39,768 research outputs found
Mobi algebra as an abstraction to the unit interval and its comparison to rings
We introduce a new algebraic structure, called mobi algebra, consisting of three constants and one ternary operation. The canonical example of a mobi algebra is the unit interval with the three constants 0, 1, and 1/2 and the ternary operation given by the formula xâyx+yz. We study some of its properties and prove that every unitary ring with one half uniquely determines and is uniquely determined by a mobi algebra with one double. Another algebraic structure, called involutive medial monoid (IMM), is considered to establish the passage between rings and mobi algebras.info:eu-repo/semantics/publishedVersio
Evidence for non-Gaussianity in the CMB
In a recent Letter we have shown how COBE-DMR maps may be used to disprove
Gaussianity at a high confidence level. In this report we digress on a few
issues closely related to this Letter. We present the general formalism for
surveying non-Gaussianity employed. We present a few more tests for
systematics. We wonder about the theoretical implications of our result.Comment: Proceedings of the Planck meeting, Santender 9
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 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.
Addendum: It is given a short proof that equation (10) is wrong, therefore
equations (12-17) are meaningless. The remaining results are correct being
generic derivations for nonmagnetized plasmas derived in a covariant QFT
framework.Comment: v1: 1+6 pages v2: Several discussions rewritten; Abstract rewritten;
References added; v3: includes Addendu
Many-body effects on the ringlike structures in two-subband wells
The longitudinal resistivity of two-dimensional electron gases
formed in wells with two subbands displays ringlike structures when plotted in
a density--magnetic-field diagram, due to the crossings of spin-split Landau
levels (LLs) from distinct subbands. Using spin density functional theory and
linear response, we investigate the shape and spin polarization of these
structures as a function of temperature and magnetic-field tilt angle. We find
that (i) some of the rings "break" at sufficiently low temperatures due to a
quantum Hall ferromagnetic phase transition, thus exhibiting a high degree of
spin polarization (%) within, consistent with the NMR data of Zhang
\textit{et al.} [Phys. Rev. Lett. {\bf 98}, 246802 (2007)], and (ii) for
increasing tilting angles the interplay between the anticrossings due to
inter-LL couplings and the exchange-correlation (XC) effects leads to a
collapse of the rings at some critical angle , in agreement with the
data of Guo \textit{et al.} [Phys. Rev. B {\bf 78}, 233305 (2008)].Comment: 4 pages, 3 figure
The 4 Year COBE DMR data is non-Gaussian
I review our recent claim that there is evidence of non-Gaussianity in the 4
Year COBE DMR data. I describe the statistic we apply, the result we obtain and
make a detailed list of the systematics we have analysed. I finish with a
qualitative understanding of what it might be and its implications.Comment: Proceedings of Rome 3K conference, 5 pages, 3 figure
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