Talk detail

Participant	Modesto, Leonardo
Institution	Southern University of Science and Technology (SUSTech) - 1088 Xueyuan Blvd., Nanshan District - Shenzhen - Guandong - China

Session	QG2	Accepted		Order	Time
Talk	Oral abstract	Title	Nonlocal Conformal Quantum Gravity
Coauthors
Abstract	We present a weakly nonlocal gravitational theory compatible with perturbative unitarity and finiteness at quantum level, but also with causality (a Shapiro's time advance never occurs in Nonlocal Gravity). Moreover, we explicitly prove that the theory is conformal invariant at classical as well as quantum level. Therefore, nonlocal quantum gravity is a conformal invariant theory in the spontaneously broken phase of the conformal Weyl symmetry.
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Session	AT1	Accepted		Order	Time
Talk	Oral abstract	Title	Inflation in Nonlocal Gravity
Coauthors
Abstract	We show that the ``Starobinsky’’ inflationary spacetime is an exact solution of the Nonlocal Gravity. This theory is ghost-free, finite at quantum level, and perturbatively unitary. Moreover, the spectrum of the theory consists of the graviton and the scalaron that is responsible for driving the inflation. Notably, any further extension of the spectrum leads to propagating ghost degrees of freedom. Further, we give a special account to the cosmological implications of this theory by considering perturbations during inflation. The Nonlocal Gravity model predicts of a modified value, in comparison to the local Starobinsky model, for the ratio of tensor and scalar power spectra r, which can surely meet future observational constraints.
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Session	EU2C	Accepted		Order	Time
Talk	Oral abstract	Title	Finite Quantum Gravity
Coauthors
Abstract	We present two proposal for quantum gravity: Nonlocal Quantum Gravity and Lee-Wick Quantum Gravity. The first one is described by a weakly nonlocal action whose perturbative spectrum at most consists on two fields, the graviton and the Starobinsky's scalaron, while the second one admits also for the presence of complex conjugate fields. Both the theories are super-renormalizable or finite at quantum level, perturbatively unitary, and macrocausal.
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Session	QG3	Accepted		Order	Time
Talk	Oral abstract	Title	Singularity-free black holes in Conformal Gravity
Coauthors
Abstract	We explicitly show that Weyl conformal symmetry solves the black hole singularity problem, otherwise unavoidable in a generally covariant local or non-local gravitational theories. Following the seminal paper by Narlikar and Kembhavi, we provide examples of syngularity-free (spherically symmetric and axi-symmetric) exact solutions for black hole spacetimes in conformal gravity. We check the absence of divergences making use of the Kretschmann-invariant and we show that the new types of black holes are geodesically complete. Indeed, no massive or massless particles can reach the former singularity in a finite amount of proper time or of affine parameter.
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Session	AT4	Accepted		Order	Time
Talk	Oral abstract	Title	Exact solutions and stability in Nonlocal Ghost-Free Gravity
Coauthors
Abstract	We study at classical level three classes of nonlocal gravitational theories finite at quantum level. We show that for the first class of theories, Ricci flat spacetimes are exact solutions stable under linear perturbations. In particular the Schwarzschild, Kerr, and BKL metrics are exact solutions. For the first and second class (A)dS is a stable exact solution, while for the second class the equations of motion are exactly solved by all FRW spacetimes which are sourced by a traceless energy tensor. In particular the Big-Bang singularity is an exact solution of the theory. Moreover, the Starobisky and Mukanov inflationary models are exact solutions. The third class of theories show up almost all the spacetime singularities of Einstein gravity, namely: black hole singularities and cosmological singularities.
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