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.

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 POSSIBLE POLARIZATION AND SPIN-DEPENDENT ASPECTS OF QUANTUM GRAVITY

2008 ◽  
Vol 17 (03n04) ◽  
pp. 495-504 ◽  
Author(s):  
D. V. AHLUWALIA ◽  
N. G. GRESNIGT ◽  
ALEX B. NIELSEN ◽  
D. SCHRITT ◽  
T. F. WATSON
Keyword(s):  
Quantum Gravity ◽  
Structure Formation ◽  
Spin Dependence ◽  
Strong Polarization ◽  
Heisenberg Algebras ◽  
Gravity Effects ◽  
Gravity Theories

We argue that quantum gravity theories that carry a Lie-algebraic modification of the Poincaré and Heisenberg algebras inevitably provide inhomogeneities that may serve as seeds for cosmological structure formation. Furthermore, in this class of theories one must expect a strong polarization and spin dependence of various quantum gravity effects.

scholarly journals Dimensions of Space

2020 ◽  
Vol 3 (11) ◽  
pp. 74-79
Author(s):  
Kedar Pansare ◽  
Meghraj Parab ◽  
Vrushabh Parmar ◽  
Yashwantrao Mitnasala ◽  
Rajni Bahuguna
Keyword(s):  
Quantum Gravity ◽  
Loop Quantum Gravity ◽  
Higher Dimensions ◽  
Superstring Theory ◽  
Unified Theories ◽  
Spatial Dimensions ◽  
The Universe ◽  
Dimensions Of Space

The existence and the mysteries of the universe could not be explained by using just 3 spatial dimensions. There was a need to think of higher dimensions as a tool to explain the phenomena happening in our universe. Therefore, unified theories such as Loop Quantum Gravity and Superstring Theory were proposed. We will be taking an overview of these theories in order to get some idea about each.

scholarly journals Quantum reduced loop gravity and the foundation of loop quantum cosmology

2016 ◽  
Vol 25 (08) ◽  
pp. 1642005 ◽  
Author(s):  
Emanuele Alesci ◽  
Francesco Cianfrani
Keyword(s):  
Quantum Gravity ◽  
Quantum Cosmology ◽  
Loop Quantum Gravity ◽  
Loop Quantum Cosmology ◽  
Quantum Description ◽  
Semiclassical Dynamics ◽  
Loop Gravity ◽  
The Universe

Quantum reduced loop gravity is a promising framework for linking loop quantum gravity and the effective semiclassical dynamics of loop quantum cosmology. We review its basic achievements and its main perspectives, outlining how it provides a quantum description of the Universe in terms of a cuboidal graph which constitutes the proper framework for applying loop techniques in a cosmological setting.

scholarly journals Semiclassical dynamics of horizons in spherically symmetric collapse

2014 ◽  
Vol 23 (07) ◽  
pp. 1450061 ◽  
Author(s):  
Yaser Tavakoli ◽  
João Marto ◽  
Andrea Dapor
Keyword(s):  
Quantum Gravity ◽  
Loop Quantum Gravity ◽  
Massless Scalar ◽  
Massless Scalar Field ◽  
Spherically Symmetric ◽  
Final State ◽  
Trapped Surfaces ◽  
Semiclassical Dynamics ◽  
Gravity Effects ◽  
Threshold Radius

In this paper, we consider a semiclassical description of the spherically symmetric gravitational collapse with a massless scalar field. In particular, we employ an effective scenario provided by holonomy corrections from loop quantum gravity (LQG), to the homogeneous interior spacetime. The singularity that would arise at the final stage of the corresponding classical collapse, is resolved in this context and is replaced by a bounce. Our main purpose is to investigate the evolution of trapped surfaces during this semiclassical collapse. Within this setting, we obtain a threshold radius for the collapsing shells in order to have horizons formation. In addition, we study the final state of the collapse by employing a suitable matching at the boundary shell from which quantum gravity effects are carried to the exterior geometry.

scholarly journals Wheeler’s it from bit proposal in loop quantum gravity

2019 ◽  
Vol 28 (10) ◽  
pp. 1950129
Author(s):  
Jarmo Mäkelä
Keyword(s):  
Phase Transition ◽  
Partition Function ◽  
Quantum Gravity ◽  
Loop Quantum Gravity ◽  
Dramatic Decrease ◽  
Spin Network ◽  
Quantum Numbers ◽  
System Of Particles ◽  
Number Formula ◽  
The Universe

As an attempt to realize Wheeler’s “it-from-bit proposal” that physics should be reduced to simple yes–no questions, we consider a model of loop quantum gravity, where the only allowed values of the quantum numbers [Formula: see text] at the punctures [Formula: see text] of the spin network on the spacelike two surfaces of spacetime are [Formula: see text] and [Formula: see text]. When [Formula: see text], the puncture is in the vacuum, and it does not contribute to the area of the two surface, whereas when [Formula: see text], the puncture is in an excited state, and the allowed values of the associated quantum number [Formula: see text] are [Formula: see text] and [Formula: see text]. As a consequence, the spin network used as a model of spacetime is analogous to a system of particles with spin [Formula: see text], and every puncture carries exactly one bit of information. When applied to spacetimes with horizon, our model enables us to find an explicit expression for the partition function of spacetime. Using this partition function we may, among other things, obtain the Bekenstein–Hawking entropy law for black holes. When applied to cosmological models with horizon, the partition function predicts a cosmic phase transition in the early universe, where the cosmological constant went through a dramatic decrease and the matter of the universe was created out of the vacuum.

scholarly journals A discrete-time interpretation of the Planck-Einstein equation

2006 ◽  
Vol 2006 ◽  
pp. 1-5
Author(s):  
A. Boyarsky
Keyword(s):  
String Theory ◽  
Quantum Gravity ◽  
Einstein Equation ◽  
Discrete Time ◽  
Loop Quantum Gravity ◽  
Empty Space ◽  
Important Conclusion ◽  
Age Of The Universe ◽  
The Times ◽  
The Universe

An important conclusion of both string theory and loop quantum gravity theory is that space and time are ultimately discrete. A consequence of discrete space is that there is empty space between the basic elements of space. Analogously, there are empty times between the times where time exists. When time does not exist, it is meaningless to consider the existence of the universe. In this note we consider a discrete-time interpretation of the Planck-Einstein equation and draw a curious conclusion about the real age of the universe.

scholarly journals Rainbow-Like Black-Hole Metric from Loop Quantum Gravity

Universe ◽  
2018 ◽  
Vol 4 (12) ◽  
pp. 139 ◽  
Author(s):  
Iarley P. Lobo ◽  
Michele Ronco
Keyword(s):  
General Relativity ◽  
Black Hole ◽  
Quantum Gravity ◽  
Loop Quantum Gravity ◽  
Effective Time ◽  
Gravity Effects ◽  
Poincaré Symmetry ◽  
Metric Functions ◽  
Rainbow Metrics

Hypersurface deformation algebra consists of a fruitful approach to derive deformedsolutions of general relativity based on symmetry considerations with quantum-gravity effects,of which the linearization has been recently demonstrated to be connected to the DSR programby k-Poincaré symmetry. Based on this approach, we analyzed the solution derived for theinterior of a black hole and we found similarities with the so-called rainbow metrics, like amomentum-dependence of the metric functions. Moreover, we derived an effective, time-dependentPlanck length and compared different regularization schemes.

Sign in / Sign up

Export Citation Format

Share Document