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A new analysis of data from the upcoming Euclid telescope will help peer into the first moments after the Big Bang.
Abstract
Primordial non-Gaussianity is the deviation of the distribution of primordial perturbations from a normal one, carrying information about the physics of inflation. The study tested a method for joint analysis of the power spectrum and bispectrum (two- and three-point correlations) of galaxies for future data from the Euclid survey. Using simulations with different initial conditions, scientists showed that adding the bispectrum improves constraints on the f_NL parameter (amplitude of non-Gaussianity) by 29–46% compared to using only the power spectrum, and a joint analysis gives an additional 8–13% gain. The quadrupole component of the bispectrum plays a key role. It's like stereoscopic vision: two "eyes" (two types of correlations) see depth that one alone cannot.
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The Universe was born in the Big Bang and immediately underwent an ultrafast expansion — inflation. Quantum jitters imprinted themselves on the fabric of space like ripples on water from a tossed stone. These ripples became the seeds of galaxies. Usually the waves are random, but if inflation was complex, some crests are slightly higher — the shape isn't a perfect circle. Catching such a skew means reading the story of the first moments.
The European Euclid telescope will be able to check this. In their model, scientists combined two approaches: one measures the overall height of the ripples, the other catches triangular patterns from neighboring crests. Together they reduce noise and double the accuracy. The cleanest signal comes from distant galaxies half the age of the Universe. To avoid being fooled, the galaxy data is correlated with a dark matter map — the invisible scaffolding of the cosmos. This way, we can tell whether inflation was simple or multi-field, much like figuring out if one stone or several made the ripples.
🎯 If the cosmic ripples were perfectly symmetric, the Universe would have remained featureless, like white noise in headphones, and complex structures would never have formed.
🎬 In Carl Sagan's 'Contact,' a message hides in the noise of the cosmic microwave background. Astrophysicists with Euclid are also searching for a hidden signal in the cosmic ripples, but its author is not an extraterrestrial intelligence, but the quantum laws of the early Universe.
