Ultralight Bosonic Dark Matter Theory

Abstract

The basic theoretical concepts motivating the hypothesis that dark matter may consist of ultralight spin-0 or spin-1 bosons are explored. The origin of bosons with masses ≪ 1 eV from spontaneous and explicit symmetry breaking is illustrated with examples. The origins and characteristics of nongravitational couplings or “portals” between ultralight bosons and Standard Model particles and fields are considered, with particular attention paid to the cases of the axion-photon and axion-fermion interactions. Theoretical motivations for the existence of ultralight bosons, besides as an explanation of dark matter, are examined, with particular focus on the Peccei-Quinn solution to the strong CP problem (resulting in the QCD axion) and a dynamical solution to the hierarchy problem (the “relaxion” hypothesis, based on a particular axion-Higgs coupling in the early universe). Mechanisms for non-thermal production of ultralight bosonic dark matter are examined.

Experimental perspectives on the matter–antimatter asymmetry puzzle: developments in electron EDM and H¯ experiments

“…The EDM experimental apparatus can often be used to detect other spin-dependent interactions or other tiny effects that would affect the atomic properties [85]. Among them is the search for ultralight bosonic dark matter [86] such as axion like particles that typically produced time-varying EDMs, the effect of which being possibly detected using atomic transitions [87,88]. This opens new perspectives for dark matter searches such as followed by the cosmic axion spin precession experiment (CASPEr) [89] or by the DEMIURGOS project [82].…”

What Can a GNOME Do? Search Targets for the Global Network of Optical Magnetometers for Exotic Physics Searches

“…Since then, a variety of other beyond‐the‐standard‐model theories have emerged predicting similar spin‐0 bosons known as ALPs. [ 1,48–51 ] Axions and ALPs are commonly thought to be ultralight (masses $$m_\text{a} \ll 1\,{\rm eV}$$). They can be copiously produced in the early universe [ 52–61 ] and have all the requisite characteristics to be the dark matter.…”

“…The corresponding Hamiltonian $$\mathcal {H}_l$$ can be derived from the Euler–Lagrange equations (see, for example, refs. [1, 65]) $$$$\begin{align} \mathcal {H}_l \psi = -\frac{{{\left(\hbar c\right)}}^{3/2}}{f_l} \gamma _0 \gamma ^\mu \gamma _5 {{\left(\partial _\mu \varphi \right)}} \psi \end{align}$$$$In the nonrelativistic limit, where the spacelike component of the derivative of φ is much larger than the timelike component $$$$\begin{align} \mathcal {H}_{li} = -\frac{{{\left(\hbar c\right)}}^{3/2}}{f_{li}} \frac{\bm{S}_i}{{\left| S_i \right|}} \cdot \bm{\nabla } \varphi \nobreakspace \end{align}$$$$where the subscript i specifies the interaction with fermion $$i=e,p,n$$. Comparing Equation (6) to Equation (1), we see that the coupling constant for ALPs in the above parameterization is given by $$g_{\Upsilon i} = {(\hbar c)}^{3/2}/f_{li}$$ and the exotic pseudo‐magnetic field is described by $$\bm{\Upsilon }_l = \bm{\nabla } \varphi$$.…”

“…A leading hypotheses to explain dark matter is that it consists of ultralight bosons such as axions or axion‐like particles (ALPs) with masses $$m_\text{a} \ll 1\,{\rm {eV}}$$. [ 1,2 ] Such ultralight bosonic dark matter (UBDM) can couple to Standard Model particles through a variety of “portals,” [ 3,4 ] one of which is the direct interaction of the UBDM field with atomic spins. [ 5,6 ] If such an interaction exists, a UBDM field would generate a spin‐dependent energy shift similar to that caused by the Zeeman effect due to an external magnetic field.…”

Calibration of the Solid‐State Nuclear Magnetic Resonance Search for Axion‐Like Dark Matter

“…However, despite decades of experimental searches, none of its non-gravitational interactions have been detected. [1][2][3][4] High energy physics models, such as grand unified theories and models with extra dimensions, incorporate light pseudoscalar bosons (axion-like particles, ALPs), which are potential dark matter candidates. [5][6][7][8][9] The ALP mass is unknown, but can be within the range of approximately 10 −21 eV to 10 −3 eV.…”