scholarly journals Gravitational waves propagation in nondynamical Chern–Simons gravity

2017 ◽  
Vol 26 (13) ◽  
pp. 1750148
Author(s):  
A. Martín-Ruiz ◽  
L. F. Urrutia
Keyword(s):  
Surface Layer ◽  
Domain Wall ◽  
Gravitational Waves ◽  
Electromagnetic Waves ◽  
Condensed Matter ◽  
Additional Contribution ◽  
Reflection And Transmission ◽  
First Derivative ◽  
Waves Propagation ◽  
Chern Simons

We investigate the propagation of gravitational waves in linearized Chern–Simons (CS) modified gravity by considering two nondynamical models for the coupling field [Formula: see text]: (i) a domain wall and (ii) a surface layer of [Formula: see text], motivated by their relevance in condensed matter physics. We demonstrate that the metric and its first derivative become discontinuous for a domain wall of [Formula: see text], and we determine the boundary conditions by realizing that the additional contribution to the wave equation corresponds to one of the self-adjoint extensions of the D'Alembert operator. Nevertheless, such discontinuous metric satisfies the area matching conditions introduced by Barrett. On the other hand, the propagation through a surface layer of [Formula: see text] behaves similarly to the propagation of electromagnetic waves in CS extended electrodynamics. In both cases, we calculate the corresponding reflection and transmission amplitudes. As a consequence of the distributional character of the additional terms in the equations that describe wave propagation, the results obtained for the domain wall are not reproduced when the thickness of the surface layer goes to zero, as one could naively expect.

scholarly journals Tunable dynamical magnetoelectric effect in antiferromagnetic topological insulator MnBi2Te4 films

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Tongshuai Zhu ◽  
Huaiqiang Wang ◽  
Haijun Zhang ◽  
Dingyu Xing
Keyword(s):  
Topological Insulator ◽  
Condensed Matter ◽  
Simons Theory ◽  
Spin Wave Excitations ◽  
Axion Field ◽  
Chern Simons ◽  
Related Compounds ◽  
The Universe ◽  
Crystalline Symmetry ◽  
Chern Simons Theory

AbstractAxion was postulated as an elementary particle to solve the strong charge conjugation and parity puzzle, and later axion was also considered to be a possible component of dark matter in the universe. However, the existence of axions in nature has not been confirmed. Interestingly, axions arise out of pseudoscalar fields derived from the Chern–Simons theory in condensed matter physics. In antiferromagnetic insulators, the axion field can become dynamical due to spin-wave excitations and exhibits rich exotic phenomena, such as axion polariton. However, antiferromagnetic dynamical axion insulator has yet been experimentally identified in realistic materials. Very recently, MnBi2Te4 was discovered to be an antiferromagnetic topological insulator with a quantized static axion field protected by inversion symmetry $${\mathcal{P}}$$ P and magnetic-crystalline symmetry $${\mathcal{S}}$$ S . Here, we studied MnBi2Te4 films in which both the $${\mathcal{P}}$$ P and $${\mathcal{S}}$$ S symmetries are spontaneously broken and found that substantially enhanced dynamical magnetoelectric effects could be realized through tuning the thickness of MnBi2Te4 films, temperature, or element substitutions. Our results show that thin films of MnBi2Te4 and related compounds could provide a promising material platform to experimentally study axion electrodynamics.

scholarly journals Inflationary birefringence and baryogenesis

2016 ◽  
Vol 25 (11) ◽  
pp. 1640013 ◽  
Author(s):  
Stephon Alexander
Keyword(s):  
Gravitational Waves ◽  
Lepton Number ◽  
Gauge Fields ◽  
Lepton Asymmetry ◽  
Complex Phase ◽  
Inflaton Field ◽  
Model Based ◽  
Cross Correlations ◽  
Chern Simons

A decade ago, the first leptogenesis model based on inflation was proposed, where the complex phase of the inflaton field carries lepton number [S. H. S. Alexander, M. E. Peskin and M. M. Sheikh-Jabbari, Phys. Rev. Lett. 96 (2006) 081301, arXiv:hep-th/0403069 ]. If the inflaton field is an axion, it can couple to gravitational waves and gauge fields via Chern–Simons invariants. Due to these couplings, birefringent gravitational and gauge primordial perturbations are created during inflation to generate a lepton asymmetry, establishing a possible connection between nonvanishing TB-parity-violating polarization cross-correlations and leptogenesis. We also discuss the prospect for a subset of these models which can directly source circular (V-mode) polarization in the CMB.

scholarly journals Electromagnetic Detectors of Gravitational Waves

1974 ◽  
Vol 64 ◽  
pp. 54-58
Author(s):  
V. B. Braginsky ◽  
L. P. Grishchuk ◽  
A. G. Doroshkievich ◽  
Ya. B. Zel'Dovich ◽  
I. D. Novikov ◽  
...  
Keyword(s):  
Gravitational Waves ◽  
Electromagnetic Waves ◽  
Reverse Process

Our group is investigating highfrequency gravitational waves (GW). The most promising approach to detection and laboratory generation of such GW seems to be through the transformation of GW into electromagnetic waves (EMW), and the reverse process: EMW→GW. The effects are small of course.

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