scholarly journals How round is the quantum de Sitter universe?

2020 ◽  
Vol 80 (10) ◽  
Author(s):  
N. Klitgaard ◽  
R. Loll
Keyword(s):  
Quantum Dynamics ◽  
Global Scale ◽  
Quantum Geometry ◽  
De Sitter ◽  
Curved Space ◽  
Causal Dynamical Triangulations ◽  
Quantum Universe ◽  
Local Properties ◽  
Dynamical Triangulations ◽  
De Sitter Universe

AbstractWe investigate the quantum Ricci curvature, which was introduced in earlier work, in full, four-dimensional quantum gravity, formulated nonperturbatively in terms of Causal Dynamical Triangulations (CDT). A key finding of the CDT approach is the emergence of a universe of de Sitter-type, as evidenced by the successful matching of Monte Carlo measurements of the quantum dynamics of the global scale factor with a semiclassical minisuperspace model. An important question is whether the quantum universe exhibits semiclassicality also with regard to its more local geometric properties. Using the new quantum curvature observable, we examine whether the (quasi-)local properties of the quantum geometry resemble those of a constantly curved space. We find evidence that on sufficiently large scales the curvature behaviour is compatible with that of a four-sphere, thus strengthening the interpretation of the dynamically generated quantum universe in terms of a de Sitter space.

scholarly journals LOCAL OBSERVED TIME AND REDSHIFT IN CURVED SPACE–TIME

2001 ◽  
Vol 16 (21) ◽  
pp. 1385-1393 ◽  
Author(s):  
SZE-SHIANG FENG
Keyword(s):  
Cosmological Constant ◽  
Time Scale ◽  
Space Time ◽  
Local Observable ◽  
Length Scale ◽  
De Sitter ◽  
Perfect Agreement ◽  
Curved Space ◽  
De Sitter Universe ◽  
Changing Rate

Using the observed time and spatial intervals defined originally by Einstein and the observational frame in the vierbein formalism, we propose that in curved space–time, for a wave received in laboratories, the observed frequency is the changing rate of the phase of the wave relative to the local observable time scale and the momentum is the changing rate of the phase relative to the local observable spatial length scale. The case of Robertson–Walker universe is especially considered and the application to de Sitter universe results in a cosmological constant in perfect agreement with the observational data.

scholarly journals CDT Quantum Toroidal Spacetimes: An Overview

Universe ◽  
2021 ◽  
Vol 7 (4) ◽  
pp. 79
Author(s):  
Jan Ambjorn ◽  
Zbigniew Drogosz ◽  
Jakub Gizbert-Studnicki ◽  
Andrzej Görlich ◽  
Jerzy Jurkiewicz ◽  
...  
Keyword(s):  
Lattice Theory ◽  
Continuum Limit ◽  
Fractal Structure ◽  
Scalar Fields ◽  
Massless Scalar ◽  
Quantum Geometry ◽  
Special Boundary ◽  
Dramatic Effect ◽  
Causal Dynamical Triangulations ◽  
Dynamical Triangulations

Lattice formulations of gravity can be used to study non-perturbative aspects of quantum gravity. Causal Dynamical Triangulations (CDT) is a lattice model of gravity that has been used in this way. It has a built-in time foliation but is coordinate-independent in the spatial directions. The higher-order phase transitions observed in the model may be used to define a continuum limit of the lattice theory. Some aspects of the transitions are better studied when the topology of space is toroidal rather than spherical. In addition, a toroidal spatial topology allows us to understand more easily the nature of typical quantum fluctuations of the geometry. In particular, this topology makes it possible to use massless scalar fields that are solutions to Laplace’s equation with special boundary conditions as coordinates that capture the fractal structure of the quantum geometry. When such scalar fields are included as dynamical fields in the path integral, they can have a dramatic effect on the geometry.

scholarly journals QUANTUM FIELD THEORY IN A SYMMETRIC CURVED SPACE FROM A SECOND QUANTIZATION ON A GROUP

2000 ◽  
Vol 15 (25) ◽  
pp. 4011-4044 ◽  
Author(s):  
M. CALIXTO ◽  
V. ALDAYA ◽  
M. NAVARRO
Keyword(s):  
Field Theory ◽  
Quantum Field Theory ◽  
Quantization Scheme ◽  
Quantum Field ◽  
De Sitter ◽  
Second Quantization ◽  
Global Hyperbolicity ◽  
General Group ◽  
Curved Space ◽  
De Sitter Universe

In this paper we propose a "second quantization" scheme especially suitable for dealing with nontrivial, highly symmetric phase spaces, implemented within a more general group approach to quantization, which recovers the standard quantum field theory (QFT) for ordinary relativistic linear fields. We emphasize, among its main virtues, greater suitability in characterizing vacuum states in a QFT on a highly symmetric curved space–time and the absence of the usual requirement of global hyperbolicity. This can be achieved in the special case of the Anti-de Sitter universe, on which we explicitly construct a QFT.

scholarly journals Impact of topology in causal dynamical triangulations quantum gravity

2016 ◽  
Vol 94 (4) ◽  
Author(s):  
J. Ambjørn ◽  
Z. Drogosz ◽  
J. Gizbert-Studnicki ◽  
A. Görlich ◽  
J. Jurkiewicz ◽  
...  
Keyword(s):  
Quantum Gravity ◽  
Causal Dynamical Triangulations ◽  
Dynamical Triangulations

scholarly journals PHANTOM AND QUANTUM MATTER IN AN ANTI DE SITTER UNIVERSE

2004 ◽  
Vol 19 (01) ◽  
pp. 29-36 ◽  
Author(s):  
EMILIO ElIZALDE ◽  
JOHN QUIROGA HURTADO
Keyword(s):  
Perfect Fluid ◽  
Quantum Effects ◽  
Energy Conditions ◽  
De Sitter ◽  
Quantum Matter ◽  
Trace Anomaly ◽  
Sitter Universe ◽  
De Sitter Universe ◽  
Phantom Matter

We consider an anti de Sitter universe filled by quantum CFT with classical phantom matter and perfect fluid. The model represents the combination of a trace-anomaly annihilated and a phantom driven anti de Sitter universes. The influence exerted by the quantum effects and phantom matter on the AdS space is discussed. Different energy conditions in this type of universe are investigated and compared with those for the corresponding model in a de Sitter universe.

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