Dr Roberto Trotta

There is no question that there is an unseen world. 
The problem is, how far is it from midtown and how late is it open? 
(Woody Allen)

I'm a cosmologist in the Astrophysics Group of Imperial College London, where I am a lecturer in physics. I am also a science communicator and I take part in numerous public engagement with science activities, from science festivals to radio broadcasts.

My research in cosmology is about analysing, interpreting and making sense of cosmological observations, in order to learn more about the properties and nature of dark matter and dark energy. I'm also interested in the early Universe and in developing connections between cosmology and particle physics. The goal is to learn more about the history and nature of the Universe, by using cosmology as a Universe-sized laboratory for particle and high energy physics.

Between 2005 and 2008 I have been the Lockyer Research Fellow of the Royal Astronomical Society at the Astrophysics Department of Oxford University. I've also been a Junior Fellow of St Anne's College. You can find more info about my academic background here. Or if you are into communication of science, then check out my outreach page.

What's new in the Universe? 

(Last updated on Dec 14th 2009)

Bayesian Methods in Cosmology: The Book 

In recent years cosmologists have advanced from largely qualitative models of the Universe to precision modelling using Bayesian methods, in order to determine the properties of the Universe to high accuracy. This timely book is the only comprehensive introduction to the use of Bayesian methods in cosmological studies, and is an essential reference for graduate students and researchers in cosmology, astrophysics and applied statistics. The first part of the book focuses on methodology, setting the basic foundations and giving a detailed description of techniques. It covers topics including the estimation of parameters, Bayesian model comparison, and separation of signals. The second part explores a diverse range of applications, from the detection of astronomical sources (including through gravitational waves), to cosmic microwave background analysis and the quantification and classification of galaxy properties. Contributions from 24 highly regarded cosmologists and statisticians make this an authoritative guide to the subject.

Buy it here.

BIG QUESTIONS DEBATE SERIES / Imperial College London 

Imperial College London Astrophysics presents a new series of debates entitled The Big Questions on topical themes in modern astrophysics and cosmology. In each debate, a member of the Astrophysics Group will discuss one of the big questions raised by cutting-edge research with a guest. The debates are aimed at the general public, who will have the opportunity to ask questions in what will be a lively and interactive discussion.

• 21 January 2010, 7-9pm: The Arabic roots of modern astronomy. Dr Rim Turkmani and Professor Jim Al-Khalili OBE
• 12 November 2009, 6.30-8.30pm: Human spaceflight: Science or spectacle? Dr David Clements vs Dr Ian Crawford
• 15 September, 6-8pm: Universe or Multiverse? Dr Roberto Trotta vs Prof. Bernard Carr
• 21 July 2009, 6-8pm: The fate of the Universe: does dark energy really exist? Prof. Andrew Jaffe vs Prof. Subir Sarkar
• 18 June 2009, 6-8pm: The origin of the Universe. Prof. Michael Rowan-Robinson vs Rev. Dr John Polkinghorne, KBE, FRS

These debates are free with registration in advance. Further information and registration here. 

STATISTICS LECTURES / Valencia, May 2009 

Advanced statistical tools for cosmology and particle physics

 

Abstract: In the last few years, the applications of Bayesian methods to cosmology has flourished, and it is presently having a considerable impact in the particle physics community, as well. In many respects, Bayesian methods have proven to be vastly superior to more traditional statistical tools, offering the advantage of higher efficiency and of a consistent conceptual basis for dealing with the problem of induction in the presence of uncertainty.

 

In these talks I will review Bayesian probability theory and its conceptual underpinnings, Bayes' Theorem and the role of priors. I will discuss the problem of parameter inference and its general solution, along with numerical techniques such as Monte Carlo Markov Chain methods. I will then discuss the theory and application of Bayesian model comparison, discussing the notions of Bayesian evidence and effective model complexity, and how to compute and interpret those quantities. I will also survey the status of Bayesian forecasting and experiment optimisation. Some recent applications to cosmology and supersymmetry phenomenology will also be briefly discussed.

COSMOSTATS09 / Ascona, Switzerland, July 26th-31st 2009 

In the last ten years, a wealth of observational data has revolutionized cosmology. The purpose of this workshop is to bring together world-class leading figures in cosmology, particle physics and from the statistical community in order to exchange knowledge and experience in dealing with large and complex data sets, and to meet the challenge of upcoming large cosmological surveys.

Furthermore, CosmoStats09 will host the GRavitational lEnsing Accuracy Testing 2008 (GREAT08) Challenge Final Workshop. 

Conference webpage

BBC RADIO 3 / Future Generation Thinkers 

You can listen here to a BBC Radio 3's "Future Generation Thinkers" programme (which aired on Nov 7th 2008) where I discuss dark energy and the place of humankind in the cosmos.

MICHELSON LECTURES / CWRU Michelson Prize Lectures 

In May 2008 I gave the 2008 Michelson Prize Lectures series at case Western Reserve University (Cleveland). You can find the pdf's of the talks below. 
May 5th: Bayes in the sky - Advanced statistical tools for cosmology 
May 6th: Probing dark energy with cosmology 
May 7th: Precision cosmology for the 21st century 
May 9th: Astrophysical probes of dark matter 

REVIEW ARTICLE / Bayes in the sky: Bayesian inference and model selection in cosmology 

An invited review for Contemporary Physics

Abstract: The application of Bayesian methods in cosmology and astrophysics has flourished over the past decade, spurred by data sets of increasing size and complexity. In many respects, Bayesian methods have proven to be vastly superior to more traditional statistical tools, offering the advantage of higher efficiency and of a consistent conceptual basis for dealing with the problem of induction in the presence of uncertainty. This trend is likely to continue in the future, when the way we collect, manipulate and analyse observations and compare them with theoretical models will assume an even more central role in cosmology. 

This review is an introduction to Bayesian methods in cosmology and astrophysics and recent results in the field. I first present Bayesian probability theory and its conceptual underpinnings, Bayes' Theorem and the role of priors. I discuss the problem of parameter inference and its general solution, along with numerical techniques such as Monte Carlo Markov Chain methods. I then review the theory and application of Bayesian model comparison, discussing the notions of Bayesian evidence and effective model complexity, and how to compute and interpret those quantities. Recent developments in cosmological parameter extraction and Bayesian cosmological model building are summarized, highlighting the challenges that lie ahead.

Go to the paper

SUPERSYMMETRY PHENOMENOLOGY / SuperBayeS package

SuperBayeS is a software for fast and efficient Markov Chain Monte Carlo sampling of supersymmetric theories. It allows to explore multidimensional SUSY parameter spaces and to compare SUSY prediction with observable quantities, including sparticle masses, dark matter abundance, direct and indirect detection quantities and much more. The current release implements an even more efficient scanning technique, called MultiNest.

SuperBayeS me!

Nature feature covering some of the results

PHYSICS AND PHILOSOPHY / Probing the arche-fossil

A conversation with the philosophical magazine COLLAPSE, centering around dark matter and the ontological perspective coming from the empirical study of `ancestral phenomena' in the history of the Universe.