119488406
Have acoustic oscillations been detected in the current cosmic microwave background data
The angular power spectrum of the cosmic microwave background has been measured out to a sufficiently small angular scale to encompass a few acoustic oscillations. We use a phenomenological fit to the angular power spectrum to quantify the statistical significance of these oscillations: we find the evidence for acoustic oscillations is not yet compelling. We discuss the cosmological implications of such a finding.
122687802
Imaging the early universe with the BOOMERanG Experiment
The BOOMERanG experiment has recently detected temperature fluctuations the Cosmic Microwave Background (CMB), the otherwise isotropic radiation coming from the early Universe. These anisotropies have a low contrast (about 30 ppm) and feature a peculiar angular power spectrum at angles corresponding to sub-horizon scales at recombination. In the current cosmological model, these structures result from acoustic oscillations in the primeval plasma. In the framework of the Hot Big Bang theory with the inflationary hypothesis, the statistical properties of the image of the CMB allow us to measure most of the cosmological parameters.
119285987
Cosmology of Axions and Moduli: A Dynamical Systems Approach
xed point attractors, repellers and saddle points, which we analyse in detail. We also provide geometric interpretations of the phase space. The xed points can be used to bound the couplings in the model. A systematic scan of certain regions of parameter space reveals that the future evolution of the universe in this model can be rich, containing multiple epochs of accelerated expansion.
36591368
Fast and precise map‐making for massively multi‐detector CMB experiments
Future cosmic microwave background (CMB) polarisation experiments aim to measure an unprecedentedly small signal - the primordial gravity wave component of the polarisation field B-mode. To achieve this, they will analyse huge dataset s, involving years worth of timeordered data (TOD) from massively multi-detector focal planes. This creates the need for fast and precise methods to complement the M-L approach in analysis pipelines. In this paper, we investigate fast map-making methods as applied to long duration, massively multi-detector, ground-based experiments, in the context of the search for B-modes. We focus on two alternative map-making approaches: destriping and TOD filtering , comparing their performance on simulated multi-detector polarisation data. We have written an optimised, parallel destriping code, the DEStriping CARTographer (DESCART), that is generalised for massive focal planes, including the potential effect of cross-correlate d TOD 1/f noise. We also determine the scaling of computing time for destriping as applied to a simulated full-season data-set for a realistic experiment. We find that destriping can out-perf orm filtering in estimating both the large-scale E and B-mode angular power spectra. In particular, filtering can produce significant spurious B-mode power via EB mixing. Whilst this can be removed, it contributes to the variance of B-mode bandpower estimates at scales near the primordial B-mode peak. For the experimental configuration we simulate, this has an effect o n the possible detection significance for primordial B-modes. Destriping is a viable alternative fast method to the full M-L approach that does not cause the problems associated with fil tering, and is flexible enough to
17421918
Living in a void: testing the Copernican principle with distant supernovae.
We show that the local redshift dependence of the luminosity distance can be used to test the Copernican principle that we are not in a central or otherwise special region of the Universe. Future surveys of type Ia supernovae that focus on a redshift range of approximately 0.1-0.4 will be ideally suited to observationally determine the validity of the Copernican principle on new scales, as well as probing the degree to which dark energy must be considered a necessary ingredient in the Universe.
119408227
CMB likelihood functions for beginners and experts
Although the broad outlines of the appropriate pipeline for cosmological likelihood analysis with CMB data has been known for several years, only recently have we had to contend with the full, large-scale, computationally challenging problem involving both highly-correlated noise and extremely large datasets (N>1000). In this talk we concentrate on the beginning and end of this process. First, we discuss estimating the noise covariance from the data itself in a rigorous and unbiased way; this is essentially an iterated minimum-variance mapmaking approach. We also discuss the unbiased determination of cosmological parameters from estimates of the power spectrum or experimental bandpowers.
118645209
Strange quark chiral phase transition in hot 2 + 1 -flavor magnetized quark matter
Using the Polyakov--Nambu--Jona-Lasinio model the strange quark chiral phase transition and the effect of its current mass on a hot magnetized three flavor quark matter at zero chemical potential is investigated. The impact of the 't Hooft mixing term on the restoration of the chiral symmetry on the light and strange sectors is studied and the critical temperature dependence on the magnetic field strength of the chiral strange transition is analyzed. It is shown that the s quark is much less sensitive to the magnetic field than the light quarks. Due to the 't Hooft term, it has a strong influence on the light quarks at all temperatures for small magnetic fields and for temperatures close to the transition temperature at zero magnetic field and above for strong magnetic fields. In particular, the large mass of the s quark makes the chiral transition of the light sector smoother and shifted to larger temperatures. A scalar coupling that weakens when the magnetic field increases will originate an inverse magnetic catalysis also in the s quark and smoothen the signature of the crossover on thermodynamical quantities such as the sound velocities or the specific heat.
118627024
Deformed self-dual magnetic monopoles
Abstract We develop a deformation method for attaining new magnetic monopole analytical solutions consistent with generalized Yang–Mills–Higgs model introduced recently. The new solutions fulfill the usual radially symmetric ansatz and the boundary conditions suitable to assure finite energy configurations. We verify our prescription by studying some particular cases involving both exactly and partially analytical initial configurations whose deformation leads to new analytic BPS monopoles. The results show consistency among the models, the deformation procedure and the profile of the new solutions.
118541985
Radiative generation of the CPT-even gauge term of the SME from a dimension-five nonminimal coupling term
Abstract In this Letter we show for the first time that the usual CPT-even gauge term of the Standard Model Extension (SME), in its full structure, can be radiatively generated, in a gauge invariant level, in the context of a modified QED endowed with a dimension-five nonminimal coupling term recently proposed in the literature. As a consequence, the existing upper bounds on the coefficients of the tensor ( K F ) can be used to improve the bounds on the magnitude of the nonminimal coupling, λ ( K σ F ) , by the factors 105 or 1025. The nonminimal coupling also generates higher-order derivative contributions to the gauge field effective action quadratic terms.