21,486 research outputs found
Oscillatory tunneling magnetoresistance in magnetic tunnel junctions with inserted nonmagnetic layer
Oscillatory tunneling magnetoresistance (TMR) as a function of spacer
thickness is investigated theoretically for a magnetic tunnel junction with a
nonmagnetic layer inserted between the tunnel barrier and the ferromagnetic
layer. TMR is characterized in an analytical form, that is expressed with the
transmission and reflection amplitudes of single interfaces at the Fermi level,
and by the extremal wavevectors. Electronic structures with multiple bands are
taken into account in the derivation characterizing the TMR, and the proposed
analytical expression can be directly applied to real junctions. Based on our
model, the features of TMR dependence on spacer thickness are discussed,
including selection rules for the oscillation period. Numerical calculations
are performed using an envelope-function theory for several cases, and we show
that our model is in good agreement with the exact result.Comment: 21 pages (preprint), 6 figure
One-dimensional wave equations defined by fractal Laplacians
We study one-dimensional wave equations defined by a class of fractal
Laplacians. These Laplacians are defined by fractal measures generated by
iterated function systems with overlaps, such as the well-known infinite
Bernoulli convolution associated with the golden ratio and the 3-fold
convolution of the Cantor measure. The iterated function systems defining these
measures do not satisfy the post-critically finite condition or the open set
condition. By using second-order self-similar identities introduced by
Strichartz et al., we discretize the equations and use the finite element and
central difference methods to obtain numerical approximations to the weak
solutions. We prove that the numerical solutions converge to the weak solution,
and obtain estimates for the rate of convergence
Minimal Flavor Violation with Axion-like Particles
We revisit the flavor-changing processes involving an axion-like particle
(ALP) in the context of generic ALP effective lagrangian with a discussion of
possible UV completions providing the origin of the relevant bare ALP
couplings. We focus on the minimal scenario that ALP has flavor-conserving
couplings at tree level, and the leading flavor-changing couplings arise from
the loops involving the Yukawa couplings of the Standard Model fermions. We
note that such radiatively generated flavor-changing ALP couplings can be
easily suppressed in field theoretic ALP models with sensible UV completion. We
discuss also the implication of our result for string theoretic ALP originating
from higher-dimensional -form gauge fields, for instance for ALP in large
volume string compactification scenario.Comment: 41 pages, 3 figures; v3: a discussion on general extended Higgs
sector added in sec. 2, version published in JHE
An empirical survey of the benefits of implementing pay for safety scheme (PFSS) in the Hong Kong construction industry
2010-2011 > Academic research: refereed > Publication in refereed journalAccepted ManuscriptPublishe
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