Results 51 to 60 of about 9,886 (203)

k-Essence, superluminal propagation, causality and emergent geometry [PDF]

, 2007
The k-essence theories admit in general the superluminal propagation of the perturbations on classical backgrounds. We show that in spite of the superluminal propagation the causal paradoxes do not arise in these theories and in this respect they are not
A. Adams, A. De Felice, A. Gruzinov, A. Vikman, A.A. Sen, A.D. Dolgov, A.D. Rendall, Alexander Vikman, B. Barbashov, B. Barbashov, C. Armendariz-Picon, C. Barcelo, C. Bonvin, D. Blas, D. Blochinzev, E. Babichev, E. Babichev, E.I. Buchbinder, Eugeny Babichev, G. Gibbons, G.B. Whitham, G.N. Felder, G.W. Gibbons, G.W. Gibbons, G.W. Gibbons, H. Friedrich, H. Nastase, I.G. Petrovsky, I.Y. Aref'eva, J. Leray, J.-P. Bruneton, K. Landsteiner, L. Landau, L.J. Wang, M. Novello ., O. Gron, P. Creminelli, P. Creminelli, R. Wald, R.C. Tolman, R.L. Mallett, R.P. Woodard, S.W. Hawking, T.J. Hollowood, V. Mukhanov, V.F. Mukhanov, V.S. Vladimirov, Viatcheslav Mukhanov, W.J. van Stockum, X.-H. Jin   +49 more
core   +1 more source

Jet stability and the generation of superluminal and stationary components

, 2001
We present a numerical simulation of the response of an expanding relativistic jet to the ejection of a superluminal component. The simulation has been performed with a relativistic time-dependent hydrodynamical code from which simulated radio maps are ...
Alan P. Marscher, Antonio Alberdi, Iván Agudo, José-Luis Gómez, José-María Ibáñez, José-María Martí, Marti J. M., Miguel-Angel Aloy, Philip E. Hardee   +8 more
core   +1 more source

On causality and superluminal behavior in classical field theories. Applications to k-essence theories and MOND-like theories of gravity [PDF]

, 2006
Field theories whose full action is Lorentz invariant (or diffeomorphism invariant) can exhibit superluminal behaviors through the breaking of local Lorentz invariance. Quantum induced superluminal velocities are well-known examples of this effect.
Bruneton, Jean-Philippe
core   +4 more sources

Studies of relativistic effects with radioastron space mission [PDF]

Serbian Astronomical Journal, 2007
In the review we discuss possible studies of GR phenomena such as gravitational microlensing and shadow analysis with the forthcoming RadioAstron space mission.
Zakharov A.F.
doaj   +1 more source

Superluminal Effects and Bulk Relativistic Motion [PDF]

Symposium - International Astronomical Union, 1984
The observational status of superluminal radio sources is reviewed, and the results for one well-studied source (3C 345) are discussed in detail. We discuss the relativistic-beam model of superluminal sources, and concentrate on one aspect, namely the geometric constraints provided by combined X-ray and proper-motion measurements.
M. H. Cohen, S. C. Unwin
openaire   +1 more source

Multi-frequency VLBA study of the blazar S5 0716+714 during the active state in 2004: I. Inner jet kinematics

, 2008
We observed the blazar \object{0716+714} with the VLBA during its active state in 2003-2004. In this paper we discuss multi-frequency analysis of the inner jet (first 1 mas) kinematics.
Agudo, Bach, Despringre, E. A. Rastorgueva, E. Valtaoja, Fuhrmann, Gomez, Hovatta, Jorstad, K. V. Sokolovsky, K. Wiik, L. O. Takalo, Montagni, Nesci, Nilsson, Ostorero, Ostorero, Quirrenbach, Sagar, Savolainen, Savolainen, Sol, T. Savolainen, Villata, Wagner, Y. N. Vetukhnovskaya   +25 more
core   +1 more source

Cloaking and Antennas: From Theoretical Paradigms to Next‐Generation Intelligent Systems

Advanced Optical Materials, Volume 13, Issue 33, November 25, 2025.
The inception of electromagnetic cloaking sparked an immediate question: Can antennas be made invisible? Two decades later, this review charts the intertwined progress of major cloaking strategies (from transformation optics to scattering cancellation), metasurface technology, and their application to antennas, revealing how AI‐enabled devices are ...
Helen Guo, Xun Li
wiley   +1 more source

Faster than Light Photons in Gravitational Fields II - Dispersion and Vacuum Polarisation

, 2002
Vacuum polarisation in QED in a background gravitational field induces interactions which effectively violate the strong equivalence principle and affect the propagation of light.
Adler, Barton, Barvinsky, Barvinsky, Barvinsky, Bassett, Bondi, Brillouin, Cai, Chandresekhar, Cho, Courant, d'Inverno, Daniels, Daniels, Dittrich, Dittrich, Dolgov, Dolgov, Dolgov, Drummond, Drummond, Friedlander, G.M. Shore, Gibbons, Gibbons, Hau, Hawking, Khriplovich, Konstantinov, Lafrance, Latorre, Leontovich, Liberati, Liberati, Sachs, Scharnhorst, Schneider, Shore, Shore, Tsai, Tsai, Visser, Wang   +43 more
core   +1 more source

On superluminal motions in photon and particle tunnellings [PDF]

Physics Letters A, 1998
It is shown that the Hartman-Fletcher effect is valid for all the known expressions of the mean tunnelling time, in various nonrelativistic approaches, for the case of finite width barriers without absorption. Then, we show that the same effect is not valid for the tunnelling time mean-square fluctuations.
Jakiel, J., Olkhovsky, V. S., Recami, Erasmo   +2 more
openaire   +2 more sources

Space–time graded‐index interfaces and related chirping

Nanophotonics, Volume 14, Issue 19, Page 3211-3221, September 2025.
Abstract Space–time modulated systems have recently emerged as a powerful platform for dynamic electromagnetic processing in both space and time. Most of the related research so far has assumed abrupt parameter profiles. This paper extends the field to generalized graded‐index (GRIN) interfaces, which are both more practical than ideal profiles and ...
Zhiyu Li, Xikui Ma, Klaas De Kinder, Amir Bahrami, Christophe Caloz   +4 more
wiley   +1 more source