Simple generalizations of anti-deSitter space-time (2009)
Magueijo, Joao, Mozaffari, Ali
We consider new cosmological solutions which generalize the cosmological patch of the anti-deSitter space-time, allowing for fluids with equations of state such that $w\neq -1$. We use them to derive...
Rotation of galaxies as a signature of cosmic strings in weak lensing surveys (2009)
Thomas, Daniel B., Contaldi, Carlo R., Magueijo, Joao
Vector perturbations sourced by topological defects can generate rotations in the lensing of background galaxies. This is a potential smoking gun for the existence of defects since rotation generates...
DSR as an explanation of cosmological structure (2008)
Deformed special relativity (DSR) is one of the possible realizations of a varying speed of light (VSL). It deforms the usual quadratic dispersion relations so that the speed of light becomes energy...
Bimetric varying speed of light theories and primordial fluctuations (2008)
We exhibit a varying speed of light (VSL) theory that implements the recently proposed decaying speed of sound mechanism for generating density fluctuations. We avail ourselves of bimetric VSL...
Anomalous CMB polarization and gravitational chirality (2008)
Contaldi, Carlo R., Magueijo, Joao, Smolin, Lee
We consider the possibility that gravity breaks parity, with left and right handed gravitons coupling to matter with a different Newton's constant and show that this would affect their zero-point...
Speedy sound and cosmic structure (2008)
If the speed of sound were vastly larger in the early Universe a near scale-invariant spectrum of density fluctuations could have been produced even if the Universe did not submit to conventional...
Observing the temperature of the Big Bang through large scale structure (2007)
Ferreira, Pedro, Magueijo, Joao
It is widely accepted that the Universe underwent a period of thermal equilibrium at very early times. One expects a residue of this primordial state to be imprinted on the large scale structure of...
Comments on "Note on varying speed of light theories" (2007)
Magueijo, Joao, Moffat, John W.
In a recent note Ellis criticizes varying speed of light theories on the grounds of a number of foundational issues. His reflections provide us with an opportunity to clarify some fundamental matters...
Near-Milne realization of scale-invariant fluctuations (2007)
A near-Milne Universe produces a very red spectrum of vacuum quantum fluctuations, but has the potential to produce near-scale invariant {\it thermal} fluctuations. This happens if the energy and...
Thermal fluctuations in loop cosmology (2007)
Magueijo, Joao, Singh, Parampreet
Quantum gravitational effects in loop quantum cosmology lead to a resolution of the initial singularity and have the potential to solve the horizon problem and generate a quasi scale-invariant...
Holography and the scale-invariance of density fluctuations (2006)
Magueijo, Joao, Smolin, Lee, Contaldi, Carlo R.
We study a scenario for the very early universe in which there is a fast phase transition from a non-geometric, high temperature phase to a low temperature, geometric phase described by a classical...
The Axis of Evil revisited (2006)
In light of the three-year data release from WMAP we re-examine the evidence for the ``Axis of Evil'' (AOE). We discover that previous statistics are not robust with respect to the data-sets...
Occam's razor meets WMAP (2006)
Magueijo, Joao, Sorkin, Rafael D.
Using a variety of quantitative implementations of Occam's razor we examine the low quadrupole, the ``axis of evil'' effect and other detections recently made appealing to the excellent WMAP data. We...
Could quantum gravity be tested with high intensity Lasers? (2006)
In quantum gravity theories Planckian behavior is triggered by the energy of {\it elementary} particles approaching the Planck energy, $E_P$, but it's also possible that anomalous behavior strikes...
MOND habitats within the solar system (2006)
Bekenstein, Jacob, Magueijo, Joao
MOdified Newtonian Dynamics (MOND) is an interesting alternative to dark matter in extragalactic systems. We here examine the possibility that mild or even strong MOND behavior may become evident...
Template fitting and the large-angle CMB anomalies (2005)
We investigate two possible explanations for the large-angle anomalies in the Cosmic Microwave Background (CMB): an intrinsically anisotropic model and an inhomogeneous model. We take as an example...
We investigate the point-parity and mirror-parity handedness of the large angle anisotropy in the cosmic microwave background (CMB). In particular we consider whether the observed low CMB quadrupole...
Cosmological Constraints on a Dynamical Electron Mass (2005)
Barrow, John D, Magueijo, Joao
Motivated by recent astrophysical observations of quasar absorption systems, we formulate a simple theory where the electron to proton mass ratio $\mu =m_{e}/m_{p}$ is allowed to vary in space-time....
The Multipole Vectors of WMAP, and their frames and invariants (2005)
We investigate the Statistical Isotropy and Gaussianity of the CMB fluctuations, using a set of multipole vector functions capable of separating these two issues. In general a multipole is broken...
Phenomenological Quantum Gravity (2005)
Kimberly, Dagny, Magueijo, Joao
These notes summarize a set of lectures on phenomenological quantum gravity which one of us delivered and the other attended with great diligence. They cover an assortment of topics on the border...
We examine previous claims for a preferred axis at $(b,l)\approx (60,-100)$ in the cosmic radiation anisotropy, by generalizing the concept of multipole planarity to any shape preference (a concept...
Multipole invariants and non-Gaussianity (2004)
We propose a framework for separating the information contained in the CMB multipoles, $a_{\ell m}$, into its algebraically independent components. Thus we cleanly separate information pertaining to...
Bouncing Universes with Varying Constants (2004)
Barrow, John D., Kimberly, Dagny, Magueijo, Joao
We investigate the behaviour of exact closed bouncing Friedmann universes in theories with varying constants. We show that the simplest BSBM varying-alpha theory leads to a bouncing universe. The...
Cubic anomalies in WMAP (2004)
We perform a frequentist analysis of the bispectrum of WMAP first year data. We find clear signal domination up to l=200, with overall consistency with Gaussianity except for the following features....
We consider a prescription for introducing deformed dispersion relations in the bosonic string action. We find that in a subset of such theories it remains true that the embedding coordinates...
"Junk" DNA as a genetic decoy (2003)
We propose that the evolutionary purpose of junk DNA is to protect the gene. Mutation agents, such as retro-viruses, hit ``decoy'' DNA most of the time. Although the argument is far from general, we...
Varying Alpha and the Electroweak Model (2003)
Kimberly, Dagny, Magueijo, Joao
Inspired by recent claims for a varying fine structure constant, alpha, we investigate the effect of ``promoting coupling constants to variables'' upon various parameters of the standard model. We...
Neutrino mixing and Lorentz invariance (2003)
Blasone, Massimo, Magueijo, Joao, Pires-Pacheco, Paulo
We use previous work on the Hilbert space for mixed fields to derive deformed dispersion relations for neutrino flavor states. We then discuss how these dispersion relations may be incorporated into...
New varying speed of light theories (2003)
We review recent work on the possibility of a varying speed of light (VSL). We start by discussing the physical meaning of a varying $c$, dispelling the myth that the constancy of $c$ is a matter of...
Non-linear special relativity (or doubly special relativity) is a simple framework for encoding properties of flat quantum space-time. In this paper we show how this formalism may be generalized to...
Could thermal fluctuations seed cosmic structure? (2002)
Magueijo, Joao, Pogosian, Levon
We examine the possibility that thermal, rather than quantum, fluctuations are responsible for seeding the structure of our universe. We find that while the thermalization condition leads to nearly...
Generalized Lorentz invariance with an invariant energy scale (2002)
The hypothesis that the Lorentz transformations may be modified at Planck scale energies is further explored. We present a general formalism for theories which preserve the relativity of inertial...
Could supermassive black holes be quintessential primordial black holes? (2002)
There is growing observational evidence for a population of supermassive black holes (SMBHs) in galactic bulges. We examine in detail the conditions under which these black holes must have originated...
Is it e or is it c? Experimental Tests of Varying Alpha (2002)
Magueijo, Joao, Barrow, John D., Sandvik, Haavard Bunes
Is the recent evidence for a time-varying fine structure 'constant' $\alpha$ to be interpreted as a varying $e$, $c$, $\hbar$, or a combination thereof? We consider the simplest varying electric...
Lorentz invariance with an invariant energy scale (2001)
We propose a modification of special relativity in which a physical energy, which may be the Planck energy, joins the speed of light as an invariant, in spite of a complete relativity of inertial...
Non-Commutative Inflation (2001)
Alexander, Stephon, Brandenberger, Robert, Magueijo, Joao
We show how a radiation dominated universe subject to space-time quantization may give rise to inflation as the radiation temperature exceeds the Planck temperature. We consider dispersion relations...
Generating non-Gaussian maps with a given power spectrum and bispectrum (2001)
Contaldi, Carlo R., Magueijo, Joao
We propose two methods for generating non-Gaussian maps with fixed power spectrum and bispectrum. The first makes use of a recently proposed rigorous, non-perturbative, Bayesian framework for...
Stars and black holes in varying speed of light theories (2000)
We investigate spherically symmetric solutions to a recently proposed covariant and locally Lorentz-invariant varying speed of light theory. We find the metrics and variations in $c$ associated with...
Bayesian joint estimation of non-Gaussianity and the power spectrum (2000)
Rocha, Graca, Magueijo, Joao, Hobson, Mike, Lasenby, Anthony
We propose a rigorous, non-perturbative, Bayesian framework which enables one jointly to test Gaussianity and estimate the power spectrum of CMB anisotropies. It makes use of the Hilbert space of an...
Covariant and locally Lorentz-invariant varying speed of light theories (2000)
We propose definitions for covariance and local Lorentz invariance applicable when the speed of light $c$ is allowed to vary. They have the merit of retaining only those aspects of the usual...
Quintessence scenarios provide a simple explanation for the observed acceleration of the Universe. Yet, explaining why acceleration did not start a long time ago remains a challenge. The idea that...
Can the Universe escape eternal acceleration? (2000)
Barrow, John, Bean, Rachel, Magueijo, Joao
Recent astronomical observations of distant supernovae light-curves suggest that the expansion of the universe has recently begun to accelerate. Acceleration is created by an anti-gravitational...
Cosmic defects and cosmology (2000)
Magueijo, Joao, Brandenberger, Robert
We provide a pedagogical overview of defect models of structure formation. We first introduce the concept of topological defect, and describe how to classify them. We then show how defects might be...
Brandenberger, Robert H., Magueijo, Joao
We review a few off-the-beaten-track ideas in cosmology. They solve a variety of fundamental problems; also they are fun. We start with a description of non-singular dilaton cosmology. In these...
New non-Gaussian feature in COBE-DMR Four Year Maps (1999)
We extend a previous bispectrum analysis of the Cosmic Microwave Background temperature anisotropy, allowing for the presence of correlations between different angular scales. We find a strong...
Can a changing $\alpha$ explain the Supernovae results? (1999)
Barrow, John D., Magueijo, Joao
We show that the Supernovae results, implying evidence for an accelerating Universe, may be closely related to the recent discovery of redshift dependence in the fine structure constant $\alpha$. The...
Battye, Richard A., Magueijo, Joao, Weller, Jochen
Quantum fluctuations created during inflation can account for the observed matter distribution in the linear regime if the universe has two components of dark matter, one which is cold and...
Big Bang riddles and their revelations (1999)
Magueijo, Joao, Baskerville, Kim
We describe how cosmology has converged towards a beautiful model of the Universe: the Big Bang Universe. We praise this model, but show there is a dark side to it. This dark side is usually called...
The statistical physics of cosmological networks of string loops (1999)
Magueijo, Joao, Sandvik, Haavard, Steer, Daniele
We solve numerically the Boltzmann equation describing the evolution of a cosmic string network which contains only loops. In Minkowski space time the equilibrium solution predicted by statistical...
Cosmological parameter dependence in local string theories of structure formation (1999)
Copeland, E. J., Magueijo, Joao, Steer, D. A.
We perform a new and accurate study of the dependence on cosmological parameters of structure formation with local cosmic strings. The crucial new ingredients are the inclusion of the effects of...
Structure formation with strings plus inflation: a new paradigm (1999)
Magueijo, Joao, Contaldi, Carlo, Hindmarsh, Mark
Recent developments in inflation model building, based on supersymmetry, have produced compelling models in which strings are produced at the end of inflation. In such models the cosmological...
Where is the COBE maps' non-Gaussianity? (1999)
Magueijo, Joao, Ferreira, Pedro G., Gorski, Krzysztof M.
We review our recent claim that there is evidence of non-Gaussianity in the 4 Year COBE DMR data. We present some new results concerning the effect of the galactic cut upon the non-Gaussian signal....
Barrow, John D., Magueijo, Joao
We define the flatness and quasi-flatness problems in cosmological models. We seek solutions to both problems in homogeneous and isotropic Brans-Dicke cosmologies with varying speed of light. We...
Varying-$\alpha $ Theories and Solutions to the Cosmological Problems (1998)
Barrow, John D., Magueijo, Joao
If the fine structure constant $\alpha =e^2/(\hbar c)$ were to change, then a number of interpretations would be possible, attributing this change either to variations in the electron charge, the...
Solutions to the Quasi-flatness and Quasi-lambda Problems (1998)
Barrow, John D., Magueijo, Joao
Big Bang models of the Universe predict rapid domination by curvature, a paradox known as the flatness problem. Solutions to this problem usually leave the Universe exactly flat for every practical...
A time varying speed of light as a solution to cosmological puzzles (1998)
Albrecht, Andreas, Magueijo, Joao
We consider the cosmological implications of light travelling faster in the early Universe. We propose a prescription for deriving corrections to the cosmological evolution equations while the speed...
CMB and LSS Power Spectra From Local Cosmic String Seeded Struture Formation (1998)
Contaldi, Carlo R., Hindmarsh, Mark, Magueijo, Joao
We evaluate the two point functions of the stress energy from the largest string simulations carried out so far. The two point functions are used to calculate the cosmic microwave background (CMB)...
CMB and density fluctuations from strings plus inflation (1998)
Contaldi, Carlo, Hindmarsh, Mark, Magueijo, Joao
In cosmological models where local cosmic strings are formed at the end of a period of inflation, the perturbations are seeded both by the defects and by the quantum fluctuations. In a subset of...
The power spectra of CMB and density fluctuations seeded by local cosmic strings (1998)
Contaldi, Carlo, Hindmarsh, Mark, Magueijo, Joao
We compute the power spectra in the cosmic microwave background and cold dark matter (CDM) fluctuations seeded by strings, using the largest string simulations performed so far to evaluate the...
A new statistic for picking out Non-Gaussianity in the CMB (1998)
Lewin, Alex, Albrecht, Andreas, Magueijo, Joao
In this paper we propose a new statistic capable of detecting non-Gaussianity in the CMB. The statistic is defined in Fourier space, and therefore naturally separates angular scales. It consists of...
Non-Gaussian sampling effects on the CMB power spectrum estimation (1997)
Cheung, Charlotte, Magueijo, Joao
We introduce a non-Gaussian model of structure formation, and show how it produces surprising sampling effects on the estimation of the CMB power spectrum. Estimates of the average power spectrum...
Cumulants as non-Gaussian qualifiers (1997)
Ferreira, Pedro G., Magueijo, Joao, Silk, Joseph
We discuss the requirements of good statistics for quantifying non-Gaussianity in the Cosmic Microwave Background. The importance of rotational invariance and statistical independence is stressed,...
The closet non-Gaussianity of anisotropic Gaussian fluctuations (1997)
Ferreira, Pedro G., Magueijo, Joao
In this paper we explore the connection between anisotropic Gaussian fluctuations and isotropic non-Gaussian fluctuations. We first set up a large angle framework for characterizing non-Gaussian...
Non-Gaussian spectra and the search for cosmic strings (1997)
We present a new tool for relating theory and experiment suited for non-Gaussian theories: non-Gaussian spectra. It does for non-Gaussian theories what the angular power spectrum $C_\ell$ does for...
Painless causality in defect calculations (1997)
Cheung, Charlotte, Magueijo, Joao
Topological defects must respect causality, a statement leading to restrictive constraints on the power spectrum of the total cosmological perturbations they induce. Causality constraints have for...
Ferreira, Pedro G., Magueijo, Joao
Gaussian cosmic microwave background skies are fully specified by the power spectrum. The conventional method of characterizing non-Gaussian skies is to evaluate higher order moments, the n-point...
Ideal scales for weighing the Universe (1996)
We investigate the performance of a large class of cosmic microwave background experiments with respect to their ability to measure various cosmological parameters. We pay special attention to the...
The Doppler peaks from a generic defect (1996)
We investigate which of the exotic Doppler peak features found for textures and cosmic strings are generic novelties pertaining to defects. We find that the ``out of phase'' texture signature is an...
The structure of Doppler peaks induced by active perturbations (1996)
Magueijo, Joao, Albrecht, Andreas, Ferreira, Pedro, Coulson, David
We investigate how the qualitative structure of Doppler peaks in the angular power spectrum of the cosmic microwave anisotropy is affected by basic assumptions going into theories of structure...
We investigate the effects of finite sky coverage on the spectral resolution $\Delta\ell$ in the estimation of the CMBR angular power spectrum $C^{\ell}$. A method is developed for obtaining...
Cosmic Microwave Background experiments targeting the cosmic strings Doppler peak signal (1996)
We investigate which experiments are better suited to test the robust prediction that cosmic strings do not produce secondary Doppler peaks. We propose a statistic for detecting oscillations in the...
Doppler peaks from active perturbations (1995)
Magueijo, Joao, Albrecht, Andreas, Coulson, David, Ferreira, Pedro
We examine how the qualitative structure of the Doppler peaks in the angular power spectrum of the cosmic microwave anisotropy depends on the fundamental nature of the perturbations which produced...
Causality, randomness, and the microwave background (1995)
Albrecht, Andreas, Coulson, David, Ferreira, Pedro, Magueijo, Joao
Fluctuations in the cosmic microwave background (CMB) temperature are being studied with ever increasing precision. Two competing types of theories might describe the origins of these fluctuations:...