Future detectors can be used as gravitational microscopes to probe the horizon structure of merging black holes with gravitational waves. But, can this microscope probe the quantum regime? We study ...this interesting question and find that (i) the error in the distance resolution is exponentially sensitive to errors in the Love number, (ii) the uncertainty principle of quantum gravity forces a fundamental resolution limit, and (iii) conclusions about the structure of spacetime at small distances rely on assumptions about the properties of the (unknown) compact objects considered.
The recent NANOGrav evidence of a common-source stochastic background provides a hint to gravitational waves (GW) radiation from the Early Universe. We show that this result can be interpreted as a ...GW spectrum produced from first order phase transitions (FOPTs) around a temperature in the keV-MeV window. Such a class of FOPTs at temperatures much below the electroweak scale can be naturally envisaged in several warm dark matter models such as Majoron dark matter.
We show that the model of superfluid dark matter developed in Refs. Khoury (Phys Rev D 91(2):024022,
https://doi.org/10.1103/PhysRevD.91.024022
,
arXiv:1409.0012
hep-th,
2015
), Berezhiani and Khoury ...(Phys Rev D 92:103510,
https://doi.org/10.1103/PhysRevD.92.103510
,
arXiv:1507.01019
astro-ph.CO,
2015
) and Berezhiani and Khoury (Phys Lett B 753:639,
https://doi.org/10.1016/j.physletb.2015.12.054
,
arXiv:1506.07877
astro-ph.CO,
2016
), which modifies the Newtonian potential and explains the galactic rotational curves, can be unitarized by the formation of classical configurations in the scattering amplitudes. The classicalization mechanism may also trigger the formation of the superfluid state from the early to the late Universe.
The hair follicle bulge in the epidermis associates with the arrector pili muscle (APM) that is responsible for piloerection (“goosebumps”). We show that stem cells in the bulge deposit nephronectin ...into the underlying basement membrane, thus regulating the adhesion of mesenchymal cells expressing the nephronectin receptor, α8β1 integrin, to the bulge. Nephronectin induces α8 integrin-positive mesenchymal cells to upregulate smooth muscle markers. In nephronectin knockout mice, fewer arrector pili muscles form in the skin, and they attach to the follicle above the bulge, where there is compensatory upregulation of the nephronectin family member EGFL6. Deletion of α8 integrin also abolishes selective APM anchorage to the bulge. Nephronectin is a Wnt target; epidermal β-catenin activation upregulates epidermal nephronectin and dermal α8 integrin expression. Thus, bulge stem cells, via nephronectin expression, create a smooth muscle cell niche and act as tendon cells for the APM. Our results reveal a functional role for basement membrane heterogeneity in tissue patterning.
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► Stem cells in the hair follicle bulge express nephronectin, an ECM protein ► Deposition of nephronectin in the basement membrane creates a unique niche ► Nephronectin induces differentiation of arrector pili muscles, which cause “goosebumps” ► Arrector pili muscles attach to nephronectin; thus, bulge stem cells serve as tendons
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