** Lecturer**: Dr. Vesselin Gueorguiev

** Place and time**: New Bulgarian University, 21.12.2018 /Friday/ 17:00, Hall 405, building I

** Abstract**: A new perspective on the Cosmological Constant Problem (CCP) is proposed and justified within the approach of Quantum Cosmology. It is assumed that each member of an ensemble of solutions of the Einstein field equations has a characteristic scale ‘a’ that can be used as an integration variable in the partition function. The estimated averaged characteristic scale is compatible with the Planck length when considering an ensemble of solutions with an effective cosmological constant. This approach to the CCP has the potential to reconcile the Planck-scale huge vacuum energy-density predicted by QFT considerations, as valid for Planck-scale solutions, with the observed small value of the cosmological constant as relevant to an a-derivable solution as observed.

**Biosketch**. Dr. Vesselin Gueorguiev was born in Sofia, Bulgaria and obtained his M.S. degree in Particle and Nuclear Physics from Sofia University, Bulgaria. He obtained his Ph.D. degree in Nuclear Physics from the Louisiana State University (LSU), Baton Rouge, Louisiana, USA; in the Spring of 2004 he went to Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain as a NATO research fellow to work on the exact solution of the Nuclear Pairing; from 2004 to 2007, he was a postdoctoral research fellow at LLNL, Livermore, CA, USA, working on the application of the three-body nuclear Interactions derived from Chiral Effective Theory to light nuclei. Dr. Gueorguiev has authored and co-authored more than 50 articles, three of which are publications in the Physical Review Letters, he has more than ten scientific papers with over ten citations each, the total citations to his papers exceeds 500 in the scientific literature. He has taught physics and astronomy at UC Merced and CSU Stanislaus in California, USA, and CUPI in Chengdu, China. Currently, he leaves in California, USA and is a research scholar at the Ronin Institute for Independent Scholarship, New Jersey, and is also an associate member of the Institute for Advanced Physical Studies, Sofia, Bulgaria. His current research topic is focused on the applications of the scale-invariant and reparametrization invariant models to the fundamental interactions in nature.