The Institute of Theoretical Physics

A cosmic window to Fundamental Physics: Primordial Non-Gaussianity and beyond


20st to 24th of September 2021
 Instituto de Física Teórica (IFT, CSIC-UAM), Madrid


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Invited speakers

  • Ana Achúcarro (U. Leiden)

  • Olivier Doré (JPL, Caltech)

  • Eva-María Mueller (U. Oxford)

  • Marco Peloso (U. Padova)

  • Fabian Schmidt (MPA)

  • Anže Slosar (BNL, TBC)

  • Obinna Umeh (ICG Portsmouth, TBC)



  • Primordial Non-Gaussianity through 2-pt function

  • Bispectrum and PNG

  • PNG from CMB

  • Lightcone GR and Modified Gravity effects on the largest scales

  • LSS Observational Systematics mitigation

  • Origin of PNGs

  • PNG in Gravitational Waves



The largest scales of the Universe serve as a probe to fundamental physics such as the origin of cosmic structure and general relativity. Whereas there is a growing consensus about cosmic inflation providing an explanation for the origin of large-scale cosmic structure, there is a huge landscape of competing inflationary models. One of the main observables that can further constrain the range of allowed models of inflation is Primordial Non-Gaussianities (PNG), parameterized through fNL. Currently the tightest constraints come from the CMB bispectrum as measured by Planck. However, in the future, we expect to reach σ(fNL)<1 (for the local type) by looking at the largest scales of the universe, where PNG would leave an imprint of a scale-dependent bias.

Synergies among different surveys will bring unprecedented measurements on the largest scales via multi-tracer methods, able to reduce the effect of cosmic variance, boosting determinations of PNG. At such scales light-cone effects (aka GR-effects)  also arise providing complementary constraints on gravity, but at the same time potentially biasing measurements of PNG if not modeled consistently.

With the Stage IV LSS experiments such as Euclid, SKA, DESI, SphereX or LSST, we are settled to explore the Universe beyond the Gigaparsec scale. Exploring these scales, however, requires us to understand with great accuracy systematic observational effects that could a priori bias the clustering measurements.

Future Stage IV CMB experiments will also contribute to reducing the uncertainty to PNG indepently, constraining also non-local types of non-gaussianities through the CMB bispectrum. CMB lensing can also be combined with other LSS probes using the aforementioned muti-tracer technique.

Furthermore, with the advent of GW interferometers we open the possibility to test PNG in a completely new window and frequency range. In particular, recent studies predict that appreciable NG could be detected both in ground based interferometers like LIGO-Virgo-Kagra and from space with LISA.

The aim of this workshop is to gather world experts on the topic of PNG and other ultra-large scale effects from different angles in order to prepare for the new generation of experiments. Potentially, the new experimental era will bring us to the σ(fNL)<1 level, being able to differentiate among the different inflationary model families (e.g. single field vs multi-field inflation). The workshop will alternate plenary and contributed talks with generous time slots for discussions.


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