Phi in the Sky Scientific Programme

The Quest for Cosmological Scalar Fields

Physics Department, University of Porto, 8-10 July 2004

Workshop Motivation and Aims

Particle physicists have been looking for scalar fields for a long time: the Higgs field, for example, is crucial in the standard particle physics model. but it has not been found so far. A similar interest has only appeared in cosmology more recently, but scalar fields have been playing an increasingly more prominent role there. A few tantalizing hints have appeared in the past few years which could be construed as direct or indirect evidence for their presence. Examples of these include the evidence for inflation in the early universe (and for a more recent epoch of acceleration), the recent claimed detection of variations of the fine-structure constant (and also the electron-to-proton mass ratio) and the possible detection of a cosmic string through its gravitational effect.

Yet astrophysicists/cosmologists and particle physicists typically have radically different approaches to the subject. Particle physicists, even when they develop their models to considerable detail, tend to consider only the simplest cosmological consequences (for example, focusing on the order-zero, background solution). Cosmologists often disregard any particle physics motivation (or lack thereof) and simply treat models as toy models, which they can put through the sieve of the basic cosmological tests. This Physics versus Astronomy divide has of course historical reasons (going back at least to ancient Greece, if not before), but only very recently people have come to realize that it is not optimal: some models that are well motivated from the particle physics point of view may fail detailed cosmological tests, while some toy models that can fit observational data very well may be very un-natural from a particle physics point of view.

This workshop aims to bring together the best of both worlds, and thereby effectively using the universe as a laboratory with which to test particle physics. It will discuss the motivations for the existence of scalar fields in nature, search the available experimental and observational data for hints of their existence, assess what their detailed consequences can be, and identify distinguishing characteristics that might provide key tests in the future. It will be remarkable is we can learn about fundamental physics (say string theory for example) by doing something as mundane as spectroscopy. A strong observational confirmation of the existence of cosmological scalar fields will start out a new revolutionary era, not just for physics and cosmology but for science as a whole.

Wednesday, July 7th: Day 0 (Arrival Day)

15:00 - 17:00 Registration (Physics Department)

18:00 - 20:00 Welcome Reception (Solar do Vinho do Porto)

Thursday, July 8th: Day 1 (*download available)

09:00 - 09:30 Opening Remarks

09:30 - 10:30 Eric Adelberger (Washington): *Tests of Newton's Inverse-Square Law: Probing the True Geometry of the Universe

10:30 - 11:00 Philippe Brax (Saclay): *Detecting Quintessence in Orbit

11:00 - 11:30 Coffee break

11:30 - 12:30 Raul Jimenez (Penn): *Observational Constraints on Scalar Fields

12:30 - 13:00 Stephane Fay (Meudon): *Scalar Field Constraints from Homogeneous Cosmology

13:00 - 15:00 Lunch Break

15:00 - 16:00 Jean-Philippe Uzan (Paris): *Variation of the Constants in the Early and Late Universe

16:00 - 16:30 Jarle Brinchmann (Porto): *Constraining the Fine-structure Constant at z ~ 2.5 using Emission Lines

16:30 - 17:00 Graça Rocha (Cambridge): *Measuring alpha in the Early Universe

17:00 - 17:30 Coffee break

17:30 - 18:00 Joana Oliveira (Porto): *Linearized Bekenstein Varying Alpha Models

18:00 - 18:30 Nelson Nunes (QMW): *Reconstructing the Dark Energy Equation of State with Varying Alpha

18:30 - 19:00 Claudio Rubano (Napoli): *Discussion on Potentials and Tracking Behaviour

Friday, July 9th: Day 2 (*download available)

09:00 - 10:00 Roy Maartens (Portsmouth): *Brane World Cosmology

10:00 - 10:30 Torsten Bringmann (Stockholm): *Stability of Homogeneous Extra Dimensions

10:30 - 11:00 Stephen Davis (Lausanne): *Scalar-Tensor Gravity on a Gauss-Bonnet Brane World

11:00 - 11:30 Coffee break

11:30 - 12:30 Gilles Esposito-Farese (Paris): *Tests of Scalar-Tensor Gravity

12:30 - 13:00 Francesca Rosati (Padova): *Dark Matter Relic Abundance and Scalar-Tensor Dark Energy

13:00 - 15:00 Lunch Break

15:00 - 16:00 Anthony Lasenby (Cambridge): *Closed Universe Boundary Conditions for Inflation and Predictions for the CMB

16:00 - 16:30 Morgan Le Delliou (Montpellier): *Quintessence and Non-linear Structure Formation

16:30 - 17:00 David Wiltshire (Canterbury): *Stable Gravastars - An Alternative to Black Holes?

17:00 - 17:30 Coffee break

17:30 - 18:00 Pedro Gonzalez Diaz (Madrid): *The Cosmic Phantom Field

19:00 - 24:00 Workshop dinner

Saturday, July 10th: Day 3 (*download available)

09:00 - 10:00 David Wands (Portsmouth): *Inflation and the Origin of Large-scale Structure

10:00 - 10:30 Katherine Mack (Princeton): *Phenomenological Classification of Inflationary Potentials

10:30 - 11:00 José Pedro Mimoso (Lisbon): *Self-similar Dynamics after Warm Inflation

11:00 - 11:30 Coffee break

11:30 - 12:30 Paul Shellard (Cambridge): *Evolution and Cosmological Consequences of Cosmic Strings

12:30 - 13:00 Sujata Gupta (Portsmouth): *Non-Gaussianity in the CMB

13:00 - 15:00 Lunch Break

15:00 - 16:00 Fernando Quevedo (Cambridge): *Inflation and String Theory

16:00 - 16:30 Laura Allen (Portsmouth): *Cosmological Perturbations Through a Simple Bounce

16:30 - 17:00 Paulo Moniz (Covilha): *Brane-world States from a Generalized Chaplygin Gas

17:00 - 17:30 Coffee break

17:30 - 18:30 Closing Discussion