19 research outputs found
The Topology and Size of the Universe from the Cosmic Microwave Background
We study the possibility that the universe has compact topologies T^3, T^2 x
R^1, or S^1 x R^2 using the seven-year WMAP data. The maximum likelihood 95%
confidence intervals for the size L of the compact direction are 1.7 < L/L_0 <
2.1, 1.8 < L/L_0 < 2.0, 1.2 < L/L_0 < 2.1 for the three cases, respectively,
where L_0=14.4 Gpc is the distance to the last scattering surface. An infinite
universe is compatible with the data at 4.3 sigma. We find using a Bayesian
analysis that the most probable universe has topology T^2 x R^1, with
L/L_0=1.9.Comment: Additional checks, Monte-Carlo skies, and study of dipole
contamination added. References added. 13 pages, 11 figure
A small universe after all?
The cosmic microwave background radiation allows us to measure both the
geometry and topology of the universe. It has been argued that the COBE-DMR
data already rule out models that are multiply connected on scales smaller than
the particle horizon. Here we show the opposite is true: compact (small)
hyperbolic universes are favoured over their infinite counterparts. For a
density parameter of Omega_o=0.3, the compact models are a better fit to
COBE-DMR (relative likelihood ~20) and the large-scale structure data (sigma_8
increases by ~25%).Comment: 4 pages, RevTeX, 7 Figure
Cosmic microwave background anisotropies in multi-connected flat spaces
This article investigates the signature of the seventeen multi-connected flat
spaces in cosmic microwave background (CMB) maps. For each such space it
recalls a fundamental domain and a set of generating matrices, and then goes on
to find an orthonormal basis for the set of eigenmodes of the Laplace operator
on that space. The basis eigenmodes are expressed as linear combinations of
eigenmodes of the simply connected Euclidean space. A preceding work, which
provides a general method for implementing multi-connected topologies in
standard CMB codes, is then applied to simulate CMB maps and angular power
spectra for each space. Unlike in the 3-torus, the results in most
multi-connected flat spaces depend on the location of the observer. This effect
is discussed in detail. In particular, it is shown that the correlated circles
on a CMB map are generically not back-to-back, so that negative search of
back-to-back circles in the WMAP data does not exclude a vast majority of flat
or nearly flat topologies.Comment: 33 pages, 19 figures, 1 table. Submitted to PR
Casimir energy in multiply connected static hyperbolic Universes
We generalize a previously obtained result, for the case of a few other
static hyperbolic universes with manifolds of nontrivial topology as spatial
sections.Comment: accepted for publicatio
Simulating Cosmic Microwave Background maps in multi-connected spaces
This article describes the computation of cosmic microwave background
anisotropies in a universe with multi-connected spatial sections and focuses on
the implementation of the topology in standard CMB computer codes. The key
ingredient is the computation of the eigenmodes of the Laplacian with boundary
conditions compatible with multi-connected space topology. The correlators of
the coefficients of the decomposition of the temperature fluctuation in
spherical harmonics are computed and examples are given for spatially flat
spaces and one family of spherical spaces, namely the lens spaces. Under the
hypothesis of Gaussian initial conditions, these correlators encode all the
topological information of the CMB and suffice to simulate CMB maps.Comment: 33 pages, 55 figures, submitted to PRD. Higher resolution figures
available on deman
Large-scale power in the CMB and new physics: An analysis using Bayesian model comparison
Published versio
High statistics study of the K- -> pi0 e- nu decay
The decay K- -> pi0 e- nu has been studied using in-flight decays detected
with the "ISTRA+" spectrometer working at the 25 GeV negative secondary beam of
the U-70 PS. About 550K events were used for the analysis. The lambda+
parameter of the vector form-factor has been measured: lambda+ = 0.0286 +-
0.0008 (stat) +- 0.0006(syst). The limits on the possible tensor and scalar
couplings have been obtained: f(T)/f+(0)=0.021 +0.064 -0.075 (stat) +-
0.026(syst) ; f(S)/f+(0)=0.002 +0.020 -0.022 (stat) +- 0.003(syst)Comment: LaTeX-2e, epsfig.sty, 10 pages, 7 figures in EPS forma
The significance of the largest scale CMB fluctuations in WMAP
We investigate anomalies reported in the Cosmic Microwave Background maps
from the Wilkinson Microwave Anisotropy Probe (WMAP) satellite on very large
angular scales and discuss possible interpretations. Three independent
anomalies involve the quadrupole and octopole:
1. The cosmic quadrupole on its own is anomalous at the 1-in-20 level by
being low (the cut-sky quadrupole measured by the WMAP team is more strikingly
low, apparently due to a coincidence in the orientation of our Galaxy of no
cosmological significance);
2. The cosmic octopole on its own is anomalous at the 1-in-20 level by being
very planar;
3. The alignment between the quadrupole and octopole is anomalous at the
1-in-60 level.
Although the a priori chance of all three occurring is 1 in 24000, the
multitude of alternative anomalies one could have looked for dilutes the
significance of such a posteriori statistics. The simplest small universe model
where the universe has toroidal topology with one small dimension of order half
the horizon scale, in the direction towards Virgo, could explain the three
items above. However, we rule this model out using two topological tests: the
S-statistic and the matched circle test.Comment: N.B. that our results do not rule out the recently proposed
dodecahedron model of Luminet, Weeks, Riazuelo, Lehoucq & Uzan, which has a
36 degree twist between matched circles. 12 pages, 5 figs; more info at
http://www.hep.upenn.edu/~angelica/topology.htm
Can COBE see the shape of the universe?
In recent years, the large angle COBE--DMR data have been used to place
constraints on the size and shape of certain topologically compact models of
the universe. Here we show that this approach does not work for generic compact
models. In particular, we show that compact hyperbolic models do not suffer the
same loss of large angle power seen in flat or spherical models. This follows
from applying a topological theorem to show that generic hyperbolic three
manifolds support long wavelength fluctuations, and by taking into account the
dominant role played by the integrated Sachs-Wolfe effect in a hyperbolic
universe.Comment: 16 Pages, 5 Figures. Version published in Phys. Rev.
Preparation and characterization of a new mutant homolog of chemotaxis protein CheY from anaerobic hyperthermophilic microorganism Thermotoga naphthophila [Poluchenie i kharakteristika novogo mutantnogo gomologa khemotaksisnogo belka CheY iz gipertermofil'nogo anaérobnogo mikroorganizma Thermotoga naphthophila]
Using genetic engineering methods the expression vectors structures have been designed to produce recombinant proteins TnaCheY and Tna CheY-mut, the homologues of the chemotaxis protein CheY from the hyperthermophilic organism Thermotoga naphthophila in Escherichia coli BL21(DE3) cells. The cultivation conditions of transformed strains were optimized. The influence of episomal expression of the heterologous chemotaxis protein CheY on growth kinetics parameters of the culture of mesophilic bacteria E. coli was studied. The optimal purification flowchart of the obtained proteins using thermolysis is proposed. Using the E. coli BL21(DE3) laboratory strain as an example, the possibility of employment the episomal expression of such proteins to control the cultivation and production time of pharmaceutically and industrially valuable metabolites due to the impact on some stages of the bacterial chemotaxis is experimentally proved.S ispol'zovaniem genno-inzhenernykh metodov skonstruirovany ékspressionnye vektornye konstruktsii, obespechivaiushchie éffektivnuiu produktsiiu rekombinantnykh belkov TnaCheY i TnaCheY-mut – gomologov khemotaksisnogo belka CheY gipertermofil'nogo mikroorganizma Thermotoga naphthophila – v kletkakh Escherichia coli BL21(DE3). Optimizirovany usloviia kul'tivirovaniia transformirovannykh shtammov. Izucheno vliianie épisomal'noĭ ékspressii geterologichnogo khemotaksisnogo belka CheY na parametry kinetiki rosta kul'tury mezofil'nogo mikroorganizma E. coli. Predlozhena optimal'naia skhema ochistki poluchennykh belkov s ispol'zovaniem termolizisa. Na osnove poluchennykh dannykh v stat'e rassmotreny potentsial'nye oblasti primeneniia rekombinantnykh variantov termostabil'nogo khemotaksisnogo belka CheY. Na primere kletok laboratornogo shtamma E. coli BL21(DE3), éksperimental'no obosnovana vozmozhnost' ispol'zovaniia épisomal'noĭ ékspressii podobnykh belkov dlia upravleniia vremenem kul'tivirovaniia i produktsii farmatsevticheski i promyshlenno tsennykh metabolitov za schet vozdeĭstviia na otdel'nye étapy khemotaksisa bakteriĭ