444 citations · 3.4k across the 60 of their papers we have counts for
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Dynamical Cosmological Constant
Giuseppe di Donato, Luigi Pilo
The dynamical realisation of the equation of state is studied. A non-pathological dynamics for the perturbations of such a system mimicking a dynamical cosmological consta…
Classical and Quantum Dynamics of Gyroscopic Systems and Dark Energy
Denis Comelli, Maicol Di Giambattista, Luigi Pilo
Gyroscopic systems in classical and quantum field theory are characterized by the presence of at least two scalar degrees of freedom and by terms that mix fields and their time der…
Quantum Corrections to the Stochastic Gravitational Wave Background
Denis Comelli, Maicol Di Giambattista, Luigi Pilo +1
We study 1-loop corrections to the primordial stochastic background of gravitational waves produced during inflation. While in single-clock, at the leading order in slow-roll, quan…
On the 6th Mode in Massive Gravity
Marco Celoria, Denis Comelli, Luigi Pilo
Generic massive gravity models in the unitary gauge correspond to a self-gravitating medium with six degrees of freedom. It is widely believed that massive gravity models with six…
Disformal invariance of continuous media with linear equation of state
M. Celoria, S. Matarrese, L. Pilo
We show that the effective theory describing single component continuous media with a linear and constant equation of state of the form is invariant under a 1-parameter fami…
Thermodynamics of perfect fluids from scalar field theory
Guillermo Ballesteros, Denis Comelli, Luigi Pilo
The low-energy dynamics of relativistic continuous media is given by a shift-symmetric effective theory of four scalar fields. These scalars describe the embedding in spacetime of…
Massive and modified gravity as self-gravitating media
Guillermo Ballesteros, Denis Comelli, Luigi Pilo
We study the effective field theory that describes the low-energy physics of self-gravitating media. The field content consists of four derivatively coupled scalar fields that can…
Living with ghosts in Horava-Lifshitz gravity
S. Ramazanov, F. Arroja, M. Celoria +2
We consider the branch of the projectable Horava-Lifshitz model which exhibits ghost instabilities in the low energy limit. It turns out that, due to the Lorentz violating structur…
New Branches of Massive Gravity
Denis Comelli, Marco Crisostomi, Kazuya Koyama +2
The basic building block for Lorentz invariant and ghost free massive gravity is the square root of the combination , where is the inverse of the physical metri…
Nonderivative Modified Gravity: a Classification
Denis Comelli, Fabrizio Nesti, Luigi Pilo
We analyze the theories of gravity modified by a generic nonderivative potential built from the metric, under the minimal requirement of unbroken spatial rotations. Using the canon…
FRW Cosmological Perturbations in Massive Bigravity
D. Comelli, M. Crisostomi, L. Pilo
Cosmological perturbations of FRW solutions in ghost free massive bigravity, including also a second matter sector, are studied in detail. At early time, we find that sub horizon e…
Cosmology in General Massive Gravity Theories
Denis Comelli, Fabrizio Nesti, Luigi Pilo
We study the cosmology of general massive gravity theories with five propagating degrees of freedom. This large class of theories includes both the case with a residual Lorentz inv…
Massive gravity: a General Analysis
Denis Comelli, Fabrizio Nesti, Luigi Pilo
Massive gravity can be described by adding to the Einstein-Hilbert action a function V of metric components. By using the Hamiltonian canonical analysis, we find the most general f…
Weak Massive Gravity
Denis Comelli, Fabrizio Nesti, Luigi Pilo
We find a new class of theories of massive gravity with five propagating degrees of freedom where only rotations are preserved. Our results are based on a non-perturbative and back…
Degrees of Freedom in Massive Gravity
D. Comelli, M. Crisostomi, F. Nesti +1
We study in a systematic way a generic nonderivative (massive) deformation of general relativity using the Hamiltonian formalism. The number of propagating degrees of freedom is an…
Perturbations in Massive Gravity Cosmology
Marco Crisostomi, Denis Comelli, Luigi Pilo
We study cosmological perturbations for a ghost free massive gravity theory formulated with a dynamical extra metric that is needed to massive deform GR. In this formulation FRW ba…
Spherically Symmetric Solutions in Ghost-Free Massive Gravity
D. Comelli, M. Crisostomi, F. Nesti +1
Recently, a class of theories of massive gravity has been shown to be ghost-free. We study the spherically symmetric solutions in the bigravity formulation of such theories. In gen…
FRW Cosmology in Ghost Free Massive Gravity
D. Comelli, M. Crisostomi, F. Nesti +1
We study FRW homogeneous cosmological solutions in the recently found ghost free massive gravity. In previous works it was shown that when the additional extra metric, needed to ge…
Finite Energy of Black Holes in Massive Gravity
Denis Comelli, Marco Crisostomi, Fabrizio Nesti +1
In GR the static gravitational potential of a self-gravitating body goes as 1/r at large distances and any slower decrease leads to infinity energy. We show that in a class of four…
Stars and (Furry) Black Holes in Lorentz Breaking Massive Gravity
Denis Comelli, Fabrizio Nesti, Luigi Pilo
We study the exact spherically symmetric solutions in a class of Lorentz-breaking massive gravity theories, using the effective-theory approach where the graviton mass is generated…
Lorentz Breaking Massive Gravity in Curved Space
D. Blas, D. Comelli, F. Nesti +1
A systematic study of the different phases of Lorentz-breaking massive gravity in a curved background is performed. For tensor and vector modes, the analysis is very close to that…
Gravity Modification with Yukawa-type Potential: Dark Matter and Mirror Gravity
Zurab Berezhiani, Fabrizio Nesti, Luigi Pilo +1
The nature of the gravitational interaction between ordinary and dark matter is still open. Any deviation from universality or the Newtonian law also modifies the standard assumpti…
Exact Spherically Symmetric Solutions in Massive Gravity
Z. Berezhiani, D. Comelli, F. Nesti +1
A phase of massive gravity free from pathologies can be obtained by coupling the metric to an additional spin-two field. We study the gravitational field produced by a static spher…
Spontaneous Lorentz Breaking and Massive Gravity
Z. Berezhiani, D. Comelli, F. Nesti +1
We study a theory where the presence of an extra spin-two field coupled to gravity gives rise to a phase with spontaneously broken Lorentz symmetry. In this phase gravity is massiv…