Boson stars: alternatives to primordial black holes?

Mielke, Eckehard W.; Schunck, Franz E.

doi:10.1016/s0550-3213(99)00492-7

Cited by 134 publications

(122 citation statements)

References 121 publications

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“…The striking feature of the plot is the maximum of the mass as a function of parameter λ = f a / (M P ∆). Maxima of M , as a function of the central value of the axion wave function have already been found in previous work [3,[6][7][8][9][10][11][12], but the maximum in figure 2 has a physical significance due to the following considerations. 2 Note that the number of axions in the condensate is approximately equal to Table 1.…”

Section: Analytic Approximations To the Physical Parameters Of Axionsupporting

confidence: 63%

“…It has been seen that complex scalar field configurations in the presence of gravity can form stable compact objects, termed boson stars [3][4][5][6][7][8][9][10]. Kaup in his original work solved the Klein-Gordon free field equation in an asymptotically flat spherically symmetric spacetime background and found localized spherically symmetric field configurations which are energy eigenstates.…”

Section: Introductionmentioning

confidence: 99%

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Axion stars in the infrared limit

Eby

Surányi

Vaz

et al. 2015

J. High Energ. Phys.

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Following Ruffini and Bonazzola, we use a quantized boson field to describe condensates of axions forming compact objects. Without substantial modifications, the method can only be applied to axions with decay constant, f a , satisfying δ = (f a / M P ) 2 1, where M P is the Planck mass. Similarly, the applicability of the Ruffini-Bonazzola method to axion stars also requires that the relative binding energy of axions satisfies1, where E a and m a are the energy and mass of the axion. The simultaneous expansion of the equations of motion in δ and ∆ leads to a simplified set of equations, depending only on the parameter, λ = √ δ / ∆ in leading order of the expansions. Keeping leading order in ∆ is equivalent to the infrared limit, in which only relevant and marginal terms contribute to the equations of motion. The number of axions in the star is uniquely determined by λ. Numerical solutions are found in a wide range of λ. At small λ the mass and radius of the axion star rise linearly with λ. While at larger λ the radius of the star continues to rise, the mass of the star, M , attains a maximum at λ max 0.58. All stars are unstable for λ > λ max . We discuss the relationship of our results to current observational constraints on dark matter and the phenomenology of Fast Radio Bursts.

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Section: Analytic Approximations To the Physical Parameters Of Axionsupporting

confidence: 63%

Section: Introductionmentioning

confidence: 99%

Axion stars in the infrared limit

Eby

Surányi

Vaz

et al. 2015

J. High Energ. Phys.

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“…The alternative explanation of the central mass as a massive boson star (Torres et al (2000); Mielke and Schunck (2000); Lu and Torres (2003) and references therein) is severely challenged by the good agreement between the measured polarized flare structure and the theoretical predictions (Gillessen et al, 2006;Eisenhauer et al, 2005;Broderick and Loeb, 2005;Ghez et al, 2004) as well as the indication of a quasi-periodicity in the data. If an ad hoc weak repulsive force between a hypothetical brand of bosons is introduced, it appears to be possible to form massive, compact objects with sizes of a few R S that are supposedly supported by the Heisenberg uncertainty principle.…”

Section: Boson Ballmentioning

confidence: 99%

The Milky Way’s Supermassive Black Hole: How Good a Case Is It?

Eckart

Hüttemann²,

Kiefer³

et al. 2017

Found Phys

123

105

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The compact and, with 4.3±0.3×106 M ⊙ , very massive object located at the center of the Milky Way is currently the very best candidate for a supermassive black hole (SMBH) in our immediate vicinity. The strongest evidence for this is provided by measurements of stellar orbits, variable X-ray emission, and strongly variable polarized near-infrared emission from the location of the radio source Sagittarius A* (SgrA*) in the middle of the central stellar cluster. Simultaneous near-infrared and X-ray observations of SgrA* have revealed insights into the emission mechanisms responsible for the powerful near-infrared and X-ray flares from within a few tens to one hundred Schwarzschild radii of such a putative SMBH at the center of the Milky Way. If SgrA* is indeed a SMBH it will, in projection onto the sky, have the largest event horizon and will certainly be the first and most important target of the Event Horizon Telescope (EHT) Very Long Baseline Interferometry (VLBI) observations currently being prepared. These observations in combination with the infrared interferometry experiment GRAVITY at the Very Large Telescope Interferometer (VLTI) and other experiments across the electromagnetic spectrum might yield proof for the presence of a black hole at the center of the Milky Way. The large body of evidence continues to discriminate the identification of SgrA* as a SMBH from alternative possibilities. It is, however, unclear when the ever mounting evidence for SgrA* being associated with a SMBH will suffice as a convincing proof. Additional compelling evidence may come from future gravitational wave observatories. This manuscript reviews the observational facts, theoretical grounds and conceptual aspects for the case of SgrA* being a black hole. We treat theory and observations in the framework of the philosophical discussions about "(Anti)Realism and Underdetermination", as this line of arguments allows us to describe the situation in observational astrophysics with respect to supermassive black holes. Questions concerning the existence of supermassive black holes and in particular SgrA* are discussed using causation as an indispensable element. We show that the results of our investigation are convincingly mapped out by this combination of concepts.

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“…Such dissent ranges from a careful sceptical analysis of what it physically means to observe an event horizon [1], through alternative models for compact objects [2], to more radical proposals that drastically modify the physics in the region where the event horizon would otherwise be expected to form [3][4][5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Stable gravastars—an alternative to black holes?

Visser¹,

Wiltshire²

2004

Class. Quantum Grav.

472

540

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The 'gravastar' picture developed by Mazur and Mottola is one of a very small number of serious challenges to our usual conception of a 'black hole'. In the gravastar picture there is effectively a phase transition at/ near where the event horizon would have been expected to form, and the interior of what would have been the black hole is replaced by a segment of de Sitter space. While Mazur and Mottola were able to argue for the thermodynamic stability of their configuration, the question of dynamic stability against spherically symmetric perturbations of the matter or gravity fields remains somewhat obscure. In this paper we construct a model that shares the key features of the Mazur-Mottola scenario, and which is sufficiently simple for a full dynamical analysis. We find that there are some physically reasonable equations of state for the transition layer that lead to stability.PACS number:

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Boson stars: alternatives to primordial black holes?

Cited by 134 publications

References 121 publications

Axion stars in the infrared limit

Axion stars in the infrared limit

The Milky Way’s Supermassive Black Hole: How Good a Case Is It?

Stable gravastars—an alternative to black holes?

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