School of Astronomy

Tehran meeting on Modified Gravity:

The standard model of cosmology (LambdaCDM) is based on Einstein's theory of gravity (general relativity; GR) with two dark species: dark energy and dark matter. Assuming the right abundance of dark matter, GR with a cosmological constant (CC) term explains all the existing cosmological data very accurately. Despite providing a surprisingly simple mechanism for the late-time acceleration of the Universe, the nature of the CC is however a matter of ambiguity, as its measured value requires an enormously large fine-tuning in order to be consistent with our current understanding of particle physics. Various mechanisms based on modifications of gravity at ultra-large scales have been proposed in order to either explain the measured value of the CC or provide alternative mechanisms for the late-time cosmic acceleration. While the efforts for building new models and theories continue, various techniques are being developed for testing these modified theories as well as the standard gravity. Future cosmological surveys, such as the ESA Euclid satellite, the Dark Energy Survey (DES), the Square Kilometre Array (SKA), the Dark Energy Spectroscopic Instrument (DESI) and the Large Synoptic Survey Telescope (LSST), are expected to improve our knowledge about the nature of gravity, and shed light on the mechanism behind the cosmic acceleration. Hopefully in a few years we will be able to exclude either our standard picture of the Universe or most of its alternatives; we are therefore living at an extremely exciting moment in the history of cosmology and fundamental physics, both theoretically and observationally.

The aim of this school/workshop is to gather some of the most prominent experts in theories of modified gravity and their observational tests to discuss the status and future prospects in the field. The program will include a combination of review lectures (both theoretical and observational), some more basic lectures suitable for graduate students, a few contributed presentations by the participants, and plenty of discussion sessions.

The cosmological constant problem
Late-time cosmic acceleration
Theoretical aspects of modified gravity
Observational tests of modified gravity
Current and future cosmological surveys

The meeting will start at 9:00 AM on January 23, and will end at 6:00 PM on January 26. On January 27 there will be an arranged daylong excursion in Tehran for participants who are interested in sightseeing activities (especially non-Iranians).

A tour to the two historical cities of Isfahan and Shiraz can be organized for the period January 28-31 (four days) for those who are interested. This will be arranged only if there will be a minimum number of interested participants. The expenses of the tour will however *not* be included in the conference registration fee and must be payed separately.