When Matter Matters

We study a recently proposed scenario for the early universe: Subluminal Galilean Genesis. We prove that without any other matter present in the spatially flat Friedmann universe, the perturbations of the Galileon scalar field propagate with a speed at most equal to the speed of light. This proof applies to all cosmological solutions -- to the whole phase space. However, in a more realistic situation, when one includes any matter which is not directly coupled to the Galileon, there always exists a region of phase space where these perturbations propagate superluminally, indeed with arbitrarily high speed. We illustrate our analytic proof with numerical computations. We discuss the implications of this result for the possible UV completion of the model.Comment: 16 pages, 3 figures. v2 reflects version accepted for publication in JCAP. Changes include a reorganisation of section order, a new figure 1 and additional reference

Dust of Dark Energy

We introduce a novel class of field theories where energy always flows along timelike geodesics, mimicking in that respect dust, yet which possess non-zero pressure. This theory comprises two scalar fields, one of which is a Lagrange multiplier enforcing a constraint between the other's field value and derivative. We show that this system possesses no wave-like modes but retains a single dynamical degree of freedom. Thus, the sound speed is always identically zero on all backgrounds. In particular, cosmological perturbations reproduce the standard behaviour for hydrodynamics with vanishing sound speed. Using all these properties we propose a model unifying Dark Matter and Dark Energy in a single degree of freedom. In a certain limit this model exactly reproduces the evolution history of Lambda-CDM, while deviations away from the standard expansion history produce a potentially measurable difference in the evolution of structure.Comment: 13 pages, 3 figures. Added references, corrected language

Models of f(R) Cosmic Acceleration that Evade Solar-System Tests

We study a class of metric-variation f(R) models that accelerates the expansion without a cosmological constant and satisfies both cosmological and solar-system tests in the small-field limit of the parameter space. Solar-system tests alone place only weak bounds on these models, since the additional scalar degree of freedom is locked to the high-curvature general-relativistic prediction across more than 25 orders of magnitude in density, out through the solar corona. This agreement requires that the galactic halo be of sufficient extent to maintain the galaxy at high curvature in the presence of the low-curvature cosmological background. If the galactic halo and local environment in f(R) models do not have substantially deeper potentials than expected in LCDM, then cosmological field amplitudes |f_R| > 10^{-6} will cause the galactic interior to evolve to low curvature during the acceleration epoch. Viability of large-deviation models therefore rests on the structure and evolution of the galactic halo, requiring cosmological simulations of f(R) models, and not directly on solar-system tests. Even small deviations that conservatively satisfy both galactic and solar-system constraints can still be tested by future, percent-level measurements of the linear power spectrum, while they remain undetectable to cosmological-distance measures. Although we illustrate these effects in a specific class of models, the requirements on f(R) are phrased in a nearly model-independent manner.Comment: 13 pages, 10 figures. Submitted to Phys. Rev.

Longitudinal impact of demographic and clinical variables on Health-Related Quality of Life in Cystic Fibrosis

Objectives: The insights that people with cystic fibrosis have concerning their health are important given that aspects of health-related quality of life (HRQoL) are independent predictors of survival and a decrease in lung function is associated with a decrease in HRQoL over time. Cross-sectional data suggest that key variables, other than lung function, are also associated with HRQoL - although study results are equivocal. This work evaluates the relationship between these key demographic and clinical variables and HRQoL longitudinally. Design: Longitudinal observational study. Observations were obtained at seven time points: approximately every two years over a twelve year period. Setting: Large Adult Cystic Fibrosis Centre in the UK. Participants: 234 participants aged 14-48 years at recruitment. Outcome measure: Nine domains of HRQoL (Cystic Fibrosis Quality of Life Questionnaire) in relation to demographic (age, gender) and clinical measures (FEV1% predicted, BMI, cystic fibrosis related diabetes, B. cepacia complex, totally implantable vascular access device, nutritional and transplant status). Results: A total of 770 patient assessments were obtained for 234 patients. The results of random coefficients modelling indicated that demographic and clinical variables were identified as being significant for HRQoL over time. In addition to lung function, transplant status, age, having a totally implantable vascular access device, cystic fibrosis related diabetes, BMI and B. cepacia complex impacted on many HRQoL domains longitudinally. Gender was important for the domain of Body image. Conclusion: Demographic and changes in clinical variables were independently associated with a change in health-related quality of life over time. Compared with these longitudinal data, cross-sectional data are inadequate when evaluating the relationships between HRQoL domains and key demographic and clinical variables, as they fail to recognise the full impact of the CF disease trajectory and its treatments on quality of life

Quantitative Determination of the Adiabatic Condition Using Force-Detected Nuclear Magnetic Resonance

The adiabatic condition governing cyclic adiabatic inversion of proton spins in a micron-sized ammonium chloride crystal was studied using room temperature nuclear magnetic resonance force microscopy. A systematic degradation of signal-to-noise was observed as the adiabatic condition became violated. A theory of adiabatic following applicable to cyclic adiabatic inversion is reviewed and implemented to quantitatively determine an adiabaticity threshold $(\gamma H_1)^2/(\omega_{osc}\Omega) = 6.0$ from our experimental results.Comment: 5 pages, 3 fig

Critical sets of the total variance of state detect all SLOCC entanglement classes

We present a general algorithm for finding all classes of pure multiparticle states equivalent under Stochastic Local Operations and Classsical Communication (SLOCC). We parametrize all SLOCC classes by the critical sets of the total variance function. Our method works for arbitrary systems of distinguishable and indistinguishable particles. We also discuss the Morse indices of critical points which have the interpretation of the number of independent non-local perturbations increasing the variance and hence entanglement of a state. We illustrate our method by two examples.Comment: 4 page

Multipartite quantum correlations: symplectic and algebraic geometry approach

We review a geometric approach to classification and examination of quantum correlations in composite systems. Since quantum information tasks are usually achieved by manipulating spin and alike systems or, in general, systems with a finite number of energy levels, classification problems are usually treated in frames of linear algebra. We proposed to shift the attention to a geometric description. Treating consistently quantum states as points of a projective space rather than as vectors in a Hilbert space we were able to apply powerful methods of differential, symplectic and algebraic geometry to attack the problem of equivalence of states with respect to the strength of correlations, or, in other words, to classify them from this point of view. Such classifications are interpreted as identification of states with `the same correlations properties' i.e. ones that can be used for the same information purposes, or, from yet another point of view, states that can be mutually transformed one to another by specific, experimentally accessible operations. It is clear that the latter characterization answers the fundamental question `what can be transformed into what \textit{via} available means?'. Exactly such an interpretations, i.e, in terms of mutual transformability can be clearly formulated in terms of actions of specific groups on the space of states and is the starting point for the proposed methods.Comment: 29 pages, 9 figures, 2 tables, final form submitted to the journa

A SCUBA Map in the Spitzer First Look Survey: Source Catalog and Number Counts

Using the SCUBA instrument on the JCMT, we have made a submillimeter mosaic at 850um of a subarea of the Spitzer First Look Survey (FLS). Our image covers the central 151 square arcmin of the northern extragalactic Continuous Viewing Zone (CVZ) field of the FLS to a median 3sigma depth of 9.7 mJy. The image contains ten 850um sources detected at 3.5sigma or higher significance, of which five are detected at greater than or equal 4sigma. We make the catalog of these SCUBA-selected FLS sources available to the community. After correcting for incompleteness and flux bias, we find that the density of sources brighter that 10mJy in our field is (1.3 +1.1 -0.7)x10^2 deg^-2 (95% Poisson confidence limits), which is consistent with other surveys that probe the bright end of the submillimeter population.Comment: ApJL, in press. Higher quality versions of Figs 1 and 3 can be obtained from the author

The Evolution of the Global Star Formation History as Measured from the Hubble Deep Field

The Hubble Deep Field (HDF) is the deepest set of multicolor optical photometric observations ever undertaken, and offers a valuable data set with which to study galaxy evolution. Combining the optical WFPC2 data with ground-based near-infrared photometry, we derive photometrically estimated redshifts for HDF galaxies with J<23.5. We demonstrate that incorporating the near-infrared data reduces the uncertainty in the estimated redshifts by approximately 40% and is required to remove systematic uncertainties within the redshift range 1<z<2. Utilizing these photometric redshifts, we determine the evolution of the comoving ultraviolet (2800 A) luminosity density (presumed to be proportional to the global star formation rate) from a redshift of z=0.5 to z=2. We find that the global star formation rate increases rapidly with redshift, rising by a factor of 12 from a redshift of zero to a peak at z~1.5. For redshifts beyond 1.5, it decreases monotonically. Our measures of the star formation rate are consistent with those found by Lilly et al. (1996) from the CFRS at z 2, and bridge the redshift gap between those two samples. The overall star formation or metal enrichment rate history is consistent with the predictions of Pei and Fall (1995) based on the evolving HI content of Lyman-alpha QSO absorption line systems.Comment: Latex format, 10 pages, 3 postscript figures. Accepted for publication in Ap J Letter

G-Bounce

We present a wide class of models which realise a bounce in a spatially flat Friedmann universe in standard General Relativity. The key ingredient of the theories we consider is a noncanonical, minimally coupled scalar field belonging to the class of theories with Kinetic Gravity Braiding / Galileon-like self-couplings. In these models, the universe smoothly evolves from contraction to expansion, suffering neither from ghosts nor gradient instabilities around the turning point. The end-point of the evolution can be a standard radiation-domination era or an inflationary phase. We formulate necessary restrictions for Lagrangians needed to obtain a healthy bounce and illustrate our results with phase portraits for simple systems including the recently proposed Galilean Genesis scenario.Comment: 28 pages. v2 reflects version accepted for publication in JCAP. References and minor comments adde