2,281 research outputs found
Motion Invariance in Visual Environments
The puzzle of computer vision might find new challenging solutions when we
realize that most successful methods are working at image level, which is
remarkably more difficult than processing directly visual streams, just as
happens in nature. In this paper, we claim that their processing naturally
leads to formulate the motion invariance principle, which enables the
construction of a new theory of visual learning based on convolutional
features. The theory addresses a number of intriguing questions that arise in
natural vision, and offers a well-posed computational scheme for the discovery
of convolutional filters over the retina. They are driven by the Euler-Lagrange
differential equations derived from the principle of least cognitive action,
that parallels laws of mechanics. Unlike traditional convolutional networks,
which need massive supervision, the proposed theory offers a truly new scenario
in which feature learning takes place by unsupervised processing of video
signals. An experimental report of the theory is presented where we show that
features extracted under motion invariance yield an improvement that can be
assessed by measuring information-based indexes.Comment: arXiv admin note: substantial text overlap with arXiv:1801.0711
On the apparent failure of the topological theory of phase transitions
The topological theory of phase transitions has its strong point in two
theorems proving that, for a wide class of physical systems, phase transitions
necessarily stem from topological changes of some submanifolds of configuration
space. It has been recently argued that the lattice -model
provides a counterexample that falsifies this theory. It is here shown that
this is not the case: the phase transition of this model stems from an
asymptotic () change of topology of the energy level sets, in spite
of the absence of critical points of the potential in correspondence of the
transition energy.Comment: 5 pages, 4 figure
An Overview on the Web of Clinical Data
In the last few years there has been an impressive growth of connections
between medicine and artificial intelligence (AI) that have been characterized
by the specific focus on single problems along with corresponding clinical
data. This paper proposes a new perspective in which the focus is on the
progressive accumulation of a universal repository of clinical hyperlinked data
in the spirit that gave rise to the birth of the Web. The underlining idea is
that this repository, that is referred to as the Web of Clinical Data (WCD),
will dramatically change the AI approach to medicine and its effectiveness. It
is claimed that research and AI-based applications will undergo an evolution
process that will likely reinforce systematically the solutions implemented in
medical apps made available in the WCD. The distinctive architectural feature
of the WCD is that this universal repository will be under control of clinical
units and hospitals, which is claimed to be the natural context for dealing
with the critical issues of clinical data
LQG Online Learning
Optimal control theory and machine learning techniques are combined to
formulate and solve in closed form an optimal control formulation of online
learning from supervised examples with regularization of the updates. The
connections with the classical Linear Quadratic Gaussian (LQG) optimal control
problem, of which the proposed learning paradigm is a non-trivial variation as
it involves random matrices, are investigated. The obtained optimal solutions
are compared with the Kalman-filter estimate of the parameter vector to be
learned. It is shown that the proposed algorithm is less sensitive to outliers
with respect to the Kalman estimate (thanks to the presence of the
regularization term), thus providing smoother estimates with respect to time.
The basic formulation of the proposed online-learning framework refers to a
discrete-time setting with a finite learning horizon and a linear model.
Various extensions are investigated, including the infinite learning horizon
and, via the so-called "kernel trick", the case of nonlinear models
Collective behavior of oscillating electric dipoles
The present work reports about the dynamics of a collection of randomly
distributed, and randomly oriented, oscillators in 3D space, coupled by an
interaction potential falling as , where r stands for the inter-particle
distance. This model schematically represents a collection of identical
biomolecules, coherently vibrating at some common frequency, coupled with a
potential stemming from the electrodynamic interaction between
oscillating dipoles. The oscillating dipole moment of each molecule being a
direct consequence of its coherent (collective) vibration. By changing the
average distance among the molecules, neat and substantial changes in the power
spectrum of the time variation of a collective observable are found. As the
average intermolecular distance can be varied by changing the concentration of
the solvated molecules, and as the collective variable investigated is
proportional to the projection of the total dipole moment of the model
biomolecules on a coordinate plane, we have found a prospective experimental
strategy of spectroscopic kind to check whether the mentioned intermolecular
electrodynamic interactions can be strong enough to be detectable, and thus to
be of possible relevance to biology.Comment: 20 pages, 4 figure
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