Can cosmic inflation be ruled out?

Cosmic inflation is a popular scenario for the earliest phase in the evolution of the Universe Credit: A. Ijjas, P.J. Steinhardt and A. Loeb (Scientific American, February 2017) Astrophysicists say that cosmic inflation - a point in the Universe's infancy when space-time expanded exponentially, and what physicists really refer to when they talk about the -Big Bang can in principle be ruled out in an assumption-free way. Is it possible in principle to test cosmic inflation in a model-independent way? Sunny Vagnozzi The astrophysicists, from the University of Cambridge, the University of Trento, and Harvard University, say that there is a clear, unambiguous signal in the cosmos which could eliminate inflation as a possibility. Their paper , published in The Astrophysical Journal Letters , argues that this signal - known as the cosmic graviton background (CGB) - can feasibly be detected, although it will be a massive technical and scientific challenge. -Inflation was theorised to explain various fine-tuning challenges of the so-called hot Big Bang model,- said the paper's first author Dr Sunny Vagnozzi, from Cambridge's Kavli Institute for Cosmology, and who is now based at the University of Trento. -It also explains the origin of structure in our Universe as a result of quantum fluctuations. -However, the large flexibility displayed by possible models for cosmic inflation which span an unlimited landscape of cosmological outcomes raises concerns that cosmic inflation is not falsifiable, even if individual inflationary models can be ruled out.