Current Search: Cosmology (x)


Title

DIFFEOMORPHISM INVARIANT COSMOLOGICAL SECTOR IN LOOP QUANTUM GRAVITY.

Creator

Mendonca, Phillip, Engle, Jonathan, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics

Abstract/Description

1In this dissertation we work out in detail a new proposal to define rigorously a sector of loop quantum gravity at the diffeomorphism invariant level corresponding to homogeneous and isotropic cosmologies, and propose how to compare in detail the physics of this sector with that of loop quantum cosmology. The key technical steps we have completed are (a) to formulate conditions for homogeneity and isotropy in a diffeomorphism covariant way on the classical phase space of general relativity,...
Show more1In this dissertation we work out in detail a new proposal to define rigorously a sector of loop quantum gravity at the diffeomorphism invariant level corresponding to homogeneous and isotropic cosmologies, and propose how to compare in detail the physics of this sector with that of loop quantum cosmology. The key technical steps we have completed are (a) to formulate conditions for homogeneity and isotropy in a diffeomorphism covariant way on the classical phase space of general relativity, and (b) to translate these conditions consistently using wellunderstood techniques to loop quantum gravity. To impose the symmetry at the quantum level, on both the connection and its conjugate momentum, the method used necessarily has similiarities to the GuptaBleuler method of quantizing the electromagnetic field. Lastly, a strategy for embedding states of loop quantum cosmology into this new homogeneous isotropic sector, and using this embedding to compare the physics, is presented.
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Date Issued

2019

PURL

http://purl.flvc.org/fau/fd/FA00013334

Subject Headings

Diffeomorphisms, Quantum gravity, Quantum cosmology, Invariants, Isotropy

Format

Document (PDF)


Title

LOOP QUANTUM GRAVITY DYNAMICS: MODELS AND APPLICATIONS.

Creator

Vilensky, Ilya, Engle, Jonathan, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics

Abstract/Description

In this dissertation we study the dynamics of loop quantum gravity and its applications. We propose a tunneling phenomenon of a black holewhite hole transition and derive an amplitude for such transition using the spinfoam framework. We investigate a special class of kinematical states for loop quantum gravity  Bell spin networks  and show that their entanglement entropy obeys the area law. We develop a new spinfoam vertex amplitude that has the correct semiclassical limit. We then apply...
Show moreIn this dissertation we study the dynamics of loop quantum gravity and its applications. We propose a tunneling phenomenon of a black holewhite hole transition and derive an amplitude for such transition using the spinfoam framework. We investigate a special class of kinematical states for loop quantum gravity  Bell spin networks  and show that their entanglement entropy obeys the area law. We develop a new spinfoam vertex amplitude that has the correct semiclassical limit. We then apply this new amplitude to calculate the graviton propagator and a cosmological transition amplitude. The results of these calculations show feasibility of computations with the new amplitude and its viability as a spinfoam model. Finally, we use physical principles to radically constrain ambiguities in the cosmological dynamics and derive unique Hamiltonian dynamics for FriedmannRobertsonWalker and Bianchi I cosmologies.
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Date Issued

2019

PURL

http://purl.flvc.org/fau/fd/FA00013349

Subject Headings

Quantum gravity, Loop quantum gravity, Cosmology, Spinfoam

Format

Document (PDF)


Title

Loop Quantum Gravity with Cosmological Constant.

Creator

Huang, Zichang, Han, Muxin, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics

Abstract/Description

The spinfoam is a covariant pathintegral style approaching to the quantization of the gravity. There exist several spinfoam models of which the most successful one is the EnglePereiraRovelliLevine/FreidelKrasnov (EPRLFK) model. Using the EPRLFK model people are able to calculate the transition amplitude and the npoint functions of 4D geometry (both Euclidean and Lorentzian) surrounding by a given triangulated 3D geometry. The semiclassical limit of the EPRLFK amplitude reproduces...
Show moreThe spinfoam is a covariant pathintegral style approaching to the quantization of the gravity. There exist several spinfoam models of which the most successful one is the EnglePereiraRovelliLevine/FreidelKrasnov (EPRLFK) model. Using the EPRLFK model people are able to calculate the transition amplitude and the npoint functions of 4D geometry (both Euclidean and Lorentzian) surrounding by a given triangulated 3D geometry. The semiclassical limit of the EPRLFK amplitude reproduces discrete classical gravity under certain assumptions, which shows that the EPRLFK model can be understood as UV completion of general relativity. On the other hand, it is very hard to dene a continuum limit and couple a cosmological constant to the EPRLFK model. In this dissertation, we addressed the problems about continuum limit and coupling a cosmological constant to the EPRLFK model. Followed by chapter one as a brief introduction of the loop quantum gravity and EPRLFK model, chapter two introduces our work about demonstrating (for the first time) that smooth curved spacetime geometries satisfying Einstein equation can emerge from discrete spinfoam models under an appropriate low energy limit, which corresponds to a semiclassical continuum limit of spinfoam models. In chapter three, we bring in the cosmological constant into the spinfoam model by coupling the SL(2, C) ChernSimons action with the EPRL action, and find that the quantum simplicity constraint is realized as the 2d surface defect in SL(2, C)ChernSimons theory in the construction of spinfoam amplitudes. In chapter four, we present a way to describe the twisted geometry with cosmological constant whose corresponding quantum states can forms the Hilbert space of the loop quantum gravity with cosmological constant. In chapter five, we introduced a new definition of the graviton propagator, and calculate its semiclassical limit in the contents of spinfoam model with the cosmological constant. Finally the chapter six will be a outlook for my future work.
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Date Issued

2019

PURL

http://purl.flvc.org/fau/fd/FA00013218

Subject Headings

Quantum gravity, Cosmological constants, Spin foam models

Format

Document (PDF)


Title

The bones of the ox: how J.R.R. Tolkien's cosmology reflects ancient Near Eastern creation myths.

Creator

Dutton, Amanda M., Dorothy F. Schmidt College of Arts and Letters, Department of English

Abstract/Description

Scholars have well established the influence of the Old and Middle English, Norse, Welsh, and also Medieval Latin and Christian mythologies that influenced the writings of J.R.R. Tolkien. In particular, the mythology contained in The Silmarillion, specific the cosmology, behaves as sacred texts do in the primary world and mirrors a number of extant mythologies when they are directly compared. Several scholars have note, but as yet no one has studied in depth, the relationship between the...
Show moreScholars have well established the influence of the Old and Middle English, Norse, Welsh, and also Medieval Latin and Christian mythologies that influenced the writings of J.R.R. Tolkien. In particular, the mythology contained in The Silmarillion, specific the cosmology, behaves as sacred texts do in the primary world and mirrors a number of extant mythologies when they are directly compared. Several scholars have note, but as yet no one has studied in depth, the relationship between the cosmology the The Silmarillion to that of a number of extant ancient Near Eastern mythologies. This thesis seeks to address that gap in the scholarship by specifically exploring Tolkien's mythological creation story in relation to those of the Mesopotamian, Egyptian, and Abrahamic of the Near East. Such a comparative study reveals a number of structural and thematic parallels that attest to the complexity of Tolkien's work that and can be used to argue that his mythology can be considered as welldeveloped and surprisingly authentic as any of these ancient mythological traditions.
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Date Issued

2012

PURL

http://purl.flvc.org/FAU/3355562

Subject Headings

Criticism and interpretation, Criticism and interpretation, Myths in literature, Symbolism in literature, Cosmology, Middle Eastern literature, Criticism and interpretation

Format

Document (PDF)