12,948 research outputs found
Twist transition of nematic hyperbolic hedgehogs
Stability of an idealized hyperbolic hedgehog in a nematic liquid crystal against a twist transition is investigated by extending the methodology of Rüdinger and Stark [Liq. Cryst. 26, 753 (1999)], where the hedgehog is confined between two concentric spheres. In the ideal hyperbolic-hedgehog the molecular orientation is assumed to rotate proportionally with respect to the inclination angle, θ (and in the opposite sense). However, when splay, k11, and bend, k33, moduli differ this proportionality is lost and the liquid crystal deforms relative to the ideal with bend and splay. Although slight, these deformations are shown to significantly shift the transition if k11/k33 is small. By increasing the degree of confinement the twist transition can be inhibited, a characteristic both hyperbolic and radial hedgehogs have in common. The twist transition of a hyperbolic defect that accompanies a particle is found to be well predicted by the earlier stability analysis of a thick shell
The neutrino puzzle in the light of SNO
SNO's neutral current measurement has added a new piece to the emerging
neutrino physics puzzle. Putting together the presently available experimental
information, an essentially unique picture emerges: The solar neutrino anomaly
is explained by nu_e --> nu_tau oscillations, the atmospheric neutrino anomaly
is explained by nu_{mu} --> nu_s and the LSND data are explained by nu_e -->
nu_{mu}. This scheme will be tested by future experiments: MiniBooNE will test
the oscillation explanation of the LSND anomaly, while the long baseline
experiments will discriminate between the nu_{mu} --> nu_s and nu_{mu} -->
nu_{tau} possibilities for resolving the atmospheric anomaly (confirming or
disconfirming the Super-Kamiokande result that the latter is favoured over the
former).Comment: about 4 pages, expanded discussio
Analytic Calculation of Neutrino Mass Eigenvalues
Implicaion of the neutrino oscillation search for the neutrino mass square
difference and mixing are discussed. We have considered the effective majorana
mass m_{ee}, related for \beta\beta_{0\nu}decay. We find limits for neutrino
mass eigen value m_{i} in the different neutrino mass spectrum,which explain
the different neutrino data.Comment: 10 page
Neutrinos and Gauge Unification
The approximate unification of gauge couplings is the best indirect evidence
for low-energy supersymmetry, although it is not perfect in its simplest
realizations. Given the experimental evidence for small non-zero neutrino
masses, it is plausible to extend the MSSM with three right-handed neutrino
chiral multiplets, with large Majorana masses below the unification scale, so
that a see-saw mechanism can be implemented. In this extended MSSM, the
unification prediction for the strong gauge coupling constant at M_Z can be
lowered by up to \sim 5%, bringing it closer to the experimental value at
1\sigma, therefore improving significantly the accuracy of gauge coupling
unification.Comment: 5 pages, LaTeX, 1 figur
The Dual Meissner Effect and Magnetic Displacement Currents
The dual Meissner effect is observed without monopoles in quenched
QCD with Landau gauge-fixing. Magnetic displacement currents which are
time-dependent Abelian magnetic fields play a role of solenoidal currents
squeezing Abelian electric fields. Monopoles are not always necessary to the
dual Meissner effect. The squeezing of the electric flux means the dual London
equation and the massiveness of the Abelian electric fields as an asymptotic
field. The mass generation of the Abelian electric fields is related to a gluon
condensate of mass dimension 2.Comment: 4 pages, 5 Postscript figures, title modified, some references added,
minor changes made ; Accepted for publication in Phys.Rev.Let
Computing Groebner Fans
This paper presents algorithms for computing the Groebner fan of an arbitrary
polynomial ideal. The computation involves enumeration of all reduced Groebner
bases of the ideal. Our algorithms are based on a uniform definition of the
Groebner fan that applies to both homogeneous and non-homogeneous ideals and a
proof that this object is a polyhedral complex. We show that the cells of a
Groebner fan can easily be oriented acyclically and with a unique sink,
allowing their enumeration by the memory-less reverse search procedure. The
significance of this follows from the fact that Groebner fans are not always
normal fans of polyhedra in which case reverse search applies automatically.
Computational results using our implementation of these algorithms in the
software package Gfan are included.Comment: 26 page
Thermoelectricity of EuCu{2}(Ge{1-x}Si{x}){2} intermetallics
The evolution of the thermopower EuCu{2}(Ge{1-x}Si{x}){2} intermetallics,
which is induced by the Si-Ge substitution, is explained by the Kondo
scattering of conduction electrons on the Eu ions which fluctuate between the
magnetic 2+ and non-magnetic 3+ Hund's rule configurations. The Si-Ge
substitution is equivalent to chemical pressure which modifies the coupling and
the relative occupation of the {\it f} and conduction states.Comment: 2 pages, Proceedings of the SCES 2005 confernece. Physica B (2006),
in pres
Maximum lepton asymmetry from active-sterile neutrino oscillations in the Early Universe
A large lepton asymmetry could be generated in the Early Universe by
oscillations of active to sterile neutrinos with a small mixing angle sin 2
\theta < 10^-2. The final order of magnitude of the lepton asymmetry \eta is
mainly determined by its growth in the last stage of evolution when the MSW
resonance dominates the kinetic equations. In this paper we present a simple
way of calculating the maximum possible lepton asymmetry which can be created.
Our results are in good agreement to previous calculations. Furthermore, we
find that the growth of asymmetry does not obey any particular power law. We
find that the maximum possible asymmetry at the freeze-out of the n/p ratio at
T \sim 1 MeV strongly depends on the mass-squared difference \delta m^2: the
asymmetry is negligible for \delta m^2 \ll 1 eV^2 and reaches asymptotically
large values for \delta m^2 \ge 50 eV^2.Comment: 14 pp, 4 figure
Maximal oscillations, Borexino and smoking guns
We examine the maximal and
oscillation solutions to the solar neutrino problem. These solutions lead to
roughly a 50% solar flux reduction for the large parameter range . It is known that the earth regeneration
effect may cause a potentially large night-day asymmetry even for maximal
neutrino oscillations. We investigate the night-day asymmetry predictions for
the forthcoming Borexino measurement of the ^7Be neutrinos for both maximal
and oscillations. If case and y = 1 for case) then the maximal
neutrino oscillations will lead to observable night-day asymmetries in Borexino
and/or superKamiokande. With Kamland covering the high mass range, and Borexino/superK covering the low mass range,
("just so" region),
essentially all of the parameter space will soon be scrutinized.Comment: Various improvements...still about 6 pages with some fig
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