Null energy condition and superluminal propagation
Sergei Dubovsky,Sergei Dubovsky,Thomas Gregoire,Thomas Gregoire,Alberto Nicolis,Riccardo Rattazzi +5 more
Reads0
Chats0
TLDR
In this paper, the null energy condition is violated in a large class of situations, including isotropic solids and fluids relevant for cosmology, and the existence of superluminal modes is shown to imply the presence of instabilities.Abstract:
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.read more
Citations
More filters
K-essence: cosmology, causality and emergent geometry
TL;DR: In this article, the authors propose a method to solve the problem of "uniformity" and "uncertainty" in the context of health care, and propose a solution.
Journal ArticleDOI
Pre-inflationary spacetime in string cosmology
TL;DR: In this article, it was shown that the spacetime geometry of the early universe is stable in the Seiberg-Witten sense, and that it is possible to avoid disaster at all times.
Journal ArticleDOI
Black Hole Thermodynamics and Massive Gravity
Fabio Capela,Peter Tinyakov +1 more
TL;DR: In this paper, the authors consider the generalized laws of thermodynamics in massive gravity and devise black hole merger processes in which the total entropy of the system decreases and the zero-temperature extremal black hole is created.
Posted Content
Classical and semi-classical energy conditions
Prado Martín-Moruno,Matt Visser +1 more
TL;DR: The standard energy conditions of classical general relativity are (mostly) linear in the stress-energy tensor, and have clear physical interpretations in terms of geodesic focussing, but suffer the significant drawback that they are often violated by semi-classical quantum effects.
Journal ArticleDOI
Stability of the aether
William Donnelly,Ted Jacobson +1 more
TL;DR: In this article, the requirements for stability of a Lorentz violating theory are analyzed and it is shown that the theory can be stable when its modes have any phase velocity, rather than only the speed of light.
References
More filters
Book
The Large Scale Structure of Space-Time
TL;DR: In this paper, the authors discuss the General Theory of Relativity in the large and discuss the significance of space-time curvature and the global properties of a number of exact solutions of Einstein's field equations.
Journal ArticleDOI
Type Ia supernova discoveries at z > 1 from the Hubble Space Telescope: Evidence for past deceleration and constraints on dark energy evolution
Adam G. Riess,Louis-Gregory Strolger,John L. Tonry,Stefano Casertano,Henry C. Ferguson,Bahram Mobasher,Peter Challis,Alexei V. Filippenko,Saurabh Jha,Weidong Li,Ryan Chornock,Robert P. Kirshner,Bruno Leibundgut,Mark Dickinson,Mario Livio,Mauro Giavalisco,Charles C. Steidel,Txitxo Benítez,Zlatan Tsvetanov +18 more
TL;DR: For a flat universe with a cosmological constant, the transition between the two epochs is constrained to be at z = 0.46 ± 0.13 as mentioned in this paper, and w = -1.02 ± (and w < -0.76 at the 95% confidence level) for an assumed static equation of state of dark energy.
Journal ArticleDOI
Type Ia Supernova Discoveries at z>1 From the Hubble Space Telescope: Evidence for Past Deceleration and Constraints on Dark Energy Evolution
Adam G. Riess,Louis-Gregory Strolger,John L. Tonry,Stefano Casertano,Henry C. Ferguson,Bahram Mobasher,Peter Challis,Alexei V. Filippenko,Saurabh Jha,Weidong Li,Ryan Chornock,Robert P. Kirshner,Bruno Leibundgut,Mark Dickinson,Mario Livio,Mauro Giavalisco,Charles C. Steidel,Narciso Benítez,Zlatan Tsvetanov +18 more
TL;DR: In this article, the first conclusive evidence for cosmic deceleration that preceded the current epoch of cosmic acceleration was provided by the discovery of 16 Type Ia supernovae with the Hubble Space Telescope (HST).
Journal ArticleDOI
4D Gravity on a Brane in 5D Minkowski Space
TL;DR: In this article, the authors propose a mechanism by which four-dimensional Newtonian gravity emerges on a 3-brane in 5D Minkowski space with an infinite size extra dimension.