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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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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
Fulltext: PDF;
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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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An exact Jacobi map in the geodesic light-cone gauge
/ Fanizza, G. (Bari U. ; INFN, Bari) ; Gasperini, M. (Bari U. ; INFN, Bari) ; Marozzi, G. (Geneva U., CAP) ; Veneziano, G. (College de France ; CERN)
The remarkable properties of the recently proposed geodesic light-cone (GLC) gauge allow to explicitly solve the geodetic-deviation equation, and thus to derive an exact expression for the Jacobi map J^A_B(s,o) connecting a generic source s to a geodesic observer o in a generic space time. In this gauge J^A_B factorizes into the product of a local quantity at s times one at o, implying similarly factorized expressions for the area and luminosity distance. [...]
arXiv:1308.4935; CERN-PH-TH-2013-196; CERN-PH-TH-2013-196.-
2013-11-07 - 25 p.
- Published in : JCAP 11 (2013) 019
Fulltext: PDF; External link: Preprint
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Average and dispersion of the luminosity-redshift relation in the concordance model
/ Ben-Dayan, I. (DESY) ; Gasperini, M. (U. Bari (main) ; INFN, Bari) ; Marozzi, G. (College de France ; Geneva U., Dept. Theor. Phys. ; Geneva U., CAP) ; Nugier, F. (Ecole Normale Superieure) ; Veneziano, G. (College de France ; CERN ; New York U., CCPP)
Starting from the luminosity-redshift relation recently given up to second order in the Poisson gauge, we calculate the effects of the realistic stochastic background of perturbations of the so-called concordance model on the combined light-cone and ensemble average of various functions of the luminosity distance, and on their variance, as functions of redshift. We apply a gauge-invariant light-cone averaging prescription which is free from infrared and ultraviolet divergences, making our results robust with respect to changes of the corresponding cutoffs. [...]
arXiv:1302.0740; DESY-13-011; CERN-PH-TH-2012-362; BA-TH-666-12; LPTENS-13-01; CERN-PH-TH-2012-362.-
2013 - 27 p.
- Published in : JCAP 06 (2013) 002
External link: Preprint
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