Space-time evolution and CMB anisotropies from quantum gravity

Hamada, Kenji; Horata, Shinichi; Yukawa, Tetsuyuki

doi:10.1103/physrevd.74.123502

Cited by 25 publications

(65 citation statements)

References 49 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…If we set the ordering of two mass scales as m pl QG ( 10 17 GeV), where m pl = 1/ √ G ( 10 19 GeV), we obtain an inflationary scenario with a sufficient number of e-foldings driven by quantum gravity effects [44][45][46][47].…”

Section: Conformal Anomalies and Effective Actionsmentioning

confidence: 99%

Renormalizable 4D Quantum Gravity as a Perturbed Theory from CFT

Hamada

2009

Found Phys

Self Cite

View full text Add to dashboard Cite

We study the renormalizable quantum gravity formulated as a perturbed theory from conformal field theory (CFT) on the basis of conformal gravity in four dimensions. The conformal mode in the metric field is managed non-perturbatively without introducing its own coupling constant so that conformal symmetry becomes exact quantum mechanically as a part of diffeomorphism invariance. The traceless tensor mode is handled in the perturbation with a dimensionless coupling constant indicating asymptotic freedom, which measures a degree of deviation from CFT. Higher order renormalization is carried out using dimensional regularization, in which the Wess-Zumino integrability condition is applied to reduce indefiniteness existing in higher-derivative actions. The effective action of quantum gravity improved by renormalization group is obtained. We then make clear that conformal anomalies are indispensable quantities to preserve diffeomorphism invariance. Anomalous scaling dimensions of the cosmological constant and the Planck mass are calculated. The effective cosmological constant is obtained in the large number limit of matter fields.

show abstract

Section: Conformal Anomalies and Effective Actionsmentioning

confidence: 99%

Renormalizable 4D Quantum Gravity as a Perturbed Theory from CFT

Hamada

2009

Found Phys

Self Cite

View full text Add to dashboard Cite

show abstract

“…Thus, spacetime is practically quantized with this scale. The existence of this scale has been indicated from the sharp falloff of the large angular component of the cosmic microwave background spectrum [44,45,46]. 10 evaluated as ∂ 2 ∂x 2…”

Section: Conclusion and Discussionmentioning

confidence: 99%

“…Since the theory is UV complete, it gives a different viewpoint on the cosmological constant problem usually discussed on the basis of the theory with a UV cutoff. The value of the physical cosmological constant will be passed on to the low-energy effective theory of gravity given by an expansion in derivatives of the metric field [45].…”

Section: Conclusion and Discussionmentioning

confidence: 99%

Physical cosmological constant in asymptotically background-free quantum gravity

Hamada

Matsuda

2017

Phys. Rev. D

Self Cite

View full text Add to dashboard Cite

We study the effective potential in renormalizable quantum gravity with a single dimensionless conformal coupling without a Landau pole. In order to describe a background-free dynamics at the Planck scale and beyond, the conformal-factor field is quantized exactly in a nonperturbative manner. Since this field does not receive renormalization, the field-independent constant in the effective potential becomes itself invariant under the renormalization group flow. That is to say, it gives the physical cosmological constant. We explicitly calculate the physical cosmological constant at the one-loop level in the Landau gauge. We find that it is given by a function of renormalized quantities of the cosmological constant, the Planck mass and the coupling constant, and it should be the observed value. It will give a new perspective on the cosmological constant problem free from an ultraviolet cutoff.

show abstract

“…The inflationary solution requires that the dynamical scale is of the order of 10 17 GeV below the Planck scale in order to explain the correct number of e-foldings and the amplitude of cosmic microwave background anisotropies observed by WMAP [14,15]. We show that this magnitude of the dynamical scale also has a significant meaning for the generation of the baryon asymmetry.…”

mentioning

confidence: 94%

“…One of the prominent features of quantum gravity scenario we employ here is that there is a dynamical energy scale separating quantum space-time and classical space-time [13,14,15]. In the early epoch of the universe the conformal symmetry has a significant meaning, because there would be a period that space-time is totally fluctuating quantum mechanically so that geometry loses its classical meaning and the scale invariant picture will emerge, while in the present universe there is no such a symmetry.…”

mentioning

confidence: 99%

Baryogenesis by Quantum Gravity

2008

Self Cite

View full text Add to dashboard Cite

A novel mechanism of baryogenesis is proposed on the basis of the phase transition from the conformal invariant space-time to the Einstein space-time in quantum gravity. Strong-coupling gravitational excitations with dynamical mass about 10 17 GeV are generated at the transition. They eventually decay into ordinary matters. As a realization of unparticle physics we show that the low energy effective interactions between the gravitational potential describing the excitation and the non-conserving matter currents by the axial anomalies can explain matter asymmetry out of thermal equilibrium.

show abstract

Space-time evolution and CMB anisotropies from quantum gravity

Cited by 25 publications

References 49 publications

Renormalizable 4D Quantum Gravity as a Perturbed Theory from CFT

Renormalizable 4D Quantum Gravity as a Perturbed Theory from CFT

Physical cosmological constant in asymptotically background-free quantum gravity

Baryogenesis by Quantum Gravity

Contact Info

Product

Resources

About