For the last few decades, researchers have been studying what the universe looked like in its first seconds. It is generally accepted that the universe expanded exponentially in the first fraction of a second after the Big Bang. Researchers use ns, the scalar spectral index, to characterize how primordial density fluctuations were distributed across different length scales in the early universe. The value of ns is a central observable in inflationary cosmology, since different inflationary scenarios predict distinct values for this quantity, making it a powerful discriminator between models.

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