Related papers: A New Solution to the Strong CP Problem
Three possible strategies have been advocated to solve the strong CP problem. The first is the axion, a dynamical mechanism that relaxes any initial value of the CP violating angle $\bar{\theta}$ to zero. The second is the imposition of new…
We propose an alternative to the axion mechanism for addressing the charge parity (CP) problem in quantum chromodynamics (QCD). Our approach involves imposing CP as an inherent symmetry of the Lagrangian, which is then spontaneously broken.…
Quantum gravity introduces a new source of the combined parity (CP) violation in gauge theories. We argue that this new CP violation gets bundled with the strong CP violation through the coloured gravitational instantons. Consequently, the…
We formulate general conditions under which the strong CP problem is solved by spontaneous CP violation. Quark-mass matrix elements are polynomials in the CP-breaking order parameters, engineered such that their determinant is a real…
We present a new mechanism to solve the strong CP problem using $N\geq2$ axions, each dynamically relaxing part of the $\bar\theta$ parameter. At high energies $M\gg\Lambda_{QCD}$ the $SU(3)_{c}$ group becomes the diagonal subgroup of an…
We show that the strong CP problem can, in principle, be solved dynamically by adding extra-dimensions with compact topology. To this aim we consider a toy model for QCD, which contains a vacuum angle and a strong CP like problem. We…
Setting aside anthropic arguments, there is no reason for CP symmetry to be obeyed within the theory of quantum chromodynamics. However, no such violation of CP symmetry has ever been observed in a strongly interacting experiment. This is…
We exhibit a solution to the strong CP problem in which ultraviolet physics renders the QCD theta angle physically unobservable. Our models involve new strong interactions beyond QCD and particles charged under both the new interactions and…
We discuss the strong CP problem in the context of quantum field theory in the presence of horizons. We argue that general covariance places constraints on the topological structure of the theory. In particular, as in QCD, it means that…
I propose a new axionic solution to the strong CP problem which involves a hypothetical vector-like quark(s) in a high-colour representation of the conventional QCD. There are two distinct scenarios. If the current mass of the exotic quark…
We examine the possibility that the strong CP problem is solved by string-theoretic axions in strong-coupling limit of the E_8 x E_8 heterotic string theory (M-theory). We first discuss some generic features of gauge kinetic functions in…
While $CP$ violation has never been observed in the strong interactions, the QCD Lagrangian admits a $CP$-odd topological interaction proportional to the so called $\theta$ angle, which weighs the contributions to the partition function…
I describe how the QCD vacuum structure, necessary to resolve the $U(1)_A$ problem, predicts the presence of a P, T and CP violating term proportional to the vacuum angle $\bar{\theta}$. To agree with experimental bounds, however, this…
We exhibit a novel solution of the strong CP problem, which does not involve any massless particles. The low energy effective Lagrangian of our model involves a discrete spacetime independent axion field which can be thought of as a…
We discuss a natural scenario to solve the strong CP problem in the framework of the higher dimensional gauge theory. An axion-like field $A_y$ has been built-in as the extra-space component of the higher dimensional gauge field. The…
Gravitational effects may interfere with the axion solution to the strong-CP problem. We point out that gravity can potentially provide a protection mechanism against itself, in the form of an additional axion-like field associated with…
We propose a new solution to the strong CP problem based on supersymmetric non-renormalization theorems. CP is broken spontaneously and it's breaking is communicated to the MSSM by radiative corrections. The strong CP phase is protected by…
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,…
Solutions of the Strong CP Problem based on the spontaneous breaking of CP must feature a non-generic structure and simultaneously explain a coincidence between a priori unrelated CP-even and CP-odd mass scales. We show that these…
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…