74,646 research outputs found
q-Deformation of the Krichever-Novikov Algebra
The recent focus on deformations of algebras called quantum algebras can be
attributed to the fact that they appear to be the basic algebraic structures
underlying an amazingly diverse set of physical situations. To date many
interesting features of these algebras have been found and they are now known
to belong to a class of algebras called Hopf algebras [1]. The remarkable
aspect of these structures is that they can be regarded as deformations of the
usual Lie algebras. Of late, there has been a considerable interest in the
deformation of the Virasoro algebra and the underlying Heisenberg algebra
[2-11]. In this letter we focus our attention on deforming generalizations of
these algebras, namely the Krichever-Novikov (KN) algebra and its associated
Heisenberg algebra.Comment: AmsTex. To appear in Letters in Mathematical Physic
Symmetric Multiplets in Quantum Algebras
We consider a modified version of the coproduct for \U(\su_q(2)) and show
that in the limit when , there exists an essentially
non-cocommutative coproduct. We study the implications of this
non-cocommutativity for a system of two spin- particles. Here it is shown
that, unlike the usual case, this non-trivial coproduct allows for symmetric
and anti-symmetric states to be present in the multiplet. We surmise that our
analysis could be related to the ferromagnetic and antiferromagnetic cases of
the Heisenberg magnets.Comment: Needs subeqnarray.sty. To be published in Mod Phys Lett.
Constraints on millicharged particles with low threshold germanium detectors at Kuo-Sheng Reactor Neutrino Laboratory
Relativistic millicharged particles () have been proposed in various
extensions to the Standard Model of particle physics. We consider the scenarios
where they are produced at nuclear reactor core and via interactions of
cosmic-rays with the earth's atmosphere. Millicharged particles could also be
candidates for dark matter, and become relativistic through acceleration by
supernova explosion shock waves. The atomic ionization cross section of
with matter are derived with the equivalent photon approximation.
Smoking-gun signatures with significant enhancement in the differential cross
section are identified. New limits on the mass and charge of are
derived, using data taken with a point-contact germanium detector with 500g
mass functioning at an energy threshold of 300~eV at the Kuo-Sheng Reactor
Neutrino Laboratory.Comment: 8 pages, 7 figure
Crystal growth and ambient and high pressure study of the reentrant superconductor Tm_2Fe_3Si_5
We report single crystal growth of the reentrant superconductor Tm_2Fe_3Si_5,
and measurements of the anisotropic static magnetic susceptibility \chi(T) and
isothermal magnetization M(H), ac susceptibility \chi_ac(T), electrical
resistivity \rho(T) and heat capacity C(T) at ambient pressure and \chi_ac(T)
at high pressure. The magnetic susceptibility along the c-axis \chi_c(T) shows
a small maximum around 250 K and does not follow the Curie-Weiss behavior while
the magnetic susceptibility along the a-axis \chi_a(T) follows a Curie-Weiss
behavior between 130 K and 300 K with a Weiss temperature \theta and an
effective magnetic moment \mu_eff which depend on the temperature range of the
fit. The easy axis of magnetization is perpendicular to the c-axis and
\chi_a/\chi_c = 3.2 at 1.8 K. The ambient pressure \chi_ac(T) and C(T)
measurements confirm bulk antiferromagnetic ordering at T_N = 1.1 K. The sharp
drop in \chi_ac below T_N is suggestive of the existence of a spin-gap. We
observe superconductivity only under applied pressures P\geq 2 kbar. The
temperature-pressure phase diagram showing the non-monotonic dependence of the
superconducting transition temperature T_c on pressure P is presented.Comment: 7 pages, 8 figure
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