Exploring the String Axiverse with Precision Black Hole Physics

By A. Arvanitaki, S. Dubovsky. 2010

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It has recently been suggested that the presence of a plenitude of light axions, an Axiverse, is evidence for the extra dimensions of string theory. We discuss the observational consequences of these axions on astrophysical black holes through the Penrose superradiance process. When an axion Compton wavelength is comparable to the size of a black hole, the axion binds to the black hole ``nucleus'' forming a gravitational atom in the sky. The occupation number of superradiant atomic levels, fed by the energy and angular momentum of the black hole, grows exponentially. The black hole spins down and an axion Bose-Einstein condensate cloud forms around it. When the attractive axion self-interactions become stronger than the gravitational binding energy, the axion cloud collapses, a phenomenon known in condensed matter physics as ``bosenova''. The existence of axions is first diagnosed by gaps in the mass vs spin plot of astrophysical black holes. For young black holes the allowed values of spin are quantized, giving rise to ``Regge trajectories'' inside the gap region. The axion cloud can also be observed directly either through precision mapping of the near-horizon geometry or through gravitational waves coming from the bosenova explosion, as well as axion transitions and annihilations in the gravitational atom. Our estimates suggest that these signals are detectable in upcoming experiments, such as Advanced LIGO, AGIS, and LISA. Current black hole spin measurements imply an upper bound on the QCD axion decay constant of $2\ifmmode\times\else\texttimes\fi{}{10}^{17}\text{ }\text{ }\mathrm{GeV}$, while Advanced LIGO can detect signals from a QCD axion cloud with a decay constant as low as the GUT scale. We finally discuss the possibility of observing the $\ensuremath{\gamma}$-rays associated with the bosenova explosion and, perhaps, the radio waves from axion-to-photon conversion for the QCD axion.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/7b5e6a66ae4c248f656f23746edc00ac095a340c

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Citations in the corpus

Detecting high-frequency gravitational waves with microwave cavities (2021, background): “[99] Asimina Arvanitaki and Sergei Dubovsky, “Exploring the String Axiverse with Precision Black Hole Physics,” Phys.”
The type IIB string axiverse and its low-energy phenomenology (2012, background): “Note that such an ALP would constitute only a tiny (O(10−9)) fraction of dark matter, and would satisfy all constraints - interestingly being just one or two orders of magnitude in mass heavier than the black hole super-radiance constraint [19,53] (see section B.”
An M theory solution to the strong CP-problem, and constraints on the axiverse (2010, background): “A recent paper [ 55 ] studies other interesting signals such as gravitational waves and gamma rays emanating from this axion-black hole”
Matter-wave Atomic Gradiometer Interferometric Sensor (MAGIS-100) (2021, unknown): “In addition, there can be dramatic monochromatic gravitational wave signals via axion annihilations or level transitions in the axion (or very light particle) cloud that superradiance produces in the vicinity of the black hole [100, 101, 103–105].”
Challenges and opportunities of gravitational-wave searches at MHz to GHz frequencies (2020, background): “5 [57].”
A model for halo formation with axion mixed dark matter (2013, background): “…matter power spectrum (Amendola & Barbieri 2006; Marsh et al. 2013), while heavier axions are probed, and in some cases ruled, out by the spins of supermassive black holes (Arvanitaki & Dubovsky 2011; Pani et al. 2012), and terrestrial axion searches (Jaeckel & Ringwald 2010; Ringwald 2012a).”
Static response and Love numbers of Schwarzschild black holes (2020, background): “Interestingly, black holes can support time-dependent scalar profiles with nontrivial boundary conditions [8– 11] as well as superradiant [12–19] clouds; see [20–22] for recent discussions.”
Cosmology and Fundamental Physics with the Euclid Satellite (2012, background): “This could lead to many interesting, and potentially observable phenomena, such as formation of vortices in the condensate, which may effect halo mass profiles (Silverman and Mallett 2002; Kain and Ling 2010), and black hole super radiance (Arvanitaki et al. 2010; Arvanitaki and Dubovsky 2011; Rosa ”
Superradiance (2015, methodology): “2), leaving just a small fraction of the cloud bound to the BH [525, 524, 526, 10].”
TASI Lectures on the Strong CP Problem and Axions (2018, background): “7 Black hole superradiance Black hole superradiance utilizes the interesting physics that happens around a spinning black hole [81, 149, 150], which has a region of space near to the horizon called the ergosphere where”
The spectra of gravitational atoms (2019, background): “e of the bosonic eld. The gravitational in uence of these superradiantly-generated ‘boson clouds’ is potentially observable, making this an interesting laboratory of physics beyond the Standard Model [5,6]. The black hole carrying the boson cloud is sometimes called a gravitational atom since the sy”
Probing ultralight bosons with binary black holes (2018, background): “roperties may be dierent. The energy-momentum tensor of a real scalar eld is always time dependent and non-axisymmetric. As a consequence, clouds made out of real elds are a continuous source of GWs [70]. For complex elds, on the other hand, certain congurations may suppress GW emission. This occurs”
Recent Progress in the Physics of Axions and Axion-Like Particles (2020, background): “10−11 eV, observations of spinning black holes and gravitational waves (GWs) can constrain the existence of axions [5, 101].”