arXiv subjects

Sebastian Hoof

Publications and source records attributed to Sebastian Hoof.

21 records · Page 2Linked to original sources

arXiv2017

QCD axions and axionlike particles in a two-inflation scenario

We investigate the phenomenology of QCD axions and axionlike particles in a scenario with two eras of inflation. In particular, we describe the possible solutions for the QCD axion field equation after the second inflation and reheating. We calculate the dilution numerically for QCD axions and give an analytic approximation for axionlike particles. While it has been realised before that such a scenario can dilute the axion energy density and open up the parameter space for the axion decay constant $f_A$, we find that even a small increase in the relative QCD axion energy density is possible.

hep-ph↗

arXiv2017

A Preview of Global Fits of Axion Models in GAMBIT

There are currently many experimental searches underway that try to detect QCD axions and axion-like particles. These, in addition to other constraints from astrophysics and cosmology, require a consistent and statistically rigorous analysis of the large landscape of axion models. Here, we present the rationale, methodology and preliminary results for global fits of axion models using the recently developed software framework GAMBIT.

hep-ph↗

arXiv2012

Enhanced quality factors and force sensitivity by attaching magnetic beads to cantilevers for atomic force microscopy in liquid

Dynamic-mode atomic force microscopy (AFM) in liquid remains complicated due to the strong viscous damping of the cantilever resonance. Here we show that a high-quality resonance (Q>20) can be achieved in aqueous solution by attaching a microgram-bead at the end of the nanogram-cantilever. The resulting increase in cantilever mass causes the resonance frequency to drop significantly. However, the force sensitivity --- as expressed via the minimum detectable force gradient --- is hardly affected, because of the enhanced quality factor. Via the enhancement of the quality factor, the attached bead also reduces the relative importance of noise in the deflection detector. It can thus yield an improved signal-to-noise ratio when this detector noise is significant. We describe and analyze these effects for a set-up which includes magnetic actuation of the cantilevers and which can be easily implemented in any AFM system that is compatible with an inverted optical microscope.

physics.ins-det↗