scholarly journals Introducing causality violation for improved DPOAE component unmixing

2018 ◽  
Author(s):  
Arturo Moleti ◽  
Renata Sisto ◽  
Christopher A. Shera
Keyword(s):  
Causality Violation

scholarly journals KINKS, ENERGY CONDITIONS AND CLOSED TIMELIKE CURVES

2000 ◽  
Vol 09 (05) ◽  
pp. 531-541 ◽  
Author(s):  
PEDRO F. GONZÁLEZ-DÍAZ
Keyword(s):  
Energy Condition ◽  
Weak Energy Condition ◽  
Energy Conditions ◽  
Closed Timelike Curves ◽  
Causality Violation ◽  
Incoherent Radiation ◽  
Cylindrically Symmetric ◽  
Cylindrically Symmetric Spacetime ◽  
Geodesically Complete ◽  
Symmetric Spacetime

A link between the possibility of extending a geodesically incomplete kinked spacetime to a spacetime which is geodesically complete and the energy conditions is discussed for the case of a cylindrically-symmetric spacetime kink. It is concluded that neither the strong nor the weak energy condition can be satisfied in the four-dimensional example, though the latter condition may survive on the transversal sections of such a spacetime. It is also shown that the matter which propagates quantum-mechanically in a kinked spacetime can always be trapped by closed timelike curves, but signaling connections between that matter and any possible observer can only be made of totally incoherent radiation, so preventing observation of causality violation.

Causality Violation and Non-local Generalization of the Lorentz-Dirac Equation

1977 ◽  
Vol 32 (3-4) ◽  
pp. 319-326
Author(s):  
P. Alber ◽  
W. Heudorfer ◽  
M. Sorg
Keyword(s):  
Dirac Equation ◽  
Equation Of Motion ◽  
Local Theory ◽  
Constant Force ◽  
Dirac Theory ◽  
Local Equation ◽  
Causality Violation ◽  
Finite Duration ◽  
Non Local

AbstractIt is demonstrated by a concrete example (constant force of finite duration) that the recently proposed, non-local equation of motion for the radiating electron does exhibit the effect of causality violation. This phenomenon, which occurs in the non-local theory in form of self-oscillations, is however less severe than in the Lorentz-Dirac theory, if only physically reasonable forces are admitted.

Faster-than-light group velocities and causality violation

1970 ◽  
Vol 316 (1527) ◽  
pp. 515-524 ◽  
Keyword(s):  
Wave Equations ◽  
Signal Propagation ◽  
Necessary Condition ◽  
Speed Of Light ◽  
Frequency Range ◽  
Classical Analysis ◽  
Causality Violation ◽  
Light Group ◽  
Group Velocities ◽  
Faster Than Light

The classical analysis of Brillouin and Sommerfeld has shown that the appearance, in some frequency range, of group velocities in excess of the speed of light does not imply causality violation. The group velocity is not always identical with the velocity of signal propagation. We show that a necessary condition for causality violation is that the infinite- frequency limit of the phase velocity shall exceed the speed of light. Application of the theorem leads to the conclusions ( a ) that all Lorentz-invariant wave equations (and in particular the Feinberg ‘tachyon’) are causal, and ( b ) that the quasi-acoustic branch of the Bludman-Ruderman model is causal.

Weakly coupled gravity beyond general relativity

2015 ◽  
Vol 24 (12) ◽  
pp. 1544031 ◽  
Author(s):  
Xián O. Camanho ◽  
José D. Edelstein ◽  
Alexander Zhiboedov
Keyword(s):  
General Relativity ◽  
Time Delay ◽  
Wave Spectrum ◽  
Riemann Tensor ◽  
Spin States ◽  
Causality Violation ◽  
Novel Structure ◽  
Weakly Coupled ◽  
Point Vertex ◽  
Higher Spin

We explore four-dimensional (4D) weakly coupled gravity beyond general relativity in an on-shell language, focusing on the graviton three-point vertex. This admits a novel structure which can be attributed to a term cubic in the Riemann tensor. We consider a generalization of the Shapiro time delay experiment that involves polarized gravitons and show that the new vertex leads to causality violation. Fixing the problem demands the inclusion of an infinite tower of massive higher spin states. Perturbative string theory provides an example of this phenomenon, the only known so far. Interestingly enough, the same argument being applied to inflation suggests that stringy signatures may be hidden in the non-Gaussianities of the primordial gravity wave spectrum.

Causality violation in spatially closed space-times

1983 ◽  
Vol 15 (2) ◽  
pp. 165-172 ◽  
Author(s):  
Gregory J. Galloway
Keyword(s):  
Closed Space ◽  
Causality Violation

scholarly journals Causality violation and naked time machines in AdS5

2001 ◽  
Vol 2001 (05) ◽  
pp. 014-014 ◽  
Author(s):  
Marco M Caldarelli ◽  
Dietmar Klemm ◽  
Wafic A Sabra
Keyword(s):  
Causality Violation ◽  
Time Machines

scholarly journals BLACK HOLES, ENTROPY BOUND AND CAUSALITY VIOLATION

2009 ◽  
Vol 24 (18n19) ◽  
pp. 3584-3591 ◽  
Author(s):  
I. P. NEUPANE
Keyword(s):  
Black Hole ◽  
Classical Limit ◽  
Gauge Theories ◽  
Black Hole Entropy ◽  
Einstein Gravity ◽  
Entropy Density ◽  
Causality Violation ◽  
High Energies ◽  
Gravity Duality ◽  
Black Hole Solutions

The gauge theory - gravity duality has provided us a way of studying QCD at high energies or short distances from straightforward calculations in classical general relativity. Among numerous results obtained so far, one of the most striking is the universality of the ratio of the shear viscosity to the entropy density. For all gauge theories with Einstein gravity dual this ratio has been found to be η/s = 1/4π. In this note, we consider higher curvature-corrected black hole solutions for which η/s can be smaller than 1/4π, thus violating the conjecture bound. Here we shall argue that the Gauss-Bonnet gravity and (Riemann)2 gravity theories, in particular, provide concrete examples in which inconsistency of a theory, such as a violation of microcausality at short distances, and a classical limit on black hole entropy are correlated.

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