Physics Letters B 803 (2020) 135288
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Physics Letters B
www.elsevier.com/locate/physletb
Signals of axion like dark matter in time dependent polarization of
light
So Chigusa
∗
, Takeo Moroi, Kazunori Nakayama
Department of Physics, University of Tokyo, Tokyo 113-0033, Japan
a r t i c l e i n f o a b s t r a c t
Article history:
Received 4 December 2019
Received in revised form 27 January 2020
Accepted 9 February 2020
Available online 13 February 2020
Editor: J. Hisano
We consider the search for axion-like particles (ALPs) by using time series data of the polarization angle
of the light. If the condensation of an ALP plays the role of dark matter, the polarization plane of the
light oscillates as a function of time and we may be able to detect the signal of the ALP by continuously
observing the polarization. In particular, we discuss that the analysis of the Fourier-transformed data
of the time-dependent polarization angle is powerful to find the signal of the ALP dark matter. We
pay particular attention to the light coming from astrophysical sources such as protoplanetary disks,
supernova remnants, the foreground emission of the cosmic microwave background, and so on. We show
that, for the ALP mass of ∼10
−22
–10
−19
eV, ALP searches in the Fourier space may reach the parameter
region which is unexplored by other searches yet.
© 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license
(http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP
3
.
1. Introduction
The existence of axion-like particles (ALPs) may be ubiquitous
in string theory [1–3] and they may have a wide range of masses
and decay constants. In particular, a very light ALP is a candi-
date
for dark matter (DM) in the present universe. The ALP field,
denoted by a, begins coherent oscillation when the Hubble pa-
rameter
becomes comparable to the ALP mass and it behaves as
a non-relativistic matter. Thus finding the evidence of such ALP
DM would be a probe of physics beyond the Standard Model. Ac-
tually,
several ideas are proposed to search for ALP DM through
the (extremely) weak interaction between the ALP and the Stan-
dard
Model particles [4–12].
One important effect of ALP is on the polarization plane of the
light propagating through the ALP condensation [13]. If the ALP
amplitude depends on time, which is the case for the ALP DM, the
polarization plane of the light becomes also time-dependent. Thus,
if the ALP plays the role of DM, we have a chance to observe the
effects of ALP condensation by precisely observing the polarization
of the light. In particular, if we consider the light from astrophys-
ical
sources, which travels a significant amount of distance before
being observed, the effects of the ALP condensation may be ac-
cumulated
in the polarization plane of the light; such an effect
may be experimentally detectable. The ALP search using the po-
larization
of light from astrophysical sources have been considered
*
Corresponding author.
E-mail address: chigusa@hep-th.phys.s.u-tokyo.ac.jp (S. Chigusa).
in literatures, using the light from radio galaxies [14], protoplan-
etary
disks [15], jets in active galaxies [16], pulsars [17,18], and
the cosmic microwave background (CMB) [19–24]. Even if the ALP
is not DM, the axion cloud may be formed around rotating black
holes through the superradiance [25], and the effect on the polar-
ization
of light passing through such axion cloud was discussed in
[26–28]. In particular, in [16–18,20,24,26,27], possibilities of using
the time dependence of the polarization of light were discussed.
In this letter, we consider how we can extract information
about the ALP DM from the time dependence of the polarization
of the light from astrophysical sources. Assuming that the ALP is
the dominant component of cold DM, the ALP potential should be
well approximated by a parabolic one in the present universe. In
such a case, the time dependence of the polarization plane be-
comes
also harmonic-oscillator-like with the angular frequency of
m
a
(with m
a
being the mass of the ALP). With such knowledge
about the time dependence of the polarization plane, we can ex-
tract
information about the ALP from the behavior of the polariza-
tion
plane by Fourier transforming the time-dependent data. While
the ALP search in the Fourier space has already been done by us-
ing
jets from active galaxies [16] and radio pulsar [18], we discuss
that we may use polarized light from a variety of astrophysical
light sources for the ALP search, like polarized light from proto-
planetary
disk, astrophysical radio sources like supernova remnant
(SNR), foreground emission of the CMB, and so on. We show that
the analysis with the Fourier transformation applies to these light
sources. We estimate the possible discovery reaches for the ALPs
using these astrophysical polarized light; our formulation is gener-
https://doi.org/10.1016/j.physletb.2020.135288
0370-2693/© 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by
SCOAP
3
.