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Universe, Volume 4, Issue 10

October 2018 - 13 articles

Cover Story: Modelling the present accelerated expansion of the universe without an ad hoc dark energy motivates modified theories of gravity that contain an effective dynamical cosmological constant, causing black holes to be non-asymptotically flat nor stationary. Other fundamental causes include backreaction of Hawking radiation, companions in binary systems, accretion, or quantum corrections. In modified and in Einstein gravity, modelling such dynamical black holes requires a new definition of black hole and the investigation of apparent horizons. Black hole mechanics and thermodynamics become much more challenging and many questions remain unanswered. Cosmological black holes constitute an interesting class of analytical solutions of the field equations of various theories of gravity. Focusing on spherical symmetry, this article reviews these solutions and their apparent horizon histories. View this paper.
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Articles (13)

  • Review
  • Open Access
33 Citations
4,207 Views
30 Pages

16 October 2018

Classic black hole mechanics and thermodynamics are formulated for stationary black holes with event horizons. Alternative theories of gravity of interest for cosmology contain a built-in time-dependent cosmological “constant” and black h...

  • Article
  • Open Access
2 Citations
2,895 Views
11 Pages

15 October 2018

We propose a generalization of the Nambu–Hamilton equation in superspace R 3 | 2 with three real and two Grassmann coordinates. We construct the even degree vector field in the superspace R 3 | 2 by means of the right-hand s...

  • Feature Paper
  • Article
  • Open Access
34 Citations
3,625 Views
16 Pages

Quantum Gravity at the Corner

  • Laurent Freidel and
  • Alejandro Perez

15 October 2018

We investigate the quantum geometry of a 2d surface S bounding the Cauchy slices of a 4d gravitational system. We investigate in detail for the first time the boundary symplectic current that naturally arises in the first-order formulation of general...

  • Article
  • Open Access
12 Citations
3,292 Views
25 Pages

Cosmological Bounce and Some Other Solutions in Exponential Gravity

  • Pritha Bari,
  • Kaushik Bhattacharya and
  • Saikat Chakraborty

12 October 2018

In this work, we present some cosmologically relevant solutions using the spatially flat Friedmann-Lemaitre-Robertson-Walker (FLRW) spacetime in metric f ( R ) gravity where the form of the gravitational Lagrangian is given by 1 α...

  • Article
  • Open Access
44 Citations
10,112 Views
26 Pages

2 October 2018

The understanding of black holes in loop quantum gravity is becoming increasingly accurate. This review focuses on the possible experimental or observational consequences of the underlying spinfoam structure of space-time. It addresses both the aspec...

  • Article
  • Open Access
38 Citations
3,718 Views
17 Pages

2 October 2018

While the equations of general relativity take the same form in any coordinate system, choosing a suitable set of coordinates is essential in any practical application. This poses a challenge in background-independent quantum gravity, where coordinat...

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Universe - ISSN 2218-1997