The Universe Before the Big Bang Cosmology and String Theory Conclusion The key message we hope to have transmitted to the reader in this book is that there are neither observational data nor incontrovertible theoretical arguments to support the belief that the Big Bang represents the beginning of the Universe, and that before the explosion … Read more
Cosmology and String Theory Recent Developments: Brane Cosmology Scenarios About ten years ago, at the end of the last century, we witnessed the appearance of two new players on the scene of physical and astronomical science. We are just beginning to appreciate their dramatic impact upon basic cosmology, and we are probably far from a … Read more
Cosmology and String Theory Recent Developments: Brane Cosmology Scenarios In contrast, in the strong coupling regime, higher-dimensional branes become light and can be produced copiously, driving the Universe to a phase of brane-domination, typical of M-theory. Such a phase, triggered by the growth of the coupling predicted in the context of pre-Big-Bang models, could be … Read more
Cosmology and String Theory: The Future of our Universe To explain why such discovery is so revolutionary and “ex- plosive”, and understand the subtle link that could exist between such acceleration and the pre-Big-Bang cosmology described in the previous chapters, it is wise to proceed step by step. Let us start by recalling that the … Read more
Cosmology and String Theory: The Future of our Universe In order to solve the equations of general relativity, and therefore to be able to predict the future behavior of the cosmic space-time geometry, it is essential to have a precise knowledge of at least three parameters peculiar to the current cosmological state. For instance, (1) … Read more
Cosmology and String Theory: Quantum Cosmology The possible cosmological scenarios outlined in this book have been approached so far from a purely classical perspective, using concepts and ideas typical of the macroscopic world, like space, time, geometry, gravitational forces, and so on. The aim of this chapter is to introduce a possible alternative description of … Read more
The Universe Before the Big Bang: Quantum Cosmology The reflection of a particle from a barrier is part of our everyday experience and – unlike the tunneling effect – it is obviously also present in the context of classical mechanics. However, within quantum mechanics, there also exists the possibility of a new, truly “quantum”, reflection … Read more
The Universe Before the Big Bang: Other Relics of the Primordial Universe When the latter conditions are satisfied, there are in principle interesting prospects for the future detection of a cosmic back- ground of massive dilatons. In fact, provided their spectrum is flat enough, they could induce an enhanced response to the non- relativistic part … Read more
The Universe Before the Big Bang: Other Relics of the Primordial Universe In addition to gravitational waves, there are other types of signal that could reach us from a primordial epoch preceding the Big Bang, and that could be (directly or indirectly) available to our present observation. Actually, as pointed out in the last chapter, … Read more
The Universe Before the Big Bang The Cosmological Background of Gravitational Radiation (P2) A too copious production of particles may present some disadvantages, however. The resulting radiation may not satisfy present experimental constraints, and may even be inconsistent with the cosmological model itself. In fact, the energy of the resulting particles could be large enough … Read more
