35321734
Cosmology with a primordial scaling field
A weakly coupled scalar field \ensuremath{\Phi} with a simple exponential potential ${V=M}_{P}^{4}\mathrm{exp}(\ensuremath{-}\ensuremath{\lambda}\ensuremath{\Phi}{/M}_{P})$ where ${M}_{P}$ is the reduced Planck mass, and $\ensuremath{\lambda}g2,$ has an attractor solution in a radiation or matter dominated universe in which it mimics the scaling of the dominant component, contributing a fixed fraction ${\ensuremath{\Omega}}_{\ensuremath{\varphi}}$ (determined by \ensuremath{\lambda}) to the energy density. Such fields arise generically in particle physics theories involving compactified dimensions, with values of \ensuremath{\lambda} which give a cosmologically relevant ${\ensuremath{\Omega}}_{\ensuremath{\varphi}}.$ For natural initial conditions on the scalar field in the early universe the attractor solution is established long before the epoch of structure formation, and in contrast with the solutions used in other scalar field cosmologies, it is one which does not involve an energy scale for the scalar field characteristic of late times. We study in some detail the evolution of matter and radiation perturbations in a standard inflation-motivated $\ensuremath{\Omega}=1$ dark-matter dominated cosmology with this extra field. Using a full Einstein-Boltzmann calculation we compare observable quantities with current data. We find that, for ${\ensuremath{\Omega}}_{\ensuremath{\varphi}}\ensuremath{\simeq}0.08\char21{}0.12,$ these models are consistent with large angle cosmic microwave background anisotropies as detected by COBE, the linear mass variance as compiled from galaxy surveys, big bang nucleosynthesis, the abundance of rich clusters and constraints from the Lyman-\ensuremath{\alpha} systems at high redshift. Given the simplicity of the model, its theoretical motivation and its success in matching observations, we argue that it should be taken on a par with other currently viable models of structure formation.
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.
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.
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.
8582068
Fractal structure of the harper map phase diagram from topological hierarchical classification
It is suggested a topological hierarchical classification of the infinite many Localized phases figuring in the phase diagram of the Harper equation for anisotropy parameter $\epsilon$ versus Energy $E$ with irrational magnetic flux $\omega$. It is also proposed a rule that explain the fractal structure of the phase diagram. Among many other applications, this system is equivalent to the Semi-classical problem of Bloch electrons in a uniform magnetic field, the Azbel-Hofstadter model, where the discrete magnetic translations operators constitute the quantum algebra $U_q(sl_2)$ with $q^2=e^{i2\pi\omega}$. The magnetic flux is taken to be the golden mean $\omega^*=(\sqrt{5}-1)/2$ and is obtained by successive rational approximants $\omega_m=F_{m-1}/F_m$ with $F_m$ given by the Fibonacci sequence $F_m$.[OUTP-00-08S, \texttt{cond-mat/0011396}]
117960699
The CP-conserving 2HDM after the 8 TeV run
We confront the most common CP-conserving 2HDM with the LHC data analysed so far while taking into account all previously available experimental data. A special allowed corner of the parameter space is analysed - the so-called wrong-sign scenario where the Higgs coupling to down-type quarks changes sign relative to the Standard Model while the coupling to the massive vector bosons does not.
15105689
Effective Electric and Magnetic Local Actions for Electromagnetism with two Gauge Fields
A simple mechanism of dynamical symmetry breaking of electromagnetism with two gauge fields (U(1) × U(1)) is considered. By considering the action variations with respect to the gauge connections F = dA and G = dC we obtain an electric and a magnetic effective actions (U(1)) that have an extra coupling to the magnetic and electric currents (respectivelly) that decouple from the classical theory, meaning that it does not contribute to the standard equations of motion obtained by varying A and C, i.e. Maxwell equations. The extra gauge field C(or A) effectivelly is fixed by the physical effective field A(or C) constituting a non-trivial configuration C = C(A) (or A = A(C)) such that the field discontinuities (Dirac string or WuYang non-trivial fiber-bundle) are encoded in the extra gauge field C (or A). Our construction is only compactible with local current densities. work supported by SFRH/BPD/17683/2004 and POCTI P-FIS-57547/2004; also at Centra
14262164
Mass for Plasma Photons from Gauge Symmetry Breaking
We derive the effective masses for photons in unmagnetized plasma waves using a quantum field theory with two vector fields (gauge fields). In order to properly define the quantum field degrees of freedom we re-derive the classical wave equations on light-front gauge. This is needed because the usual scalar potential of electromagnetism is, in quantum field theory, not a physical degree of freedom that renders negative energy eigenstates. We also consider a background local fluid metric that allows for a covariant treatment of the problem. The different masses for the longitudinal (plasmon) and transverse photons are in our framework due to the local fluid metric. We apply the mechanism of mass generation by gauge symmetry breaking recently proposed by the authors by giving a non-trivial vacuum-expectation-value to the second vector field (gauge field). The Debye length λ D is interpreted as an effective compactification length and we compute an explicit solution for the large gauge transformations that correspond to the specific mass eigenvalues derived here. Using an usual quantum field theory canonical quantization we obtain the usual results in the literature. Although none of these ingredients are new to physicist, as far as the authors are aware it is the first time that such constructions are applied to Plasma Physics. Also we give a physical interpretation (and realization) for the second vector field in terms of the plasma background in terms of known physical phenomena.
15523763
Canonical Functional Quantization of Pseudo‐Photons in Planar Systems
Extended Ue(1)×Ug(1) electromagnetism containing both a photon and a pseudo‐photon is introduced at the variational level and is justified by the violation of the Bianchi identities in conceptual systems, either in the presence of magnetic monopoles or non‐regular external fields, not being accounted for by the standard Maxwell Lagrangian. A dimensional reduction is carried out that yields a Ue(1)×Ug(1) Maxwell‐BF type theory and a canonical functional quantization in planar systems is considered which may be relevant in Hall systems.