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Constraints on the Pre-Big Bang scenario from a cosmological interpretation of the NANOGrav data
/ Conzinu, P. (INFN, Parma ; U. Parma (main)) ; Fanizza, G. (U. Lisbon (main)) ; Gasperini, M. (INFN, Bari ; U. Bari (main)) ; Pavone, E. (INFN, Bari ; U. Bari (main)) ; Tedesco, L. (INFN, Bari ; U. Bari (main)) ; Veneziano, G. (CERN ; College de France)
We discuss a recently proposed fit of the 15-year data set obtained from the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) in terms of a relic stochastic background of primordial gravitons, produced in the context of the string cosmology pre-big bang scenario. [...]
arXiv:2412.01734 ; CERN-TH-2024-210 ; BA-TH/809-24.
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From the string vacuum to FLRW or de Sitter via $\alpha'$ corrections
/ Conzinu, P. (Pisa U. ; INFN, Pisa) ; Fanizza, G. (Lisbon U.) ; Gasperini, M. (Bari U. ; INFN, Bari) ; Pavone, E. (Bari U. ; INFN, Bari) ; Tedesco, L. (Bari U. ; INFN, Bari) ; Veneziano, G. (CERN ; College de France)
We first make more precise a recent "Hamiltonian" reformulation of the Hohm-Zwiebach approach to the tree-level, $O(d,d)$-invariant string cosmology equations at all orders in the $\alpha'$ expansion, and recall how it allows to give a simple characterization of a large class of cosmological scenarios connecting, through a non-singular bounce, two duality-related perturbative solutions at early and late times. We then discuss the effects of adding to the action a non-perturbative, $O(d,d)$-breaking, dilaton potential $V(\phi)$. [...]
arXiv:2308.16076; BA-TH/808-23; CERN-TH-2023-163.-
2023-12-12 - 30 p.
- Published in : JCAP 2312 (2023) 019
Fulltext: 2308.16076 - PDF; document - PDF;
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The skewness of the distance-redshift relation in $\Lambda$CDM
/ Schiavone, T. (Lisbon U. ; INFN, Pisa ; Pisa U.) ; Di Dio, E. (CERN) ; Fanizza, G. (Lisbon U.)
Starting from a recently proposed framework for the evaluation of the cosmological averages, we evaluate the higher-order moments for the distribution of a given observable. Then, we explicitly discuss the case of the Hubble-Lemaître diagram and evaluate its skewness at the leading order in the cosmological perturbative expansion of the gravitational potential. [...]
arXiv:2307.13455; CERN-TH-2023-141.-
2024-02-26 - 32 p.
- Published in : JCAP 2402 (2024) 050
Fulltext: document - PDF; 2307.13455 - PDF;
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Observation angles, Fermi coordinates, and the Geodesic-Light-Cone gauge
/ Fanizza, Giuseppe (INFN, Pisa ; Zurich U.) ; Gasperini, Maurizio (Bari U. ; INFN, Bari) ; Marozzi, Giovanni (Pisa U. ; INFN, Pisa) ; Veneziano, Gabriele (CERN ; College de France)
We show that the angular directions locally measured by a static geodesic observer in a generic cosmological background and expressed in the system of Fermi Normal Coordinates always coincide with those expressed in the Geodesic-Light-Cone (GLC) gauge, up to a local transformation which exploits the residual gauge freedom of the GLC coordinates. This is not the case for other gauges - like, for instance, the synchronous and longitudinal gauge - commonly used in the context of observational cosmology. [...]
arXiv:1812.03671; BA-TH/716-18; CERN-TH-2018-253.-
2019-01-03 - 14 p.
- Published in : JCAP 1901 (2019) 004
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Time of flight of ultra-relativistic particles in a realistic Universe: a viable tool for fundamental physics?
/ Fanizza, G. (Geneva U., CAP ; Bari U. ; Geneva U., Dept. Theor. Phys. ; INFN, Bari) ; Gasperini, M. (Bari U. ; INFN, Bari) ; Marozzi, G. (Rio de Janeiro, CBPF ; Geneva U., CAP ; Geneva U., Dept. Theor. Phys.) ; Veneziano, G. (College de France ; CERN ; Rome U.)
Including the metric fluctuations of a realistic cosmological geometry we reconsider an earlier suggestion that measuring the relative time-of-flight of ultra-relativistic particles can provide interesting constraints on fundamental cosmological and/or particle parameters. Using convenient properties of the geodetic light-cone gauge we first compute, to leading order in the Lorentz factor and for a generic (inhomogeneous, anisotropic) space-time, the relative arrival times of two ultra-relativistic particles as a function of their masses and energies as well as of the details of the large-scale geometry. [...]
arXiv:1512.08489; CERN-PH-TH-2015-306; CERN-PH-TH-2015-306.-
2016-06-10 - 5 p.
- Published in : Phys. Lett. B 757 (2016) 505-509
Article from SCOAP3: PDF; Elsevier Open Access article: PDF; Fulltext: PDF; External link: Preprint
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