Constraints on Lorentz Invariance Violation with Multiwavelength Polarized Astrophysical Sources

Abstract

Possible violations of Lorentz invariance (LIV) can produce vacuum birefringence, which results in a frequency-dependent rotation of the polarization plane of linearly polarized light from distant sources. In this paper, we try to search for a frequency-dependent change of the linear polarization angle arising from vacuum birefringence in the spectropolarimetric data of astrophysical sources. We collect five blazars with multiwavelength polarization measurements in different optical bands (UBVRI). Taking into account the observed polarization angle contributions from both the intrinsic polarization angle and the rotation angle induced by LIV, and assuming that the intrinsic polarization angle is an unknown constant, we obtain new constraints on LIV by directly fitting the multiwavelength polarimetric data of the five blazars. Here, we show that the birefringence parameter η quantifying the broken degree of Lorentz invariance is limited to be in the range of −9.63×10−8<η<6.55×10−6 at the 2σ confidence level, which is as good as or represents one order of magnitude improvement over the results previously obtained from ultraviolet/optical polarization observations. Much stronger limits can be obtained by future multiwavelength observations in the gamma-ray energy band.

Tests of Lorentz Invariance

“…( 12) that the larger the distance of the polarized source, and the higher the energy band of the polarization observation, the greater the sensitivity to small values of η. As expected, less stringent constraints on η were obtained from the optical polarization data [40,95,96].…”

“…Instead of requiring the more complicated and indirect assumption that |∆ φ (E 2 )− ∆ φ (E 1 )| ≤ π/2, some authors simply assume that all photons in the observed energy band are emitted with the same (unknown) intrinsic polarization angle [40,95,96]. If the rotation angle of the linear polarization plane arising from the birefringent effect ∆ φ LIV (E) is considered here, the observed linear polarization angle at a certain E with an intrinsic polarization angle φ 0 should be…”

“…Ref. [96] applied the same analysis method to multiband optical polarimetry of five blazars and obtained η constraints with similar accuracy. It is clear from Eq.…”

Lorentz Symmetry Violation of Cosmic Photons

“…where L Pl is the Planck length and ω is the frequency of the observed photon. If we consider the expansion of the Universe, we can get the LV rotation angle ∆φ LV during propagation from the source at redshift z to the observer [123]:…”

“…If we consider both the intrinsic polarization angle φ in caused by the source effects and the rotation angle ∆φ LV caused by the LV effects, the observed polarization angle should contain two items [123]:…”