2,580 research outputs found
The Science Case for a Scanning Electron Microscope on Mars
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Supergraph techniques for D=3,N=1 broken supersymmetric theories
We enlarge the usual D=3 N=1 supergraph techniques to include the case of
(explicitly or spontaneously) broken supersymmetric gauge theories. To
illustrate the utility of these techniques, we calculate the two-loop effective
potential of the SQED3 by using the tadpole and the vacuum bubble methods. In
these methods, to investigate the possibility of supersymmetry breaking, the
superfields must be shifted by dependent classical superfields (vacuum
expectation values), what implies in the explicit breakdown of supersymmetry in
the intermediate steps of the calculation. Nevertheless, after studying the
minimum of the resulting effective potential, we find that supersymmetry is
conserved, while gauge symmetry is dynamically broken, with a mass generated
for the gauge superfield.Comment: revtex4, 14 pages, 2 figures, Journal versio
Point Source Detection using the Spherical Mexican Hat Wavelet on simulated all-sky Planck maps
We present an estimation of the point source (PS) catalogue that could be
extracted from the forthcoming ESA Planck mission data. We have applied the
Spherical Mexican Hat Wavelet (SMHW) to simulated all-sky maps that include
CMB, Galactic emission (thermal dust, free-free and synchrotron), thermal
Sunyaev-Zel'dovich effect and PS emission, as well as instrumental white noise.
This work is an extension of the one presented in Vielva et al. (2001a). We
have developed an algorithm focused on a fast local optimal scale
determination, that is crucial to achieve a PS catalogue with a large number of
detections and a low flux limit. An important effort has been also done to
reduce the CPU time processor for spherical harmonic transformation, in order
to perform the PS detection in a reasonable time. The presented algorithm is
able to provide a PS catalogue above fluxes: 0.48 Jy (857 GHz), 0.49 Jy (545
GHz), 0.18 Jy (353 GHz), 0.12 Jy (217 GHz), 0.13 Jy (143 GHz), 0.16 Jy (100 GHz
HFI), 0.19 Jy (100 GHz LFI), 0.24 Jy (70 GHz), 0.25 Jy (44 GHz) and 0.23 Jy (30
GHz). We detect around 27700 PS at the highest frequency Planck channel and
2900 at the 30 GHz one. The completeness level are: 70% (857 GHz), 75% (545
GHz), 70% (353 GHz), 80% (217 GHz), 90% (143 GHz), 85% (100 GHz HFI), 80% (100
GHz LFI), 80% (70 GHz), 85% (44 GHz) and 80% (30 GHz). In addition, we can find
several PS at different channels, allowing the study of the spectral behaviour
and the physical processes acting on them. We also present the basic procedure
to apply the method in maps convolved with asymmetric beams. The algorithm
takes ~ 72 hours for the most CPU time demanding channel (857 GHz) in a Compaq
HPC320 (Alpha EV68 1 GHz processor) and requires 4 GB of RAM memory.Comment: 18 pages, 11 figures, revised version (minor changes). MNRAS
accepted; high quality color figures upon request to the author
Coleman-Weinberg mechanism in a three-dimensional supersymmetric Chern-Simons-matter model
Using the superfield formalism, we study the dynamical breaking of gauge
symmetry in the N=1 three-dimensional supersymmetric Chern-Simons model,
coupled to a complex scalar superfield with a quartic self-coupling. This is an
analogue of the conformally invariant Coleman-Weinberg model in four spacetime
dimensions. We show that a mass for the gauge and matter superfields are
dynamically generated after two-loop corrections to the effective
superpotential. We also discuss the N=2 extension of our work, showing that the
Coleman-Weinberg mechanism in such model is not feasible, because it is
incompatible with perturbation theory.Comment: 14 pages, 2 figures. Minor corrections, references added. Journal
versio
Dynamical (super)symmetry vacuum properties of the supersymmetric Chern-Simons-matter model
By computing the two-loop effective potential of the D=3 N=1 supersymmetric
Chern-Simons model minimally coupled to a massless self-interacting matter
superfield, it is shown that supersymmetry is preserved, while the internal
U(1) and the scale symmetries are broken at two-loop order, dynamically
generating masses both for the gauge superfield and for the real component of
the matter superfield.Comment: revtex4, 12 pages, 2 figures, journal versio
A New Pleiades Member at the Lithium Substellar Boundary
We present the discovery of an object in the Pleiades open cluster, named
Teide 2, with optical and infrared photometry which place it on the cluster
sequence slightly below the expected substellar mass limit. We have obtained
low- and high-resolution spectra that allow us to determine its spectral type
(M6), radial velocity and rotational broadening; and to detect H in
emission and Li I 670.8 nm in absorption. All the observed properties strongly
support the membership of Teide 2 into the Pleiades. This object has an
important role in defining the reappearance of lithium below the substellar
limit in the Pleiades. The age of the Pleiades very low-mass members based on
their luminosities and absence or presence of lithium is constrained to be in
the range 100--120 Myr.Comment: 17 pages, 3 figure
Spherical Mexican Hat wavelet: an application to detect non-Gaussianity in the COBE-DMR maps
The spherical Mexican Hat wavelet is introduced in this paper, with the aim
of testing the Gaussianity of the Cosmic Microwave Background temperature
fluctuations. Using the information given by the wavelet coefficients at
several scales, we have performed several statistical tests on the COBE-DMR
maps to search for evidence of non-Gaussianity. Skewness, kurtosis, scale-scale
correlations (for two and three scales) and Kolmogorov-Smirnov tests indicate
that the COBE-DMR data are consistent with a Gaussian distribution. We have
extended the analysis to compare temperature values provided by COBE-DMR data
with distributions (obtained from Gaussian simulations) at each pixel and at
each scale. The number of pixels with temperature values outside the 95% and
the 99% is consistent with that obtained from Gaussian simulations, at all
scales. Moreover, the extrema values for COBE-DMR data (maximum and minimum
temperatures in the map) are also consistent with those obtained from Gaussian
simulations.Comment: to be published in MNRA
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