12,465 research outputs found
Constraints on modified gravity from Planck 2015: when the health of your theory makes the difference
We use the effective field theory of dark energy (EFT of DE) formalism to
constrain dark energy models belonging to the Horndeski class with the recent
Planck 2015 CMB data. The space of theories is spanned by a certain number of
parameters determining the linear cosmological perturbations, while the
expansion history is set to that of a standard CDM model. We always
demand that the theories be free of fatal instabilities. Additionally, we
consider two optional conditions, namely that scalar and tensor perturbations
propagate with subliminal speed. Such criteria severely restrict the allowed
parameter space and are thus very effective in shaping the posteriors. As a
result, we confirm that no theory performs better than CDM when CMB
data alone are analysed. Indeed, the healthy dark energy models considered here
are not able to reproduce those phenomenological behaviours of the effective
Newton constant and gravitational slip parameters that, according to previous
studies, best fit the data.Comment: 21 pages, 8 figures. Added Mu-Sigma plane in Fig.7 plus some changes
in the text with respect to the previous version. This is an author-created
un-copyedited version of the article published in JCAP. IOP Publishing Ltd is
not responsible for any errors or omissions in this version of the manuscrip
The azimuth structure of nuclear collisions -- I
We describe azimuth structure commonly associated with elliptic and directed
flow in the context of 2D angular autocorrelations for the purpose of precise
separation of so-called nonflow (mainly minijets) from flow. We extend the
Fourier-transform description of azimuth structure to include power spectra and
autocorrelations related by the Wiener-Khintchine theorem. We analyze several
examples of conventional flow analysis in that context and question the
relevance of reaction plane estimation to flow analysis. We introduce the 2D
angular autocorrelation with examples from data analysis and describe a
simulation exercise which demonstrates precise separation of flow and nonflow
using the 2D autocorrelation method. We show that an alternative correlation
measure based on Pearson's normalized covariance provides a more intuitive
measure of azimuth structure.Comment: 27 pages, 12 figure
Spectral transfer morphisms for unipotent affine Hecke algebras
In this paper we will give a complete classification of the spectral transfer
morphisms between the unipotent affine Hecke algebras of the various inner
forms of a given quasi-split absolutely simple algebraic group, defined over a
non-archimidean local field and split over an unramified extension
of . As an application of these results, the results of [O4] on the
spectral correspondences associated with such morphisms and some results of
Ciubotaru, Kato and Kato [CKK] we prove a conjecture of Hiraga, Ichino and
Ikeda [HII] on the formal degrees and adjoint gamma factors for all unipotent
discrete series characters of unramified simple groups of adjoint type defined
over .Comment: 61 pages; We explained the comparison with Lusztig's parameterization
of unipotent representations in more detai
Prague's Emission Fourier Transform Microwave Spectrometer - Design and Preliminary Results
The design, performance and operation of the high resolution microwave spectrometer are described. The spectrometer is based on the Fabry-Perot resonator supplemented by a pulsed supersonic nozzle for adiabatic cooling of the sample. The spectrometer’s high sensitivity and resolution are demonstrated by several examples
Commuting self-adjoint extensions of symmetric operators defined from the partial derivatives
We consider the problem of finding commuting self-adjoint extensions of the
partial derivatives {(1/i)(\partial/\partial x_j):j=1,...,d} with domain
C_c^\infty(\Omega) where the self-adjointness is defined relative to
L^2(\Omega), and \Omega is a given open subset of R^d. The measure on \Omega is
Lebesgue measure on R^d restricted to \Omega. The problem originates with I.E.
Segal and B. Fuglede, and is difficult in general. In this paper, we provide a
representation-theoretic answer in the special case when \Omega=I\times\Omega_2
and I is an open interval. We then apply the results to the case when \Omega is
a d-cube, I^d, and we describe possible subsets \Lambda of R^d such that
{e^(i2\pi\lambda \dot x) restricted to I^d:\lambda\in\Lambda} is an orthonormal
basis in L^2(I^d).Comment: LaTeX2e amsart class, 18 pages, 2 figures; PACS numbers 02.20.Km,
02.30.Nw, 02.30.Tb, 02.60.-x, 03.65.-w, 03.65.Bz, 03.65.Db, 61.12.Bt,
61.44.B
The Statistics of Cosmological Lyman-alpha Absorption
We study the effect of the non-Gaussianity induced by gravitational evolution
upon the statistical properties of absorption in quasar (QSO) spectra. Using
the generic hierarchical ansatz and the lognormal approximation we derive the
analytical expressions for the one-point PDF as well as for the joint two-point
probability distribution (2PDF) of transmitted fluxes in two neighbouring QSOs.
These flux PDFs are constructed in 3D as well as in projection (i.e. in 2D).
The PDFs are constructed by relating the lower-order moments, i.e. cumulants
and cumulant correlators, of the fluxes to the 3D neutral hydrogen distribution
which is, in turn, expressed as a function of the underlying dark matter
distribution. The lower-order moments are next modelled using a generating
function formalism in the context of a {\em minimal tree-model} for the
higher-order correlation hierarchy. These different approximations give nearly
identical results for the range of redshifts probed, and we also find a very
good agreement between our predictions and outputs of hydrodynamical
simulations. The formalism developed here for the joint statistics of
flux-decrements concerning two lines of sight can be extended to multiple lines
of sight, which could be particularly important for the 3D reconstruction of
the cosmic web from QSO spectra (e.g. in the BOSS survey). These statistics
probe the underlying projected neutral hydrogen field and are thus linked to
"hot-spots" of absorption. The results for the PDF and the bias presented here
use the same functional forms of scaling functions that have previously been
employed for the modelling of other cosmological observation such as the
Sunyaev-Zel'dovich effect.Comment: 17 pages, 8 figure
Weighing the Light Gravitino Mass with Weak Lensing Surveys
We explore the discovery potential of light gravitino mass m_{3/2} by
combining future cosmology surveys and collider experiments. The former probe
the imprint of light gravitinos in the cosmic matter density field, whereas the
latter search signatures of a supersymmetry breaking mechanism. Free-streaming
of light gravitinos suppresses the density fluctuations at galactic and
sub-galactic length scales, where weak gravitational lensing can be used as a
powerful probe. We perform numerical simulations of structure formation to
quantify the effect. We then run realistic ray-tracing simulations of
gravitational lensing to measure the cosmic shear in models with light
gravitino. We forecast the possible reach of future wide-field surveys by
Fisher analysis; the light gravitino mass can be determined with an accuracy of
m_{3/2}=4\pm 1 eV by a combination of the Hyper Suprime Cam survey and cosmic
microwave background anisotropy data obtained by Planck satellite. The
corresponding accuracy to be obtained by the future Large Synoptic Survey
Telescope is \delta m_{3/2}=0.6 eV. Data from experiments at Large Hadron
Collider at 14 TeV will provide constraint at m_{3/2} \simeq 5 eV in the
minimal framework of gauge-mediated supersymmetry breaking (GMSB) model. We
conclude that a large class of the GMSB model can be tested by combining the
cosmological observations and the collider experiments.Comment: 22 pages, 9 figure
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