742 research outputs found
Microscopic Conductivity of Lattice Fermions at Equilibrium - Part I: Non-Interacting Particles
We consider free lattice fermions subjected to a static bounded potential and
a time- and space-dependent electric field. For any bounded convex region
() of space, electric fields
within drive currents. At leading order, uniformly
with respect to the volume of and
the particular choice of the static potential, the dependency on
of the current is linear and described by a conductivity distribution. Because
of the positivity of the heat production, the real part of its Fourier
transform is a positive measure, named here (microscopic) conductivity measure
of , in accordance with Ohm's law in Fourier space. This finite
measure is the Fourier transform of a time-correlation function of current
fluctuations, i.e., the conductivity distribution satisfies Green-Kubo
relations. We additionally show that this measure can also be seen as the
boundary value of the Laplace-Fourier transform of a so-called quantum current
viscosity. The real and imaginary parts of conductivity distributions satisfy
Kramers-Kronig relations. At leading order, uniformly with respect to
parameters, the heat production is the classical work performed by electric
fields on the system in presence of currents. The conductivity measure is
uniformly bounded with respect to parameters of the system and it is never the
trivial measure . Therefore, electric fields generally
produce heat in such systems. In fact, the conductivity measure defines a
quadratic form in the space of Schwartz functions, the Legendre-Fenchel
transform of which describes the resistivity of the system. This leads to
Joule's law, i.e., the heat produced by currents is proportional to the
resistivity and the square of currents
Estruturação de base cartográfica digital para o extremo Sul do RS.
bitstream/item/56042/1/COMUNICADO-142.pd
Eficiência de fungos micorrÃzicos na produção de matéria seca e de grãos na consorciação sorgo granÃfero (Sorghum bicolor (L.) Moench) e soja (Glycine max L.).
Mudanças na geografia agrÃcola no âmbito de microrregiões: Sergipe, 1990 e 2004.
bitstream/CPATC/19589/1/Doc-105.pd
Correlation of sorghum and soybean shoot dry matter weight with carbon and nitrogen assimilation enzymes.
Edição de resumos do 7º Congresso Brasileiro de Fisiologia Vegetal, BrasÃlia, 1999
Transferência de N entre sorgo granÃfero (Sorghum bicolor L. Moench) e soja (Glycine max L.) consorciados e inoculados com fungos micorrÃzicos.
Mudanças na geografia agrÃcola das microrregiões alagoanas nos anos de 1990 a 2004.
bitstream/CPATC/19585/1/Doc-101.pd
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