1. Department of Mathematics and Physics “E. De Giorgi”, University of Salento, Via Arnesano, CP 193, I-73100 Lecce, Italy
2. INFN, Sezione di Lecce, CP 193, I-73100 Lecce, Italy
3. Center for Cosmology and Astrophysics, Alikhanian National Laboratory and Yerevan State University, Yerevan, Armenia
4. SIA, Sapienza University of Rome, Rome, Italy
5. School of Natural Sciences, National University of Sciences and Technology, Islamabad, Pakistan