Inflationary α\alpha-Attractor Models with Singular Derivative of Potential

A generalization of inflationary $\alpha$-attractor models (``polynomial $\alpha$-attractor'') was recently proposed by Kallosh and Linde, in which the potential involves logarithmic functions of the inflaton so that the derivative of the potential but not potential itself has a singularity. We find that the models can lead to viable inflationary observables even without the pole in the kinetic term. Also, the generalization with a pole order other than two does not significantly change the functional form of the potential. This allows a systematic analysis of the predictions of this class of models. Our models predict larger spectral index $n_s$ and tensor-to-scalar ratio $r$ than in the polynomial $\alpha$-attractor: typically, $n_s$ around 0.97--0.98 and $r$ observable by LiteBIRD. Taking advantage of the relatively large $n_s$, we discuss the modification of the potential to produce primordial black holes as the whole dark matter and gravitational waves induced by curvature perturbations detectable by LISA and BBO/DECIGO, while keeping $n_s$ in agreement with the Planck/BICEP/Keck data.Comment: 25 pages, 9 figures, 1 table. Published version; references and table adde

On spin optics for gravitational waves lensed by a rotating object

We study gravitational lensing of gravitational waves taking into account the spin of a graviton coupled with a dragged spacetime made by a rotating object. We decompose the phase of gravitational waves into helicity-dependent and independent components with spin optics, analyzing waves whose wavelengths are shorter than the curvature radius of a lens object. We analytically confirm that the trajectory of gravitational waves splits depending on the helicity, generating additional time delay and elliptical polarization onto the helicity-independent part. We exemplify monotonic gravitational waves lensed by a Kerr black hole and derive the analytical expressions of corrections in phase and magnification. The corrections are enhanced for longer wavelengths, potentially providing a novel probe of rotational properties of lens objects in low-frequency gravitational-wave observations in the future.Comment: 14 pages, 6 figure

Electrical Characteristics of Pentacene Films on Cross-Linked Polymeric Insulators of Varying Thicknesses

Pentacene films vacuum-sublimed on a cross-linked polymeric insulator (CPVP–C₆) prepared using poly­(4-vinylphenol) (PVP) and 1,6-bis­(trichlorosilyl)­hexane (C₆) were studied with a special concern on possible influences of the CPVP–C₆ thickness on the electrical characteristics of the pentacene films. It was found that the conductivities of the pentacene films on a thin CPVP–C₆ film (10 nm) were approximately 2 orders of magnitude higher than those on a glass substrate and increased slightly with the increase in the thickness of the underlying CPVP–C₆ film. In addition, the X-ray diffraction measurements showed that the stacking structure of pentacene molecules was remarkably enhanced by increasing the thickness of the CPVP–C₆ film, suggesting that the increase in conductivity is due, at least in part, to the improvement in carrier mobilities caused by the growth of large pentacene grains. An attempt to directly evaluate carrier mobilities using pentacene/CPVP–C₆ field-effect transistors was made, and a seeming increase in the carrier mobilities observed with the increase in the CPVP–C₆ thickness was ascribed to a hygroscopic nature of the CPVP–C₆ film, which was evidenced by the capacitance and quartz crystal microbalance measurements. Possible reasons are discussed to explain the enhanced conductivities of the pentacene films on the increased thicknesses of CPVP–C₆