Recent debates around the testability of the inflationary paradigm raise the question of how to model-independently discriminate it from competing scenarios. We argue that a detection of the cosmic graviton background (CGB), the relic radiation from gravitons decoupling around Planck time, would rule out the inflationary paradigm, as realistic inflationary models would dilute the CGB to an unobservable level. The CGB contribution to the effective number of relativistic species, ΔNeff,g ≈ 0.054, is well within the reach of next-generation cosmological probes. We argue that detecting the high-frequency stochastic gravitational wave background associated to the CGB will be challenging but potentially feasible. We briefly discuss expectations within alternatives to inflation, focusing on bouncing cosmologies and emergent scenarios.

The Challenge of Ruling Out Inflation via the Primordial Graviton Background / Vagnozzi, Sunny; Loeb, Abraham. - In: THE ASTROPHYSICAL JOURNAL LETTERS. - ISSN 2041-8205. - 939:2(2022), p. L22. [10.3847/2041-8213/ac9b0e]

The Challenge of Ruling Out Inflation via the Primordial Graviton Background

Vagnozzi, Sunny;
2022-01-01

Abstract

Recent debates around the testability of the inflationary paradigm raise the question of how to model-independently discriminate it from competing scenarios. We argue that a detection of the cosmic graviton background (CGB), the relic radiation from gravitons decoupling around Planck time, would rule out the inflationary paradigm, as realistic inflationary models would dilute the CGB to an unobservable level. The CGB contribution to the effective number of relativistic species, ΔNeff,g ≈ 0.054, is well within the reach of next-generation cosmological probes. We argue that detecting the high-frequency stochastic gravitational wave background associated to the CGB will be challenging but potentially feasible. We briefly discuss expectations within alternatives to inflation, focusing on bouncing cosmologies and emergent scenarios.
2022
2
Vagnozzi, Sunny; Loeb, Abraham
The Challenge of Ruling Out Inflation via the Primordial Graviton Background / Vagnozzi, Sunny; Loeb, Abraham. - In: THE ASTROPHYSICAL JOURNAL LETTERS. - ISSN 2041-8205. - 939:2(2022), p. L22. [10.3847/2041-8213/ac9b0e]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11572/360451
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