Einstein's Theory of Gravity and the Problem of Missing Mass (2009)
Ferreira, Pedro G., Starkmann, Glenn
The observed matter in the universe accounts for just 5 percent of the observed gravity. A possible explanation is that Newton's and Einstein's theories of gravity fail where gravity is either weak...
Errors in Estimating Omega_Lambda due to the Fluid Approximation (2009)
Clifton, Timothy, Ferreira, Pedro G.
The matter content of the Universe is strongly inhomogeneous on small scales. Motivated by this fact, we consider a model of the Universe that has regularly spaced discrete masses, rather than a...
XXI Simpósio Brasileiro de Banco de Dados Query Driven Sequence Pattern Mining (2009)
Pedro G. Ferreira, Paulo J. Azevedo
Abstract. The discovery of frequent patterns present in biological sequences has a large number of applications, ranging from classification, clustering and understanding sequence structure and...
90 years on – the 1919 eclipse expedition at Príncipe (2009)
Ellis, Richard, Ferreira, Pedro G., Massey, Richard, Weszkalnys , Gisa
Richard Ellis, Pedro G Ferreira, Richard Massey and Gisa Weszkalnys return to Príncipe in the International Year of Astronomy to celebrate the 1919 RAS expedition led by Sir Arthur Eddington.
Clifton, Timothy, Ferreira, Pedro G.
We consider a model of the Universe in which the matter content is in the form of discrete islands, rather than a continuous fluid. In the appropriate limits the resulting large-scale dynamics...
What the small angle CMB really tells us about the curvature of the Universe (2009)
Clifton, Timothy, Ferreira, Pedro G., Zuntz, Joe
It is well known that observations of the cosmic microwave background (CMB) are highly sensitive to the spatial curvature of the Universe, k. Here we find that what is in fact being tightly...
Eddington-Born-Infeld gravity and the large scale structure of the Universe (2008)
Bañados, Máximo, Ferreira, Pedro G., Skordis, Constantinos
It has been argued that a Universe governed by Eddington-Born-Infeld gravity can be compatible with current cosmological constraints. The extra fields introduced in this theory can behave both as...
Living in a Void: Testing the Copernican Principle with Distant Supernovae (2008)
Clifton, Timothy, Ferreira, Pedro G., Land, Kate
A fundamental presupposition of modern cosmology is the Copernican Principle; that we are not in a central, or otherwise special region of the Universe. Studies of Type Ia supernovae, together with...
Mining Approximate Motifs in Time Series (2008)
Pedro G. Ferreira, Paulo J. Azevedo, Cândida G. Silva
Abstract. The problem of discovering previously unknown frequent patterns in time series, also called motifs, has been recently introduced. A motif is a subseries pattern that appears a significant...
Query Driven Sequence Pattern Mining (2008)
Pedro G. Ferreira, Paulo J. Azevedo
Abstract. The discovery of frequent patterns present in biological sequences has a large number of applications, ranging from classification, clustering and understanding sequence structure and...
Constraining primordial magnetic fields with CMB polarization experiments (2008)
Kristiansen, Jostein R., Ferreira, Pedro G.
We calculate the effect that a primordial homogeneous magnetic field, $\B_0$, will have on the different CMB power spectra due to Faraday rotation. Concentrating on the $TB$, $EB$ and $BB$...
Generalized Einstein-Aether theories and the Solar System (2007)
Bonvin, Camille, Durrer, Ruth, Ferreira, Pedro G., Starkman, Glenn, Zlosnik, Tom G.
It has been shown that generalized Einstein-Aether theories may lead to significant modifications to the non-relativistic limit of the Einstein equations. In this paper we study the effect of a...
The State of the Universe : A Primer in Modern Cosmology (2006)
978-0-7538-2256-2
Fast and reliable MCMC for cosmological parameter estimation (2004)
Dunkley, Joanna, Bucher, Martin, Ferreira, Pedro G., Moodley, Kavilan, Skordis, Constantinos
Markov Chain Monte Carlo (MCMC) techniques are now widely used for cosmological parameter estimation. Chains are generated to sample the posterior probability distribution obtained following the...
The angular power spectrum of NVSS radio galaxies (2004)
Blake, Chris, Ferreira, Pedro G., Borrill, Julian
We measure the angular power spectrum of radio galaxies in the NRAO VLA Sky Survey (NVSS) using two independent methods: direct spherical harmonic analysis and maximum likelihood estimation. The...
The angular power spectrum of NVSS radio galaxies (2004)
Blake, Chris, Ferreira, Pedro G., Borrill, Julian
We measure the angular power spectrum Cℓ of radio galaxies in the NRAO VLA Sky Survey (NVSS) using two independent methods: direct spherical harmonic analysis and maximum likelihood estimation...
The angular power spectrum of NVSS radio galaxies (2004)
Blake, Chris, Ferreira, Pedro G., Borrill, Julian
We measure the angular power spectrum Cℓ of radio galaxies in the NRAO VLA Sky Survey (NVSS) using two independent methods: direct spherical harmonic analysis and maximum likelihood estimation...
Scale of Homogeneity of the Universe from WMAP (2003)
Castro, Patricia G., Douspis, Marian, Ferreira, Pedro G.
We review the physics of the Grishchuck-Zel'dovich effect which describes the impact of large amplitude, super-horizon gravitational field fluctuations on the Cosmic Microwave Background anisotropy...
Simultaneous Estimation of Noise and Signal in Cosmic Microwave Background Experiments (1999)
Ferreira, Pedro G., Jaffe, Andrew H.
To correctly analyse data sets from current microwave detection technology, one is forced to estimate the sky signal and experimental noise simultaneously. Given a time-ordered data set we propose a...
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....
The impact on cosmology of a primordial scaling field (1998)
A scalar field with an exponential potential has the particular property that it is attracted into a solution in which its energy scales as the dominant component (radiation or matter) of the...
Cosmology with a Primordial Scaling Field (1997)
Ferreira, Pedro G., Joyce, Michael
A weakly coupled scalar field $\Phi$ with a simple exponential potential $V=M_P^4\exp(-\lambda\Phi/M_P)$ where $M_P$ is the reduced Planck mass, and $\lambda > 2$, has an attractor solution in a...
Structure formation with a self-tuning scalar field (1997)
Ferreira, Pedro G., Joyce, Michael
A scalar field with an exponential potential has the particular property that it is attracted into a solution in which its energy scales as the dominant component (radiation or matter) of the...
Polarization-Temperature Correlation from a Primordial Magnetic Field (1997)
Scannapieco, Evan S., Ferreira, Pedro G.
We propose a new method for constraining a primordial homogeneous magnetic field with the cosmic microwave background. Such a field will induce an observable parity odd cross correlation between the...
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 in the Cosmic Microwave Background (1997)
We propose a set of new statistics which can be extracted out of the angular distribution of the Fourier transform of the temperature anisotropies in the small field limit. They quantify generic...
Constraints on a Primordial Magnetic Field (1997)
Barrow, John D., Ferreira, Pedro G., Silk, Joseph
We derive an upper limit of $B_0
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...
Microwave Anisotropies from Random Sources (1996)
I report on recent developments in the theory of cosmic background radiation perturbations. I describe ways of modeling alternatives to the canonical Gaussian theories within the standard framework...