31,691 research outputs found
Generalized -conformal change and special Finsler spaces
In this paper, we investigate the change of Finslr metrics which we refer to as a
generalized -conformal change. Under this change, we study some special
Finsler spaces, namely, quasi C-reducible, semi C-reducible, C-reducible,
-like, -like and -like Finsler spaces. We also obtain the
transformation of the T-tensor under this change and study some interesting
special cases. We then impose a certain condition on the generalized
-conformal change, which we call the b-condition, and investigate the
geometric consequences of such condition. Finally, we give the conditions under
which a generalized -conformal change is projective and generalize some
known results in the literature.Comment: References added, some modifications are performed, LateX file, 24
page
Cuntz-Pimsner C*-algebras associated with subshifts
By using C*-correspondences and Cuntz-Pimsner algebras, we associate to every
subshift (also called a shift space) a C*-algebra , which is a
generalization of the Cuntz-Krieger algebras. We show that is the
universal C*-algebra generated by partial isometries satisfying relations given
by . We also show that is a one-sided conjugacy invariant of .Comment: 28 pages. This is a slightly updated version of a preprint from 2004.
Submitted for publication. In version 2 the Introduction has been changed,
two remarks (Remark 7.6 and 7.7) have been added and the list of references
has been update
Universal Reduction of Effective Coordination Number in the Quasi-One-Dimensional Ising Model
Critical temperature of quasi-one-dimensional general-spin Ising ferromagnets
is investigated by means of the cluster Monte Carlo method performed on
infinite-length strips, L times infty or L times L times infty. We find that in
the weak interchain coupling regime the critical temperature as a function of
the interchain coupling is well-described by a chain mean-field formula with a
reduced effective coordination number, as the quantum Heisenberg
antiferromagnets recently reported by Yasuda et al. [Phys. Rev. Lett. 94,
217201 (2005)]. It is also confirmed that the effective coordination number is
independent of the spin size. We show that in the weak interchain coupling
limit the effective coordination number is, irrespective of the spin size,
rigorously given by the quantum critical point of a spin-1/2 transverse-field
Ising model.Comment: 12 pages, 6 figures, minor modifications, final version published in
Phys. Rev.
Topological Origin of Zero-Energy Edge States in Particle-Hole Symmetric Systems
A criterion to determine the existence of zero-energy edge states is
discussed for a class of particle-hole symmetric Hamiltonians. A ``loop'' in a
parameter space is assigned for each one-dimensional bulk Hamiltonian, and its
topological properties, combined with the chiral symmetry, play an essential
role. It provides a unified framework to discuss zero-energy edge modes for
several systems such as fully gapped superconductors, two-dimensional d-wave
superconductors, and graphite ribbons. A variants of the Peierls instability
caused by the presence of edges is also discussed.Comment: Completely rewritten. Discussions on coexistence of is- or
id_{xy}-wave order parameter near edges in d_{x^{2}-y^{2}}-wave
superconductors are added; 4 pages, 3 figure
Gravitino Dark Matter with Weak-Scale Right-Handed Sneutrino
We consider cosmological implications of supersymmetric models with
right-handed (s)neutrinos where the neutrino masses are purely Dirac-type. We
pay particular attention to the case where gravitino is the lightest
superparticle while one of the right-handed sneutrinos is next-to-the-lightest
superparticle. We study constraints from big-bang nuleosynthesis and show that
the constraints could be relaxed compared to the case without right-handed
sneutrinos. As a result, the gravitino-dark-matter scenario becomes viable with
relatively large value of the gravitino mass. We also discuss constraints from
the structure formation; in our model, the free-streaming length of the
gravitino dark matter may be as long as O(1 Mpc), which is comparable to the
present observational upper bound on the scale of free-streaming.Comment: 18 pages, 6 figure
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