13,795 research outputs found
Controlled switching between paramagnetic and diamagnetic Meissner effect in Pb/Co nanocomposites
A hybrid system which consists of a superconducting (SC) Pb film (100 nm
thickness) containing 1 vol% single domain ferromagnetic (FM) Co
particles of mean-size 4.5 nm reveal unusual magnetic properties: (i) a
controlled switching between the usual diamagnetic and the unusual paramagnetic
Meissner effect in field cooling as well as in zero-field cooling experiments
(ii) amplification of the positive magnetization when the sample enters the SC
state below T. These experimental findings can be explained by the
formation of spontaneous vortices and the possible alignment of these vortices
due to the foregoing alignment of the Co particle FM moments by an external
magnetic field.Comment: 5 pages, 3 figure
Can the Lepton Flavor Mixing Matrix Be Symmetric?
Current neutrino oscillation data indicate that the 3x3 lepton flavor mixing
matrix V is likely to be symmetric about its V_{e3}-V_{\mu 2}-V_{\tau 1} axis.
This off-diagonal symmetry corresponds to three pairs of {\it congruent}
unitarity triangles in the complex plane. Terrestrial matter effects can
substantially modify the genuine CP-violating parameter and off-diagonal
asymmetries of V in realistic long-baseline experiments of neutrino
oscillations.Comment: RexTex 14 pages (4 PS figures). More discussions adde
Distinguishable RGE running effects between Dirac neutrinos and Majorana neutrinos with vanishing Majorana CP-violating phases
In a novel parametrization of neutrino mixing and in the approximation of
-lepton dominance, we show that the one-loop renormalization-group
equations (RGEs) of Dirac neutrinos are different from those of Majorana
neutrinos even if two Majorana CP-violating phases vanish. As the latter can
keep vanishing from the electroweak scale to the typical seesaw scale, it makes
sense to distinguish between the RGE running effects of neutrino mixing
parameters in Dirac and Majorana cases. The differences are found to be quite
large in the minimal supersymmetric standard model with sizable ,
provided the masses of three neutrinos are nearly degenerate or have an
inverted hierarchy.Comment: 12 pages, 5 figure
Multiscale Technicolor and the Zbb-bar Vertex
We estimate the correction to the Zbb-bar vertex arising from the exchanges
of the sideways extended technicolor (ETC) boson and the flavor-diagonal ETC
boson in the multiscale walking technicolor model. The obtained result is too
large to explain the present data. However, if we introduce a new self-
interaction for the top quark to induce the top quark condensate serving as the
origin of the large top quark mass, the corrected R_b=Gamma_b/Gamma_h can be
consistent with the recent LEP data. The corresponding correction to
R_c=Gamma_c/Gamma_h is shown to be negligibly small.Comment: 9-page LaTex fil
Nearly Bi-Maximal Neutrino Mixing, Muon g-2 Anomaly and Lepton-Flavor-Violating Processes
We interpret the newly observed muon g-2 anomaly in the framework of a
leptonic Higgs doublet model with nearly degenerate neutrino masses and nearly
bi-maximal neutrino mixing. Useful constraints are obtained on the rates of
lepton-flavor-violating rare decays ,
and as well as the - conversion ratio .
We find that , and
depend crucially on possible non-zero but samll values of the
neutrino mixing matrix element , and they are also sensitive to the
Dirac-type CP-violating phase. In particular, we show that , and are approximately in the ratio if is much larger than , and in the
ratio if is much lower than , where and are the corresponding mass-squared
differences of atmospheric and solar neutrino oscillations.Comment: LaTex 6 pages (2 PS figures). Phys. Rev. D (in printing
More Straightforward Extraction of the Fundamental Lepton Mixing Parameters from Long-Baseline Neutrino Oscillations
We point out the simple reversibility between the fundamental neutrino mixing
parameters in vacuum and their effective counterparts in matter. The former can
therefore be expressed in terms of the latter, allowing more straightforward
extraction of the genuine lepton mixing quantities from a variety of
long-baseline neutrino oscillation experiments. In addition to the
parametrization-independent results, we present the formulas based on the
standard parametrization of the lepton flavor mixing matrix and give a typical
numerical illustration.Comment: RevTex 10 pages. Minor changes. Phys. Rev. D in printin
Anomalous elasticity of nematic elastomers
We study the anomalous elasticity of nematic elastomers by employing the
powers of renormalized field theory. Using general arguments of symmetry and
relevance, we introduce a minimal Landau-Ginzburg-Wilson elastic energy for
nematic elastomers. Performing a diagrammatic low temperature expansion, we
analyze the fluctuations of the displacement fields at and below the upper
critical dimension 3. Our analysis reveals an anomaly of certain elastic moduli
in the sense that they depend on the length scale. In this dependence
is logarithmic and below it is of power law type with anomalous scaling
exponents. One of the 4 relevant shear moduli vanishes at long length scales
whereas the only relevant bending modulus diverges.Comment: 4 page
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