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Register a new userAn Estimate of Lambda in Resummed Quantum Gravity in the Context of Asymptotic Safety and Planck Scale Cosmology: Constraints on SUSY GUTS
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We use the amplitude-based resummation of Feynman`s formulation of Einstein`s theory to arrive at a UV finite approach to quantum gravity. We show that we recover the UV fixed point recently claimed by the exact field-space renormalization group approach. We use our approach in the context of the attendant Planck scale cosmology formulation of Bonanno and Reuter to estimate the value of the cosmological constant as rho_Lambda=(0.0024 eV)^4. We show that the closeness of this estimate to experiment constrains susy GUT models.
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Working in the context of the Planck scale cosmology formulation of Bonanno and Reuter, we use our resummed quantum gravity approach to Einsteins general theory of relativity to estimate the value of the cosmological constant as $rho_Lambda =(0.0024 eV)^4$. We show that susy GUT models are constrained by the closeness of this estimate to experiment. We also address various consistency checks on the calculation. In particular, we use the Heisenberg uncertainty principle to remove a large part of the remaining uncertainty in our estimate of $rho_Lambda$
We show that, by using resummation techniques based on the extension of the methods of Yennie, Frautschi and Suura to Feynmans formulation of Einsteins theory, we get quantum field theoretic predictions for the UV fixed-point values of the dimensionless gravitational and cosmological constants. Connections to the phenomenological asymptotic safety analysis of Planck scale cosmology by Bonanno and Reuter are discussed.
We give a status report on the theory of resummed quantum gravity. We recapitulate the use of our resummed quantum gravity approach to Einsteins general theory of relativity to estimate the value of the cosmological constant as $rho_Lambda=(0.0024{mathrm{eV}})^4$. The estimate is made in the context of the Planck scale cosmology formulation of Bonanno and Reuter. We discuss the constraints on susy GUT models that follow from the closeness of the estimate to experiment. Various consistency checks on the calculation are addressed and we use the Heisenberg uncertainty principle to remove a large part of the remaining uncertainty in our estimate of $rho_Lambda$.
We study the ultraviolet stability of gravity-matter systems for general numbers of minimally coupled scalars and fermions. This is done within the functional renormalisation group setup put forward in cite{Christiansen:2015rva} for pure gravity. It includes full dynamical propagators and a genuine dynamical Newtons coupling, which is extracted from the graviton three-point function. We find ultraviolet stability of general gravity-fermion systems. Gravity-scalar systems are also found to be ultraviolet stable within validity bounds for the chosen generic class of regulators, based on the size of the anomalous dimension. Remarkably, the ultraviolet fixed points for the dynamical couplings are found to be significantly different from those of their associated background counterparts, once matter fields are included. In summary, the asymptotic safety scenario does not put constraints on the matter content of the theory within the validity bounds for the chosen generic class of regulators.
We argue that the exact degeneracy of vacua in N=1 supergravity can shed light on the smallness of the cosmological constant. The presence of such vacua, which are degenerate to very high accuracy, may also result in small values of the quartic Higgs coupling and its beta function at the Planck scale in the phase in which we live.
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