54917997
Tensor tilt from primordial B modes
A primordial cosmic microwave background B mode is widely considered a ‘smoking gun’ signature of an early period of inflationary expansion. However, competing theories of the origin of structure, including string gases (SG) and bouncing cosmologies, also produce primordial tensor perturbations that give rise to a B mode. These models can be differentiated by the scale dependence of their tensor spectra: inflation predicts a red tilt (nT 0), while a non-singular matter bounce gives a zero tilt (nT = 0). We perform a Bayesian analysis to determine how far |nT| must deviate from zero before a tilt can be detected with current and future B-mode experiments. We find that Planck in conjunction with Q/U Imaging Experiment II will decisively detect nT � 0i f |nT| > 0.3, too large to distinguish either single-field inflation or SG from the case nT = 0. While a future mission like CMBPol will offer improvement, only an ideal satellite mission will be capable of providing sufficient Bayesian evidence to distinguish between each model considered.
119275153
Optimizing future experimental probes of inflation
The discovery of many novel realizations of the inflationary universe paradigm has led to a degeneracy problem: many different inflationary Lagrangians generate the same perturbation spectra. Resolving this problem requires the future discovery of additional observables beyond the scalar adiabatic and tensor two-point functions on CMB scales. One important source of degeneracy arises in models where the density perturbation is generated by a noninflationary degree of freedom, for example, through curvatons or modulated reheating. We consider the curvaton scenario as representative of this class, and analyze the degeneracy with single field, canonical inflation that results if the curvaton goes undetected by future observations. We perform Monte Carlo potential reconstructions in the absence of distinguishing observables, such as non-Gaussiantities or isocurvature modes. The resulting degeneracy is considerable and the improved measurements of spectral parameters from future probes like CMBPol offer little to better the situation. Given a degeneracy-breaking observation, the observables must still be inverted to obtain the inflationary potential, with different observations resulting in reconstructions of varying quality. We find that a future detection of isocurvature modes or a precision measurement of the tensor spectral index will enable the most successful reconstructions in the presence of curvatons.
24800285
Identifying the inflaton with primordial gravitational waves.
We explore the ability of experimental physics to uncover the underlying structure of the gravitational Lagrangian describing inflation. While the observable degeneracy of the inflationary parameter space is large, future measurements of observables beyond the adiabatic and tensor two-point functions, such as non-gaussianity or isocurvature modes, might reduce this degeneracy. We show that, even in the absence of such observables, the range of possible inflaton potentials can be reduced with a precision measurement of the tensor spectral index, as might be possible with a direct detection of primordial gravitational waves.
119466610
Photometric Decomposition of Barred Galaxies
We present a nonparametric method for decomposition of the light of disk galaxies into disk, bulge, and bar components. We have developed and tested the method on a sample of 68 disk galaxies for which we have acquired I-band photometry. The separation of disk and bar light relies on the single assumption that the bar is a straight feature with a different ellipticity and position angle from that of the projected disk. Here we present the basic method, but we recognize that it can be significantly refined. We identify bars in only 47% of the more nearly face-on galaxies in our sample. The fraction of light in the bar has a broad range, from 1.3% to 40% of the total galaxy light. If low-luminosity galaxies have more dominant halos, and if halos contribute to bar stability, the luminosity functions of barred and unbarred galaxies should differ markedly; while our sample is small, we find only a slight difference of low significance.
118690762
Cosmological constraints on rapid roll inflation
We obtain cosmological constraints on models of inflation which exhibit rapid roll solutions. Rapid roll attractors exist for potentials with large mass terms and are thus of interest for inflationary model building within string theory. We constrain a general ansatz for the power spectrum arising from rapid roll inflation that, in the small field limit, can be associated with tree level hybrid potentials with variable mass terms and nonminimal gravitational coupling ?R2. We consider perturbations generated through modulated reheating and/or curvaton mechanisms in place of the observationally unacceptable primary spectra generated by inflaton fluctuations in these models. The lack of a hierarchy amongst higher-order k-dependencies of the power spectrum results in models with potentially large runnings, allowing us to impose tight constraints on such models using CMB and LSS data. In particular, we find ns < 1 and |?| < 0.01. We conclude with a concrete realization of rapid roll inflation within warped throat brane inflation that is in good agreement with current data.
107817247
THE HPD MARK 2 FLYING-SPOT DIGITIZER AT CERN.
59671228
Further notes on the work done using HPD 1
115543079
Bubble chamber picture measurement
133664820
CHANGES IN MIST
117918920
Procedure for the adjustement of the HPD I optics