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Enhanced diffusion, which describes the accelerated spread of passive scalars due to the interaction between advection and molecular diffusion, has been extensively studied in simplified geometries, such as uniform shear and radial flows.…

Analysis of PDEs · Mathematics 2024-11-04 Rômulo Damasclin Chaves dos Santos , Jorge Henrique de Oliveira Sales

In recent years, hyperspectral imaging, also known as imaging spectroscopy, has been paid an increasing interest in geoscience and remote sensing community. Hyperspectral imagery is characterized by very rich spectral information, which…

Computer Vision and Pattern Recognition · Computer Science 2020-07-20 Danfeng Hong , Jing Yao , Xin Wu , Jocelyn Chanussot , Xiao Xiang Zhu

We show that intensity of a wave created by a source embedded inside a three-dimensional disordered medium exhibits a non-universal space-time correlation which depends explicitly on the short-distance properties of disorder, source size,…

Disordered Systems and Neural Networks · Physics 2009-10-31 S. E. Skipetrov , R. Maynard

We consider an evaporating Schwarzschild black hole in a framework in which the spectral dimension of spacetime varies continuously from four at large distances to a number smaller than three at small distances, as suggested by various…

General Relativity and Quantum Cosmology · Physics 2013-06-18 S. Carlip , D. Grumiller

Our aim is to study invariant hypersurfaces immersed in the Euclidean space $\mathbb{R}^{n+1}$, whose mean curvature is given as a linear function in the unit sphere $\mathbb{S}^n$ depending on its Gauss map. These hypersurfaces are closely…

Differential Geometry · Mathematics 2019-08-21 Antonio Bueno , Irene Ortiz

Simplicial complexes are increasingly used to study complex system structure and dynamics including diffusion, synchronization and epidemic spreading. The spectral dimension of the graph Laplacian is known to determine the diffusion…

Disordered Systems and Neural Networks · Physics 2020-02-19 Ginestra Bianconi , Sergey N. Dorogovtsev

In this paper, we associate a growth graph and a length operator to a quotient space of a semisimple compact Lie group. Under certain assumptions, we show that the spectral dimension of a homogeneous space is greater than or equal to…

Operator Algebras · Mathematics 2018-03-28 Bipul Saurabh

We consider globally hyperbolic flat spacetimes in 2+1 and 3+1 dimensions, in which a uniform light signal is emitted on the $r$-level surface of the cosmological time for $r\to 0$. We show that the frequency of this signal, as perceived by…

General Relativity and Quantum Cosmology · Physics 2018-03-28 Francesco Bonsante , Catherine Meusburger , Jean-Marc Schlenker

This paper investigates score-based diffusion models when the underlying target distribution is concentrated on or near low-dimensional manifolds within the higher-dimensional space in which they formally reside, a common characteristic of…

Machine Learning · Computer Science 2025-01-03 Gen Li , Yuling Yan

Planck-scale dynamical dimensional reduction is attracting more and more interest in the quantum-gravity literature since it seems to be a model independent effect. However different studies base their results on different concepts of…

General Relativity and Quantum Cosmology · Physics 2016-07-29 Michele Ronco

Fractons and other subdimensional particles are an exotic class of emergent quasi-particle excitations with severely restricted mobility. A wide class of models featuring these quasi-particles have a natural description in the language of…

Strongly Correlated Electrons · Physics 2019-08-21 Kevin Slagle , Abhinav Prem , Michael Pretko

The unification of general relativity with quantum theory will also require a coming together of the two quite different mathematical languages of general relativity and quantum theory, i.e., of differential geometry and functional analysis…

Mathematical Physics · Physics 2016-04-27 Mikhail Panine , Achim Kempf

We propose a new method of the analytical computation of the spectral dimension which is based on the equivalence of the random walk and the q-state Potts model with non-zero magnetic field in the limit $q\to 0$. Calculating the critical…

High Energy Physics - Theory · Physics 2009-09-10 Igor Goncharenko

The emergence and vanishing of superdiffusion in quasi-two-dimensional Yukawa systems are investigated by molecular dynamics simulations. Using both the asymptotic behaviour of the mean-squared displacement of the particles and the…

Plasma Physics · Physics 2009-11-13 T. Ott , Z. Donko , P. Hartmann , M. Bonitz

Several lines of evidence hint that quantum gravity at very small distances may be effectively two-dimensional. I summarize the evidence for such ``spontaneous dimensional reduction,'' and suggest an additional argument coming from the…

General Relativity and Quantum Cosmology · Physics 2010-09-07 Steven Carlip

A new approach to quantum gravity is described which joins the loop representation formulation of the canonical theory to the causal set formulation of the path integral. The theory assigns quantum amplitudes to special classes of causal…

General Relativity and Quantum Cosmology · Physics 2010-04-06 Fotini Markopoulou , Lee Smolin

Diffusion models achieve state-of-the-art performance in various generation tasks. However, their theoretical foundations fall far behind. This paper studies score approximation, estimation, and distribution recovery of diffusion models,…

Machine Learning · Computer Science 2023-02-15 Minshuo Chen , Kaixuan Huang , Tuo Zhao , Mengdi Wang

We extend the diffusion-map formalism to data sets that are induced by asymmetric kernels. Analytical convergence results of the resulting expansion are proved, and an algorithm is proposed to perform the dimensional reduction. In this work…

Machine Learning · Computer Science 2024-01-24 Alvaro Almeida Gomez , Antonio Silva Neto , Jorge zubelli

Treatment effects in a wide range of economic, environmental, and epidemiological applications often vary across space, and understanding the heterogeneity of causal effects across space and outcome quantiles is a critical challenge in…

Methodology · Statistics 2025-09-03 Yan Gong , Reetam Majumder , Brian J. Reich , Raphaël Huser

Unmeasured spatial confounding complicates exposure effect estimation in environmental health studies. This problem is exacerbated in studies with multiple health outcomes and environmental exposure variables, as the source and magnitude of…

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