Theoretical Cosmology
Lead Research Organisation:
University of Portsmouth
Department Name: Institute of Cosmology and Gravitation
Abstract
In recent years there has been an explosion in the amount and precision of observational data with which we can probe models of our Universe. This enables us to test speculative ideas about the physics at work in the very early Universe, the material content of the universe today, and even the nature of gravity and spacetime. A period of rapid, accelerated expansion in the very early universe, known as cosmological inflation provides the initial conditions from which the large scale structure of our universe can subsequently evolve. Quantum fluctuations during inflation are swept up to astrophysical scales by the rapid expansion, and we can distinguish between different possible models of inflation by the spectrum of fluctuations they leave behind. We intend to study the type of density fluctuations they produce, and the statistical properties of these fluctuations both in large galaxy surveys and in the pattern of temperature fluctuations in the cosmic microwave background radiation, which survives as a relic of the hot big bang. The most dramatic discovery in science in the past decade has been the revelation that the expansion of our Universe is actually accelerating today. This implies that the expansion must be driven, not by ordinary matter but by an unknown dark energy, similar to the quantum fields that drove inflation at high energies in the very early universe. However we have no clear idea what low-energy physics could lie behind the dark energy. It is important to distinguish the whether this dark energy is a cosmological constant, or whether it could vary in space and time. The growth of structure in our Universe revealed by observational surveys will be used to study the clustering of dark energy. In particular we will use weak gravitational lensing to probe the distribution of energy density in our Universe and an effect known as the integrated Sachs-Wolfe effect which probes the evolution of the gravitational potential as structure forms. We will also develop geometrical tests of the expansion history of our Universe, preparing for the next generation of massive cosmological data-sets that will be available to researchers in Portsmouth. We will develop advanced methods for cosmological data analysis with such surveys and make projections of the accuracy of geometrical tests. We will be seeking to distinguish models of dark energy from an alternative possibility that Einstein's theory of general relativity iteslf is modified on large scales. Our view of gravity and spacetime has been revolutionised in recent years by brane-world models which propose that our observed Universe may in fact be a four-dimensional 'brane' (with three space dimensions plus time) embedded in a higher-dimensional bulk spacetime. This could reconcile our observed four-dimensional world with string theory that requires extra, hidden spatial dimensions. We will continue work to study the implications of such brane-world models through their effect on models of inflation in the early universe, the evolution of cosmological structure, and the late-time acceleration of our Universe.
Organisations
Publications
Abazajian K
(2009)
THE SEVENTH DATA RELEASE OF THE SLOAN DIGITAL SKY SURVEY
in The Astrophysical Journal Supplement Series
Ananda K
(2007)
Cosmological gravitational wave background from primordial density perturbations
in Physical Review D
Arroja F
(2007)
Low energy effective theory on a regularized brane in 6D gauged chiral supergravity
in Journal of Cosmology and Astroparticle Physics
Arroja F
(2008)
Non-Gaussianity from the trispectrum in general single field inflation
in Physical Review D
Arroja F
(2009)
Cosmological matching conditions for gravitational waves at second order
in Physical Review D
Arroja F
(2009)
Full trispectrum in single field DBI inflation
in Physical Review D
Arroja F
(2008)
Non-Gaussianity from the bispectrum in general multiple field inflation
in Journal of Cosmology and Astroparticle Physics
Assadullahi H
(2009)
Gravitational waves from an early matter era
in Physical Review D
Assadullahi H
(2007)
Primordial non-Gaussianity from two curvaton decays
in Physical Review D
Assadullahi H
(2010)
Constraints on primordial density perturbations from induced gravitational waves
in Physical Review D
Balbi A
(2007)
? a DM : Observational constraints on unified dark matter with constant speed of sound
in Physical Review D
Barrow J
(2007)
Cosmology with inhomogeneous magnetic fields
in Physics Reports
Beynon E
(2010)
Weak lensing predictions for modified gravities at non-linear scales
in Monthly Notices of the Royal Astronomical Society
Bozza V
(2009)
A solution to the anisotropy problem in bouncing cosmologies
in Journal of Cosmology and Astroparticle Physics
Byrnes C
(2010)
Scale dependence of local f NL
in Journal of Cosmology and Astroparticle Physics
Byrnes C
(2007)
Diagrammatic approach to non-Gaussianity from inflation
in Journal of Cosmology and Astroparticle Physics
Böhmer C
(2008)
Dynamics of dark energy with a coupling to dark matter
in Physical Review D
Cailleteau T
(2008)
Singularities in loop quantum cosmology.
in Physical review letters
Caldera-Cabral G
(2009)
Dynamics of interacting dark energy
in Physical Review D
Caldera-Cabral G
(2009)
The growth of structure in interacting dark energy models
in Journal of Cosmology and Astroparticle Physics
Cardoso A
(2008)
Cosmological perturbations in the DGP braneworld: Numeric solution
in Physical Review D
Cardoso A
(2008)
Generalized perturbation equations in bouncing cosmologies
in Physical Review D
Copeland E
(2007)
Cosmological matching conditions
in Journal of Cosmology and Astroparticle Physics
Corradini O
(2008)
Induced gravity on intersecting brane worlds: Maximally symmetric solutions
in Physical Review D
Corradini O
(2008)
Induced gravity on intersecting brane worlds. II. Cosmology
in Physical Review D
Cotta-Ramusino L
(2007)
Low-energy effective theory for a Randall-Sundrum scenario with a moving bulk brane
in Physical Review D
Cresswell J
(2009)
Scale-dependent galaxy bias in the Sloan Digital Sky Survey as a function of luminosity and colour
in Monthly Notices of the Royal Astronomical Society
Crittenden R
(2009)
Investigating dark energy experiments with principal components
in Journal of Cosmology and Astroparticle Physics
Crittenden R
(2007)
Measuring deviations from a cosmological constant: a field-space parametrization.
in Physical review letters
Crittenden R
(2008)
Summary of sessions B5 and B6: recent progress on dark energy and the cosmological constant
in Classical and Quantum Gravity
De Risi G
(2007)
Graceful exit via polymerization of pre-big-bang cosmology
in Physical Review D
Durrer R
(2007)
Dark energy and dark gravity: theory overview
in General Relativity and Gravitation
Ellis G
(2007)
Editorial on the GRG special issue on dark energy
in General Relativity and Gravitation
Ellis G
(2007)
Causality and the speed of sound
in General Relativity and Gravitation
Esposito-Farèse G
(2010)
Vector theories in cosmology
in Physical Review D
Giannantonio T
(2008)
Combined analysis of the integrated Sachs-Wolfe effect and cosmological implications
in Physical Review D
Giannantonio T
(2007)
The effect of reionization on the cosmic microwave background-density correlation
in Monthly Notices of the Royal Astronomical Society
Giannantonio T
(2008)
Detectability of a phantom-like braneworld model with the integrated Sachs-Wolfe effect
in Physical Review D
Hikage C
(2009)
Limits on isocurvature perturbations from non-Gaussianity in WMAP temperature anisotropy
in Monthly Notices of the Royal Astronomical Society
Hollenstein L
(2009)
Constraints on early dark energy from CMB lensing and weak lensing tomography
in Journal of Cosmology and Astroparticle Physics
Hollenstein L
(2008)
Challenges for creating magnetic fields by cosmic defects
in Physical Review D
Keskitalo R
(2007)
Hints of isocurvature perturbations in the cosmic microwave background?
in Journal of Cosmology and Astroparticle Physics
Kobayashi T
(2007)
Cosmological magnetic fields from nonlinear effects
in Physical Review D
Koyama K
(2009)
Velocities as a probe of dark sector interactions
in Journal of Cosmology and Astroparticle Physics
Koyama K
(2007)
Primordial perturbations from slow-roll inflation on a brane
in Journal of Cosmology and Astroparticle Physics
Koyama K
(2007)
Non-Gaussianities from ekpyrotic collapse with multiple fields
in Journal of Cosmology and Astroparticle Physics
Koyama K
(2010)
Non-Gaussianity of quantum fields during inflation
in Classical and Quantum Gravity
Koyama K
(2009)
Ghosts in asymmetric brane gravity and the decoupled stealth limit
in Journal of High Energy Physics
Koyama K
(2008)
Brane-world inflation: Slow-roll corrections to the spectral index
in Physical Review D
Koyama K
(2007)
Ghosts in the self-accelerating universe
in Classical and Quantum Gravity