The QCD axion at finite density

Balkin, Reuven; Serra, Javi; Springmann, Konstantin; Weiler, Andreas

doi:10.1007/jhep07(2020)221

Cited by 32 publications

(54 citation statements)

References 92 publications

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“…Following refs. [37,108], one can compute the finite density effects on the axion potential by considering the quark condensates in a medium made of non-relativistic neutrons and protons [109,110]. Applying the Hellmann-Feynman theorem, the quark condensate at a finite density n N of a given nucleon N can be expressed as…”

Section: Jhep05(2021)184mentioning

confidence: 99%

An even lighter QCD axion

Luzio

Gavela

Quílez

et al. 2021

J. High Energ. Phys.

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We explore whether the axion which solves the strong CP problem can naturally be much lighter than the canonical QCD axion. The $$ {Z}_{\mathcal{N}} $$ Z N symmetry proposed by Hook, with $$ \mathcal{N} $$ N mirror and degenerate worlds coexisting in Nature and linked by the axion field, is considered in terms of generic effective axion couplings. We show that the total potential is safely approximated by a single cosine in the large $$ \mathcal{N} $$ N limit, and we determine the analytical formula for the exponentially suppressed axion mass. The resulting universal enhancement of all axion interactions relative to those of the canonical QCD axion has a strong impact on the prospects of axion-like particle experiments such as ALPS II, IAXO and many others: experiments searching for generic axion-like particles have in fact discovery potential to solve the strong CP problem. The finite density axion potential is also analyzed and we show that the $$ {Z}_{\mathcal{N}} $$ Z N asymmetric background of high-density stellar environments sets already significant model-independent constraints: 3 ≤ $$ \mathcal{N} $$ N ≲ 47 for an axion scale fa ≲ 2.4 × 1015 GeV, with tantalizing discovery prospects for any value of fa and down to $$ \mathcal{N} $$ N ∼ 9 with future neutron star and gravitational wave data, down to the ultra-light mass region. In addition, two specific ultraviolet $$ {Z}_{\mathcal{N}} $$ Z N completions are developed: a composite axion one and a KSVZ-like model with improved Peccei-Quinn quality.

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Section: Jhep05(2021)184mentioning

confidence: 99%

An even lighter QCD axion

Luzio

Gavela

Quílez

et al. 2021

J. High Energ. Phys.

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show abstract

“…One way to search for axion dark matter is by observing its decay into two photons [13][14][15][16][17][18][19][20][21][22][23][24]. However, compact objects have long been known to offer a useful avenue in which to probe axions and ALPs in a variety of ways [25][26][27][28][29][30][31][32][33].…”

Section: Jhep09(2021)105mentioning

confidence: 99%

Radio line properties of axion dark matter conversion in neutron stars

Battye

Garbrecht

McDonald

et al. 2021

J. High Energ. Phys.

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Axions are well-motivated candidates for dark matter. Recently, much interest has focused on the detection of photons produced by the resonant conversion of axion dark matter in neutron star magnetospheres. Various groups have begun to obtain radio data to search for the signal, however, more work is needed to obtain a robust theory prediction for the corresponding radio lines. In this work we derive detailed properties for the signal, obtaining both the line shape and time-dependence. The principal physical effects are from refraction in the plasma as well as from gravitation which together lead to substantial lensing which varies over the pulse period. The time-dependence from the co-rotation of the plasma with the pulsar distorts the frequencies leading to a Doppler broadened signal whose width varies in time. For our predictions, we trace curvilinear rays to the line of sight using the full set of equations from Hamiltonian optics for a dispersive medium in curved spacetime. Thus, for the first time, we describe the detailed shape of the line signal as well as its time dependence, which is more pronounced compared to earlier results. Our prediction of the features of the signal will be essential for this kind of dark matter search.

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“…Axions [1][2][3][4][5] represent one of the leading candidates for dark matter [6][7][8] and are predicted by a range of theories beyond the standard model [9,10]. One possibility to detect axions is via their astrophysical signatures, for instance via galactic halo axions decaying into two photons [11][12][13][14][15][16][17][18][19][20][21][22] or through observations of neutron stars [14,[23][24][25][26][27][28][29][30][31][32]. It is also of vital importance to complement these efforts through laboratory searches and there are a number of current and proposed experiments aiming to detect axion dark matter here on earth.…”

Section: Introductionmentioning

confidence: 99%

Scanning the landscape of axion dark matter detectors: applying gradient descent to experimental design

McDonald

2021

Preprint

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The hunt for dark matter remains one of the principal objectives of modern physics and cosmology. Searches for dark matter in the form of axions are proposed or underway across a range of experimental collaborations. As we look to the next generation of detectors, a natural question to ask is whether there are new experimental designs waiting to be discovered and how we might find them. Here we take a new approach to the experimental design procedure by using gradient descent techniques to search for optimal detector designs. We provide a proof of principle for this technique by searching 1D detectors varying the bulk properties of the detector until the optimal detector design is obtained. Remarkably, we find the detector is capable of out-performing a human designed experiment on which the search was initiated. This opens the door to further gradient descent searches of more complex 2D and 3D designs across a wider variety of materials and boundary geometries of the detector. There is also an opportunity to use more sophisticated gradient descent algorithms to complete a more exhaustive scan of the landscape of designs.

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The QCD axion at finite density

Cited by 32 publications

References 92 publications

An even lighter QCD axion

An even lighter QCD axion

Radio line properties of axion dark matter conversion in neutron stars

Scanning the landscape of axion dark matter detectors: applying gradient descent to experimental design

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