Advances in Theoretical High Energy Physics - Solving Quantum Field Theory

A special issue of Symmetry (ISSN 2073-8994). This special issue belongs to the section "Physics".

Deadline for manuscript submissions: 31 December 2024 | Viewed by 7351

Special Issue Editors

Istituto Nazionale di Fisica Nucleare, Sezione di Firenze, 50019 Sesto Fiorentino (FI), Italy
Interests: strong interactions within and without the standard model; phases and phase transitions of quantum chromodynamics; lattice field theory; computational physics
Dipartimento di Fisica, Università di Napoli Federico II, Napoli, Italy
Interests: flavour physics; theory QCD; neutrino oscillations; exotic and beyond the standard model physics
1. Department of Physics Ettore Pancini, Polytechnic and Basic Sciences School, University of Naples Federico II, Naples, Italy
2. CP3-Origins and Danish IAS, University of Southern Denmark, Odense, Denmark
Interests: theoretical high energy physics
Dipartimento di Fisica, Università degli Studi di Bologna, I-40126 Bologna, Italy
Interests: theoretical physics; quantum field theory

Special Issue Information

Dear Colleagues,

Quantum Field Theory (QFT) provides an extraordinarily successful description of natural phenomena, working from the largest to the smallest scales. Its applications range from fundamental physics to condensed matter and reach out to health sciences, including the highly topical subject of the dynamics of epidemics. Such a broad range of applications calls for different, highly specialized, approaches. This variety may obscure the substantial unity of the field, which, however, has to be nurtured and recognized, in order to preserve our capability to identify new avenues of research and further expand the attendant methodologies. The main objective of this Special Issue is to present a comprehensive overview of Quantum Field Theory, emphasizing the opportunities for cross-fertilization and identifying new directions. This Special Issue will be articulated in six main lines, each of them comprising one or more review articles: Structure and Phases of Quantum Field Theory; Lattice and Semiclassical Approaches to Quantum Field Theories; Bridging Quantum Field Theory and Experiments in Particle Physics; Quantum Field Theories for Gravity; and Field Theory Approaches for infectious diseases.

Dr. Maria Lombardo
Prof. Dr. Giulia Ricciardi
Prof. Dr. Francesco Sannino
Dr. Gian Paolo Vacca
Guest Editors

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Published Papers (4 papers)

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Research

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64 pages, 2492 KiB  
Article
Nonlocal Fractional Quantum Field Theory and Converging Perturbation Series
by Nikita A. Ignatyuk, Stanislav L. Ogarkov and Daniel V. Skliannyi
Symmetry 2023, 15(10), 1823; https://doi.org/10.3390/sym15101823 - 25 Sep 2023
Cited by 1 | Viewed by 834
Abstract
The main purpose of this paper is to derive a new perturbation theory (PT) that has converging series. Such series arise in the nonlocal scalar quantum field theory (QFT) with fractional power potential. We construct a PT for the generating functional (GF) of [...] Read more.
The main purpose of this paper is to derive a new perturbation theory (PT) that has converging series. Such series arise in the nonlocal scalar quantum field theory (QFT) with fractional power potential. We construct a PT for the generating functional (GF) of complete Green functions (including disconnected parts of functions) Zj as well as for the GF of connected Green functions Gj=lnZj in powers of coupling constant g. It has infrared (IR)-finite terms. We prove that the obtained series, which has the form of a grand canonical partition function (GCPF), is dominated by a convergent series—in other words, has majorant, which allows for expansion beyond the weak coupling g limit. Vacuum energy density in second order in g is calculated and researched for different types of Gaussian part S0[ϕ] of the action S[ϕ]. Further in the paper, using the polynomial expansion, the general calculable series for Gj is derived. We provide, compare and research simplifications in cases of second-degree polynomial and hard-sphere gas (HSG) approximations. The developed formalism allows us to research the physical properties of the considered system across the entire range of coupling constant g, in particular, the vacuum energy density. Full article
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20 pages, 355 KiB  
Article
Gravity as a Quantum Field Theory
by Roberto Percacci
Symmetry 2023, 15(2), 449; https://doi.org/10.3390/sym15020449 - 08 Feb 2023
Cited by 5 | Viewed by 2329
Abstract
Classical gravity is understood as the geometry of spacetime, and it seems very different from the other known interactions. In this review, I will instead stress the analogies: Like strong interactions, the low energy effective field theory of gravity is related to a [...] Read more.
Classical gravity is understood as the geometry of spacetime, and it seems very different from the other known interactions. In this review, I will instead stress the analogies: Like strong interactions, the low energy effective field theory of gravity is related to a nonlinearly realized symmetry, and like electroweak interactions, it is a gauge theory in Higgs phase, with a massive connection. I will also discuss the possibility of finding a UV complete quantum field theoretic description of all interactions. Full article
18 pages, 338 KiB  
Article
Purely Virtual Particles in Quantum Gravity, Inflationary Cosmology and Collider Physics
by Damiano Anselmi
Symmetry 2022, 14(3), 521; https://doi.org/10.3390/sym14030521 - 03 Mar 2022
Cited by 1 | Viewed by 1835
Abstract
We review the concept of purely virtual particle and its uses in quantum gravity, primordial cosmology and collider physics. The fake particle, or “fakeon”, which mediates interactions without appearing among the incoming and outgoing states, can be introduced by means of a new [...] Read more.
We review the concept of purely virtual particle and its uses in quantum gravity, primordial cosmology and collider physics. The fake particle, or “fakeon”, which mediates interactions without appearing among the incoming and outgoing states, can be introduced by means of a new diagrammatics. The renormalization coincides with one of the parent Euclidean diagrammatics, while unitarity follows from spectral optical identities, which can be derived by means of algebraic operations. The classical limit of a theory of physical particles and fakeons is described by an ordinary Lagrangian plus Hermitian, micro acausal and micro nonlocal self-interactions. Quantum gravity propagates the graviton, a massive scalar field (the inflaton) and a massive spin-2 fakeon, and leads to a constrained primordial cosmology, which predicts the tensor-to-scalar ratio r in the window 0.41000r3.5. The interpretation of inflation as a cosmic RG flow allows us to calculate the perturbation spectra to high orders in the presence of the Weyl squared term. In models of new physics beyond the standard model, fakeons evade various phenomenological bounds, because they are less constrained than normal particles. The resummation of self-energies reveals that it is impossible to get too close to the fakeon peak. The related peak uncertainty, equal to the fakeon width divided by 2, is expected to be observable. Full article

Review

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12 pages, 300 KiB  
Review
Soft-Theorems for Scalar Particles: The Dilatons Story
by Raffaele Marotta
Symmetry 2022, 14(3), 574; https://doi.org/10.3390/sym14030574 - 14 Mar 2022
Cited by 1 | Viewed by 1292
Abstract
We summarize recent results regarding single and double soft theorems of two different particles named dilatons, the Nambu-Goldstone boson of the spontaneously broken conformal field theories and the massless scalar particle of the closed string theories. Similarities and differences between the soft theorems [...] Read more.
We summarize recent results regarding single and double soft theorems of two different particles named dilatons, the Nambu-Goldstone boson of the spontaneously broken conformal field theories and the massless scalar particle of the closed string theories. Similarities and differences between the soft theorems of these two particles are discussed as well as their connections with the symmetries of the theories. Full article
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