Related papers: QCD, Strong CP and Axions
The QCD axion is the leading solution to the strong-CP problem, a dark matter candidate, and a possible result of string theory compactifications. However, for axions produced before inflation, symmetry-breaking scales of $f_a \gtrsim…
In the world with axion the precise measurement of gravitational force and check of the equivalence principle at small distances, $\lambda\sim 1cm$ and less, could provide an additional test of CP symmetry. Using the chiral approach, we…
We present a comprehensive study of axion condensed neutron stars that arise in models of an exceptionally light axion that couples to quantum chromodynamics (QCD). These axions solve the strong-charge-parity (CP) problem, but have a…
In this lecture we review several cosmological issues associated with the axion. Axion solves the strong CP problem and is a good candidate for the dark matter. Limits, which are imposed by the value of isocurvature fluctuations fraction in…
Recently, it was shown that modular symmetry may solve the strong CP problem without axions, by producing a vanishing QCD angle while generating a large quark CP violation phase. We extend this framework to finite modular groups,…
We construct a theory in which the solution to the strong CP problem is an emergent property of the background of the dark matter in the Universe. The role of the axion degree of freedom is played by multi-body collective excitations…
We introduce a class of composite axion models that provide a natural solution to the strong CP problem, and possibly account for the observed dark matter abundance. The QCD axion arises as a composite Nambu-Goldstone boson (NGB) from the…
In this contribution, I'll discuss two classes of effects--additional sources of CP violation and PQ breaking--that offer a slightly different take on axion physics. Both are tied to the idea that the axion solution to the strong CP problem…
Dark matter constitutes about $23\%$ of the total energy density of the universe but its properties are still little known besides that it should be composed by cold and weakly interacting particles. Many beyond standard model theories can…
By identifying the recently introduced Barbero-Immirzi field with the QCD axion, the strong CP problem can be solved through the Peccei-Quinn mechanism. A specific energy scale for the Peccei-Quinn symmetry breaking is naturally predicted…
We use a non-invertible symmetry to construct a three-zero texture for the down-type quark mass matrix, which can resolve the strong CP problem without invoking the axion, in four-dimensional spacetime with three quark families in QCD. We…
There has been an attempt to revive the visible QCD axion at the 10 MeV scale assuming that it exclusively couples to the first-generation quarks and the electron. This variant of the QCD axion is claimed to remain phenomenologically…
We argue that the QCD axion can arise from many aligned axions with decay constants much smaller than the conventional axion window. If the typical decay constant is of {\cal O}{(100)} GeV to 1 TeV, one or more of the axions or saxions may…
It has been recently shown that the requirement of anomaly cancellation in a (non-supersymmetric) six-dimensional version of the standard model fixes the field content to the known three generations. We discuss the phenomenological…
We review the landscape of QCD axion models. Theoretical constructions that extend the window for the axion mass and couplings beyond conventional regions are highlighted and classified. Bounds from cosmology, astrophysics and experimental…
We propose a unified model that simultaneously addresses the hierarchy problem and the strong CP problem by considering the most simple fundamental composite Higgs setup and showing that it can feature a viable emergent axion that could be…
It is difficult to construct a post-inflation QCD axion model that solves the axion quality problem (and hence the Strong CP problem) without introducing a cosmological disaster. In a post-inflation axion model, the axion field value is…
The QCD axion is a leading dark matter candidate that emerges as part of the solution to the strong CP problem in the Standard Model. The coupling of the axion to photons is the most common experimental probe, but much parameter space…
R-parity can be extended to a continuous global U(1)${}_R$ symmetry. We investigate whether an anomalous U(1)${}_R$ can be identified as the PQ symmetry suitable for solving the strong CP problem within supersymmetric extensions of the…
Axions and axion like particles in general are consequences of the extensions of the standard model in particle physics. Axions have been proposed as hypothetical pseudo-scalar particles in particle physics to solve the strong Charge-Parity…