Imperial College London

Carlo R. Contaldi

Faculty of Natural SciencesDepartment of Physics

Professor of Theoretical Physics
 
 
 
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Contact

 

+44 (0)20 7594 1527c.contaldi

 
 
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Location

 

505Huxley BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

132 results found

Contaldi CR, Magueijo J, 2001, Generating non-Gaussian maps with a given power spectrum and bispectrum, PHYSICAL REVIEW D, Vol: 63, ISSN: 0556-2821

Journal article

Contaldi CR, 2000, Cosmic strings in the age of Boomerang

We show how two simple modifications to the standard cosmic string scenariofor structure formation compare to the recently released Boomerang data set.Namely we consider pure string closed models and mixed models where bothinflation and strings are responsible for the perturbations. In the closedmodels we find that pure string models would require a universe with roughly$\Omega_M=0.8$, $\Omega_{\Lambda}=1.6$ to agree with the peak position revealedby the data and in agreement with the SNIa data. In the hybrid scenario withlocal strings we find that we require even more tilt and baryon content($n_s\sim 0.8$, $\Omega_b=0.08$, $H_0=70$) to match the data than with pureinflation models. The case with global strings fares better with a standardperiod of $\Lambda$CDM inflation and a $\sim30%$ contribution from stringsbeing in good agreement with the data.

Journal article

Contaldi CR, Ferreira PG, Magueijo J, Gorski KMet al., 2000, A Bayesian estimate of the skewness of the cosmic microwave background, ASTROPHYSICAL JOURNAL, Vol: 534, Pages: 25-28, ISSN: 0004-637X

Journal article

Contaldi CR, Hindmarsh M, Magueijo J, 2000, CMB and LSS power spectra from local cosmic string seeded structure formation, Workshop on Cosmic Microwave Background and the Planck Mission, Publisher: GORDON BREACH SCI PUBL LTD, Pages: 415-420, ISSN: 0888-6512

Conference paper

Contaldi CR, Bean R, Magueijo J, 1999, Photographing the wave function of the Universe, PHYSICS LETTERS B, Vol: 468, Pages: 189-194, ISSN: 0370-2693

Journal article

Contaldi C, Hindmarsh H, Magueijo J, 1999, Cosmic microwave background and density fluctuations from strings plus inflation, PHYSICAL REVIEW LETTERS, Vol: 82, Pages: 2034-2037, ISSN: 0031-9007

Journal article

Contaldi C, Hindmarsh M, Magueijo J, 1999, Power spectra of the cosmic microwave background and density fluctuations seeded by local cosmic strings, PHYSICAL REVIEW LETTERS, Vol: 82, Pages: 679-682, ISSN: 0031-9007

Journal article

Magueijo J, Contaldi C, Hindmarsh M, 1999, Structure formation with strings plus inflation: a new paradigm, EC-TMR Conference on 3K Cosmology, Publisher: AMER INST PHYSICS, Pages: 38-42, ISSN: 0094-243X

Conference paper

Contaldi CR, COVID-19: Nowcasting Reproduction Factors Using Biased Case Testing Data

Timely estimation of the current value for COVID-19 reproduction factor $R$has become a key aim of efforts to inform management strategies. $R$ is animportant metric used by policy-makers in setting mitigation levels and is alsoimportant for accurate modelling of epidemic progression. This brief paperintroduces a method for estimating $R$ from biased case testing data. Usingtesting data, rather than hospitalisation or death data, provides a muchearlier metric along the symptomatic progression scale. This can be hugelyimportant when fighting the exponential nature of an epidemic. We develop apractical estimator and apply it to Scottish case testing data to infer acurrent (20 May 2020) $R$ value of $0.74$ with $95\%$ confidence interval$[0.48 - 0.86]$.

Journal article

Golat S, Contaldi CR, Geodesic Noise and Gravitational Wave Observations by Pulsar Timing Arrays

Signals from millisecond pulsars travel to us along geodesics that areaffected by the space--time metric along the line-of-sight. The exact lengthand redshifting along the geodesics determine the Time-of-Arrival (ToA) of thepulses. The metric is determined by the distribution of dark matter, gas, andstars in the galaxy and, in the final stages of travel, by the distribution ofsolar system bodies. The inhomogeneous distribution of stellar masses can havea small but significant statistical effect on the ToAs through the perturbationof geodesics. This will result in additional noise in ToA observations that mayaffect Pulsar Timing Array (PTA) constraints on gravitational waves at very lowfrequencies. We employ a simple model for the stellar distribution in ourgalaxy to estimate the scale of both static and dynamic sources of what we termgenerically ``geodesic noise''. We find that geodesic noise is ${\cal O}(10)$ns for typical lines-of-sight. This indicates that it is relevant for estimatesof PTA sensitivity and may limit future efforts for detection of gravitationalwaves by PTAs.

Journal article

Margalit A, Contaldi CR, Pieroni M, Phase Decoherence of Gravitational Wave Backgrounds

Metric perturbations affect the phase of gravitational waves as theypropagate through the inhomogeneous universe. This effect causes StochasticGravitational Wave Backgrounds (SGWBs) to lose any phase coherence that mayhave been present at emission or horizon entry. We show that, for a standardcosmological model, this implies complete loss of coherence above frequencies$f \sim 10^{-12}$ Hz. The result is that any attempts to map SGWBs usingphase-coherent methods have no foreseeable applications. Incoherent methodsthat solve directly for the intensity of the SGWBs are the only methods thatcan reconstruct the angular dependence of any SGWB.

Journal article

Alonso D, Contaldi CR, Cusin G, Ferreira PG, Renzini AIet al., The $N_\ell$ of gravitational wave background experiments

We construct a model for the angular power spectrum of the instrumental noisein interferometer networks mapping gravitational wave backgrounds (GWBs) as afunction of detector noise properties, network configuration and scan strategy.We use the model to calculate the noise power spectrum for current and futureground-based experiments, as well as for planned space missions. We present ourresults in a language similar to that used in cosmic microwave background andintensity mapping experiments, and connect the formalism with the sensitivitycurves that are common lore in GWB analyses. Our formalism is implemented in alightweight python module that we make publicly available athttps://github.com/damonge/schNell.

Journal article

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