9,575 research outputs found
Solving simple quaternionic differential equations
The renewed interest in investigating quaternionic quantum mechanics, in
particular tunneling effects, and the recent results on quaternionic
differential operators motivate the study of resolution methods for
quaternionic differential equations. In this paper, by using the real matrix
representation of left/right acting quaternionic operators, we prove existence
and uniqueness for quaternionic initial value problems, discuss the reduction
of order for quaternionic homogeneous differential equations and extend to the
non-commutative case the method of variation of parameters. We also show that
the standard Wronskian cannot uniquely be extended to the quaternionic case.
Nevertheless, the absolute value of the complex Wronskian admits a
non-commutative extension for quaternionic functions of one real variable.
Linear dependence and independence of solutions of homogeneous (right) H-linear
differential equations is then related to this new functional. Our discussion
is, for simplicity, presented for quaternionic second order differential
equations. This involves no loss of generality. Definitions and results can be
readily extended to the n-order case.Comment: 9 pages, AMS-Te
Graphene tests of Klein phenomena
Graphene is characterized by chiral electronic excitations. As such it
provides a perfect testing ground for the production of Klein pairs
(electron/holes). If confirmed, the standard results for barrier phenomena must
be reconsidered with, as a byproduct, the accumulation within the barrier of
holes.Comment: 8 page
Quaternionic eigenvalue problem
We discuss the (right) eigenvalue equation for , and
linear quaternionic operators. The possibility to introduce an
isomorphism between these operators and real/complex matrices allows to
translate the quaternionic problem into an {\em equivalent} real or complex
counterpart. Interesting applications are found in solving differential
equations within quaternionic formulations of quantum mechanics.Comment: 13 pages, AMS-Te
Right eigenvalue equation in quaternionic quantum mechanics
We study the right eigenvalue equation for quaternionic and complex linear
matrix operators defined in n-dimensional quaternionic vector spaces. For
quaternionic linear operators the eigenvalue spectrum consists of n complex
values. For these operators we give a necessary and sufficient condition for
the diagonalization of their quaternionic matrix representations. Our
discussion is also extended to complex linear operators, whose spectrum is
characterized by 2n complex eigenvalues. We show that a consistent analysis of
the eigenvalue problem for complex linear operators requires the choice of a
complex geometry in defining inner products. Finally, we introduce some
examples of the left eigenvalue equations and highlight the main difficulties
in their solution.Comment: 24 pages, AMS-Te
Universal Elasticity and Fluctuations of Nematic Gels
We study elasticity of spontaneously orientationally-ordered amorphous
solids, characterized by a vanishing transverse shear modulus, as realized for
example by nematic elastomers and gels. We show that local heterogeneities and
elastic nonlinearities conspire to lead to anomalous nonlocal universal
elasticity controlled by a nontrivial infared fixed point. Namely, at long
scales, such solids are characterized by universal shear and bending moduli
that, respectively, vanish and diverge at long scales, are universally
incompressible and exhibit a universal negative Poisson ratio and a non-Hookean
elasticity down to arbitrarily low strains. Based on expansion about five
dimensions, we argue that the nematic order is stable to thermal fluctuation
and local hetergeneities down to d_lc < 3.Comment: 4 RevTeX pgs, submitted to PR
Dirac Equation Studies in the Tunnelling Energy Zone
We investigate the tunnelling zone V0 < E < V0+m for a one-dimensional
potential within the Dirac equation. We find the appearance of superluminal
transit times akin to the Hartman effect.Comment: 12 pages, 4 figure
The EGNoG Survey: Gas Excitation in Normal Galaxies at z~0.3
As observations of molecular gas in galaxies are pushed to lower star
formation rate galaxies at higher redshifts, it is becoming increasingly
important to understand the conditions of the gas in these systems to properly
infer their molecular gas content. The rotational transitions of the carbon
monoxide (CO) molecule provide an excellent probe of the gas excitation
conditions in these galaxies. In this paper we present the results from the gas
excitation sample of the Evolution of molecular Gas in Normal Galaxies (EGNoG)
survey at the Combined Array for Research in Millimeter-wave Astronomy (CARMA).
This subset of the full EGNoG sample consists of four galaxies at z~0.3 with
star formation rates of 40-65 M_Sun yr^-1 and stellar masses of ~2x10^11 M_Sun.
Using the 3 mm and 1 mm bands at CARMA, we observe both the CO(1-0) and CO(3-2)
transitions in these four galaxies in order to probe the excitation of the
molecular gas. We report robust detections of both lines in three galaxies (and
an upper limit on the fourth), with an average line ratio, r_31 = L'_CO(3-2) /
L'_CO(1-0), of 0.46 \pm 0.07 (with systematic errors \lesssim 40%), which
implies sub-thermal excitation of the CO(3-2) line. We conclude that the
excitation of the gas in these massive, highly star-forming galaxies is
consistent with normal star-forming galaxies such as local spirals, not
starbursting systems like local ultra-luminous infrared galaxies. Since the
EGNoG gas excitation sample galaxies are selected from the main sequence of
star-forming galaxies, we suggest that this result is applicable to studies of
main sequence galaxies at intermediate and high redshifts, supporting the
assumptions made in studies that find molecular gas fractions in star forming
galaxies at z~1-2 to be an order of magnitude larger than what is observed
locally.Comment: Accepted for publication in the Astrophysical Journal, to appear
January 2013; 18 pages, 10 figures, 6 table
The role of personal information sources on the decision-making process of Costa Rican dairy farmers
The attitudes of farmers in relation to the importance of different people as information and opinion sources (InfS) for different phases of the decision-making process were studied in 91 Costa Rican dairy farmers. The InfS studied were: Family members, Other farmers, Technical advisors, Farm staff and Commercial agents, while the phases were: Problem detection, Seeking for problem solutions, Seeking for new practices and Seeking for opinion. A Multidimensional Preference Analysis (MDPREF) was used to obtain a two-dimensional map of preference of the farmers. A factor analysis was used to define new variables representing the farmers' predilection towards the InfS. A canonical correlation analysis was performed to find-out simple and canonical correlation between farmers'/farms' characteristics and the InfS preferences. Informational profiles in the population were defined through a Cluster Analysis. The MDPREF suggests that Family members and Technical advisors were the most preferred InfS. However their relative importance changed throughout the phases. Farm staff were rated in third place and their role became more important in the âProblem detectionâ phase. Other farmers and Commercial agents were, in general, the less preferred information sources. The former became slightly more important in the âSeeking for new practicesâ phase. The canonical correlation analysis found three low-medium correlations between the farmers'/farms' characteristics and the InfS factors. These correlations showed that the farmers' age, educational level and dedication and the farms' characteristics of area, herd size and distance to population centres had significant influence on the preference of the farmers towards different information sources. The cluster analysis found nine groups of similar farmers according to their preferences towards informational sources. Some implications mainly for extension activities are also stated and discussed. The importance of different informational sources slightly change throughout the decision-making steps, the family and farm staff being the most preferred information sources
WP: 4.2 Effects of Ocean Acidification and Warming on the functioning of fish heart mitochondria
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