Ghosts in the self-accelerating brane universe

By K. Koyama. 2005

134 citations recorded by the source corpus.

We study the spectrum of gravitational perturbations about a vacuum de Sitter brane with the induced 4D Einstein-Hilbert term, in a 5D Minkowski spacetime (DGP model). We consider solutions that include a self-accelerating universe, where the accelerating expansion of the universe is realized without introducing a cosmological constant on the brane. The mass of the discrete mode for the spin-2 graviton is calculated for various Hrc, where H is the Hubble parameter and rc is the crossover scale determined by the ratio between the 5D Newton constant and the 4D Newton constant. We show that, if we introduce a positive cosmological constant on the brane (Hrc>1), the spin-2 graviton has mass in the range 01/2. In a self-accelerating universe Hrc=1, the spin-2 graviton has mass m2=2H2, which coincides with the mass of the brane fluctuation mode. Then there arises a mixing between the brane fluctuation mode and the spin-2 graviton. We argue that this mixing presumably gives a ghost in the self-accelerating universe by continuity across Hrc=1, although a careful calculation of the effective action is required to verify this rigorously

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/3bc8dca42ffcb53f8a3d292e003b967d785b19ed

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Citations in the corpus

Massive Gravity (2014, background): “We summarize the three case scenario following [357, 98] • In [304] it was shown that when the effective mass is within the forbidden Higuchi-region, the helicity-0 mode of graviton has the wrong sign kinetic term and is a ghost.”
The phenomenology of Dvali–Gabadadze–Porrati cosmologies (2005, background): “Koyama suggests that, in fact, around the self-accelerating empty space solution itself, the brane fluctuation mode is not a ghost [104], implying that there may be a subtlety involving the self-consistent treatment of perturbations around the background.”
Categorizing Different Approaches to the Cosmological Constant Problem (2004, background): “This is however a controversial result, also argued for in [182], yet waived away in [187].”
A systematic approach to generalisations of General Relativity and their cosmological implications (2018, background): “However, it was quickly realised that this branch of solutions seems to be plagued by ghost-like instabilities [27, 28].”