The Primordial Inflation Explorer (PIXIE): A Nulling Polarimeter for Cosmic Microwave Background Observations

The Primordial Inflation Explorer (PIXIE) is an Explorer-class mission to measure the gravity-wave signature of primordial inflation through its distinctive imprint on the linear polarization of the cosmic microwave background. The instrument consists of a polarizing Michelson interferometer configured as a nulling polarimeter to measure the difference spectrum between orthogonal linear polarizations from two co-aligned beams. Either input can view the sky or a temperature-controlled absolute reference blackbody calibrator. PIXIE will map the absolute intensity and linear polarization (Stokes I, Q, and U parameters) over the full sky in 400 spectral channels spanning 2.5 decades in frequency from 30 GHz to 6 THz (1 cm to 50 um wavelength). Multi-moded optics provide background-limited sensitivity using only 4 detectors, while the highly symmetric design and multiple signal modulations provide robust rejection of potential systematic errors. The principal science goal is the detection and characterization of linear polarization from an inflationary epoch in the early universe, with tensor-to-scalar ratio r < 10^{-3} at 5 standard deviations. The rich PIXIE data set will also constrain physical processes ranging from Big Bang cosmology to the nature of the first stars to physical conditions within the interstellar medium of the Galaxy.Comment: 37 pages including 17 figures. Submitted to the Journal of Cosmology and Astroparticle Physic

Density pertubation of unparticle dark matter in the flat Universe

The unparticle has been suggested as a candidate of dark matter. We investigated the growth rate of the density perturbation for the unparticle dark matter in the flat Universe. First, we consider the model in which unparticle is the sole dark matter and find that the growth factor can be approximated well by $f=(1+3\omega_u)\Omega^{\gamma}_u$, where $\omega_u$ is the equation of state of unparticle. Our results show that the presence of $\omega_u$ modifies the behavior of the growth factor $f$. For the second model where unparticle co-exists with cold dark matter, the growth factor has a new approximation $f=(1+3\omega_u)\Omega^{\gamma}_u+\alpha \Omega_m$ and $\alpha$ is a function of $\omega_u$. Thus the growth factor of unparticle is quite different from that of usual dark matter. These information can help us know more about unparticle and the early evolution of the Universe.Comment: 6pages, 4 figures, accepted for publication in Eur. Phys. J.

Is cosmology consistent?

We perform a detailed analysis of the latest CMB measurements (including BOOMERaNG, DASI, Maxima and CBI), both alone and jointly with other cosmological data sets involving, e.g., galaxy clustering and the Lyman Alpha Forest. We first address the question of whether the CMB data are internally consistent once calibration and beam uncertainties are taken into account, performing a series of statistical tests. With a few minor caveats, our answer is yes, and we compress all data into a single set of 24 bandpowers with associated covariance matrix and window functions. We then compute joint constraints on the 11 parameters of the ``standard'' adiabatic inflationary cosmological model. Out best fit model passes a series of physical consistency checks and agrees with essentially all currently available cosmological data. In addition to sharp constraints on the cosmic matter budget in good agreement with those of the BOOMERaNG, DASI and Maxima teams, we obtain a heaviest neutrino mass range 0.04-4.2 eV and the sharpest constraints to date on gravity waves which (together with preference for a slight red-tilt) favors ``small-field'' inflation models.Comment: Replaced to match accepted PRD version. 14 pages, 12 figs. Tiny changes due to smaller DASI & Maxima calibration errors. Expanded neutrino and tensor discussion, added refs, typos fixed. Combined CMB data, window and covariance matrix at http://www.hep.upenn.edu/~max/consistent.html or from [email protected]

Morphology, geographical variation and the subspecies of marsh tit Poecile palustris in Britain and central Europe

Capsule: All British Marsh Tits belong to subspecies Poecile palustris dresseri, being smaller than nominate P. p. palustris of central Europe. Aims: Determining the subspecies of Marsh Tit in Britain to test whether ssp. P. p. palustris occurs in northern England and Scotland, by assessing regional variation in size compared with central European birds. Methods: 1147 wing length and 250 tail length measurements from 953 Marsh Tits were compared between eight British locations to test for regional variation. Biometrics were compared between birds from Britain and six locations within the continental European range of ssp. palustris. Results: There was no regional variation in wing or tail lengths among British Marsh Tits, indicating that all resident birds belong to ssp. dresseri. There was no evidence supporting the existence of ssp. palustris in northern England. British birds were significantly smaller than those from continental Europe, with proportionately shorter tails, consistent across all age and sex classes. Conclusion: All British Marsh Tits should be considered as ssp. dresseri, with ssp. palustris being limited to continental Europe. With no evidence of regional variation in size within Britain, reliable sexing methods based on biometrics could be applied in demographic studies throughout the country

The growth factor of matter perturbations in an f(R) gravity

The growth of matter perturbations in the $f(R)$ model proposed by Starobinsky is studied in this paper. Three different parametric forms of the growth index are considered respectively and constraints on the model are obtained at both the $1\sigma$ and $2\sigma$ confidence levels, by using the current observational data for the growth factor. It is found, for all the three parametric forms of the growth index examined, that the Starobinsky model is consistent with the observations only at the $2\sigma$ confidence level.Comment: 15 pages, 5 figure

Discovery of widespread transcription initiation at microsatellites predictable by sequence-based deep neural network

Using the Cap Analysis of Gene Expression (CAGE) technology, the FANTOM5 consortium provided one of the most comprehensive maps of transcription start sites (TSSs) in several species. Strikingly, ~72% of them could not be assigned to a specific gene and initiate at unconventional regions, outside promoters or enhancers. Here, we probe these unassigned TSSs and show that, in all species studied, a significant fraction of CAGE peaks initiate at microsatellites, also called short tandem repeats (STRs). To confirm this transcription, we develop Cap Trap RNA-seq, a technology which combines cap trapping and long read MinION sequencing. We train sequence-based deep learning models able to predict CAGE signal at STRs with high accuracy. These models unveil the importance of STR surrounding sequences not only to distinguish STR classes, but also to predict the level of transcription initiation. Importantly, genetic variants linked to human diseases are preferentially found at STRs with high transcription initiation level, supporting the biological and clinical relevance of transcription initiation at STRs. Together, our results extend the repertoire of non-coding transcription associated with DNA tandem repeats and complexify STR polymorphism