Talk detail

Participant	Pasechnik, Roman
Institution	Department of Astronomy and Theoretical Physics - Sölvegatan 14A - Lund - Skåne - Sweden

Session	NS1	Accepted		Order	Time
Talk	Oral abstract	Title	Domain-wall structure and self-screening of quantum Yang-Mills vacua in expanding Universe
Coauthors
Abstract	The dynamical cancellation of the vacuum energy of the QCD sector in the infrared regime is a relevant problem for both particle physics and cosmology. We find an argument related to the existence of a ℤ2-symmetry for the renormalization group flow derived from the bare Yang-Mills Lagrangian, and show that the cancellation of the vacuum energy may arise motivated both from the renormalization group flow solutions and the effective Yang-Mills action. At the cosmological level, we explore the stability of the electric and magnetic attractor solutions, both within and beyond the perturbation theory, and find that thanks these latter the cancellation between the electric and the magnetic vacua components is achieved at macroscopic space and time separations. This implies the disappearance of the conformal anomaly in the classical limit of an effective Yang-Mills theory. A new type of non-perturbative non-local configurations in the Yang-Mills vacua, space-time instanton-like objects separated by domain walls, is emerged and their properties and implications are discussed.
Pdf file

Session	DE1	Accepted		Order	Time
Talk	Oral abstract	Title	Quantum gravity correction to the QCD vacuum density and the cosmological constant
Coauthors
Abstract	To the zeroth order in gravitational interactions, the averaged QCD (quark-gluon) vacuum condensate density is dynamically self-screened and is eliminated at macroscopic space-time separations. We argue that the observable cosmological constant can then be generated as a quantum gravity correction to QCD vacuum energy density after the QCD phase transition epoch. In order to incorporate the latter, we compute the leading-order quantum correction to the classical Einstein equations due to metric fluctuations induced by the non-perturbative vacuum fluctuations of the gluon and quark fields in the quasi classical approximation (valid at the considered energy scales). The resulting contribution to the cosmological constant is positive and approaches the observed value within a factor of few.
Pdf file

Session	GW1	Accepted		Order	Time
Talk	Oral abstract	Title	Multi-peaked signatures of primordial gravitational waves from multi-step electroweak phase transition
Coauthors
Abstract	The first-order electroweak phase transition in the early universe could occur in multiple steps leading to specific multi-peaked signatures in the primordial gravitational wave (GW) spectrum. We argue that these signatures are generic phenomena in multi-scalar extensions of the Standard Model particularly relevant for electroweak baryogenesis. In a simple example of such an extension, we have studied the emergence of reoccuring and nested vacuum bubble configurations and their role in the formation of multiple peaks in the GW spectrum. The conditions for potential detectability of these features by the forthcoming generation of interferometers have been studied.
Pdf file