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The spectrum of primordial gravitational waves is one of the most robust inflationary observables, often thought of as a direct probe of the energy scale of inflation. We present a simple model, where the dynamics controlling this observable is very different than in the standard paradigm of inflation. The model is based on a peculiar finite density phase-the magnetic gaugid -which stems from a highly non-linear effective theory of a triplet of abelian gauge fields. The gaugid extends the notion of homogeneous isotropic solid, in that its spectrum of fluctuations includes helicity-2 phonons. We show how, upon implementing the gaugid to drive inflation, the helicity-2 phonon mixes with the graviton, significantly affecting the size of the primordial tensor spectrum. The rest of the features of the theory, in particular the vector and scalar perturbations, closely resemble those of solid inflation. arXiv:1706.03402v1 [hep-th] 11 Jun 2017 * .

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One contribution to any dark sector’s abundance comes from its gravitational production during inflation. If the dark sector is weakly coupled to the inflaton and the Standard Model, this can be its only production mechanism. For non-interacting dark sectors, such as a free massive fermion or a free massive vector field, this mechanism has been studied extensively. In this paper we show, via the example of dark massive QED, that the presence of interactions can result in a vastly different mass for the dark matter (DM) particle, which may well coincide with the range probed by upcoming experiments.In the context of dark QED we study the evolution of the energy density in the dark sector after inflation. Inflation produces a cold vector condensate consisting of an enormous number of bosons, which via interesting processes — Schwinger pair production, strong field electromagnetic cascades, and plasma dynamics — transfers its energy to a small number of “dark electrons” and triggers thermalization of the dark sector. The resulting dark electron DM mass range is from 50 MeV to 30 TeV, far different from both the 10−5 eV mass of the massive photon dark matter in the absence of dark electrons, and from the 109 GeV dark electron mass in the absence of dark photons. This can significantly impact the search strategies for dark QED and, more generally, theories with a self-interacting DM sector. In the presence of kinetic mixing, a dark electron in this mass range can be searched for with upcoming direct detection experiments, such as SENSEI-100g and OSCURA.

Retinoic acid (RA) signaling is essential for multiple developmental processes, including appropriate pancreas formation from the foregut endoderm. RA is also required to generate pancreatic progenitors from human pluripotent stem cells. However, the role of RA signaling during endocrine specification has not been fully explored. In this study, we demonstrate that the disruption of RA signaling within the NEUROG3-expressing endocrine progenitor population impairs mouse β cell differentiation and induces ectopic expression of crucial δ cell genes, including somatostatin. In addition, the inhibition of the RA pathway in hESC-derived pancreatic progenitors downstream of NEUROG3 induction impairs insulin expression. We further determine that RA-mediated regulation of endocrine cell differentiation occurs through Wnt pathway components. Together, these data demonstrate the importance of RA signaling in endocrine specification and identify conserved mechanisms by which RA signaling directs pancreatic endocrine cell fate.

Aberrant brain oscillations are a hallmark of Parkinson's disease (PD) pathophysiology and may be related to motor and non-motor symptoms. Mild cognitive impairment (MCI) affects many people with PD even at the time of diagnosis and conversion risks to PD dementia (PDD) are very high. Unfortunately, pharmacotherapies are not addressing cognitive symptoms in PD. Profiling PD cognitive phenotypes (eg. MCI, PDD...) may therefore help inform future treatments. Neurophysiological methods, such as magnetoencephalography (MEG), offer the advantage of observing oscillatory patterns, whose regional and temporal profiles may elucidate how cognitive changes relate to neural mechanisms. We conducted a resting state MEG cross-sectional study of 89 persons with PD stratified into three phenotypic groups: normal cognition, MCI and PDD, in order to identify brain regions and frequencies most associated with each cognitive profile. In addition, a neuropsychological battery was administered to assess each domain of cognition. Our data showed higher power in lower frequency bands (delta and theta) observed along with more severe cognitive impairment, and associated with memory, language, attention and global cognition. Of the total 119 brain parcels assessed during source analysis, widespread group differences were found in the beta band, with significant changes mostly occurring between the normal cognition and MCI groups. Moreover, bilateral frontal and left-hemispheric regions were particularly affected in the other frequencies as cognitive decline becomes more pronounced. Our results suggest MCI and PDD may be qualitatively distinct cognitive phenotypes, and most dramatic changes seem to have happened when the PD brain shows mild cognitive decline.