12,972 research outputs found
From sensorimotor dependencies to perceptual practices: making enactivism social
Proponents of enactivism should be interested in exploring what notion of action best captures the type of action-perception link that the view proposes, such that it covers all the aspects in which our doings constitute and are constituted by our perceiving. This article proposes and defends the thesis that the notion of sensorimotor dependencies is insufficient to account for the reality of human perception, and that the central enactive notion should be that of perceptual practices. Sensorimotor enactivism is insufficient because it has no traction on socially dependent perceptions, which are essential to the role and significance of perception in our lives. Since the social dimension is a central desideratum in a theory of human perception, enactivism needs a notion that accounts for such an aspect. This article sketches the main features of the Wittgenstein-inspired notion of perceptual practices as the central notion to understand perception. Perception, I claim, is properly understood as woven into a type of social practices that includes food, dance, dress, music, etc. More specifically, perceptual practices are the enactment of culturally structured, normatively rich techniques of commerce of meaningful multi- and inter-modal perceptible material. I argue that perceptual practices explain three central features of socially dependent perception: attentional focus, aspects’ saliency, and modal-specific harmony-like relations
Directed paths on hierarchical lattices with random sign weights
We study sums of directed paths on a hierarchical lattice where each bond has
either a positive or negative sign with a probability . Such path sums
have been used to model interference effects by hopping electrons in the
strongly localized regime. The advantage of hierarchical lattices is that they
include path crossings, ignored by mean field approaches, while still
permitting analytical treatment. Here, we perform a scaling analysis of the
controversial ``sign transition'' using Monte Carlo sampling, and conclude that
the transition exists and is second order. Furthermore, we make use of exact
moment recursion relations to find that the moments always determine,
uniquely, the probability distribution $P(J)$. We also derive, exactly, the
moment behavior as a function of $p$ in the thermodynamic limit. Extrapolations
($n\to 0$) to obtain for odd and even moments yield a new signal for
the transition that coincides with Monte Carlo simulations. Analysis of high
moments yield interesting ``solitonic'' structures that propagate as a function
of . Finally, we derive the exact probability distribution for path sums
up to length L=64 for all sign probabilities.Comment: 20 pages, 12 figure
Spin superfluidity and spin-orbit gauge symmetry fixing
The Hamiltonian describing 2D electron gas, in a spin-orbit active medium,
can be cast into a consistent non-Abelian gauge field theory leading to a
proper definition of the spin current. The generally advocated gauge symmetric
version of the theory results in current densities that are gauge covariant, a
fact that poses severe concerns on their physical nature. We show that in fact
the problem demands gauge fixing, leaving no room to ambiguity in the
definition of physical spin currents. Gauge fixing also allows for polarized
edge excitations not present in the gauge symmetric case. The scenario here is
analogous to that of superconductivity gauge theory. We develop a variational
formulation that accounts for the constraints between U(1) physical fields and
SU(2) gauge fields and show that gauge fixing renders a physical matter and
radiation currents and derive the particular consequences for the Rashba SO
interaction.Comment: to appear in EP
Strongly Localized Electrons in a Magnetic Field: Exact Results on Quantum Interference and Magnetoconductance
We study quantum interference effects on the transition strength for strongly
localized electrons hopping on 2D square and 3D cubic lattices in a magnetic
field B. In 2D, we obtain closed-form expressions for the tunneling probability
between two arbitrary sites by exactly summing the corresponding phase factors
of all directed paths connecting them. An analytic expression for the
magnetoconductance, as an explicit function of the magnetic flux, is derived.
In the experimentally important 3D case, we show how the interference patterns
and the small-B behavior of the magnetoconductance vary according to the
orientation of B.Comment: 4 pages, RevTe
Good agricultural practices for more resilient agriculture: guidelines for producers and governments.
Good agricultural practices (GAPs) are an indispensable tool for risk management due to the close relationship between agriculture and climate, as well as the climate variability currently being experienced. The implementation of these tools, however, involves fostering innovation, increasing knowledge and giving stakeholders, small producers in particular, a holistic view, so that they may improve their production systems, increase their resilience, and ensure their sustainability.Inter-American Institute for Cooperation on Agriculture, Empresa Brasileira de Pesquisa Agropecuári
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