Theoretical Cosmology

Lead Research Organisation: University of Portsmouth
Department Name: Institute of Cosmology and Gravitation

Abstract

Our research seeks to understand the physics and gravity at work in the Universe, from very high energies in the early Universe, to low energies in the present Universe. By studying the large-scale structure of the Universe revealed by the cosmic microwave background sky and the largest galaxy surveys, we can build up a picture of the physical processes by which structure originated and subsequently evolved. We can also advance our understanding of the late-time acceleration of the Universe, which represents one of the biggest unsolved problems in cosmology and fundamental physics. We will develop tools with which to confront theoretical models with the growing amount of data from massive cosmological surveys, including galaxy surveys in which Portsmouth is directly involved (e.g. the Sloan Digital Sky Survey and the forthcoming Dark Energy Survey). Our research is focussed on 3 main areas: (1) Primordial cosmological perturbations: Quantum fluctuations in the very early universe can provide the seeds for the growth of galaxies and clusters of galaxies. In a period of cosmological inflation, small vacuum fluctuations of the vacuum are swept up by the rapid expansion to seed the structure we see in the Universe today. The distribution of radiation and matter which we observe today contains clues to the physical processes that operated in the very early universe. This may be one of the only ways to test fundamental theories of physics such as string theory. We will compare the predictions of string theory models of inflation against alternative models such as ekpyrotic or cyclic models which invoke different physical mechanisms which would lead to a different distribution of matter in the Universe. To exploit all the available data we also need to improve our understanding of the evolution of structure at lower energies in order to disentangle the primordial distribution from what is seen today. (2) Testing general relativity on cosmological scales: Einstein's theory of general relativity provides an elegant description of gravity which has been verified on terrestrial scales and in the solar system. But to explain the accelerated expansion of the universe which we observe in the universe today, requires either some form of dark energy or a modification of Einstein gravity on cosmological scales. Our work will develop new methods to test general relativity using astronomical observations, including the massive data sets available to Portsmouth researchers. This will include developing numerical simulations of the growth of structure in modified gravity models. We will also study models of dark energy which may interact with matter and cluster on smaller scales, and determine whether it is possible to distinguish such models from modifications of Einstein's equations. (3) Theoretical uncertainties in dark energy models: Many of the largest astronomical surveys are currently focussed on determining the nature of the dark energy which appears to dominate the present energy density of the Universe. To improve significantly beyond the current level of precision requires an improved understanding of systematic uncertainties in the astronomical probes being used and the covariances between different measurements. Our work will reduce uncertainties associated with the use of weak gravitational lensing and peculiar velocities (relative to the overall Hubble flow) in order to constrain both the overall expanion of the Universe and the growth of structure in the Universe. This will require numerical simulations to model the systematic uncertainties in a range of observables in the same physical volume.

Publications

10 25 50

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Aihara H (2011) THE EIGHTH DATA RELEASE OF THE SLOAN DIGITAL SKY SURVEY: FIRST DATA FROM SDSS-III in The Astrophysical Journal Supplement Series

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Assadullahi H (2012) Curvaton and the inhomogeneous end of inflation in Journal of Cosmology and Astroparticle Physics

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Assadullahi H (2013) Modulated curvaton decay in Journal of Cosmology and Astroparticle Physics

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Avgoustidis A (2015) Zipping and unzipping in string networks: Dynamics of Y-junctions in Physical Review D

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Bacon D (2010) Measuring dark matter substructure with galaxy-galaxy flexion statistics Galaxy-galaxy flexion statistics in Monthly Notices of the Royal Astronomical Society

 
Description - We produced the first numerical Einstein-Boltzmann code (CMBquick) able to estimate the intrinsic bispectrum of temperature anisotropies in the cosmic microwave background (CMB) which would contribute to non-Gaussian correlations in the CMB sky observed by the Planck satellite.
- We calculated the power spectrum of the magnetic field generated at the epoch of recombination in the early universe.
- We studied non-Gaussianity in primordial density perturbations produced by models of inflation in the very early universe, including multi-field models, DBI and Galilean inflation. In some cases this could lead to scale-dependent or inhomogeneous non-Gaussianity, potentially observable in the CMB.
- We made significant contributions to the study of modified gravity models, including Galileon models and models with massive gravitons.
- We created a new numerical code (ECOSMOG) to run large numerical simulations of structure formation in modified gravity.
- We showed that combinations of astrophysical data, including weak gravitational lensing by large-scale structure, the integrated Sachs-Wolfe effect in the CMB and redshift-space distortions in galaxy surveys, can provide complementary constraints on gravity and dark energy.
- We have developed non-parametric methods for reconstructing the equation of state of dark energy from a combination of astrophysical data.
Exploitation Route Our results have influenced the development of theoretical cosmology and related astronomical surveys, including:
- Our pioneering work on the intrinsic bispectrum of the CMB anisotropies has led to several groups producing faster codes allowing more detailed numerical estimates of the CMB bispectrum and non-Gaussianity of large-scale structure.
- Our models of primordial non-Gaussianity from inflation have been tested against observations by ESA's Planck satellite.
- Our predictions for structure formation in modified gravity are being used as a target for future large-scale structure surveys such as the ESA Euclid satellite mission.
- Non-parametric methods are being applied to a range of dark energy models.
Sectors Education,Culture, Heritage, Museums and Collections

URL http://www.icg.port.ac.uk/research-overview/
 
Description We have given popular talks at local schools, societies, festivals and other public events, including a major Stargazing live event at Portsmouth's Spinnaker Tower in 2012 with 450 ticketed visitors. Our research contributes to our annual Cosmology Masterclass and work experience for local school students. We have also engaged with local and national media.
First Year Of Impact 2010
Sector Education
Impact Types Cultural,Societal

 
Description Leverhulme Prize Fellowship
Amount £70,000 (GBP)
Funding ID PLP/09/0062 
Organisation The Leverhulme Trust 
Sector Charity/Non Profit
Country United Kingdom
Start 10/2010 
End 09/2013
 
Description Royal Society Daiwa Adrian Prize
Amount £11,000 (GBP)
Funding ID 8204/8824 
Organisation The Royal Society 
Sector Charity/Non Profit
Country United Kingdom
Start 09/2010 
End 08/2013
 
Description Royal Society International Travel Grant
Amount £855 (GBP)
Funding ID TG101622 
Organisation The Royal Society 
Sector Charity/Non Profit
Country United Kingdom
Start 08/2010 
End 09/2010
 
Description Astronomy in City 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? Yes
Type Of Presentation Workshop Facilitator
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact Telescopes were setup in a public space and passers-by were invited to use them to view the Moon or planet Jupiter. About 50 people (children and adults) attended each night, with most people having never looked through a telescope before.

Chaz Shapiro was encouraged by Gunwharf Quays to continue holding the event, including during Portsmouth Festivities, a large festival at GQ (June 17-19). Led to several mentions in local newspaper (The News) and CS was interviewed on local radio (Express FM).
Year(s) Of Engagement Activity 2011
 
Description BBC Stargazing Spinnaker Tower Event 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Type Of Presentation Workshop Facilitator
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact Information not available
Year(s) Of Engagement Activity 2011
 
Description BBC Three Counties Radio interview 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Type Of Presentation Keynote/Invited Speaker
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact David Wands was interviewed on BBC local radio show. According to mediauk.com, 178,000 people listen each week to BBC Three Counties Radio.

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Year(s) Of Engagement Activity 2011
 
Description Cafe Scientifique, Very First Light 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? Yes
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact Brief introductory talk, followed by questions.

Information not available
Year(s) Of Engagement Activity 2010,2011
 
Description Charterhouse School, Godalming 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact approx 20 students attended the talk, which led to a range of questions and discussion afterwards.

5.8 Students were encouraged to pursue physics and astronomy at University.
Year(s) Of Engagement Activity 2010
 
Description Cody Astronomical Society, Farnborough 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact Approx 50 people attended the talk, which led to a large number of questions and much discussion afterwards.

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Year(s) Of Engagement Activity 2010
 
Description EXMOOR DARK SKY DISCOVERY 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? Yes
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact Presenters gave several 15 minute demonstrations about comets. Each session was attended by about 200 people (children and adults) and was followed by a question and answer period.

Feedback was extremely positive. Exmoor Park is committed to running regular astronomy events as part of its application to become a national dark-sky reserve (pending). ICG members will be invited back.
Year(s) Of Engagement Activity 2009,2011
 
Description Maths Society at 6th-form College Farnborough 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact round 50 A-level maths students attended a talk and some students asked many questions after the talk.

Teachers told me that students discussed about the talk in class rooms and I was asked to give a talk regularly to the first year A-level maths students.
Year(s) Of Engagement Activity 2010
 
Description Museum Visit "Meet the Scientist" 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? Yes
Type Of Presentation Keynote/Invited Speaker
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact Chaz Shapiro gave three 15 minute talks (with slides) about cosmology and being a scientist. Each session was attended by about 30 people (children and adults) and was followed by a question and answer period.

CS made contacts at Intech, which periodically offers opportunities for more outreach.
Year(s) Of Engagement Activity 2010
 
Description Nuffield Science Bursary student 2010 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? Yes
Type Of Presentation Workshop Facilitator
Geographic Reach Local
Primary Audience Schools
Results and Impact David Wands supervised 6th-form student project working on inflationary cosmology.

Student was awarded an Exscitec Platinum Award for his project report. Student has been offered an undergraduate place to study mathematics at Cambridge University. School has asked for more placements this summer.
Year(s) Of Engagement Activity 2010
 
Description Petersfield Scouts 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Type Of Presentation Workshop Facilitator
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact David Wands visited a local scout group. Approx 20 scouts and 2 parent helpers attended, asked questions and joined in activities.

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Year(s) Of Engagement Activity 2011
 
Description Public Talk for National Science and Engineering Week 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? Yes
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact Approx 100 people attended the talk, which led to a large number of questions and much discussion afterwards.

Children were encouraged to pursue physics at school.
Year(s) Of Engagement Activity 2011
 
Description Radio Solent interview 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact Listeners to Radio Solent breakfast radio heard about the ICG cosmology supercomputer, and discussion of the importance of blue-skies research.

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Year(s) Of Engagement Activity 2011
 
Description Short film on BBC Big Screens 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact passers-by will learn about cosmology and supercomputing.

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Year(s) Of Engagement Activity 2011
 
Description Space Week, Intech Science Centre, Winchester 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? Yes
Geographic Reach Local
Primary Audience Schools
Results and Impact Approx 100 people came by our stall, most of whom had questions or joined in discussions

School children really enjoyed handling meteroits.
Year(s) Of Engagement Activity 2010
 
Description Spinnaker Tower "Aim High for the Summer" Inspire Week Event "Be an Astronomer for the Day" 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Type Of Presentation Workshop Facilitator
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact * Information not available
Year(s) Of Engagement Activity 2012
 
Description Stargazing at Portsmouth Historic Dockyard 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? Yes
Type Of Presentation Workshop Facilitator
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact 450 people attended a Stargazing Live partner event at Portsmouth Historic Dockyard, organised by the ICG. There were a variety of activities linked to our research and the opportunity for members of the public to ask our researchers questions which sparked discussion

Many members of the public who attended the event were not previously aware of the ICG or that cosmology research was being carried out in their home city.
Year(s) Of Engagement Activity 2013
 
Description Talk to Isle of Wight School Children 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact Approx 20 students attended the talk, which led to a large number of questions and much discussion afterwards.

Students were encouraged to pursue physics and astronomy at University.
Year(s) Of Engagement Activity 2011
 
Description Talk: Mapping the Universe 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact Prof Will Percival's inaugural lecture, attended by VIPs, members of the ICG and the general public

The lecture was recorded.
Year(s) Of Engagement Activity 2013
 
Description Wessex Astronomical Society 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact Approx 100 people attended the talk, which led to a large number of questions and much discussion afterwards.

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Year(s) Of Engagement Activity 2011