Talk detail

Participant	Velhinho, Jose
Institution	Universidade Beira Interior - Marques Avila e Bolama - Covilha - - Portugal

Session	CM4	Accepted	Yes	Order	6	Time
Talk	Oral abstract	Title	Quantization of the massless scalar field in de Sitter space with unitary dynamics
Co-authors
Abstract	The quantization of the massless scalar field in de Sitter space is revisited. It is well known that in the massless case the so called Bunch-Davies vacuum, i.e. the de Sitter invariant Fock state, breaks down. However, this does not prevent a consistent Fock quantization from being obtained, e.g. by means of O(4) invariant states. We show explicitely that a Fock quantization can be achieved such that the dynamics of the massless field is unitarily implemented at the quantum level. This result is in full agreement with more general results obtained in the context of fields with a time dependent mass. On the other hand, this result corrects recent wrong statements in the literature, which incorrectly state that no unitary dynamics can be achieved for the massless field in de Sitter. Moreover, one can show that the obtained quantization is in fact unique, in the sense that any other O(4) invariant Fock representation which also allows unitary dynamics is necessarily unitarily equivalent. In particular, the Fock representation that naturally emerges from our approach is seen to be unitarily equivalent to the O(4) invariant quantizations proposed some time ago by Allen and Folacci.

Session	QG4	Accepted	Yes	Order	7	Time	17:00 - 17:30
Talk	Oral abstract	Title	Uniqueness of the Fock quantization of scalar fields with time dependent mass
Co-authors
Abstract	In the hybrid approach to inhomogeneous quantum cosmology, a combination of Loop Quantum Cosmology techniques for the homogeneous sector and a standard Fock quantization for the inhomogeneous degres of freedoom is used. It turns out, in the case of spatialy compact manifolds - or modulo long wavelenght modes in the noncompact case - that it is possible to choose a field description and a Fock representation for the inhomogeneous sector such that the corresponding dynamics (of the inhomogeneous sector) is unitarily implemented at the quantum level. Moreover, it was also recently shown that this quantization is in fact unique. These particular results in the context of cosmology are rooted on general mathematical-physics results concerning the Fock quantization of linear scalar fields with an explicitely time-dependent mass. We present a survey of those recent results.