Modified Maxwell Theory Research Articles

Greybody factor for a non accelerated charged modified black hole in anti-de sitter regime

This paper investigates the greybody factor for a non accelerated black hole with modified Maxwell electrodynamics in an anti-de Sitter regime. For this purpose, we compute the radial equation for a massless scalar field with the help of Klein–Gordon equation. We then formulate effective potential by transforming this equation into Schrodinger wave equation. We analyze the graphical behavior of effective potential for different values of mass, parameter characterizing the modified Maxwell theory, anti-de Sitter radius and electromagnetic charge parameters. The exact solutions are computed at two different horizons, i.e., event and cosmological horizons through the radial equation. Furthermore, we match the obtained solutions in an intermediate regime to enhance feasibility of the greybody factor over the entire domain and check its behavior graphically. It is found that the greybody factor has a direct relation with the radius, electromagnetic charge as well as angular momentum of the black hole and an inverse relation with the anti-de Sitter radius and modification parameter. We conclude that the modified Maxwell solution reduces the emission rate of the black hole.

Relativistic scalar Aharonov–Bohm effect for a neutral particle under Lorentz symmetry breaking effects in the cosmic string space–time

We search for relativistic quantum phases for a Dirac neutral particle with a permanent magnetic dipole moment in the cosmic string space–time under the effects of the violation of the Lorentz symmetry. This general relativity background is built based on the modified Maxwell theory coupled to gravity. Hence, we analyze analogues of the scalar Aharonov–Bohm effect for neutral particles in two different scenarios of the Lorentz symmetry violation in the cosmic string space–time.

One-dimensional experimental investigation and simulation on the transport characteristics of heterogeneous colloidal Mg(OH)2 in saturated porous media

Recent laboratory studies have shown the injection of colloidal Mg(OH)2 could provide an effective and low cost alternative as a long term pH buffering system. In this study, Mg(OH)2 was modified by Tween 80 and SDS and the modified suspension had the properties of high stability, small particle size (the average particle diameter D50 was smaller than 1 μm) and negative charge (zeta potential = −14.26 mV at pH = 10.54). All of these properties demonstrated that colloidal Mg(OH)2 may have satisfactory transport performance in porous media. However, colloidal Mg(OH)2 is heterogeneous colloids with a high concentration, the transport performance in porous media is significantly different from homogeneous colloids, and the model simulation is relatively complex. To solve these problems, method of calculus combined with colloid filtration theory (CFT), T-E equation and modified Maxwell theory was used to simulate the transport performance of high concentration of Mg(OH)2 colloids. Results indicated that the observed experimental results matched well with the model simulations. Hydrodynamic force, DLVO attractive force and colloid diffusion are the major factors controlling the migration of colloidal Mg(OH)2 in porous media and could quantitatively describe the influence of injection velocity, porous media size and ionic strength on colloidal Mg(OH)2 transport properties by model calculation.

Radiation reaction in a Lorentz-violating modified Maxwell theory

We study the radiation reaction in Lorentz-violating electrodynamics [D. Colladay and V. Alan Kostelecky, Phys. Rev. D 58, 116002 (1998)]. We explore the possible modification whatsoever present in the radiation reaction force experienced by an accelerating charge in the modified Maxwell theory. However, it turns out that radiation reaction receives no change due to Lorentz violation, whereas electromagnetic mass manifests anisotropy.

Relativistic Anandan quantum phase and the Aharonov–Casher effect under Lorentz symmetry breaking effects in the cosmic string spacetime

From the modified Maxwell theory coupled to gravity, we establish a possible scenario of the violation of the Lorentz symmetry and write an effective metric for the cosmic string spacetime. Then, we investigate the arising of an analogue of the Anandan quantum phase for a relativistic Dirac neutral particle with a permanent magnetic dipole moment in the cosmic string spacetime under Lorentz symmetry breaking effects. Besides, we analyse the influence of the effects of the Lorentz symmetry violation and the topology of the defect on the Aharonov–Casher geometric quantum phase in the nonrelativistic limit.

Lorentz symmetry breaking effects on relativistic EPR correlations

Lorentz symmetry breaking effects on relativistic EPR (Einstein-Podolsky-Rosen) correlations are discussed. From the modified Maxwell theory coupled to gravity, we establish a possible scenario of the Lorentz symmetry violation and write an effective metric for the Minkowski spacetime. Then, we obtain the Wigner rotation angle via the Fermi-Walker transport of spinors and consider the WKB ((Wentzel-Kramers-Brillouin) approximation in order to study the influence of Lorentz symmetry breaking effects on the relativistic EPR correlations.

Parton-model calculation of a nonstandard decay process in isotropic modified Maxwell theory

We have performed a calculation in the parton-model approximation of a nonstandard decay process in isotropic modified Maxwell theory coupled to standard Dirac theory, with a single Lorentz-violating parameter $\kappa$ in the photonic sector. Previous calculations of this process (vacuum Cherenkov radiation by a proton for the theory with $\kappa>0$) were performed for pointlike particles, and an upper bound on $\kappa$ at the $10^{-19}$ level was obtained from experimental data on ultra-high-energy cosmic rays. The parton-model results change the decay rate by about an order of magnitude but give the same upper bound on $\kappa$ because the threshold energy is unchanged. The previous point-particle calculation of photon decay into an electron-positron pair for the theory with $\kappa<0$ remains valid, and experimental results on cosmic gamma rays provide a lower bound on $\kappa$ at the $-10^{-15}$ level.

Geometric quantum phases from Lorentz symmetry breaking effects in the cosmic string spacetime

By starting from the modified Maxwell theory coupled to gravity, the arising of geometric quantum phases in the relativistic and nonrelativistic quantum dynamics of a Dirac neutral particle from the effects of the violation of the Lorentz symmetry in the cosmic string spacetime is investigated. It is shown that the Dirac equation can be written in terms of an effective metric and a relativistic geometric phase stems from the topology of the cosmic string spacetime and the Lorentz symmetry breaking effects. Further, the nonrelativistic limit of the Dirac equation is discussed and it is shown that both Lorentz symmetry breaking effects and the topology of the defect yields a phase shift in the wave function of the nonrelativistic spin-1/2 particle.

Quantum field theory based on birefringent modified Maxwell theory

In the current paper the properties of a birefringent Lorentz-violating extension of quantum electrodynamics is considered. The theory results from coupling modified Maxwell theory, which is a CPT-even Lorentz-violating extension of the photon sector, to a Dirac theory of standard spin-1/2 particles. It is then restricted to a special birefringent case with one nonzero Lorentz-violating coefficient. The modified dispersion laws of electromagnetic waves are obtained plus their phase and group velocities are considered. After deriving the photon propagator and the polarization vectors for a special momentum configuration we prove both unitarity at tree-level and microcausality for the quantum field theory based on this Lorentz-violating modification. These analytical proofs are done for a spatial momentum with two vanishing components and the proof of unitarity is supported by numerical investigations in case all components are nonvanishing. The upshot is that the theory is well-behaved within the framework of our assumptions where there is a possible issue for negative Lorentz-violating coefficients. The paper shall provide a basis for the future analysis of alternative birefringent quantum field theories.

Analysis of the consistency of parity-odd nonbirefringent modified Maxwell theory

There exist two deformations of standard electrodynamics that describe Lorentz symmetry violation in the photon sector: CPT-odd Maxwell-Chern-Simons theory and CPT-even modified Maxwell theory. In this article, we focus on the parity-odd nonbirefringent sector of modified Maxwell theory. It is coupled to a standard Dirac theory of massive spin-1/2 fermions resulting in a modified quantum electrodynamics (QED). This theory is discussed with respect to properties such as microcausality and unitarity, where it turns out that these hold. Furthermore, a priori, the limit of the theory for vanishing Lorentz-violating parameters seems to be discontinuous. Since it is not clear, whether this is a gauge artifact, the cross section for a physical process - modified Compton scattering - is calculated numerically. Despite the numerical instabilities occurring for scattering of unpolarized electrons off polarized photons in the second physical polarization state, it is shown that for Lorentz-violating parameters much smaller than 1 the modified theory approaches standard QED, which is strengthened by analytical investigations. Hence, the theory proves to be consistent, at least with regard to the investigations performed. This leads to the interesting result of having a well-defined parity-odd extension of QED.

Models for low-energy Lorentz violation in the photon sector: Addendum to ‘Consistency of isotropic modified Maxwell theory’

In a previous article, Klinkhamer and Schreck (2011) [1], we established the consistency of isotropic modified Maxwell theory for a finite range of the Lorentz-violating parameter κ ˜ tr , which includes both positive and negative values of κ ˜ tr . As an aside, we mentioned the existence of a physical model which, for low-energy photons, gives rise to isotropic modified Maxwell theory with a positive parameter κ ˜ tr (corresponding to a “slow” photon). Here, we present a related model which gives rise to isotropic modified Maxwell theory with a negative parameter κ ˜ tr (corresponding to a “fast” photon). Both models have an identical particle content, photon and Dirac particles, but differ in the type of spacetime manifold considered.

Consistency of isotropic modified Maxwell theory: Microcausality and unitarity

The Lorentz-violating isotropic modified Maxwell theory minimally coupled to standard Dirac theory is characterized by a single real dimensionless parameter which is taken to vanish for the case of the standard (Lorentz-invariant) theory. A finite domain of positive and negative values of this Lorentz-violating parameter is determined, in which microcausality and unitarity hold. The main focus of this article is on isotropic modified Maxwell theory, but similar results for an anisotropic nonbirefringent case are presented in Appendix A.

Potential sensitivities to Lorentz violation from nonbirefringent modified Maxwell theory of Auger, HESS, and CTA

Present and future ultra-high-energy-cosmic-ray facilities (e.g., the South and North components of the Pierre Auger Observatory) and TeV-gamma-ray telescope arrays (e.g., HESS and CTA) have the potential to set stringent bounds on the nine Lorentz-violating parameters of nonbirefringent modified Maxwell theory minimally coupled to standard Dirac theory. A concrete example is given how to obtain, in the coming decennia, two-sided bounds on the eight anisotropic parameters at the ${10}^{\ensuremath{-}20}$ level and an upper (lower) bound on the single isotropic parameter at the $+{10}^{\ensuremath{-}20}$ ($\ensuremath{-}{10}^{\ensuremath{-}16}$) level. Comparison is made with existing and potential direct bounds from laboratory experiments.

EFFECTS OF CHERN–SIMONS CORRECTIONS ON CONSERVED QUANTITIES OF RELATIVISTIC FLUID

We consider relativistic fluid flow under Chern–Simons modified Maxwell theory and under Chern–Simons modified gravity theory. We take account of the effects of Chern–Simons corrections on the quantities of fluid flow that is conserved without the Chern–Simons corrections. We find that the conservations of several quantities are generally broken by the Chern–Simons corrections.

Lorentz violation and black-hole thermodynamics: Compton scattering process

A Lorentz-noninvariant modification of quantum electrodynamics (QED) is considered, which has photons described by the nonbirefringent sector of modified Maxwell theory and electrons described by the standard Dirac theory. These photons and electrons are taken to propagate and interact in a Schwarzschild spacetime background. For appropriate Lorentz-violating parameters, the photons have an effective horizon lying outside the Schwarzschild horizon. A particular type of Compton scattering event, taking place between these two horizons (in the photonic ergoregion) and ultimately decreasing the mass of the black hole, is found to have a nonzero probability. These events perhaps allow for a violation of the generalized second law of thermodynamics in the Lorentz-noninvariant theory considered.

Lorentz violation and black-hole thermodynamics

We consider nonstandard photons from nonbirefringent modified Maxwell theory and discuss their propagation in a fixed Schwarzschild spacetime background. This particular modification of Maxwell theory is Lorentz-violating and allows for maximal photon velocities differing from the causal speed c of the asymptotic background spacetime. In the limit of geometrical optics, light rays from modified Maxwell theory are found to propagate along null geodesics in an effective metric. We observe that not every Lorentz-violating theory with multiple maximal velocities different from the causal speed c modifies the notion of the event horizon, contrary to naive expectations. This result implies that not every Lorentz-violating theory with multiple maximal velocities necessarily leads to a contradiction with the generalized second law of thermodynamics.

Addendum: Ultrahigh-energy cosmic-ray bounds on nonbirefringent modified Maxwell theory

Nonbirefringent modified-Maxwell theory, coupled to standard Dirac particles, involves nine dimensionless parameters, which can be bounded by the inferred absence of vacuum Cherenkov radiation for ultrahigh-energy cosmic rays (UHECRs). With selected UHECR events, two-sided bounds on the eight nonisotropic parameters are obtained at the 10{sup -18} level, together with an improved one-sided bound on the single isotropic parameter at the 10{sup -19} level.

Ultrahigh-energy cosmic-ray bounds on nonbirefringent modified Maxwell theory

A particularly simple Lorentz-violating modification of the Maxwell theory of photons maintains gauge invariance, $CPT$, and renormalization. This modified Maxwell theory, coupled to standard Dirac particles, involves 19 dimensionless ``deformation parameters.'' Ten of these parameters lead to birefringence and are already tightly constrained by astrophysics. New bounds on the remaining nine nonbirefringent parameters can be obtained from the absence of vacuum Cherenkov radiation for ultrahigh-energy cosmic rays (UHECRs). Using selected UHECR events recorded at the Pierre Auger Observatory and assigning pseudorandom directions (i.e., assuming large-scale isotropy), Cherenkov bounds are found at the ${10}^{\ensuremath{-}18}$ level, which improve considerably upon current laboratory bounds. Future UHECR observations may reduce these Cherenkov bounds to the ${10}^{\ensuremath{-}23}$ level.