Relativistic kinematics beyond Special Relativity

In the context of departures from Special Relativity written as a momentum power expansion in the inverse of an ultraviolet energy scale M, we derive the constraints that the relativity principle imposes between coefficients of a deformed composition law, dispersion relation, and transformation laws, at first order in the power expansion. In particular, we find that, at that order, the consistency of a modification of the energy-momentum composition law fixes the modification in the dispersion relation. We therefore obtain the most generic modification of Special Relativity that preserves the relativity principle at leading order in 1/M.Comment: Version with minor corrections, to appear in Phys. Rev.

K-essence Explains a Lorentz Violation Experiment

Recently, a state of the art experiment shows evidence for Lorentz violation in the gravitational sector. To explain this experiment, we investigate a spontaneous Lorentz violation scenario with a generalized scalar field. We find that when the scalar field is nonminimally coupled to gravity, the Lorentz violation induces a deformation in the Newtonian potential along the direction of Lorentz violation.Comment: 8 pages, the final version, discussion and references adde

Remarks on the consistency of minimal deviations from General Relativity

We study the consequences of the modification of the phase space structure of General Relativity imposed by breaking the full diffeomorphism invariance but retaining the time foliation preserving diffeomorphisms. We examine the different sectors in phase space that satisfy the new structure of constraints. For some sectors we find an infinite tower of constraints. In spite of that, we also show that these sectors allow for solutions, among them some well known families of black hole and cosmologies which fulfill all the constraints. We raise some physical concerns on the consequences of an absolute Galilean time, on the thermodynamical pathologies of such models and on their unusual vacuum structure.Comment: latex 28 pages, 1 figure. Added comments and a reference. Text improved

Correlation Study of the Simulation of Gemini Extravehicular Activity with Flight Results

Correlation study of simulation of Gemini extravehicular activity with flight result

Planck-scale modifications to Electrodynamics characterized by a space-like symmetry-breaking vector

In the study of Planck-scale ("quantum-gravity induced") violations of Lorentz symmetry, an important role was played by the deformed-electrodynamics model introduced by Myers and Pospelov. Its reliance on conventional effective quantum field theory, and its description of symmetry-violation effects simply in terms of a four-vector with nonzero component only in the time-direction, rendered it an ideal target for experimentalists and a natural concept-testing ground for many theorists. At this point however the experimental limits on the single Myers-Pospelov parameter, after improving steadily over these past few years, are "super-Planckian", {\it i.e.} they take the model out of actual interest from a conventional quantum-gravity perspective. In light of this we here argue that it may be appropriate to move on to the next level of complexity, still with vectorial symmetry violation but adopting a generic four-vector. We also offer a preliminary characterization of the phenomenology of this more general framework, sufficient to expose a rather significant increase in complexity with respect to the original Myers-Pospelov setup. Most of these novel features are linked to the presence of spatial anisotropy, which is particularly pronounced when the symmetry-breaking vector is space-like, and they are such that they reduce the bound-setting power of certain types of observations in astrophysics

Dirichlet boundary value problem for Chern-Simons modified gravity

Chern-Simons modified gravity comprises the Einstein-Hilbert action and a higher-derivative interaction containing the Chern-Pontryagin density. We derive the analog of the Gibbons-Hawking-York boundary term required to render the Dirichlet boundary value problem well-defined. It turns out to be a boundary Chern-Simons action for the extrinsic curvature. We address applications to black hole thermodynamics.Comment: 4 pages, revtex4, v2: added Refs., made one statement stronger, added footnote and added paragraph on single field inflatio

About Locality and the Relativity Principle Beyond Special Relativity

Locality of interactions is an essential ingredient of Special Relativity. Recently, a new framework under the name of relative locality \cite{AmelinoCamelia:2011bm} has been proposed as a way to consider Planckian modifications of the relativistic dynamics of particles. We note in this paper that the loss of absolute locality is a general feature of theories beyond Special Relativity with an implementation of a relativity principle. We give an explicit construction of such an implementation and compare it both with the previously mentioned framework of relative locality and the so-called Doubly Special Relativity theories.Comment: 10 pages, no figure

A Medieval Boom in the North-west Sahara: Evolving Oasis Landscapes in the Wadi Draa, Morocco (c.700–1500 AD)

Modern scholarship on the medieval Sahara has focused on a handful of famous entrepôt sites that have their origins in the 8th century or later, and as a result we still understand very poorly the nature and extent of Saharan oasis settlement and agriculture in the golden age of Saharan trade. This article presents the first securely dated chronology for oasis development in the north-west Sahara based on three seasons of archaeological survey and a comprehensive radiocarbon dating programme in the Wadi Draa, Morocco. The Draa Valley contains some of the largest, most populous and most productive oases in the Sahara, as well as serving as an important travel corridor for trading caravans coming from West Africa to access the Atlas passes and reach Marrakech. Focusing on evidence from a large zone of abandoned oases on the Kasr Bounou Plain, this article demonstrates that while oasis agriculture and settlement was taking place between the 4th–8th centuries—well before the Muslim conquest of Morocco—there was a significant increase in settlement and agricultural exploitation from the 9th century. This phenomenon is marked by the appearance of substantial mudbrick settlements, along with irrigation and field systems, and is coterminous with the development of the medieval trading entrepôt of Sijilmasa. A settlement boom and significant investment in irrigated oasis agriculture occurred between the 11th and 13th centuries, contemporary with Almoravid and Almohad rule of the Draa, followed by a retraction and abandonment of much of the oasis by the 16th century. The new evidence from the Draa challenges the long-held belief that sedentarization and irrigated oasis agriculture were unique to the medieval period in the north-west Sahara

Induced deformation of the canonical structure and UV/IR duality in (1+1)D(1+1)D

The purpose of this work is two fold. Working in the framework of $(1+1)D$ Lorentz violating field theories we will investigate in the first place the general claim that fermionic interactions may be equivalent to a deformation of the canonical structure of the theory. Second the deformed theory will be studied using duality reasoning to address the behavior of the Infra-Red and Ultra-Violet regimes.Comment: revtex4 file, 19 pages, typos corrected, reference added, appendix added, accepted for publication in Physical Review

Limits on isotropic Lorentz violation in QED from collider physics

We consider the possibility that Lorentz violation can generate differences between the limiting velocities of light and charged matter. Such effects would lead to efficient vacuum Cherenkov radiation or rapid photon decay. The absence of such effects for 104.5 GeV electrons at the Large Electron Positron collider and for 300 GeV photons at the Tevatron therefore constrains this type of Lorentz breakdown. Within the context of the standard-model extension, these ideas imply an experimental bound at the level of -5.8 x 10^{-12} <= \tilde{\kappa}_{tr}-(4/3)c_e^{00} <= 1.2 x 10^{-11} tightening existing laboratory measurements by 3-4 orders of magnitude. Prospects for further improvements with terrestrial and astrophysical methods are discussed.Comment: Replaced with final version published in PR