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Mass-Singularity Structure of QED and Perturbative Quantum Gravity Scatterings

Londono Castillo, Santiago LU (2020) FYTK02 20201
Theoretical Particle Physics - Undergoing reorganization
Abstract
In this thesis, the mass singularities occurring in the cross-section of electron scattering processes are investigated. Two types of scatterings are studied: Quantum Electrodynamics (QED) scatterings, and Perturbative Quantum Gravity (PQG) scatterings. We show how mass singularities in QED and PQG cancel when real and virtual diagrams are included in the scattering cross-section. We find that in both theories, the scattering cross-section is infrared (IR) finite and that IR singularities are regulated by the finite energy resolution of the detector. Finally, the differences in the eikonal factorization and the mass singularity structure in QED and PQG are studied. From this, some important properties of PQGare inferred and discussed.
Popular Abstract
Throughout history, the quest to find a theory that can explain nature and all of its interactions has inspired the physics community. From the ancient Greeks and their classical four-element model to Mendeleev’s periodic table, humans have always sought to understand the universe at its most fundamental level. In the 20th century, two theories that would completely revolutionize our understanding of the universe were conceived: general relativity and quantum field theory.

Formulated by Albert Einstein in 1915, general relativity describes the fundamental force of gravity as a geometric property of spacetime. General relativity allowed physicists to study the large-scale properties of the universe, such as the dynamics of planets,... (More)
Throughout history, the quest to find a theory that can explain nature and all of its interactions has inspired the physics community. From the ancient Greeks and their classical four-element model to Mendeleev’s periodic table, humans have always sought to understand the universe at its most fundamental level. In the 20th century, two theories that would completely revolutionize our understanding of the universe were conceived: general relativity and quantum field theory.

Formulated by Albert Einstein in 1915, general relativity describes the fundamental force of gravity as a geometric property of spacetime. General relativity allowed physicists to study the large-scale properties of the universe, such as the dynamics of planets, stars, and galaxies, and predicted the existence of gravitational waves and black holes. On the other hand, our understanding of the smallest particles and their interaction comes from a quantum field theory, the Standard Model (SM) of particle physics. The SM describes three of the four fundamental forces: the weak force, the strong force, and the electromagnetic
force. The fourth force, gravity, has not yet been incorporated into the SM.

Quantum field theories are like mathematical machines that take certain information in, e.g. the energies of particles and their masses, and return quantities involving the interaction of those particles, such as the probability of a process occurring or the direction in which the particles will fly after the interaction. However, these machines can sometimes malfunction
and return singular results, i.e. when the \machine" outputs infinite quantities. These results are unphysical since we all know that it’s impossible to have particles with infinite energies or a process occurring with infinite probability. Thus, if we want a theory to make any physical sense, we must make sure such singularities do not occur.

The goal of this work is to remove some of the singularities occurring in Perturbative Quantum Gravity (PQG). PQG is one of the many attempts to incorporate gravity into the SM. Removing singularities is not important only because singularities are unphysical. The process of removing such singularities can also teach us a lot about the theory itself and its properties. By studying singularities in PQG, we hope to get one step closer to understanding gravity and its quantum properties. (Less)
Please use this url to cite or link to this publication:
author
Londono Castillo, Santiago LU
supervisor
organization
alternative title
Mass-Singularity Structure of quantum electrodynamics and Perturbative Quantum Gravity Scatterings
course
FYTK02 20201
year
type
M2 - Bachelor Degree
subject
keywords
perturbative quantum gravity, QED, mass singularities, collinear singularities, soft singularities, singularity cancellation, graviton
language
English
id
9024096
date added to LUP
2020-07-03 10:43:27
date last changed
2020-07-03 10:43:27
@misc{9024096,
  abstract     = {{In this thesis, the mass singularities occurring in the cross-section of electron scattering processes are investigated. Two types of scatterings are studied: Quantum Electrodynamics (QED) scatterings, and Perturbative Quantum Gravity (PQG) scatterings. We show how mass singularities in QED and PQG cancel when real and virtual diagrams are included in the scattering cross-section. We find that in both theories, the scattering cross-section is infrared (IR) finite and that IR singularities are regulated by the finite energy resolution of the detector. Finally, the differences in the eikonal factorization and the mass singularity structure in QED and PQG are studied. From this, some important properties of PQGare inferred and discussed.}},
  author       = {{Londono Castillo, Santiago}},
  language     = {{eng}},
  note         = {{Student Paper}},
  title        = {{Mass-Singularity Structure of QED and Perturbative Quantum Gravity Scatterings}},
  year         = {{2020}},
}