19317675
Tensor interpretation of BICEP2 results severely constrains axion dark matter.
The recent detection of B modes by the BICEP2 experiment has nontrivial implications for axion dark matter implied by combining the tensor interpretation with isocurvature constraints from Planck observations. In this Letter the measurement is taken as fact, and its implications considered, though further experimental verification is required. In the simplest inflation models, r=0.2 implies HI=1.1×10(14)  GeV. If the axion decay constant fa1 accounts for theoretical uncertainty). If fa>HI/2π then vacuum fluctuations of the axion field place conflicting demands on axion DM: isocurvature constraints require a DM abundance which is too small to be reached when the backreaction of fluctuations is included. High-fa QCD axions are thus ruled out. Constraints on axionlike particles, as a function of their mass and DM fraction, are also considered. For heavy axions with ma≳10(-22)  eV we find Ωa/Ωd≲10(-3), with stronger constraints on heavier axions. Lighter axions, however, are allowed and (inflationary) model-independent constraints from the CMB temperature power spectrum and large scale structure are stronger than those implied by tensor modes.
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.
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.
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.
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
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.
15662898
Toroidal compactification in string theory from Chern–Simons theory
A detailed study of the charge spectrum of three-dimensional Abelian Topological Massive Gauge Theory (TMGT) is given. When this theory is defined on a manifold with two disconnected boundaries there are induced chiral Conformal Field Theories (CFT's) on the boundaries which can be interpreted as the left and right sectors of closed strings. We show that Narain constraints on toroidal compactification (integer, even, self-dual momentum lattice) have a natural interpretation in purely three-dimensional terms. This is an important result which is necessary to construct toroidal compactification and heterotic string from Topological Membrane (TM) approach to string theory. We also derive the block structure of c=1 Rational Conformal Field Theory (RCFT) from the three-dimensional gauge theory.
125353396
From compact U(1) Maxwell Chern-Simons to Azbel-Hofstadter: Testing magnetic monopoles and gravity to approximately 10**-17 meters on a nearby laboratory
118970889
Minimisation of a one-loop charge breaking effective potential
Abstract We compute the field derivatives of a one-loop charge breaking effective potential and analyse their effect in its minimisation. The impact on charge breaking bounds on the MSSM parameters is discussed.
16906939
Effect of Pions in Cosmic Rays
The effects of pions for vacuum polarization in background magnetic fields are considered. The effects of quark condensates is also briefly addresses. Although these effects are out of the measurement accuracy of laboratory experiments they may be relevant for gamma‐ray burst propagation. In particular, for emissions from the center of the galaxy, we show that the mixing between the neutral pion and photons results in a deviation of the gamma‐ray spectrum from the standard power‐law in the TeV range.
119286402
Fast simulations for intensity mapping experiments
We present a code to generate mock observations of 21 cm intensity mapping experiments. The emphasis of the code is on reducing the computational cost of running a full-blown simulation, trading computational time for accuracy. The code can be used to generate independent realizations of the cosmological signal and foregrounds, which are necessary, for instance, in order to obtain realistic forecasts for future intensity mapping experiments. The code is able to reproduce the correct angular and radial clustering pattern for the cosmological signal, including redshift-space distortions, lightcone evolution and bias. Furthermore, it is possible to simulate a variety of foregrounds, including the potentially problematic polarized synchrotron emission.