SPACE seminar: Giuseppe Filiberto Vitale; Sara Rufrano Aliberti

Tuesday 7 Jul 2026, 12:00 → 13:00 Europe/Rome

Aula 4 (San Marcellino)

Speaker 1: Giuseppe Filiberto Vitale (University of Salerno)

Title 1:  Microscopic Primordial Black Holes as Macroscopic Dark Matter from Large Extra Dimensions

Abstract 1: We study the coupled cosmological evolution of primordial black holes (PBHs) and radiation in the Arkani-Hamed-Dimopoulos-Dvali (ADD) framework with $n$ large extra dimensions and a fundamental gravity scale $M_\star$ at the TeV scale. For PBHs with horizon radius smaller than the compactification scale,  the higher-dimensional geometry implies a larger horizon size at fixed mass and therefore a suppressed Hawking temperature. As a result, radiation accretion can overcome evaporation in the early Universe and drive a "runaway'' phase of rapid mass growth. By numerically solving the coupled mass and energy-density evolution equations, we show that for $n \geq 2$ initially microscopic PBHs with initial mass $M_i \gtrsim 10^{12}\,$g can grow by many orders of magnitude and potentially reach macroscopic, even solar-mass, scales by matter-radiation equality. We determine the critical initial abundance $\beta_{\rm crit}$ required for PBHs to account for the observed dark matter density and find that extra dimensions dramatically lower this threshold, allowing viable scenarios with $\beta_{\rm crit}\sim 10^{-44}$. This identifies a previously unexplored region of parameter space in which the dark matter abundance is achieved through dynamical mass growth rather than large initial collapse fractions.

References 1:

1. G.F. Vitale, G. Lambiase, T.K. Poddar and L. Visinelli, arXiv:2604.14871 [astro-ph.CO]
2. N. Arkani-Hamed, S. Dimopoulos, and G.R. Dvali, Phys. Lett. B 429, 263 (1998), arXiv:hep-ph/9803315
3. A. Friedlander, K.J. Mack, S. Schon, N. Song, and A.C. Vincent, Phys. Rev. D 105, 103508 (2022), arXiv:2201.11761 [hep-ph]
4. B. Nayak and L.P. Singh, Pramana 76, 173 (2011), arXiv:0905.3243 [gr-qc] 

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Speaker 2: Sara Rufrano Aliberti (SSM)

Title 2: Radiation-Reaction Correction to Scattering Binary Dynamics at Next-to-Leading Post-Newtonian Order

Abstract 2: Radiation-reaction force encodes dissipative effects in a binary system emitting gravitational waves. Within the post-Newtonian framework, radiation-reaction terms enter the equations of motion starting at 2.5PN order and affect the system’s dynamics accordingly. These effects can be incorporated as corrections to the quasi-Keplerian orbital parameters in the center-of-mass frame. This presentation focuses on the Lagrange method of variation of constants, which we used to determine the radiation-reaction corrections to the quasi-hyperbolic orbit at 3.5PN order.

References 2:

1. D. Bini, A. Geralico, S. Rufrano Aliberti, “Radiation-reaction correction to scattering binary dynamics at the Next-to-Leading Post-Newtonian Order”, Phys. Rev. D 112, 104005 (2025)
2. B. R. Iyer and C. M. Will, “Post-Newtonian gravitational radiation reaction for two-body systems: Nonspinning bodies”, Phys. Rev. D 52, 6882 (1995)
3. T. Damour, “Gravitational Radiation Reaction in the Binary Pulsar and the Quadrupole-Formula Controversy”, Phys. Rev. Lett. 51, 1019 (1983)
4. D. Bini, T. Damour, A. Geralico, “Radiated momentum and radiation reaction in gravitational two-body scattering including time-asymmetric effects“, Phys. Rev. D 107, 024012 (2023)

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