30 research outputs found
Efimov Trimers in a Harmonic Potential
We study the Efimov effect in a harmonic oscillator in the hyperspherical
formulation, and show how a reduced model allows for a description that is a
generalization of the Efimov effect in free space and leads to results that are
easily interpreted. Efimov physics may be observed by varying the value of the
scattering length, since in the regime where the trimers have a mixed harmonic
oscillator and Efimov character, the inelastic properties of these states are
still manageable. The model also allows for the study of non-universal Efimov
trimers by including the effective range scattering parameter. While we find
that in a certain regime the effective range parameter can take over the role
of the three-body parameter, interestingly, we obtain a numerical relationship
between these two parameters different from what was found in other models.Comment: 15 pages, 9 figure
Arrow Contraction and Expansion in Tropical Diagrams
Arrow contraction applied to a tropical diagram of probability spaces is a
modification of the diagram, replacing one of the morphisms by an isomorphims,
while preserving other parts of the diagram. It is related to the rate regions
introduced by Ahlswede and K\"orner. In a companion article we use arrow
contraction to derive information about the shape of the entropic cone. Arrow
expansion is the inverse operation to the arrow contraction.Comment: 20 pages, V2 updated reference
Tropical Limits of Probability Spaces, Part I: The Intrinsic Kolmogorov-Sinai Distance and the Asymptotic Equipartition Property for Configurations
The entropy of a finite probability space measures the observable
cardinality of large independent products of the probability
space. If two probability spaces and have the same entropy, there is an
almost measure-preserving bijection between large parts of and
. In this way, and are asymptotically equivalent.
It turns out to be challenging to generalize this notion of asymptotic
equivalence to configurations of probability spaces, which are collections of
probability spaces with measure-preserving maps between some of them.
In this article we introduce the intrinsic Kolmogorov-Sinai distance on the
space of configurations of probability spaces. Concentrating on the large-scale
geometry we pass to the asymptotic Kolmogorov-Sinai distance. It induces an
asymptotic equivalence relation on sequences of configurations of probability
spaces. We will call the equivalence classes \emph{tropical probability
spaces}.
In this context we prove an Asymptotic Equipartition Property for
configurations. It states that tropical configurations can always be
approximated by homogeneous configurations. In addition, we show that the
solutions to certain Information-Optimization problems are
Lipschitz-con\-tinuous with respect to the asymptotic Kolmogorov-Sinai
distance. It follows from these two statements that in order to solve an
Information-Optimization problem, it suffices to consider homogeneous
configurations.
Finally, we show that spaces of trajectories of length of certain
stochastic processes, in particular stationary Markov chains, have a tropical
limit.Comment: Comment to version 2: Fixed typos, a calculation mistake in Lemma 5.1
and its consequences in Proposition 5.2 and Theorem 6.
Tropical probability theory and an application to the entropic cone
In a series of articles, we have been developing a theory of tropical
diagrams of probability spaces, expecting it to be useful for information
optimization problems in information theory and artificial intelligence. In
this article, we give a summary of our work so far and apply the theory to
derive a dimension-reduction statement about the shape of the entropic cone.Comment: 18 pages, 1 figure, V2 - updated reference
Conditioning in tropical probability theory
We define a natural operation of conditioning of tropical diagrams of
probability spaces and show that it is Lipschitz continuous with respect to the
asymptotic entropy distance.Comment: 12 pages, V2 - updated reference
Well-posedness of a parabolic moving-boundary problem in the setting of Wasserstein gradient flows
We develop a gradient-flow framework based on the Wasserstein metric for a
parabolic moving-boundary problem that models crystal dissolution and
precipitation. In doing so we derive a new weak formulation for this
moving-boundary problem and we show that this formulation is well-posed. In
addition, we develop a new uniqueness technique based on the framework of
gradient flows with respect to the Wasserstein metric. With this uniqueness
technique, the Wasserstein framework becomes a complete well-posedness setting
for this parabolic moving-boundary problem.Comment: 26 page
Diffusion Variational Autoencoders
A standard Variational Autoencoder, with a Euclidean latent space, is
structurally incapable of capturing topological properties of certain datasets.
To remove topological obstructions, we introduce Diffusion Variational
Autoencoders with arbitrary manifolds as a latent space. A Diffusion
Variational Autoencoder uses transition kernels of Brownian motion on the
manifold. In particular, it uses properties of the Brownian motion to implement
the reparametrization trick and fast approximations to the KL divergence. We
show that the Diffusion Variational Autoencoder is capable of capturing
topological properties of synthetic datasets. Additionally, we train MNIST on
spheres, tori, projective spaces, SO(3), and a torus embedded in R3. Although a
natural dataset like MNIST does not have latent variables with a clear-cut
topological structure, training it on a manifold can still highlight
topological and geometrical properties.Comment: 10 pages, 8 figures Added an appendix with derivation of asymptotic
expansion of KL divergence for heat kernel on arbitrary Riemannian manifolds,
and an appendix with new experiments on binarized MNIST. Added a previously
missing factor in the asymptotic expansion of the heat kernel and corrected a
coefficient in asymptotic expansion KL divergence; further minor edit