Course

19S1 D. Anselmi
Theories of gravitation

Program

PDF

Book

D. Anselmi
From Physics To Life

A journey to the infinitesimally small and back

In English and Italian

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Recent Papers

Recent papers and theorems

20A2 Damiano Anselmi, Eugenio Bianchi and Marco Piva
Predictions of quantum gravity in inflationary cosmology: effects of the Weyl-squared term

We derive the predictions of quantum gravity with fakeons on the amplitudes and spectral indices of the scalar and tensor fluctuations in inflationary cosmology. The action is $R+R^{2}$ plus the Weyl-squared term. The ghost is eliminated by turning it into a fakeon, that is to say a purely virtual particle. ... [more]

20A1 Damiano Anselmi
The quest for purely virtual quanta: fakeons versus Feynman-Wheeler particles

The search for purely virtual quanta has attracted interest in the past. We consider various proposals and compare them to the concept of fake particle, or "fakeon". In particular, the Feynman-Wheeler propagator, which amounts to using the Cauchy principal value inside Feynman diagrams, violates renormalizability, unitarity and stability, due to ... [more]

19S13 Damiano Anselmi
A predictive theory of quantum gravity from fake particles

Talk given at Penn State University, Dec 17, 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 (together with a scalar field) allows us to ... [more]

19S12 Damiano Anselmi
Quantum gravity al pub (in Italian)

Conferenza pubblica al pub "Lo spaventapasseri" di Pisa, il 28/11/2019 alle ore 20.00, sul tema della gravità ... [more]

19R2 Damiano Anselmi
Fakeons, quantum gravity and the correspondence principle

The correspondence principle made of unitarity, locality and renormalizability has been very successful in quantum field theory. Among the other things, it helped us build the standard model. However, it also showed important limitations. For example, it failed to restrict the gauge group and the matter sector in a powerful ... [more]

19S11 Damiano Anselmi
A predictive theory of quantum gravity from fake particles

Talk given at the conference "Quantum Gravity and Quantum Geometry", Nijmegen Oct 29 - Nov 1, 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]

19A3 Damiano Anselmi and Antonio Marino
Fakeons and microcausality: light cones, gravitational waves and the Hubble constant

The concept of fake particle, or "fakeon", allows us to make sense of quantum gravity as an ultraviolet complete theory, by renouncing causality at very small distances. We investigate whether the violation of microcausality can be amplified or detected in the most common settings. We show that it is actually ... [more]

19A2 Damiano Anselmi
Fakeons, unitarity, massive gravitons and the cosmological constant

We give a simple proof of perturbative unitarity in gauge theories and quantum gravity using a special gauge that allows us to separate the physical poles of the free propagators, which are quantized by means of the Feynman prescription, from the poles that belong to the gauge-trivial sector, which are ... [more]

19S10 Marco Piva
One-loop effective action of quantum gravity with fakeons and its phenomenology

Talk given by Marco Piva at the conference "Avenues of quantum field theory in curved spacetime", Modena, Sept 9th, ... [more]

19S9 Damiano Anselmi
Quantum gravity from fakeons – Perimeter Institute

Talk given at the conference "Cosmological Frontiers in Fundamental Physics 2019" - Perimeter ... [more]

19S8 Damiano Anselmi
Quantum gravity from fakeons – Marseille

Talk given at the Centre de Physique Theorique of the University of Marseille on June 28th, 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]

19S7 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]

19S6 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 fakeon of spin ... [more]

19R1 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]

19S5 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]

We derive the predictions of quantum gravity with fakeons on the amplitudes and spectral indices of the scalar and tensor fluctuations in inflationary cosmology. The action is $R+R^{2}$ plus the Weyl-squared term. The ghost is eliminated by turning it into a fakeon, that is to say a purely virtual particle. We work to the next-to-leading order of the expansion around the de Sitter background. The consistency of the approach puts a lower bound ($m_{\chi }>m_{\phi }/4$) on the mass $m_{\chi }$ of the fakeon with respect to the mass $m_{\phi }$ of the inflaton. The tensor-to-scalar ratio $r$ is predicted within less than an order of magnitude ($4/3 < N^{2}r<12$ to the leading order in the number of $e$-foldings $N$). Moreover, the relation $r\simeq -8n_{T}$ is not affected by the Weyl-squared term. No vector and no other scalar/tensor degree of freedom is present.

PDF

arXiv: 2005.10293 [hep-th]

The search for purely virtual quanta has attracted interest in the past. We consider various proposals and compare them to the concept of fake particle, or “fakeon”. In particular, the Feynman-Wheeler propagator, which amounts to using the Cauchy principal value inside Feynman diagrams, violates renormalizability, unitarity and stability, due to the coexistence of the prescriptions $\pm i\epsilon $. We contrast the Feynman, fakeon and Feynman-Wheeler prescriptions in ordinary as well as cut diagrams. The fakeon does not have the problems of the Feynman-Wheeler propagator and emerges as the correct concept of purely virtual quantum. It allows us to make sense of quantum gravity at the fundamental level, and places it on an equal footing with the standard model. The resulting theory of quantum gravity is perturbative up to an incredibly high energy.

PDF

J. High Energ. Phys. 03 (2020) 142 | DOI: 10.1007/JHEP03(2020)142

arXiv: 2001.01942 [hep-th]

Talk given at Penn State University, Dec 17, 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 (together with a scalar field) allows us to build a theory of quantum gravity that is both renormalizable and unitary, and to some extent unique. The theory predicts that causality is lost at sufficiently small distances, where time makes no longer sense. After presenting the general formulation of the theory, I explain its nontrivial classical limit, the modifications of the FLRW metric and the role of the cosmological constant. Finally, I discuss the possibility that the Higgs boson might be a fakeon.

PDF

Conferenza pubblica al pub “Lo spaventapasseri” di Pisa, il 28/11/2019 alle ore 20.00, sul tema della gravità quantistica

PDF

The correspondence principle made of unitarity, locality and renormalizability has been very successful in quantum field theory. Among the other things, it helped us build the standard model. However, it also showed important limitations. For example, it failed to restrict the gauge group and the matter sector in a powerful way. After discussing its effectiveness, we upgrade it to make room for quantum gravity. The unitarity assumption is better understood, since it allows for the presence of physical particles as well as fake particles (fakeons). The locality assumption is applied to an interim classical action, since the true classical action is nonlocal and emerges from the quantization and a later process of classicization. The renormalizability assumption is refined to single out the special role of the gauge couplings. We show that the upgraded principle leads to an essentially unique theory of quantum gravity. In particular, in four dimensions, a fakeon of spin 2, together with a scalar field, is able to make the theory renormalizable while preserving unitarity. We offer an overview of quantum field theories of particles and fakeons in various dimensions, with and without gravity.

Proceedings of 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 2018

PDF

arXiv: 1911.10343 [hep-th]

OSF preprints | DOI: 10.31219/osf.io/kxj3r

Philpapers ANSFQG

Preprints 2019, 2019110321

The Youtube Channel has just crossed the threshold of 100 subscribers, which is the amount required by YouTube to obtain a unique URL for it. Now the channel is reachable at the address http://youtube.com/c/QuantumGravityTheory.

Quick statistics up to date, at one year since creation:

Total number of views: 14353
Total watched time: 1583 hours
Number of subscribers: 180
Number of videos: 72

Most watched videos:

Quantum gravity from fakeons – Catania 2019: 2369 views, 20 likes
Theories of Gravitation Lecture 1: 1179 views, 12 likes
A predictive theory of quantum gravity from fake particles: 758 views, 10 likes
Quantum gravity from fakeons – Marseille: 598 views, 4 likes
La fisica e la vita – Viaggio nell’infinitamente piccolo, e ritorno: 505 views, 7 likes
Quantum gravity al pub: 443 views, 9 likes
The corr. principle in quantum field th. and quantum grav.: 410 views, 2 likes

From fakeons to quantum gravity: 324 views, 5 likes
Let the dice play God: 326 views, 2 like2

Number of visits to this website since creation (2013): 41924

Download count for the papers posted on archives other than arXiv (which does not allow download count):

18A5 The corr. principle in q. field th. and q. grav.: 1107 downloads (5 archives)
17A3 On the quantum field theory of the grav. interactions: 403 downloads (2 archives)
18A6 Let the dice play God: 329 downloads (4 archives)
18A7 On The Nature of the Higgs Boson: 256 downloads (4 archives)

The list will be updated from time to time. Last update: 17/05/2020

Talk given at the conference “Quantum Gravity and Quantum Geometry“, Nijmegen Oct 29 – Nov 1, 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 (together with a scalar field) allows us to build a theory of quantum gravity that is both renormalizable and unitary, and to some extent unique. The theory predicts that causality is lost at sufficiently small distances, where time makes no longer sense. After formulating the theory, I explain its main properties. In particular: the nontrivial classical limit, the modifications of the FLRW metric and the roles of the cosmological constant and the Hubble constant.

PDF

The concept of fake particle, or “fakeon”, allows us to make sense of quantum gravity as an ultraviolet complete theory, by renouncing causality at very small distances. We investigate whether the violation of microcausality can be amplified or detected in the most common settings. We show that it is actually short range for all practical purposes. Due to our experimental limitations, the violation does not propagate along the light cones or by means of gravitational waves. In some cases, the universe even conspires to make the effect disappear. For example, the positivity of the Hubble constant appears to be responsible for the direction of time in the early universe.

PDF

Class. Quantum Grav. 37 (2020) 095003 | DOI: 10.1088/1361-6382/ab78d2

arXiv: 1909.12873 [gr-qc]

We give a simple proof of perturbative unitarity in gauge theories and quantum gravity using a special gauge that allows us to separate the physical poles of the free propagators, which are quantized by means of the Feynman prescription, from the poles that belong to the gauge-trivial sector, which are quantized by means of the fakeon prescription. The proof applies to renormalizable theories, including the ultraviolet complete theory of quantum gravity with fakeons formulated recently, as well as low-energy (nonrenormalizable) theories. We clarify a number of subtleties related to the study of scattering processes in the presence of a cosmological constant $\Lambda$. The scattering amplitudes, defined by expanding the metric around flat space, obey the optical theorem up to corrections due to $\Lambda$, which are negligible for all practical purposes. Problems of interpretation would arise if such corrections became important. In passing, we obtain local, unitary (and “almost” renormalizable) theories of massive gravitons and gauge fields, which violate gauge invariance and general covariance explicitly.

PDF

J. High Energy Phys. 12 (2019) 027 | DOI: 10.1007/JHEP12(2019)027

arXiv: 1909.04955 [hep-th]

Talk given by Marco Piva at the conference “Avenues of quantum field theory in curved spacetime“, Modena, Sept 9th, 2019

PDF

Book

14B1 D. Anselmi
Renormalization

Course on renormalization, taught in Pisa in 2015. (More chapters will be added later.)

Last update: May 9th 2015, 230 pages

Avaibable on Amazon:

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Contents:
Preface
1. Functional integral
2. Renormalization
3. Renormalization group
4. Gauge symmetry
5. Canonical formalism
6. Quantum electrodynamics
7. Non-Abelian gauge field theories
Notation and useful formulas
References


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