118316369
The Parameterized Post-Friedmann Framework for Theories of Modified Gravity: Concepts, Formalism and Examples.
A unified framework for theories of modified gravity will be an essential tool for interpreting the forthcoming deluge of cosmological data. We present such a formalism, the Parameterized Post-Friedmann framework (PPF), which parameterizes the cosmological perturbation theory of a wide variety of modified gravity models. PPF is able to handle spin-0 degrees of freedom from new scalar, vector and tensor fields, meaning that it is not restricted to simple models based solely on cosmological scalar fields. A direct correspondence is maintained between the parameterization and the underlying space of theories, which allows us to build up a `dictionary' of modified gravity theories and their PPF correspondences. In this paper we describe the construction of the parameterization and demonstrate its use through a number of worked examples relevant to the current literature. We indicate how the formalism will be implemented numerically, so that the dictionary of modified gravity can be pitted against forthcoming observations.
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.
11014726
Initial conditions of the universe: how much isocurvature is allowed?
We investigate the constraints imposed by current data on correlated mixtures of adiabatic and nonadiabatic primordial perturbations. We discover subtle flat directions in parameter space that tolerate large (approximately 60%) fractions of nonadiabatic fluctuations. In particular, larger values of the baryon density and a spectral tilt are allowed. The cancellations in the degenerate directions are explored and the role of priors is elucidated.
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
118483060
Can we build a sensible theory with broken charge and colour symmetries
Charge and colour symmetries are broken using the vevs of scalar fields, but it is shown the theory possesses a photon-like massless particle and electroweak interactions almost identical to those of the Standard Model. We consider experimental signatures of this theory.
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.
748074
A Pseudo-Photon in Non-Trivial Background Fields
We show that in the presence of external fields for which either Ḃ 6= 0 or ∇ × E 6= 0 it is not possible to derive the classical Maxwell equations from an action with only one gauge field. We suggest that one possible solution is to consider a second physical pseudo-vector gauge field C. The action for this theory is originally motivated by the inclusion of magnetic monopoles. These particles play no role in this work and our argument is only based in, that the violation of the Bianchi identities, cannot be accounted at the action level with only the standard gauge field. We give a particular example for a periodic rotating external magnetic field. Our construction holds that at classical level both the vector and pseudo-vector gauge fields A and C are regular. We compare pseudo-photon with paraphoton (graviphoton) theories concluding that, besides the mechanisms of gauge symmetry already studied by the authors, the Bianchi identities violation are a crucial difference between both theories. We also show that the effects in PVLAS experiment due to the inclusion of pseudo-photons cannot be distinguished from the usual classical induced electric and magnetic fields due to the standard Maxwell equations. Therefore, although this kind of optical experiments cannot test the existence of pseudo-photons, they do not exclude its existence. PACS: ?03.50.De, ?03.70.+k, ?11.15.-q
85524781
Contributions from flavour changing effective operators to the physics of the top quark at LHC
We consider all relevant dimension six operators to perform a model independent analysis of flavour changing single top production at the LHC.