at The University of Western Ontario

MAY 6th - MAY 7th 2011

Chu International Centre, 2130 Western Student Services Building

Speakers and Abstracts

Aether, Quantum Gravity, and Cosmology

- Abstract
- In this talk, I outline several theoretical and observational arguments for revisiting a modern version of gravitational aether. The arguments range from quantum gravity to cosmological constant problem, and dark energy.

Cosmography: The Hubble flow and the Supernova data

- Abstract
- The acceleration of the expansion of the universe, no matter how it is derived, is taken to imply the existence of dark energy via the Friedmann (Einstein) equations in the standard cosmological model. We will explore what the situation and the key challenges are in terms of the observational data and its interpretation within a cosmographic model. Cosmography is the part of cosmology that proceeds by making minimal dynamic assumptions, that is, one does not assume the Friedmann equations unless and until absolutely necessary. By doing so it is possible to concentrate more directly on the observational situation in a model-independent framework. The cosmological parameters contained in the Hubble relation between distance and redshift provide information on the behaviour of the universe (expansion, acceleration etc...). We can perform a number of inter-related cosmographic fits to supernova datasets, and pay particular attention to the extent to which the choice of distance scale and manner of representing the redshift scale affect the cosmological parameters.

Independent, agreeing measurements and Dark Energy

- Abstract
- In this paper we will first articulate and defend the claim that successful physical theories meet a higher empirical standard than mere predictive success or falsifiability. Our best physical theories allow a variety of independent observations and experiments to constrain parameters introduced by the theory. The agreement of these independent measurements of theoretical parameters is a much more demanding requirement than mere predictive success. Second, we aim to pose the question of whether this type of success has been achieved in observations related to dark energy. Kirshner has argued that independent agreeing measurements of $\Omega_{\Lambda}$ persuaded the cosmological community to accept dark energy rapidly, despite theoretical problems with the idea. We consider the case of dark energy using the framework developed in the first part of the talk, and pose various questions regarding the degree of independence of the different observational results related to dark energy.

The Accelerating Universe

- Abstract
- The discovery, made a decade ago, that the expansion of the universe is speeding up has generated waves in the field of cosmology. Currently, all cosmological observations are in concordance with the model where dark energy - the stuff that causes the accelerated expansion - forms 75% of the energy in the universe, while the other 25% is comprised of dark and visible matter, as well as a small admixture of radiation. Therefore we have a twofold grand mystery: What is the origin and nature of dark energy and the accelerating universe? And why is the composition of the universe rather complicated, with dark energy, dark matter, visible matter, and radiation all present and non-negligible today? I will address these issues, and some - mostly unsuccessful - attempts to explain them.

The Trials and Tribulations of Modern Cosmology: The Good, the Bad, and the Just Plain Ugly

- Abstract
- Cosmology has always been a subject where religion, philosophy, and science collide. As a physical science, modern cosmology is supported by three empirical pillars: the Hubble expansion, big bang nucleosynthesis, and the cosmic microwave background. However, we have been obliged in recent years to add to these not one but two invisible components: dark matter and dark energy. These "tooth fairies" pose serious challenges in the philosophy of science as they are not explicitly falsifiable. To complicate matters, these general concepts are readily conflated with specific, legitimately testable hypotheses. Lurking about like the proverbial elephant in the room are the repeated predictive successes of a radically different hypothesis, the modified Newtonian dynamics. I will outline the challenges to the present world view and enumerate the facts that must be explained by any successful theory.

Epistemology of cosmological simulations

- Abstract
- In this talk I am planning to capture key elements of the special role that cosmological N-body simulations have played in the establishment of the current paradigm of a dark matter and dark energy dominated Universe.

Newtonian spacetime in the light of cosmology

- Abstract
- Newton appears to have left cosmological considerations to theology. Had he not done so, he might have been led to a spacetime structure very close to Newton-Cartan spacetime, even given the mathematical tools available at the time.

Foundational issues in cosmology in the light of the dark energy problem

- Abstract
- I describe some of the foundational issues facing theories of cosmology and then discuss how different proposals to the mystery of dark energy may figure in their resolutions.

There is no fee to attend the workshop, but please contact us if you plan to attend. Send an email message to rotman@uwo.ca with the subject line "Cosmology Workshop" so that we can estimate attendance.

in conjunction with the Logic, Math, and Physics Graduate Philosophy (LMP) Conference,

Workshop attendees are invited to participate in the LMP Conference.