8,525 research outputs found
Microscopic observation of superconducting fluctuations in -(BEDT-TTF)Cu[N(CN)]Br by C NMR spectroscopy
We performed C-NMR experiment and measured spin-lattice relaxation
rate divided by temperature near the superconducting (SC) transition
temperature in -(BEDT-TTF)Cu[N(CN)]Br (-Br
salt), and -(BEDT-TTF)Cu(NCS) (-NCS salt). We
observed the reduction of starting at the temperature higher than
in -Br salt. Microscopic observation of quasi-particle density of
states in the fluctuating SC state revealed the effects of short-range Cooper
pairs induced in the normal state to the quasi-particle density of states. We
also performed systematic measurements in the fields both parallel and
perpendicular to the conduction plane in -Br and -NCS salts,
and confirmed that the reduction of above is observed only
in -Br salt regardless of the external field orientation.Comment: Accepted for publication in PR
Destabilizing Heegaard splittings of knot exteriors
AbstractWe give a necessary and sufficient condition for Heegaard splittings of knot exteriors to admit destabilizations. As an application, we show the following: let K1 and K2 be a pair of knots which is introduced by Morimoto as an example giving degeneration of tunnel number under connected sum. The Heegaard splitting of the exterior of K1#K2 derived from certain minimal unknotting tunnel systems of K1 and K2 is stabilized
When are KE-closed subcategories torsion-free classes?
Let be a commutative noetherian ring and denote by the
category of finitely generated -modules. In this paper, we study KE-closed
subcategories of , that is, additive subcategories closed under
kernels and extensions. We first give a characterization of KE-closed
subcategories: a KE-closed subcategory is a torsion-free class in a
torsion-free class. As an immediate application of the dual statement, we give
a conceptual proof of Stanley-Wang's result about narrow subcategories. Next,
we classify the KE-closed subcategories of when and when is a two-dimensional normal domain. More precisely, in
the former case, we prove that KE-closed subcategories coincide with
torsion-free classes in . Moreover, this condition implies
when is a homomorphic image of a Cohen-Macaulay ring
(e.g. a finitely generated algebra over a regular ring). Thus, we give a
complete answer for the title.Comment: 16 pages, comments welcome
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