Nobuyoshi Ohta
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Shadow of black holes with consistent thermodynamics Open
Quantum effects in general induce scale dependence in the coupling constants. We explore this possibility in gravity, with a scale-dependent Newton coupling. When applied to Kerr black holes with such a running coupling, the consistency of…
Essential renormalization group equation for gravity coupled to a scalar field Open
We study the essential renormalization group equation, in which inessential couplings are removed via field redefinitions, for Einstein gravity coupled to a massive scalar field in the presence of a cosmological constant. Our results indic…
Standard running, “physical running”, cosmological constant and Newton coupling Open
Recently it is asserted that the standard beta function does not describe the correct running of the coupling constant in some theories. We show that the problem arises from the assumption μ=p (μ is a renormalization point) and that a suit…
Essential Renormalization Group Equation for Gravity coupled to a Scalar field Open
We study the essential renormalization group equation, in which inessential couplings are removed via field redefinitions, for Einstein gravity coupled to a massive scalar field in the presence of a cosmological constant. Our results indic…
Standard Running, "Physical Running", Cosmological Constant and Newton Coupling Open
Recently it is asserted that the standard beta function does not describe the correct running of the coupling constant in some theories. We show that the problem arises from the assumption $μ=p$ ($μ$ is a renormalization point) and that a …
On the cutoff scale identification of FLRW cosmology in asymptotically safe gravity Open
We examine Friedmann–Lemaître–Robertson–Walker cosmology, incorporating quantum gravitational corrections through the functional renormalisation group flow of the effective action for gravity. We solve the Einstein equation with quantum im…
Wave function renormalization in asymptotically safe quantum gravity Open
We discuss the effect of wave function renormalization (WFR) in asymptotically safe gravity. We show that there are two WFR-invariant quantities, and the renormalization (RG) equations may be written entirely in terms of these quantities. …
Wave Function Renormalization in Asymptotically Safe Quantum Gravity Open
We discuss the effect of wave function renormalization (WFR) in asymptotically safe gravity. We show that there are two WFR-invariant quantities, and the renormalization (RG) equations may be written entirely in terms of these quantities. …
An observation on the beta functions in quadratic gravity Open
We study the beta functions for the dimensionless couplings in quadratic curvature gravity, and find that there is a simple argument to restrict the possible form of the beta functions as derived from the counterterms at an arbitrary loop.…
An Observation on the Beta Functions in Quadratic Gravity Open
We study the beta functions for the dimensionless couplings in quadratic curvature gravity, and find that there is a simple argument to restrict the possible form of the beta functions as derived from the counterterms at an arbitrary loop.…
Local term in the anomaly-induced action of Weyl quantum gravity Open
The finite local conformally noninvariant ${R}^{2}$ term emerges in the one-loop effective action of the model of quantum gravity based on the Weyl-squared classical action. This term is related to the $\ensuremath{\square}R$ contribution …
Phase structure of quantum improved Schwarzschild-(Anti)de Sitter black holes Open
We study the phase structure of quantum improved Schwarzschild–(A)dS black holes in asymptotically safe gravity. Our results confirm some of the well-known properties of quantum black holes. For example, the quantum effect provides a repul…
Quantum Improved Regular Kerr Black Holes Open
We study the quantum improvement of Kerr black holes with mass-dependent scale identifications in asymptotically safe gravity. We find that a physically sensible identification can only be a function of $Mr$ and the area $A=4π(r^2+a^2)$ wh…
On the local term in the anomaly-induced action of Weyl quantum gravity Open
The finite local conformally non-invariant $R^2$-term emerges in the one-loop effective action of the model of quantum gravity based on the Weyl-squared classical action. This term is related to the $\Box R$ contribution to the conformal a…
Wave function renormalization and flow of couplings in asymptotically safe quantum gravity Open
The importance of the proper treatment of the wave function renormalization in the renormalization group analysis of quantum gravity is pointed out. The renormalization factor, sometimes called an inessential coupling, can be used to fix a…
Wave Function Renormalization and Flow of Couplings in Asymptotically Safe Quantum Gravity Open
The importance of the proper treatment of the wave function renormalization in the renormalization group analysis of quantum gravity is pointed out. The renormalization factor, sometimes called an inessential coupling, can be used to fix a…
Phase Structure of Quantum Improved Schwarzschild-(Anti)de Sitter Black Holes Open
We study the phase structure of quantum improved Schwarzschild-(A)dS black holes in asymptotically safe gravity. Our results confirm some of the well-known properties of quantum black holes. For example, the quantum effect provides a repul…
One-loop divergences in higher-derivative gravity Open
We give a review of the one-loop divergences in higher derivative gravity theories. We first make the bilinear expansion in the quantum fluctuation on arbitrary backgrounds, introduce a higher-derivative gauge fixing and show that higher-d…
Running Newton coupling, scale identification, and black hole thermodynamics Open
We discuss the quantum improvement of black hole solutions in the context of\nasymptotic safety. The Newton coupling in this formulation depends on an energy\nscale, which must be identified with some length scale in order to study\nphysic…
Covariant BRST quantization of unimodular gravity. II. Formulation with a vector antighost Open
In our previous paper, we have presented a covariant BRST quantization of unimodular gravity which may account for the smallness of the cosmological constant, and have shown that the physical degrees of freedom in the theory are the same a…
Covariant BRST quantization of unimodular gravity: Formulation with antisymmetric tensor ghosts Open
Unimodular gravity (UG) is an interesting theory that may explain why the cosmological constant is extremely small, in contrast to general relativity (GR). The theory has only the transverse diffeomorphism invariance and this causes a lot …
Covariant BRST Quantization of Unimodular Gravity II -- Formulation with\n a vector antighost -- Open
In our previous paper, we have presented a covariant BRST quantization of\nunimodular gravity which may account for the smallness of the cosmological\nconstant, and have shown that the physical degrees of freedom in the theory are\nthe sam…
Covariant BRST Quantization of Unimodular Gravity I -- Formulation with antisymmetric tensor ghosts -- Open
Unimodular gravity (UG) is an interesting theory that may explain why the cosmological constant is extremely small, in contrast to general relativity (GR). The theory has only the transverse diffeomorphism invariance and this causes lots o…
Higgs scalar potential coupled to gravity in the exponential parametrization in arbitrary gauge Open
We study the parametrization and gauge dependences in the Higgs field coupled to gravity in the context of asymptotic safety. We use the exponential parametrization to derive the fixed points for the cosmological constant, Planck mass, Hig…
BRST quantization of general relativity in unimodular gauge and unimodular gravity Open
Unimodular gravity (UG) is an important theory which may explain the\nsmallness of the cosmological constant. To get insight into the covariant\nquantization of UG, we discuss the BRST quantization of General Relativity (GR)\nwith a cosmol…
Quantum improved charged black holes Open
We consider quantum effects of gravitational and electromagnetic fields in spherically symmetric black hole spacetimes in the asymptotic safety scenario. Introducing both the running gravitational and electromagnetic couplings from the ren…
General procedure of gauge fixings and ghosts Open
We revisit the general procedure of gauge fixings and ghosts based on BRST\ninvariance principle. It is shown that when this is applied to the\nhigher-derivative gauge fixings, it gives the correct structure of gauge\nfixings and ghosts in…
Towards the determination of the dimension of the critical surface in asymptotically safe gravity Open
We compute the beta functions of Higher Derivative Gravity within the\nFunctional Renormalization Group approach, going beyond previously studied\napproximations. We find that the presence of a nontrivial Newtonian coupling\ninduces, in ad…
Beta functions in Higher Derivative Gravity Open
Beta functions in Higher Derivative Gravity