Null energy condition and superluminal propagation

By S. Dubovsky, T. Grégoire, Alberto Nicolis, R. Rattazzi. 2005

399 citations recorded by the source corpus.

We study whether a violation of the null energy condition necessarily implies the presence of instabilities. We prove that this is the case in a large class of situations, including isotropic solids and fluids relevant for cosmology. On the other hand we present several counter-examples of consistent effective field theories possessing a stable background where the null energy condition is violated. Two necessary features of these counter-examples are the lack of isotropy of the background and the presence of superluminal modes. We argue that many of the properties of massive gravity can be understood by associating it to a solid at the edge of violating the null energy condition. We briefly analyze the difficulties of mimicking u H > 0 in scalar tensor theories of gravity.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics, Statistical and Nonlinear Physics

View Paper: https://www.semanticscholar.org/paper/06ee24b6ebda3126244df4c9c566d52f0636192e

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

In Nuclear and High Energy Physics

In Statistical and Nonlinear Physics

Citations in the corpus

Solid Inflation (2012, methodology): “10)—whose structure is protected by the volume-preserving diff symmetry— features vanishing propagation speed for the transverse phonons [8, 9], as can be checked explicitly in (2.”
Holographic complexity in Vaidya spacetimes. Part II (2018, background): “of ‘ (and in this sense it represents a redundancy in the description) but we will keep it to 4There is an enormous literature on the subject of the action principle for relativistic uids, e.g., see [69,70] for further discussions of perfect uids and [71{75] for recent developments in describing dis”
A Measure of de Sitter entropy and eternal inflation (2007, background): “In a very broad class of systems, including conventional relativistic fluids, these instability can be proven [55] to originate from the“clock and rod” sector of the system—one of the Goldstones of the spontaneously broken space-time translations is either a ghost or has an imaginary propagation spe”
Cosmology and Fundamental Physics with the Euclid Satellite (2012, background): “It is well known that any such background made up of either a perfect fluid or a minimally coupled scalar field suffers from gradient instabilities, ghosts or both [435].”
Massive Gravity (2014, background): “The physical interpretation of these superluminal propagations was studied in other non-Galileon models in [199, 43] and see [206, 469] for their potential connection with classicalization [214, 213, 205, 11].”
Galilean Genesis: An Alternative to inflation (2010, background): “It is worth emphasizing that the NEC is usually taken for granted not due to lack of imagination, but because of its exceptional robustness—it is especially hard to construct consistent effective field theories that violate it [1].”
Imperfect Dark Energy from Kinetic Gravity Braiding (2010, result): “[56], in the model presented in section §5 there is a period during which the null-energy condition is violated on an isotropic background while the speed of sound is sublumninal, see Figs 4 or 5.”
New Ekpyrotic Cosmology (2007, neutral): “gy condition (NEC). This is no small feat, however, since non-singular theories that violate the NEC generally 1 suﬀer from violent instabilities, such as ghosts or tachyons of arbitrarily large mass [8]. In the Big Bang/Big Crunch ekpyrotic scenario of [2, 3], as well as in the cyclic model [4], on”
Averaged null energy condition from causality (2016, background): “1 The connection between causality and null energy is well known in the gravitational context (see for example [20, 21] and the references above) and in AdS/CFT (see for example [22, 23]).”
Energy’s and amplitudes’ positivity (2009, background): “[1] for a discussion about this point.”
Cosmological non-linearities as an effective fluid (2010, background): “In fact, from a Lagrangian/Hamiltonian viewpoint the mechanical degrees of freedom parameterizing a fluid’s configuration space are three scalar fields φ(x, t), I = 1, 2, 3—the internal coordinates of the fluid element located at x at time t [21].”
The imperfect fluid behind kinetic gravity braiding (2011, background): “[84]; for a recent development in this direction see e.”
Zoology of condensed matter: framids, ordinary stuff, extra-ordinary stuff (2015, background): “of ordinary matter (solids, fluids, superfluids, supersolids), where each Goldstone field in the Lagrangian carries at least one derivative, and so at the two-derivative level there are no interactions [3, 26].”