Course

19R1 D. Anselmi
Theories of gravitation

Program

PDF

Recent papers and theorems

19R8 Damiano Anselmi
Quantum gravity from fakeons – Gravity and other fields under the volcano

Talk given at the conference "Gravity and other fields under the volcano", Catania, Italy, June 10th, 2019 A new quantization prescription is able to endow quantum field theory with a new type of “particle”, the fakeon (fake particle), which mediates interactions, but cannot be observed. A massive fakeon of spin 2 ... [more]

19R7 Damiano Anselmi
Quantum gravity from fakeons – Bologna

Seminar given at the Department of Physics and Astronomy of the University of Bologna on May 30th, 2019 A new quantization prescription is able to endow quantum field theory with a new type of "particle", the fakeon (fake particle), which mediates interactions, but cannot be observed. A massive ... [more]

19R6 Marco Piva
On the behavior of gravitational force at small scales

We point out the idea that, at small scales, gravity can be described by the standard degrees of freedom of general relativity, plus a scalar particle and a degree of freedom of a new type: the fakeon. This possibility leads to fundamental implications in understanding gravitational force at quantum level ... [more]

19R5 Damiano Anselmi
Fakeons and Quantum Gravity – Cargese

Talk given at the conference Hot topics in modern cosmology. Spontaneous Workshop XIII, 5 - 11 May 2019 — IESC, Cargèse A new quantization prescription is able to endow quantum field theory with a new type of “particle”, the fakeon (fake particle), which mediates interactions, but cannot be observed. A massive ... [more]

19R4 Damiano Anselmi
Fakeons and quantum gravity – Vietri sul Mare

Talk given at the conference PAFT 2019 - Current problems in theoretical physics. Aspects of nonperturbative QFT, foundations of quantum theory, quantum spacetime. XXV edition, Vietri sul Mare (Salerno, Italy), April 13-17, 2019 A new quantization prescription is able to endow quantum field theory with a new type of "particle", the ... [more]

19R2 Damiano Anselmi
Fakeons, quantum gravity and the classical limit

Talk given at the Conference "Scale invariance in particle physics and cosmology", CERN, on January 29th, 2019 A new quantization prescription is able to endow quantum field theory with a new type of "particle", the fakeon (fake particle), which mediates interactions, but cannot be observed. A massive fakeon of spin 2 ... [more]

19A1 Damiano Anselmi
Fakeons and the classicization of quantum gravity: the FLRW metric

Under certain assumptions, it is possible to make sense of higher derivative theories by quantizing the unwanted degrees of freedom as fakeons, which are later projected away. Then the true classical limit is obtained by classicizing the quantum theory. Since quantum field theory is formulated perturbatively, the classicization is also ... [more]

19R1 Damiano Anselmi
Theories of gravitation

Program Differential geometry topological spaces, manifolds, differential manifolds, derivations, vector fields, differential forms, tangent space, cotangent space, tangent bundle, cotangent bundle, Lie derivative, metric, covariant derivative, torsion, curvature, metric compatibility, tetrad, spin connection, Christoffel symbols, Riemann tensor, Ricci tensor, Ricci scalar, Bianchi identities. General relativity Hilbert action, Palatini formulation, field equations. Coupling of gravity to ... [more]

18R2 Damiano Anselmi
From fakeons to quantum gravity

Talk given at the Department of Physics and Astronomy of Southampton University, UK, on Nov 16th, 2018 I introduce the concept of fake particle and study how it is used to formulate a consistent theory of quantum gravity. Fakeons arise from a new quantization prescription, alternative to the Feynman one, for ... [more]

18A7 Damiano Anselmi
On the nature of the Higgs boson

Several particles are not observed directly, but only through their decay products. We consider the possibility that they might be fakeons, i.e. fake particles, which mediate interactions but are not asymptotic states. A crucial role to determine the true nature of a particle is played by the imaginary parts of ... [more]

18A6 Damiano Anselmi
Let the dice play God

We define life as the amplification of quantum uncertainty up to macroscopic scales. A living being is any amplifier that achieves this goal. We argue that everything we know about life can be explained from this idea. We study a ladder mechanism to estimate the probability that the amplification occurs ... [more]

18R1 Damiano Anselmi
The correspondence principle in quantum field theory and quantum gravity

Talk given at the conference Progress and Visions in Quantum Theory in View of Gravity: Bridging foundations of physics and mathematics Max Planck Institute for Mathematics in the Sciences, Leipzig October 04, 2018 I claim that the best correspondence principle for quantum field theory and quantum gravity is made of unitarity, locality and proper ... [more]

18A5 Damiano Anselmi
The correspondence principle in quantum field theory and quantum gravity

We discuss the fate of the correspondence principle beyond quantum mechanics, specifically in quantum field theory and quantum gravity, in connection with the intrinsic limitations of the human ability to observe the external world. We conclude that the best correspondence principle is made of unitarity, locality, proper renormalizability (a refinement ... [more]

18A4 Damiano Anselmi
Fakeons, microcausality and the classical limit of quantum gravity

We elaborate on the idea of fake particle and study its physical consequences. When a theory contains fakeons, the true classical limit is determined by the quantization and a subsequent process of "classicization". One of the major predictions due to the fake particles is the violation of microcausality, which survives ... [more]

18A3 Damiano Anselmi and Marco Piva
Quantum gravity, fakeons and microcausality

We investigate the properties of fakeons in quantum gravity at one loop. The theory is described by a graviton multiplet, which contains the fluctuation $h_{\mu \nu }$ of the metric, a massive scalar $\phi$ and the spin-2 fakeon $\chi _{\mu \nu }$. The fields $\phi$ and $\chi _{\mu ... [more] Several particles are not observed directly, but only through their decay products. We consider the possibility that they might be fakeons, i.e. fake particles, which mediate interactions but are not asymptotic states. A crucial role to determine the true nature of a particle is played by the imaginary parts of the one-loop radiative corrections, which are affected in nontrivial ways by the presence of fakeons in the loop. The knowledge we have today is sufficient to prove that most non directly observed particles are true physical particles. However, in the case of the Higgs boson the possibility that it might be a fakeon remains open. The issue can be resolved by means of precision measurements in existing and future accelerators. PDF Mod. Phys. Lett. A 34 (2019) 1950123 | DOI: 10.1142/S0217732319501232 arXiv: 1811.02600 [hep-ph] hal-01911950 We define life as the amplification of quantum uncertainty up to macroscopic scales. A living being is any amplifier that achieves this goal. We argue that everything we know about life can be explained from this idea. We study a ladder mechanism to estimate the probability that the amplification occurs spontaneously in nature. The amplification mechanism is so sensitive to small variations of its own parameters that it acts as a bifurcation itself, i.e. it implies that the universe is either everywhere dead or alive wherever possible. Since the first option is excluded by the existence of life on earth, we infer that the universe hosts a huge number of inhabited planets (possibly one per star on average). We also investigate models of conscious and unconscious learning processes, as well as the structure of the brain and evolution. Finally, we address the problem of creating artificial life. PDF hal-01911993 Talk given at the conference Progress and Visions in Quantum Theory in View of Gravity: Bridging foundations of physics and mathematics Max Planck Institute for Mathematics in the Sciences, Leipzig October 04, 2018 I claim that the best correspondence principle for quantum field theory and quantum gravity is made of unitarity, locality and proper renormalizability (which is a refinement of strict renormalizability), combined with fundamental local symmetries and the requirement of having a finite number of fields. Quantum gravity is identified in an essentially unique way. It emerges from a new quantization prescription, which introduces the notion of fake particle, or “fakeon”, and uses it to resolve the long-standing problem of the higher-derivative ghosts. I discuss the major physical prediction of the theory, which is the violation of causality at small distances. The correspondence principle identifies the gauge interactions uniquely in form, but does not predict the gauge group. On the other hand, the matter sector remains almost completely unrestricted. PDF We discuss the fate of the correspondence principle beyond quantum mechanics, specifically in quantum field theory and quantum gravity, in connection with the intrinsic limitations of the human ability to observe the external world. We conclude that the best correspondence principle is made of unitarity, locality, proper renormalizability (a refinement of strict renormalizability), combined with fundamental local symmetries and the requirement of having a finite number of fields. Quantum gravity is identified in an essentially unique way. The gauge interactions are uniquely identified in form. Instead, the matter sector remains basically unrestricted. The major prediction is the violation of causality at small distances. PDF hal-01900207 We elaborate on the idea of fake particle and study its physical consequences. When a theory contains fakeons, the true classical limit is determined by the quantization and a subsequent process of “classicization”. One of the major predictions due to the fake particles is the violation of microcausality, which survives the classical limit. This fact gives hope to detect the violation experimentally. A fakeon of spin 2, together with a scalar field, is able to make quantum gravity renormalizable while preserving unitarity. We claim that the theory of quantum gravity emerging from this construction is the right one. By means of the classicization, we work out the corrections to the field equations of general relativity. We show that the finalized equations have, in simple terms, the form$\langle F\rangle =ma$, where$\langle F\rangle $is an average that includes a little bit of “future”. PDF Class. and Quantum Grav. 36 (2019) 065010 | DOI: 10.1088/1361-6382/ab04c8 arXiv: 1809.05037 [hep-th] We investigate the properties of fakeons in quantum gravity at one loop. The theory is described by a graviton multiplet, which contains the fluctuation$h_{\mu \nu }$of the metric, a massive scalar$\phi $and the spin-2 fakeon$\chi _{\mu \nu }$. The fields$\phi $and$\chi _{\mu \nu }$are introduced explicitly at the level of the Lagrangian by means of standard procedures. We consider two options, where$\phi $is quantized as a physical particle or a fakeon, and compute the absorptive part of the self-energy of the graviton multiplet. The width of$\chi _{\mu \nu }$, which is negative, shows that the theory predicts the violation of causality at energies larger than the fakeon mass. We address this issue and compare the results with those of the Stelle theory, where$\chi _{\mu \nu }$is a ghost instead of a fakeon. PDF J. High Energy Phys. 11 (2018) 21 | DOI: 10.1007/JHEP11(2018)021 arXiv: 1806.03605 [hep-th] A theory of quantum gravity has been recently proposed by means of a novel quantization prescription, which is able to turn the poles of the free propagators that are due to the higher derivatives into fakeons. The classical Lagrangian contains the cosmological term, the Hilbert term,$