36,084 research outputs found
Why Successful Performance in Imagery Tasks Does not Require the Manipulation of Mental Imagery
Nanay (2017) argues for unconscious mental imagery, inter alia based on the assumption that successful performance in imagery tasks requires the manipulation of mental imagery. I challenge this assumption with the help of results presented in Shepard and Metzler (1971), Zeman et al. (2010), and Keogh and Pearson (2018). The studies suggest that imagery tasks can be successfully performed by means of cognitive/propositional strategies which do not rely on imagery
Sensitivity to interaural time differences in the medial superior olive of a small mammal, the Mexican free-tailed bat
Neurons in the medial superior olive (MSO) are thought to encode interaural time differences (ITDs), the main binaural cues used for localizing low-frequency sounds in the horizontal plane. The underlying mechanism is supposed to rely on a coincidence of excitatory inputs from the two ears that are phase-locked to either the stimulus frequency or the stimulus envelope. Extracellular recordings from MSO neurons in several mammals conform with this theory. However, there are two aspects that remain puzzling. The first concerns the role of the MSO in small mammals that have relatively poor low-frequency hearing and whose heads generate only very small ITDs. The second puzzling aspect of the scenario concerns the role of the prominent binaural inhibitory inputs to MSO neurons. We examined these two unresolved issues by recording from MSO cells in the Mexican free-tailed bat. Using sinusoidally amplitude-modulated tones, we found that the ITD sensitivities of many MSO cells in the bat were remarkably similar to those reported for larger mammals. Our data also indicate an important role for inhibition in sharpening ITD sensitivity and increasing the dynamic range of ITD functions. A simple model of ITD coding based on the timing of multiple inputs is proposed. Additionally, our data suggest that ITD coding is a by-product of a neuronal circuit that processes the temporal structure of sounds. Because of the free-tailed bat's small head size, ITD coding is most likely not the major function of the MSO in this small mammal and probably other small mammals
Precautionary Saving, Borrowing Constraints, and Fiscal Policy
Recent empirical studies suggest that the average marginal propensity to consume (MPC) has declined. This paper explains the declining trend of the MPC with a standard representative consumer model where borrowing constraints become more relaxed as suggested by data. With an increase in available credit, the consumer can easily spread out negative income shocks by credit card borrowing or consumer loans. As a result, consumers under relaxed borrowing constraints have lower MPCs than they had a generation ago. This result suggests that policy makers should now account for the less responsiveness of consumers to fiscal stimulus plans aiming at boosting consumptiMarginal Propensity to Consume, Borrowing Constraints, Precautionary Saving, Consumption Function, Effectiveness of Fiscal Policy
Quantum backgrounds and QFT
We introduce the concept of a quantum background and a functor QFT. In the
case that the QFT moduli space is smooth formal, we construct a flat quantum
superconnection on a bundle over QFT which defines algebraic structures
relevant to correlation functions in quantum field theory. We go further and
identify chain level generalizations of correlation functions which should be
present in all quantum field theories.Comment: 28 pages, published versio
126 GeV Higgs in Next-to-Minimal Universal Extra Dimensions
Discovery of a Higgs boson and precise measurements of its properties open a
new window to test physics beyond the standard model. Models with Universal
Extra Dimensions are not exception. Kaluza-Klein excitations of the standard
model particles contribute to the production and decay of the Higgs boson. In
particular, the parameters associated with third generation quarks are
constrained by Higgs data, which are relatively insensitive to other searches
often involving light quarks and leptons. We investigate implications of the
126 GeV Higgs in Next-to-Minimal Universal Extra Dimensions, and show that
boundary terms and bulk masses allow a lower compactification scale as compared
to in Minimal Universal Extra Dimensions.Comment: 12 pages, 4 figure
Possible Suppression of Resonant Signals for Split-UED by Mixing at the LHC?
The mixing of the imaginary parts of the transition amplitudes of nearby
resonances via the breakdown of the Breit-Wigner approximation has been shown
to lead to potentially large modifications in the signal rates for new physics
at colliders. In the case of suppression, this effect may be significant enough
to lead to some new physics signatures being initially missed in searches at,
e.g., the LHC. Here we explore the influence of this `width mixing' on the
production of the nearly degenerate, level-2 Kaluza-Klein (KK) neutral gauge
bosons present in Split-UED. We demonstrate that in this particular case large
cross section modifications in the resonance region are necessarily absent and
explain why this is so based on the group theoretical structure of the SM.Comment: 10 pages, 2 figures; discussion and references adde
Cohomological Yang-Mills Theories on Kahler 3-Folds
We study topological gauge theories with N=(2,0) supersymmetry based on
stable bundles on general Kahler 3-folds. In order to have a theory that is
well defined and well behaved, we consider a model based on an extension of the
usual holomorphic bundle by including a holomorphic 3-form. The correlation
functions of the model describe complex 3-dimensional generalizations of
Donaldson-Witten type invariants. We show that the path integral can be written
as a sum of contributions from stable bundles and a complex 3-dimensional
version of Seiberg-Witten monopoles. We study certain deformations of the
theory, which allow us to consider the situation of reducible connections. We
shortly discuss situations of reduced holonomy. Afterdimensional reduction to a
Kahler 2-fold, the theory reduces to Vafa-Wittentheory. On a Calabi-Yau 3-fold,
the supersymmetry is enhanced to N=(2,2). This model may be used to describe
classical limits of certain compactifications of(matrix) string theory.Comment: 32 pages, LaTe
Crossover in the Slow Decay of Dynamic Correlations in the Lorentz Model
The long-time behavior of transport coefficients in a model for spatially
heterogeneous media in two and three dimensions is investigated by Molecular
Dynamics simulations. The behavior of the velocity auto-correlation function is
rationalized in terms of a competition of the critical relaxation due to the
underlying percolation transition and the hydrodynamic power-law anomalies. In
two dimensions and in the absence of a diffusive mode, another power law
anomaly due to trapping is found with an exponent -3 instead of -2. Further,
the logarithmic divergence of the Burnett coefficient is corroborated in the
dilute limit; at finite density, however, it is dominated by stronger
divergences.Comment: Full-length paragraph added that exemplifies the relevance for dense
fluids and makes a connection to recently observed, novel long-time tails in
a hard-sphere flui
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