Supercooled First Order Phase Transitions and Gravitational Waves in a B − L-like Model
(2026) FYSK04 20261Department of Physics
Particle and nuclear physics
- Abstract
- This thesis studies first-order phase-transition dynamics and the associated stochastic gravitational-wave background in classically conformal B − L-like extensions of the Standard Model. The scalar and gauge sectors are formulated at tree level and at one-loop order using a modified on-shell renormalization prescription designed to keep the vacuum structure fixed while allowing the tree-level flat-direction scalar to acquire a loop-induced mass. The finite-temperature effective potential is then used to analyse supercooled first-order phase transitions and the resulting gravitational-wave spectra. Numerical benchmark studies are performed with the Python package TransitionSolver. For the limited benchmark points considered here, the... (More)
- This thesis studies first-order phase-transition dynamics and the associated stochastic gravitational-wave background in classically conformal B − L-like extensions of the Standard Model. The scalar and gauge sectors are formulated at tree level and at one-loop order using a modified on-shell renormalization prescription designed to keep the vacuum structure fixed while allowing the tree-level flat-direction scalar to acquire a loop-induced mass. The finite-temperature effective potential is then used to analyse supercooled first-order phase transitions and the resulting gravitational-wave spectra. Numerical benchmark studies are performed with the Python package TransitionSolver. For the limited benchmark points considered here, the predicted gravitational-wave signals are below the projected detectability of LISA and current pulsar-timing-array searches. These results should therefore be interpreted as an exploratory benchmark analysis rather than as a general exclusion of the model class. (Less)
- Popular Abstract
- The Standard Model is the central theoretical framework of particle physics. It describes the fundamental particles that give rise to all known matter in the universe; quarks that give rise to baryons like protons and neutrons, leptons such as the electron, and bosons such as the photon or the Higgs boson. Crucially, it has always been known to be limited, lacking explanations for dark matter, gravity and more. This was felt in September 2015, when a gravitational wave passed through the earth, measured by the gravitational wave measurement experiment LIGO. Waves of gravitational radiation, known as gravitational waves, have been theorised, derived from Einstein’s equation of general relativity, yet it took one hundred years to finally... (More)
- The Standard Model is the central theoretical framework of particle physics. It describes the fundamental particles that give rise to all known matter in the universe; quarks that give rise to baryons like protons and neutrons, leptons such as the electron, and bosons such as the photon or the Higgs boson. Crucially, it has always been known to be limited, lacking explanations for dark matter, gravity and more. This was felt in September 2015, when a gravitational wave passed through the earth, measured by the gravitational wave measurement experiment LIGO. Waves of gravitational radiation, known as gravitational waves, have been theorised, derived from Einstein’s equation of general relativity, yet it took one hundred years to finally measure one, resulting in the Nobel Prize in physics in 2017. Predictably, fervour for research into gravitational waves skyrocketed, resulting eventually in this thesis.
The gravitational waves detected at LIGO were the result of two black holes merging; however, this is not the only possible origin of gravitational waves. In the early universe, the plasma filling the universe was in an excited state. As the universe expanded and cooled, the plasma began to transition, from the excited state, to the true vacuum of the universe known to us.
This thesis investigates an extension to the Standard Model of particle physics by an extra force and an extra Higgs-like boson. In the Standard Model, electromagnetic charge conservation gives rise to the (gauge) boson governing electromagnetic interactions, the photon. Analogously, the extra force introduced causes the conservation of the difference between baryon (B) and lepton (L) numbers, B − L is conserved in any interaction of this model, giving rise to a new gauge boson. The B − L model is widely studied, both due to its simplicity, and due to its wide range of applicability, giving an explanation for dark matter, the matter anti-matter asymmetry in the universe, and gravitational waves from the early universe.
The plasma’s transition from the excited, false vacuum, to the true vacuum, happens spontaneously, and is dictated by the Higgs and B − L contributions. The transition occurs, leaving behind bubbles of the true vacuum, which rapidly expand, until the universe is entirely filled with true vacuum, as we know it today. This rapid motion of the bubbles through the plasma, and collisions of bubbles with each other, results in large amounts of energy being released, in the form of gravitational waves. These gravitational waves, arising from the predictions of the B − L model, are numerically calculated, and then compared to the data of gravitational wave discoveries, and the measurement range of the planned gravitational wave detector LISA. If a gravitational wave signal with compatible properties were detected in the future, it could provide important evidence for physics beyond the Standard Model and help constrain models of this type. However, such a signal would not by itself uniquely confirm the model, since different models can lead to similar gravitational wave spectra. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/student-papers/record/9231928
- author
- Ruckstuhl, Lux LU
- supervisor
- organization
- course
- FYSK04 20261
- year
- 2026
- type
- M2 - Bachelor Degree
- subject
- keywords
- B-L, First Order Phase Transition, Gravitational Waves
- language
- English
- id
- 9231928
- date added to LUP
- 2026-06-09 10:24:47
- date last changed
- 2026-06-09 10:24:47
@misc{9231928,
abstract = {{This thesis studies first-order phase-transition dynamics and the associated stochastic gravitational-wave background in classically conformal B − L-like extensions of the Standard Model. The scalar and gauge sectors are formulated at tree level and at one-loop order using a modified on-shell renormalization prescription designed to keep the vacuum structure fixed while allowing the tree-level flat-direction scalar to acquire a loop-induced mass. The finite-temperature effective potential is then used to analyse supercooled first-order phase transitions and the resulting gravitational-wave spectra. Numerical benchmark studies are performed with the Python package TransitionSolver. For the limited benchmark points considered here, the predicted gravitational-wave signals are below the projected detectability of LISA and current pulsar-timing-array searches. These results should therefore be interpreted as an exploratory benchmark analysis rather than as a general exclusion of the model class.}},
author = {{Ruckstuhl, Lux}},
language = {{eng}},
note = {{Student Paper}},
title = {{Supercooled First Order Phase Transitions and Gravitational Waves in a B − L-like Model}},
year = {{2026}},
}