scholarly journals String theory, loop quantum gravity and eternalism

2020 ◽  
Vol 10 (2) ◽  
Author(s):  
Baptiste Le Bihan
Keyword(s):  
String Theory ◽  
Quantum Gravity ◽  
Loop Quantum Gravity

scholarly journals Quantum gravity: A brief history of ideas and some prospects

2015 ◽  
Vol 24 (11) ◽  
pp. 1530028 ◽  
Author(s):  
Steven Carlip ◽  
Dah-Wei Chiou ◽  
Wei-Tou Ni ◽  
Richard Woodard
Keyword(s):  
Black Hole ◽  
String Theory ◽  
Quantum Gravity ◽  
Loop Quantum Gravity ◽  
Black Hole Thermodynamics ◽  
History Of Ideas ◽  
Foreseeable Future ◽  
Gravitational Effects ◽  
History Of

We present a bird's-eye survey on the development of fundamental ideas of quantum gravity, placing emphasis on perturbative approaches, string theory, loop quantum gravity (LQG) and black hole thermodynamics. The early ideas at the dawn of quantum gravity as well as the possible observations of quantum gravitational effects in the foreseeable future are also briefly discussed.

scholarly journals A quantized spacetime based on Spin(3,1) symmetry

2016 ◽  
Vol 25 (13) ◽  
pp. 1645004
Author(s):  
Pisin Chen ◽  
Hsu-Wen Chiang ◽  
Yao-Chieh Hu
Keyword(s):  
String Theory ◽  
Quantum Gravity ◽  
Uncertainty Principle ◽  
Loop Quantum Gravity ◽  
Generalized Uncertainty Principle ◽  
Spin Network ◽  
Fundamental Symmetry ◽  
New Type ◽  
Gravity Theories

We introduce a new type of the spacetime quantization based on the spinorial description suggested by loop quantum gravity. Specifically, we build our theory on a string theory inspired [Formula: see text] worldsheet action. Because of its connection with quantum gravity theories, our proposal may in principle link back to string theory, connect to loop quantum gravity where SU(2) is suggested as the fundamental symmetry, or serve as a Lorentzian spin network. We derive the generalized uncertainty principle and demonstrate the holographic nature of our theory. Due to the quantization of spacetime, geodesics in our theory are fuzzy, but the fuzziness is shown to be much below conceivable astrophysical bounds.

Time in Quantum Gravity

2011 ◽  
Author(s):  
Claus Kiefer
Keyword(s):  
Quantum Theory ◽  
String Theory ◽  
Quantum Gravity ◽  
Special Relativity ◽  
Loop Quantum Gravity ◽  
Problem Of Time ◽  
Canonical Quantum Gravity ◽  
Time Loop ◽  
Canonical Quantum

This chapter notes that quantum gravity places the concept of time on a new level. In the absence of experimental hints, mathematical and conceptual issues must be chosen as the guides in the search for such a theory. Just as reconceiving classical notions of time was key for Einstein, in his discovery of special relativity, so too many believe that time will again hold the clue for theoretical advancement, but this time with quantum gravity. The chapter details the challenge of reconciling quantum theory with relativity, concentrating especially on why time in particular causes trouble. It describes a result in canonical quantum gravity which is possibly of signal importance, namely, that fundamentally there is no time at all, and discusses the problem of time, quantization, semiclassical time, loop quantum gravity, and string theory.

scholarly journals Emergence of stringlike physics from Lorentz invariance in loop quantum gravity

2014 ◽  
Vol 23 (12) ◽  
pp. 1442023 ◽  
Author(s):  
Rodolfo Gambini ◽  
Jorge Pullin
Keyword(s):  
Field Theory ◽  
Quantum Field Theory ◽  
String Theory ◽  
Quantum Gravity ◽  
Loop Quantum Gravity ◽  
Lorentz Invariance ◽  
Spherically Symmetric ◽  
Quantum Field ◽  
Spin Network ◽  
Symmetric Quantum

We consider a quantum field theory on a spherically symmetric quantum spacetime described by loop quantum gravity. The spin network description of spacetime in such a theory leads to equations for the quantum field that are discrete. We show that to avoid significant violations of Lorentz invariance, one needs to consider specific nonlocal interactions in the quantum field theory similar to those that appear in string theory. This is the first sign that loop quantum gravity places restrictions on the type of matter considered, and points to a connection with string theory physics.

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.

6. Frontiers of gravitational physics

2017 ◽  
pp. 83-97
Author(s):  
Timothy Clifton
Keyword(s):  
Quantum Mechanics ◽  
String Theory ◽  
Quantum Gravity ◽  
Cosmological Constant ◽  
Loop Quantum Gravity ◽  
Gravitational Interaction ◽  
Theoretical Description ◽  
Theoretical Physics ◽  
Cosmic Inflation ◽  
The World

‘Frontiers of gravitational physics’ considers some of the issues involved in the theoretical description of gravity. Since 1915, it has been Einstein’s theory that has shaped our understanding of the gravitational interaction, but a lot has happened in the world of theoretical physics since then. Quantum mechanics, devised by Bohr, Heisenberg, and Schrödinger, is incompatible with gravity and so has raised numerous questions. Several theories, including String Theory and Loop Quantum Gravity, have been proposed with some success. The concepts of cosmic inflation, the cosmological constant, and the possibility of multiple universes are also discussed. It concludes that with further astrophysical studies a new fundamental theory may explain it all.

scholarly journals Priority Monism Beyond Spacetime

Metaphysica ◽  
2018 ◽  
Vol 19 (1) ◽  
pp. 95-111 ◽  
Author(s):  
Baptiste Le Bihan
Keyword(s):  
String Theory ◽  
Quantum Gravity ◽  
Loop Quantum Gravity ◽  
Temporal Structure ◽  
Fundamental Structure ◽  
Research Programs ◽  
Priority Monism ◽  
Spatio Temporal ◽  
Mereological Composition

AbstractI will defend two claims. First, Schaffer’s priority monism is in tension with many research programs in quantum gravity. Second, priority monism can be modified into a view more amenable to this physics. The first claim is grounded in the fact that promising approaches to quantum gravity such as loop quantum gravity or string theory deny the fundamental reality of spacetime. Since fundamental spacetime plays an important role in Schaffer’s priority monism by being identified with the fundamental structure, namely the cosmos, the disappearance of spacetime in these views might undermine classical priority monism. My second claim is that priority monism can avoid this issue with two moves: first, in dropping one of its core assumption, namely that the fundamental structure is spatio-temporal, second, by identifying the connection between the non-spatio-temporal structure and the derivative spatio-temporal structure with mereological composition.

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