Connecting Early Universe Physics to Modern Advances in Observational Astronomy
Lead Research Organisation:
University of Cambridge
Department Name: Institute of Astronomy
Abstract
We are living in a golden age for cosmology. Thanks in large part to our observations of the tiny fluctuations in the afterglow of the Big Bang, the cosmic microwave background, we now have a concordance model of cosmology which provides a precise inventory of the amount and type of matter and energy that makes up the Universe and a timeline of the Universe's development from a fraction of a second on. However, a few nagging uncertainties remain. It has become largely accepted that at early times the Universe underwent a rapid expansion known as inflation. However, in the nearly three decades since inflation was proposed, we are still unable to answer some basic questions about it, such as how it started, how it ended, and what kept the expansion going. There are countless models attempting to describe inflation, but we still don't have a basic underlying theory to ground it in. String theory, our current best hope for a 'theory of everything,' is notoriously hostile to inflation, though attempts to unite the two are ongoing. In order to make progress, therefore, we need to find ways to distinguish among the inflationary models being proposed, all of which, by design, produce a universe similar to what we see today . My approach is to seek out the most distinctive features of inflationary models so as to confirm or rule out as much as possible. One of the most enticing possibilities is the production of relics from the Big Bang -- actual physical objects produced in the early universe that may still exist today, or whose signatures we might still see. Although relics are speculative, their presence would be dramatic enough that the pay-off for either discovering or ruling them out would be huge, allowing us to distinguish among entire classes of models. I have been looking in particular at three kinds of Big Bang relics. First are primordial black holes. These tiny black holes, which could have been produced in the dense environment of the early universe, would show up either by pulling in and heating up the matter around them, which puts out x-ray radiation, or by 'evaporating' -- radiating themselves away as gamma rays. Second are cosmic strings: strings of high energy stretching across the universe would bend the light of distant stars and galaxies around them in a phenomenon known as gravitational lensing. Cosmic strings are particularly exciting to search for because they could be the very strings of string theory, and are therefore our best hope for directly observing something that would confirm the theory. A third type of relic is a particle known as an axion. If axions existed during inflation, they could make up the elusive dark matter that holds galaxies and clusters of galaxies together. However, my work has shown that axions are difficult to fit in with current observations if both string theory and inflation are correct. One of the most valuable tools we have for learning about the early universe is the study of the cosmological Dark Ages, a period after the Big Bang, but before stars and galaxies started to turn on, when the Universe was mostly neutral hydrogen gas. It was dark for two reasons: first, nothing much was shining; and second, neutral hydrogen gas is particularly good at absorbing radiation. Several ambitious radio telescope arrays are currently being built in order to try to get closer to observations of the neutral hydrogen in the Dark Ages so we can fill in the gap between the background radiation we see from the Big Bang and the stars and galaxies we can observe today. Cosmology, which was once the work of philosophers and theologians, is now a precision science. However, that precision needs to be balanced by a clear conceptual picture of what it is we're measuring. I hope to bring us closer to that understanding through my work of connecting early universe physics to the observations we can make today.
People |
ORCID iD |
Katherine Mack (Principal Investigator / Fellow) |
Publications
Mack K
(2011)
Axions, inflation and the anthropic principle
in Journal of Cosmology and Astroparticle Physics
Mack K
(2012)
Detecting the redshifted 21 cm forest during reionization Detecting the 21 cm forest
in Monthly Notices of the Royal Astronomical Society
Mack K
(2011)
Cosmological problems with multiple axion-like fields
in Journal of Cosmology and Astroparticle Physics
Description | Working in collaboration with others, I pointed out major theoretical problems with a popular axion dark matter model. I also demonstrated an innovative new method for extracting information about the earliest star formation by examining the spectrum of distant radio sources with 21cm radio measurements. |
Exploitation Route | Other researchers in astrophysics have cited and utilized my findings in further research. |
Sectors | Education |
Description | Australian Research Council Discovery Early Career Researcher Award |
Amount | $375,000 (AUD) |
Funding ID | DE120101859 |
Organisation | Australian Research Council |
Sector | Public |
Country | Australia |
Start | 09/2012 |
End | 06/2017 |
Description | Collaboration with Professor Stuart Wyithe |
Organisation | University of Melbourne |
Department | School of Physics |
Country | Australia |
Sector | Academic/University |
PI Contribution | I was the primary researcher on a research project. I carried out the research and wrote the resulting publication. |
Collaborator Contribution | My collaborator, Professor Stuart Wyithe, helped guide the research, provided the original idea, and facilitated my two visits to Melbourne University. |
Impact | Publication in Monthly Notices of the Royal Astronomical Society. |
Start Year | 2009 |
Description | Participation in Institute of Astronomy Open Day |
Form Of Engagement Activity | Participation in an open day or visit at my research institution |
Part Of Official Scheme? | Yes |
Type Of Presentation | Poster Presentation |
Geographic Reach | Local |
Primary Audience | Public/other audiences |
Results and Impact | I helped run activities for visitors (mainly children) and introduced the public to the research being carried out at the Institute of Astronomy. N/A. |
Year(s) Of Engagement Activity | 2010,2012 |
Description | Public talk for Institute of Physics, Edinburgh |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | Yes |
Type Of Presentation | Keynote/Invited Speaker |
Geographic Reach | Local |
Primary Audience | Public/other audiences |
Results and Impact | The venue was full, standing room only, in a lecture hall seating about 150. I spoke on the subject of the search for dark matter. The reception and comments were very positive. None that I'm aware of. |
Year(s) Of Engagement Activity | 2011 |
Description | Public talks at schools (several) |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Type Of Presentation | Keynote/Invited Speaker |
Geographic Reach | Local |
Primary Audience | Schools |
Results and Impact | On several occasions, I was invited by teachers to speak to science classes at secondary schools. I presented information about cosmology as well as insight into the scientific career structure. N/A. |
Year(s) Of Engagement Activity | 2010,2011,2012 |