Cosmological implications of the standard model and beyond
Lead Research Organisation:
Newcastle University
Department Name: Mathematics and Statistics
Abstract
Discovery of the Higgs boson has raised some intriguing cosmological questions surrounding issues such vacuum stability and the nature of the inflationary mechanism. This project seeks to develop the tools necessary to explore these issues and to make cosmological predictions thereby placing limits on particle parameters such as the top quark mass. This project will involve the theory of density fluctuations, bubble nucleation and stochastic field theory. Further work will seek to apply some of these tools to late universe, dark energy driven, cosmological evolution and to cosmological structure formation.
People |
ORCID iD |
| Ian Moss (Primary Supervisor) | |
| Katie Marshall (Student) |
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| ST/N504191/1 | 01/10/2015 | 30/09/2020 | |||
| 1654183 | Studentship | ST/N504191/1 | 01/10/2015 | 28/02/2019 | Katie Marshall |
| Description | The Higgs field is believed to exist in a state of false vacuum-that is, it occupies a local minimum energy state, but a lower energy state may exist. It is therefore possible for a vacuum decay event to occur in which the field transitions from this false vacuum state to the lower energy level, resulting in the formation of a true vacuum bubble. Such bubbles grow rapidly once formed and would be catastrophic for any region of space they expand to cover, as inside the bubble physics would function very differently. The likelihood of such a decay occurring depends on the shape of the spacetimes inside and outside the bubble and the exact form of the Higgs potential, which itself depends on parameters including the Higgs boson and top quark masses. We are confident that in usual circumstances, false vacuum decay is unlikely enough that it should be a negligible cause for concern. This project sought to investigate cases where the decay rate may be enhanced, which provides insight into beyond-Standard Model physics. This project developed numerical techniques to investigate Higgs vacuum decay rates and applied them to models using a close approximation to the Higgs potential with black holes in four and five dimensions. It was found that microscopic black holes, such as those potentially formed in extremely high energy cosmic ray collisions, may seed false vacuum decay. Our findings rule out the possibility of primordial black holes in the early universe, but allow for the possibility of vacuum decay from rare high energy cosmic ray collisions. Decay rates were also investigated in a five-dimensional spacetime without a black hole. The presence of a fifth dimension was not found to enhance the vacuum decay rate compared to the four-dimensional case. Other work provided the first look at negative modes of solutions to the field equations in asymptotically flat space and found that realistic solutions have exactly one negative mode, which can be interpreted as corresponding to a scaling up or down of the size of the true vacuum bubble. |
| Exploitation Route | Further work may consider other models for the catalysis of vacuum decay by black holes. Techniques using black hole analogues in a Bose gas may provide laboratory insights into false vacuum decay. |
| Sectors | Other |
| Description | Cosmology group collaboration on Higgs vacuum decay |
| Organisation | Durham University |
| Country | United Kingdom |
| Sector | Academic/University |
| PI Contribution | Newcastle University contributed to analysis and development of numerical techniques for investigating decay rates and verification and checking of results. My main contribution was in developing C++ code to model vacuum decay, which was applied to the models with black holes and a braneworld. I also contributed to the derivation of the first negative mode for an instanton in asymptotically flat space. |
| Collaborator Contribution | Durham University contributed to analytical and numerical modelling of vacuum decay and verification and checking of results, considering the cases of vacuum decay with black holes, vacuum decay on the brane, and negative modes of instantons in asymptotically flat space and with black holes. |
| Impact | Collaborative work by researchers from Newcastle University and Durham University produced three papers on vacuum decay (detailed in the publications section). The topics of each of these were vacuum decay with black holes, vacuum decay in a braneworld, and negative modes of Coleman-de Luccia instantons. |
| Start Year | 2016 |
| Description | Three Minute Thesis - Newcastle |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | Local |
| Primary Audience | Postgraduate students |
| Results and Impact | The Newcastle heat of the national Three Minute Thesis competition involved a very brief presentation summarising the project in under three minutes to an audience of the general public as well as staff and students from outside of physics. |
| Year(s) Of Engagement Activity | 2017 |