42,765 research outputs found
The Neural Representation Benchmark and its Evaluation on Brain and Machine
A key requirement for the development of effective learning representations
is their evaluation and comparison to representations we know to be effective.
In natural sensory domains, the community has viewed the brain as a source of
inspiration and as an implicit benchmark for success. However, it has not been
possible to directly test representational learning algorithms directly against
the representations contained in neural systems. Here, we propose a new
benchmark for visual representations on which we have directly tested the
neural representation in multiple visual cortical areas in macaque (utilizing
data from [Majaj et al., 2012]), and on which any computer vision algorithm
that produces a feature space can be tested. The benchmark measures the
effectiveness of the neural or machine representation by computing the
classification loss on the ordered eigendecomposition of a kernel matrix
[Montavon et al., 2011]. In our analysis we find that the neural representation
in visual area IT is superior to visual area V4. In our analysis of
representational learning algorithms, we find that three-layer models approach
the representational performance of V4 and the algorithm in [Le et al., 2012]
surpasses the performance of V4. Impressively, we find that a recent supervised
algorithm [Krizhevsky et al., 2012] achieves performance comparable to that of
IT for an intermediate level of image variation difficulty, and surpasses IT at
a higher difficulty level. We believe this result represents a major milestone:
it is the first learning algorithm we have found that exceeds our current
estimate of IT representation performance. We hope that this benchmark will
assist the community in matching the representational performance of visual
cortex and will serve as an initial rallying point for further correspondence
between representations derived in brains and machines.Comment: The v1 version contained incorrectly computed kernel analysis curves
and KA-AUC values for V4, IT, and the HT-L3 models. They have been corrected
in this versio
1/t pressure and fermion behaviour of water in two dimensions
A variety of metal vacuum systems display the celebrated 1/t pressure, namely
power-law dependence on time t, with the exponent close to unity, the origin of
which has been a long-standing controversy. Here we propose a chemisorption
model for water adsorbates, based on the argument for fermion behaviour of
water vapour adsorbed on a stainless-steel surface, and obtain analytically the
power-law behaviour of pressure, with an exponent of unity. Further, the model
predicts that the pressure should depend on the temperature T according to
T^(3/2), which is indeed confirmed by our experiment. Our results should help
elucidate the unique characteristics of the adsorbed water.Comment: 11 pages, 4 figure
Single-particle Green's functions of the Calogero-Sutherland model at couplings \lambda = 1/2, 1, and 2
At coupling strengths lambda = 1/2, 1, or 2, the Calogero-Sutherland model
(CSM) is related to Brownian motion in a Wigner-Dyson random matrix ensemble
with orthogonal, unitary, or symplectic symmetry. Using this relation in
conjunction with superanalytic techniques developed in mesoscopic conductor
physics, we derive an exact integral representation for the CSM two-particle
Green's function in the thermodynamic limit. Simple closed expressions for the
single-particle Green's functions are extracted by separation of points. For
the advanced part, where a particle is added to the ground state and later
removed, a sum of two contributions is found: the expected one with just one
particle excitation present, plus an extra term arising from fractionalization
of the single particle into a number of elementary particle and hole
excitations.Comment: 19 REVTeX page
Green Function of the Sutherland Model with SU(2) internal symmetry
We obtain the hole propagator of the Sutherland model with SU(2) internal
symmetry for coupling parameter , which is the simplest nontrivial
case. One created hole with spin down breaks into two quasiholes with spin down
and one quasihole with spin up. While these elementary excitations are
energetically free, the form factor reflects their anyonic character. The
expression for arbitrary integer is conjectured.Comment: 13pages, Revtex, one ps figur
Singular Cucker-Smale Dynamics
The existing state of the art for singular models of flocking is overviewed,
starting from microscopic model of Cucker and Smale with singular communication
weight, through its mesoscopic mean-filed limit, up to the corresponding
macroscopic regime. For the microscopic Cucker-Smale (CS) model, the
collision-avoidance phenomenon is discussed, also in the presence of bonding
forces and the decentralized control. For the kinetic mean-field model, the
existence of global-in-time measure-valued solutions, with a special emphasis
on a weak atomic uniqueness of solutions is sketched. Ultimately, for the
macroscopic singular model, the summary of the existence results for the
Euler-type alignment system is provided, including existence of strong
solutions on one-dimensional torus, and the extension of this result to higher
dimensions upon restriction on the smallness of initial data. Additionally, the
pressureless Navier-Stokes-type system corresponding to particular choice of
alignment kernel is presented, and compared - analytically and numerically - to
the porous medium equation
N_pN_n dependence of empirical formula for the lowest excitation energy of the 2^+ states in even-even nuclei
We examine the effects of the additional term of the type on the recently proposed empirical formula for the lowest excitation
energy of the states in even-even nuclei. This study is motivated by the
fact that this term carries the favorable dependence of the valence nucleon
numbers dictated by the scheme. We show explicitly that there is not
any improvement in reproducing by including the extra
term. However, our study also reveals that the excitation energies
, when calculated by the term alone (with the mass number
dependent term), are quite comparable to those calculated by the original
empirical formula.Comment: 14 pages, 5 figure
Deep Neural Networks Rival the Representation of Primate IT Cortex for Core Visual Object Recognition
The primate visual system achieves remarkable visual object recognition
performance even in brief presentations and under changes to object exemplar,
geometric transformations, and background variation (a.k.a. core visual object
recognition). This remarkable performance is mediated by the representation
formed in inferior temporal (IT) cortex. In parallel, recent advances in
machine learning have led to ever higher performing models of object
recognition using artificial deep neural networks (DNNs). It remains unclear,
however, whether the representational performance of DNNs rivals that of the
brain. To accurately produce such a comparison, a major difficulty has been a
unifying metric that accounts for experimental limitations such as the amount
of noise, the number of neural recording sites, and the number trials, and
computational limitations such as the complexity of the decoding classifier and
the number of classifier training examples. In this work we perform a direct
comparison that corrects for these experimental limitations and computational
considerations. As part of our methodology, we propose an extension of "kernel
analysis" that measures the generalization accuracy as a function of
representational complexity. Our evaluations show that, unlike previous
bio-inspired models, the latest DNNs rival the representational performance of
IT cortex on this visual object recognition task. Furthermore, we show that
models that perform well on measures of representational performance also
perform well on measures of representational similarity to IT and on measures
of predicting individual IT multi-unit responses. Whether these DNNs rely on
computational mechanisms similar to the primate visual system is yet to be
determined, but, unlike all previous bio-inspired models, that possibility
cannot be ruled out merely on representational performance grounds.Comment: 35 pages, 12 figures, extends and expands upon arXiv:1301.353
Making a smart city legible
This chapter discusses Lancaster City Council's AI for Lancaster Programme. The programme has been a collaboration between the City Council, the International Organization for Artificial Intelligence Legibility, PETRAS and Imagination Lancaster. The chapter describes the design concepts implemented in the city in order to communicate the use of artificial intelligence (AI) to citizens, juxtaposing the designs themselves with extracts from interviews and research conducted to evaluate them. Any innovation supporting the implementation of responsible AI systems in urban contexts should be welcomed, and tools like Design Fiction should be employed to smooth the way for this process. In conclusion, the chapter also discusses how the insights derived from the AI for Lancaster Programme can help inform smart city initiatives while supporting the emergence of hybrid sociologies to describe the urban, social, and technological world we live in
A well-posedness theory in measures for some kinetic models of collective motion
We present existence, uniqueness and continuous dependence results for some
kinetic equations motivated by models for the collective behavior of large
groups of individuals. Models of this kind have been recently proposed to study
the behavior of large groups of animals, such as flocks of birds, swarms, or
schools of fish. Our aim is to give a well-posedness theory for general models
which possibly include a variety of effects: an interaction through a
potential, such as a short-range repulsion and long-range attraction; a
velocity-averaging effect where individuals try to adapt their own velocity to
that of other individuals in their surroundings; and self-propulsion effects,
which take into account effects on one individual that are independent of the
others. We develop our theory in a space of measures, using mass transportation
distances. As consequences of our theory we show also the convergence of
particle systems to their corresponding kinetic equations, and the
local-in-time convergence to the hydrodynamic limit for one of the models
Spin-Charge Separation at Finite Temperature in the Supersymmetric t-J Model with Long-Range Interactions
Thermodynamics is derived rigorously for the 1D supersymmetric {\it t-J}
model and its SU() generalization with inverse-square exchange. The system
at low temperature is described in terms of spinons, antispinons, holons and
antiholons obeying fractional statistics. They are all free and make the spin
susceptibility independent of electron density, and the charge susceptibility
independent of magnetization. Thermal spin excitations responsible for the
entropy of the SU() model are ascribed to free para-fermions of order
.Comment: 10 pages, REVTE
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