Making sense of the bizarre behavior of horizons in the McVittie spacetime

Faraoni, Valerio; Moreno, Andres F. Zambrano; Nandra, Roshina

doi:10.1103/physrevd.85.083526

Cited by 67 publications

(117 citation statements)

References 145 publications

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“…We note that this expression becomes singular at any point where g 2 1 = g 2 2 , which be can shown to correspond to the locations of apparent horizons [29]. Note that these do not usually coincide with where the metric and fluid pressure become singular, which occurs when g 1 = 0.…”

Section: Particle At Rest In the Object's Interiormentioning

confidence: 86%

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Dynamics of a spherical object of uniform density in an expanding universe

Nandra¹,

Lasenby²,

Hobson³

2013

Phys. Rev. D

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We present Newtonian and fully general-relativistic solutions for the evolution of a spherical region of uniform interior density ρi(t), embedded in a background of uniform exterior density ρe(t). In both regions, the fluid is assumed to support pressure. In general, the expansion rates of the two regions, expressed in terms of interior and exterior Hubble parameters Hi(t) and He(t), respectively, are independent. We consider in detail two special cases: an object with a static boundary, Hi(t) = 0; and an object whose internal Hubble parameter matches that of the background, Hi(t) = He(t).In the latter case, we also obtain fully general-relativistic expressions for the force required to keep a test particle at rest inside the object, and that required to keep a test particle on the moving boundary. We also derive a generalised form of the Oppenheimer-Volkov equation, valid for general time-dependent spherically-symmetric systems, which may be of interest in its own right.

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Section: Particle At Rest In the Object's Interiormentioning

confidence: 86%

“…The final generalised Oppenheimer-Volkov equation is obtained by substituting equations (30), (31) and (32) into (29) to give…”

Section: B Densities Pressures and Forcesmentioning

confidence: 99%

Dynamics of a spherical object of uniform density in an expanding universe

Nandra¹,

Lasenby²,

Hobson³

2013

Phys. Rev. D

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“…We have shown in [4] that there are two apparent horizons associated with this metric: The 'black hole horizon' and the 'cosmological horizon'. Since, the metric is time-dependent, these horizons are dynamical.…”

Section: Dynamical Apparent Horizonsmentioning

confidence: 99%

Interplay between cosmological expansion and massive objects

Nandra

Lasenby

Hobson

2014

J. Phys.: Conf. Ser.

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Abstract.We have derived a metric for a point mass in an expanding universe. In the spatially flat case, a simple coordinate transformation relates our metric to that derived by McVittie. Nonetheless, our use of non-comoving (physical) coordinates greatly facilitates physical interpretation. We have also derived a coordinate-free expression for the force required to keep a particle at rest in this spacetime. For redshift z > 0.67, we have identified two important time-dependent physical radii; the largest possible circular orbit rF (t), and the largest stable circular orbit rS(t), which lies inside rF (t), either of which could be interpreted the egde of an object of mass m. In the case of a dynamical background dominated by a phantom fluid, we can use our force expression to predict the time of the 'Big Rip' when the universe ends. For open and closed universes, our metrics describe different spacetimes to McVittie's metrics; we believe the latter to be incorrect. In the closed case, our metric possesses an image mass at the antipodal point of the universe.

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“…Another possibility is that of a "background" FLRW universe sourced by a phantom fluid [55], defined by the equation of state parameter w Á P= < 1 and violating the weak energy condition. Phantom fluids have raised much interest in relation with the present acceleration of the universe [5].…”

Section: Phantom Mcvittie Spacetimementioning

confidence: 99%

“…The old McVittie solution [119] has been largely overlooked for decades and recent studies show that its structure and details are not yet completely understood [38,55,85,94,123,124]. Relatively few other solutions describing central condensations in otherwise spatially homogeneous universes have been reported over the years (see Ref.…”

mentioning

confidence: 99%