Program

Abstracts

G. Efstathiou: LCDM: Successes and status (45m)

The LCDM model has survived more than a decade of  —increasingly stringent— precision tests, which culminated, recently with the announcement of the latest results from the Planck satellite. I will present a summary of the Planck 2014 cosmological results highlighting the successes of the LCDM model. The Planck data impose tight limits on possible new physics beyond the LCDM model.

R. Durrer: LCDM: Theoretical problems (45m)

Discussion based on pre-conference survey

H. Peiris: LCDM: Anomalies (45m)

Anomaly detection drives scientific discovery - it is correlated with the cutting edge of the research frontier, and thus inevitably involves small signal-to-noise. In astronomy, the prevalence of systematics -- both "known unknowns" and "unknown unknowns" -- combined with increasingly large datasets, the prevalence of ad hoc estimators for anomaly detection, and the "look elsewhere" effect, can lead to spurious false detections. I will argue that anomaly detection leading to discoveries of new (astro)physics needs a combination of physical understanding, careful experimental design to avoid confirmation bias, and self-consistent statistical methods. I will illustrate these points with several concrete examples from cosmology. 

P. G. Ferreira: Gravity in Cosmology (30m)

I will discuss the possibility that we might constrain gravity- Newtonian and General Relativistic- with cosmological observations. Such constraints should be competitive and complementary with solar system and pulsar constraints. I will also point out the real problems we face in achieving such constraints.

C. Burgess: Cosmology and the Cosmological Constant Problem: A Bad Cop Wrapped in a Wet Blanket Standing in a Cold Shower (30m)

We live at a time of contradictory messages about how successfully we understand gravity. General Relativity seems to work well in the Earth’s immediate neighborhood, but arguments abound that it needs modification at very small and/or very large distances. This talk tries to put this discussion into the broader context of similar situations in other areas of physics, and summarizes some of the lessons, which our good understanding of gravity in the solar system has for proponents for its modification over very long and very short distances. The main message is mixed: On one hand cosmology seems to like features (like light scalars and small vacuum energies) that are not generic to the long-wavelength limit of fundamental theories, and this is a crucial clue that would be silly to ignore. On the other hand, although some ways are known to contrive light scalars (and so among which we can seek explanations for observations), so far none are known that all agree could incorporate small vacuum energies (even in principle), making this a clue that is very difficult to use (at least until a convincing example is found).

R. Teyssier: Constituents: Simulating the Universe (30m)

Computer simulations play an important role in predicting the properties of the mass distribution in the Lambda CDM scenario of structure formation. I will address the following questions: How reliable are these predictions using present-day computer and N body codes ? Is the extreme level of accuracy required by present and future surveys reached? What is the effect of baryonic physics? What are the challenges in simulating baryonic physics and galaxy formation? How well do we understand these effects? Do we need to understand these effects? I will finally discuss the challenges of simulating models beyond standard gravity, and the challenges of detecting their signature.

O. Lahav: Constituents: Observing dark energy with many surveys: Interplay (30m)

The talk will start by commenting on the chequered history of Lambda and how the paradigm shifted in the 1990’s from the ‘Standard CDM’ towards the ‘Lambda CDM’. We shall then review how the combination of current and future imaging and spectroscopic galaxy surveys (e.g. DES, DESI, LSST, Euclid) could explore Physics beyond the ‘vanilla LCDM’. In particular we focus on multi-probe approaches for characterising the dark energy equation of state, modified gravity, neutrino mass, and gravitational redshift in clusters. We also comment on how to treat ‘nuisance parameters’ in cosmological studies.

B. Reid: Constituents: Observing dark energy with galaxy surveys (30m)

S. Mukhanov: Constituents: What happened in the early universe? (30m)

R. Maartens: Testing foundational assumptions of LCDM (30m)

The LCDM model is built on a large inter-connecting set of physical assumptions. Perhaps the most basic assumption is the Cosmological Principle. How confident can we be that the Universe is well described by a Friedmann model on large scales? I will describe some of the tests that have been devised to probe this. I will also discuss the role of the CP in tests of dark energy and gravity. The next key assumption is that GR describes the Universe. Others will investigate alternatives to GR as a theory of gravity. I will instead highlight the fact that sometimes we forget to apply GR consistently and thoroughly - for example, when assuming that a Newtonian approximation is always sufficient for analysing galaxy survey data. I will explore some of the problems and consequences of applying GR consistently in LCDM.

G. Starkman: An Uncooperative Universe: Large Scale Anomalies in the CMB (30m)

The Cosmic Microwave Background Radiation is our most important source of information about the early universe. Many of its features are in good agreement with the predictions of the so-called standard model of cosmology -- the Lambda Cold Dark Matter Inflationary Big Bang Theory. However, the large-angle fluctuations of the microwave background are uncooperative with "the program" -- they continue to exhibit several statistically significant anomalies. On the one hand, if we look at the whole sky the lowest multipoles seem to be correlated both with each other and with the geometry of the solar system.  On the other hand, when we look just at the part of the sky that we most trust – the part outside the galactic plane - there is a dramatic lack of large angle correlations. So much so that it challenges basic predictions of the standard model. We will discuss these anomalies and how we might test whether they reflect profound underlying physics, or just statistical flukes.

C. Boehm: Constituents: New particles and structure formation (30m)

J. Magueijo: Radical solutions (in the spirit of Hoyle) (30m)

What if the basic assumptions we have made in our models of the universe are completely wrong? In this talk I step back and examine how cosmology could be radically different and this explain the unsolved problems of the standard model.

A. Heavens: Summary and directions: What next? (60m)