Course
19R1 D. Anselmi
Theories of gravitation
Program
Recent Papers
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19A1 Damiano AnselmiFakeons 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 ... (read more)
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18A7 Damiano AnselmiOn 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 ... (read more)
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18A6 Damiano AnselmiLet 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 ... (read more)
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18A5 Damiano AnselmiThe 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 ... (read more)
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18A4 Damiano AnselmiFakeons, 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 ... (read more)
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18A3 Damiano Anselmi and Marco PivaQuantum 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 ... (read more)
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18A2 Damiano Anselmi and Marco PivaThe ultraviolet behavior of quantum gravity
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 ... (read more)
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18A1 Damiano AnselmiFakeons and Lee-Wick models
The “fakeon” is a fake degree of freedom, i.e. a degree of freedom that does not belong to the physical spectrum, but propagates inside the ... (read more)
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17A3 Damiano AnselmiOn the quantum field theory of the gravitational interactions
We study the main options for a unitary and renormalizable, local quantum field theory of the gravitational interactions. The first model is a Lee-Wick superrenormalizable ... (read more)
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17A2 Damiano Anselmi and Marco PivaPerturbative unitarity of Lee-Wick quantum field theory
We study the perturbative unitarity of the Lee-Wick models, formulated as nonanalytically Wick rotated Euclidean theories. The complex energy plane is divided into disconnected regions ... (read more)
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17A1 Damiano Anselmi and Marco PivaA new formulation of Lee-Wick quantum field theory
The Lee-Wick models are higher-derivative theories that are claimed to be unitary thanks to a peculiar cancelation mechanism. In this paper, we provide a new ... (read more)
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16A3 Damiano AnselmiAlgebraic cutting equations
The cutting equations are diagrammatic identities that are used to prove perturbative unitarity in quantum field theory. In this paper, we derive algebraic, upgraded versions ... (read more)
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16A2 Ugo G. Aglietti and Damiano AnselmiInconsistency of Minkowski higher-derivative theories
We show that Minkowski higher-derivative quantum field theories are generically inconsistent, because they generate nonlocal, non-Hermitian ultraviolet divergences, which cannot be removed by means of ... (read more)
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16A1 Damiano AnselmiAspects of perturbative unitarity
We reconsider perturbative unitarity in quantum field theory and upgrade several arguments and results. The minimum assumptions that lead to the largest time equation, the ... (read more)
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15A4 Damiano AnselmiBackground field method and the cohomology of renormalization
Using the background field method and the Batalin-Vilkovisky formalism, we prove a key theorem on the cohomology of perturbatively local functionals of arbitrary ghost numbers, ... (read more)
Ward identities
15A2 Damiano AnselmiAdler-Bardeen theorem and cancellation of gauge anomalies to all orders in nonrenormalizable theories
We prove the Adler-Bardeen theorem in a large class of general gauge theories, including nonrenormalizable ones. We assume that the gauge symmetries are general covariance, local Lorentz symmetry and Abelian and non-Abelian Yang-Mills symmetries, and that the local functionals of vanishing ghost numbers satisfy a variant of the Kluberg-Stern–Zuber conjecture. We show that if the gauge anomalies are trivial at one loop, for every truncation of the theory there exists a subtraction scheme where they manifestly vanish to all orders, within the truncation. Outside the truncation the cancellation of gauge anomalies can be enforced by fine-tuning local counterterms. The framework of the proof is worked out by combining a recently formulated chiral dimensional regularization with a gauge invariant higher-derivative regularization. If the higher-derivative regularizing terms are placed well beyond the truncation, and the energy scale $\Lambda $ associated with them is kept fixed, the theory is super-renormalizable and has the property that, once the gauge anomalies are canceled at one loop, they manifestly vanish from two loops onwards by simple power counting. When the $\Lambda $ divergences are subtracted away and $\Lambda $ is sent to infinity, the anomaly cancellation survives in a manifest form within the truncation and in a nonmanifest form outside. The standard model coupled to quantum gravity satisfies all the assumptions, so it is free of gauge anomalies to all orders.
Phys. Rev. D 91 (2015) 105016 | DOI: 10.1103/PhysRevD.91.105016
15A1 Damiano AnselmiWard identities and gauge independence in general chiral gauge theories
Using the Batalin-Vilkovisky formalism, we study the Ward identities and the equations of gauge dependence in potentially anomalous general gauge theories, renormalizable or not. A crucial new term, absent in manifestly nonanomalous theories, is responsible for interesting effects. We prove that gauge invariance always implies gauge independence, which in turn ensures perturbative unitarity. Precisely, we consider potentially anomalous theories that are actually free of gauge anomalies thanks to the Adler-Bardeen theorem. We show that when we make a canonical transformation on the tree-level action, it is always possible to re-renormalize the divergences and re-fine-tune the finite local counterterms, so that the renormalized $\Gamma $ functional of the transformed theory is also free of gauge anomalies, and is related to the renormalized $\Gamma $ functional of the starting theory by a canonical transformation. An unexpected consequence of our results is that the beta functions of the couplings may depend on the gauge-fixing parameters, although the physical quantities remain gauge independent. We discuss nontrivial checks of high-order calculations based on gauge independence and determine how powerful they are.
Phys. Rev. D 92 (2015) 025027 | DOI: 10.1103/PhysRevD.92.025027
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Book
14B1 D. Anselmi
Renormalization
Last update: May 9th 2015, 230 pages
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
Course on renormalization, taught in Pisa in 2015. (More chapters will be added later.)
Sections
- Quantum gravity (24)
- Standard model (5)
- Adler-Bardeen theorem (5)
- Background field method (3)
- Unitarity of quantum field theory (13)
- Fakeons (10)
- Renormalization of general gauge theories (14)
- Field-covariant quantum field theory (4)
- Lorentz violating quantum field theory (11)
- Renormalization group (14)
- Infinite reduction of couplings (5)
- Regularization (5)
- Conformal field theory (20)
- Topological field theory (5)
- Instantons (4)
- Field redefinitions (4)
- Dimensional regularization (5)
- Philosophy of science (3)
- Biophysics (1)
- Videos (5)
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