Leading logs in QCD axion effective field theory

The axion is much lighter than all other degrees of freedom introduced by the Peccei-Quinn mechanism to solve the strong CP problem. It is therefore natural to use an effective field theory (EFT) to describe its interactions. Loop processes calculated in the EFT may however explicitly depend on the ultraviolet cutoff. In general, the UV cutoff is not uniquely defined, but the dimensionful couplings suggest to identify it with the Peccei-Quinn symmetry-breaking scale. An example are K+ → π+ + a decays that will soon be tested to improved precision in NA62 and KOTO and whose amplitude is dominated by the term logarithmically dependent on the cutoff. In this paper, we critically examine the adequacy of using such a naive EFT approach to study loop processes by comparing EFT calculations with ones performed in complete QCD axion models. In DFSZ models, for example, the cutoff is found to be set by additional Higgs degrees of freedom and to therefore be much closer to the electroweak scale than to the Peccei-Quinn scale. In fact, there are non-trivial requirements on axion models where the cutoff scale of loop processes is close to the Peccei-Quinn scale, such that the naive EFT result is reproduced. This suggests that the existence of a suitable UV embedding may impose restrictions on axion EFTs. We provide an explicit construction of a model with suitable fermion couplings and find promising prospects for NA62 and IAXO.

Nonlocal SU(5) GUT

We show that in nonlocal generalization of standard nonsupersymmetric SU(5) GUT, it is possible to solve the problems with the proton lifetime and the Weinberg angle without introduction of additional particles in the spectrum of the theory. Nonlocal scale [Formula: see text] responsible for ultraviolet cutoff coincides (up to some factor) with GUT scale [Formula: see text]. We find that in the simplest nonlocal modification of the SU(5) model, [Formula: see text]GeV. In the general case, the value of [Formula: see text] is an arbitrary and the most interesting option [Formula: see text] could be realized.

Naturally-Coupled Dark Sectors

The dark sector, composed of fields that are neutral under the standard model (SM) gauge group, can couple to the SM through the Higgs, hypercharge and neutrino portals, and pull the SM towards its scale by loop corrections. This instability, which is not possible to prevent in the known SM completions, such as supersymmetry, due to the sizable couplings to the SM, calls for alternative mechanisms that can neutralize sensitivities of the SM to the dark sector scale and to the ultraviolet cutoff above it. Here we review such a mechanism in which incorporation of gravity into the SM predicts the existence of a dark sector and allows it to be naturally coupled to the SM. We discuss and illustrate salient processes that can probe the naturally coupled dark sectors.

Ba2B7O12F with novel FBB [B7O16F] and deep-ultraviolet cut-off edge

A new fluorooxoborate Ba2B7O12F features novel FBB [B7O16F] and two different sizes of channels in its anionic structure, which possesses a deep-ultraviolet cutoff edge of 180 nm and a large bandgap of 6.67 eV.

Li5Cs(SO4)3: A Potential Zero-order Wave Plate Material with Short Deep-ultraviolet Cutoff Edge

Zero-order wave plates play an important role in the polarization measurements and laser industry, while few materials can satisfy both small birefringence and a deep-ultraviolet (DUV; λ < 200 nm)...

Investigating inflation driven by DBI-essence scalar field

Motivated by the work of Nojiri et al., Phys. Lett. B 797, 134829 (2019), the present study demonstrates inflation driven by holographic DBI-essence scalar field. Considering a simple correction due to the Ultraviolet cutoff, we have studied the slow-roll parameters. It has been observed that the role of the UV-cutoff is not negligible and in the limiting case of [Formula: see text] the inflationary model is characterized by Type-III singularity but can avoid Big-Rip singularity. Finally, it has been observed that the trajectories in [Formula: see text] are compatible with the observational bound found by Planck. It has been concluded that the tensor to scalar ratio for this model can explain the primordial fluctuation in the early universe as well. However, under the purview of [Formula: see text] inflation, although the DBI-essence scalar field can explain primordial fluctuation, the holographic DBI-essence scalar field does not lead to [Formula: see text] trajectory satisfying the Planck’s observational bound.