum Measurements in the Cosmic Microwave Background and Large-Scale Structure

2010 ◽  
Vol 2010 ◽  
pp. 1-64 ◽  
Author(s):  
Michele Liguori ◽  
Emiliano Sefusatti ◽  
James R. Fergusson ◽  
E. P. S. Shellard
Keyword(s):  
Cosmic Microwave Background ◽  
Large Scale ◽  
Initial Conditions ◽  
Temperature Fluctuations ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Future Prospects ◽  
Microwave Background ◽  
Galaxy Distribution ◽  
Non Gaussian

The most direct probe of non-Gaussian initial conditions has come from bispectrum measurements of temperature fluctuations in the Cosmic Microwave Background and of the matter and galaxy distribution at large scales. Such bispectrum estimators are expected to continue to provide the best constraints on the non-Gaussian parameters in future observations. We review and compare the theoretical and observational problems, current results, and future prospects for the detection of a nonvanishing primordial component in the bispectrum of the Cosmic Microwave Background and large-scale structure, and the relation to specific predictions from different inflationary models.

scholarly journals Non Gaussian Minkowski functionals and extrema counts for CMB maps

2014 ◽  
Vol 11 (S308) ◽  
pp. 61-66 ◽  
Author(s):  
Dmitri Pogosyan ◽  
Sandrine Codis ◽  
Christophe Pichon
Keyword(s):  
Cosmic Microwave Background ◽  
Orthogonal Polynomials ◽  
Gaussian Fields ◽  
Spherical Space ◽  
Matter Distribution ◽  
Microwave Background ◽  
Minkowski Functionals ◽  
Second Derivatives ◽  
Non Gaussian ◽  
The Universe

AbstractIn the conference presentation we have reviewed the theory of non-Gaussian geometrical measures for 3D Cosmic Web of the matter distribution in the Universe and 2D sky data, such as Cosmic Microwave Background (CMB) maps that was developed in a series of our papers. The theory leverages symmetry of isotropic statistics such as Minkowski functionals and extrema counts to develop post Gaussian expansion of the statistics in orthogonal polynomials of invariant descriptors of the field, its first and second derivatives. The application of the approach to 2D fields defined on a spherical sky was suggested, but never rigorously developed. In this paper we present such development treating the effects of the curvature and finiteness of the spherical space $S_2$ exactly, without relying on flat-sky approximation. We present Minkowski functionals, including Euler characteristic and extrema counts to the first non-Gaussian correction, suitable for weakly non-Gaussian fields on a sphere, of which CMB is the prime example.

scholarly journals Neutrino Mass from Cosmology

2012 ◽  
Vol 2012 ◽  
pp. 1-34 ◽  
Author(s):  
Julien Lesgourgues ◽  
Sergio Pastor
Keyword(s):  
Beta Decay ◽  
Large Scale ◽  
Neutrinoless Double Beta Decay ◽  
Double Beta Decay ◽  
Neutrino Masses ◽  
Microwave Background ◽  
Complementary Information ◽  
Cosmological Observations ◽  
Cosmological Data ◽  
The Universe

Neutrinos can play an important role in the evolution of the universe, modifying some of the cosmological observables. In this contribution we summarize the main aspects of cosmological relic neutrinos, and we describe how the precision of present cosmological data can be used to learn about neutrino properties, in particular their mass, providing complementary information to beta decay and neutrinoless double-beta decay experiments. We show how the analysis of current cosmological observations, such as the anisotropies of the cosmic microwave background or the distribution of large-scale structure, provides an upper bound on the sum of neutrino masses of order 1 eV or less, with very good perspectives from future cosmological measurements which are expected to be sensitive to neutrino masses well into the sub-eV range.

scholarly journals Cosmic microwave background: probing the universe from z = 6 to 1100

2006 ◽  
Vol 2 (14) ◽  
pp. 254-254
Author(s):  
David N. Spergel
Keyword(s):  
Cosmic Microwave Background ◽  
Initial Conditions ◽  
Wilkinson Microwave Anisotropy Probe ◽  
Line Of Sight ◽  
Microwave Background ◽  
Physical Conditions ◽  
Cosmic Microwave Background Temperature ◽  
Background Temperature ◽  
The Universe

Observations of cosmic microwave background temperature and polarization fluctuations are sensitive to both physical conditions at recombination (z = 1100) and physical process along the line of sight. I will discuss recent results from the Wilkinson Microwave Anisotropy Probe and planned ground and space-based observations. The talk will emphasize the role of CMB observations in determining the initial conditions for the growth of structure and as a probe of the physics of re-ionization.

scholarly journals Primordial Fluctuations From Quantum Gravity

2021 ◽  
Vol 7 ◽  
Author(s):  
Francesco Gozzini ◽  
Francesca Vidotto
Keyword(s):  
Quantum Gravity ◽  
Structure Formation ◽  
Loop Quantum Gravity ◽  
Cosmological Horizon ◽  
Strong Correlations ◽  
Quantum Regime ◽  
Horizon Problem ◽  
Large Fluctuations ◽  
Gravity Effects ◽  
The Universe

We study the fluctuations and the correlations between spatial regions generated in the primordial quantum gravitational era of the universe. We point out that these can be computed using the Lorentzian dynamics defined by the Loop Quantum Gravity amplitudes. We evaluate these amplitudes numerically in the deep quantum regime. Surprisingly, we find large fluctuations and strong correlations, although not maximal. This suggests the possibility that early quantum gravity effects might be sufficient to account for structure formation and solve the cosmological horizon problem.

scholarly journals Primordial Non-Gaussianity in the Large-Scale Structure of the Universe

2010 ◽  
Vol 2010 ◽  
pp. 1-23 ◽  
Author(s):  
Vincent Desjacques ◽  
Uroš Seljak
Keyword(s):  
Structure Formation ◽  
Large Scale ◽  
Initial Conditions ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Microwave Background ◽  
Set Constraints ◽  
Physical Mechanisms ◽  
Observational Techniques ◽  
The Universe

Primordial non-Gaussianity is a potentially powerful discriminant of the physical mechanisms that generated the cosmological fluctuations observed today. Any detection of significant non-Gaussianity would thus have profound implications for our understanding of cosmic structure formation. The large-scale mass distribution in the Universe is a sensitive probe of the nature of initial conditions. Recent theoretical progress together with rapid developments in observational techniques will enable us to critically confront predictions of inflationary scenarios and set constraints as competitive as those from the Cosmic Microwave Background. In this paper, we review past and current efforts in the search for primordial non-Gaussianity in the large-scale structure of the Universe.

scholarly journals The perturbed universe in the deformed algebra approach of loop quantum cosmology

2016 ◽  
Vol 25 (08) ◽  
pp. 1642003 ◽  
Author(s):  
Julien Grain
Keyword(s):  
Quantum Gravity ◽  
Quantum Cosmology ◽  
Initial Conditions ◽  
Power Spectra ◽  
Quantum Corrections ◽  
Loop Quantum Cosmology ◽  
Algebra Approach ◽  
Deformed Algebra ◽  
Contracting Phase ◽  
The Universe

Loop Quantum Cosmology (LQC) is a tentative approach to model the universe down to the Planck era where quantum gravity settings are needed. The quantization of the universe as a dynamical spacetime is inspired by Loop Quantum Gravity (LQG) ideas. In addition, LQC could bridge contact with astronomical observations, and thus potentially investigate quantum cosmology modelings in the light of observations. To do so however, modeling both the background evolution and its perturbations is needed. The latter described cosmic inhomogeneities that are the main cosmological observables. In this context, we present the so-called deformed algebra approach implementing the quantum corrections to the perturbed universe at an effective level by taking great care of gauge issues. We particularly highlight that in this framework, the algebra of hypersurface deformation receives quantum corrections, and we discuss their meaning. The primordial power spectra of scalar and tensor inhomogeneities are then presented, assuming initial conditions are set in the contracting phase preceding the quantum bounce and the well-known expanding phase of the cosmic history. These spectra are subsequently propagated to angular power spectra of the anisotropies of the cosmic microwave background. It is then shown that regardless of the choice for the initial conditions inside the effective approach for the background evolution (except that they are set in the contracting phase), the predicted angular power spectra of the polarized [Formula: see text]-modes exceed the upper bound currently set by observations. The exclusion of this specific version of LQC establishes the falsifiability of the approach, though one shall not conclude here that either LQC or LQG excluded.

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