arXiv subjects

Julius Lehmann

Publications and source records attributed to Julius Lehmann.

5 recordsLinked to original sources

arXiv2024

A Note on and Generalization of "Exploring Modified Kaniadakis Entropy: MOND Theory and the Bekenstein Bound Conjecture"

In a recent paper by Ambr\'osio et al. [arXiv:2405.14799], it was shown that the gravitational force law of the Modified Newtonian Dynamics (MOND) phenomenology can be derived within the framework of entropic gravity and the holographic principle by assuming an entropy function other than the conventional Boltzmann-Gibbs entropy. In particular, they derived the standard interpolation function of MOND together with an analytical expression for the acceleration constant $a_0$ by utilizing Kaniadakis' modified entropy. In this short note, using the same methodology, we generalize this result and show that MONDian behavior is a rather general consequence of combining entropic gravity with non-Boltzmann-Gibbs entropies, which depends on only a few conditions imposed on the generalized entropy function.

gr-qc↗

arXiv2024

Operational Methods Applied to the Spherical Mean and X-Ray Transform

We employ the framework of operational calculus to derive the operators associated with the spherical mean and a class of related averaging means of a function in $n$-dimensional space. Beginning with the classical definition of the spherical mean, we obtain a compact operator representation in terms of confluent hypergeometric functions of the Laplacian. This operator-based formulation provides a straightforward approach to the analysis of spherical means, allowing us to determine their power series expansions, construct series solutions to the corresponding inversion problems, derive the partial differential equations they satisfy, and give meaning to iterated and fractional spherical means. Finally, we apply the spherical mean operator to derive the inversion formula for the X-ray transform in an operational manner.

math.CA↗

arXiv2024

Analogs to Ramanujan's Master Theorem and Operational Methods

In this paper, we utilize operational methods to obtain closed-form solutions for certain classes of integrals in the spirit of Ramanujan's Master Theorem and provide several analogs to it. Although the use of operational calculus makes the proofs formal in nature, they can still yield interesting and correct results and may stimulate further rigorous investigations in the future.

math.CA↗

arXiv2022

Fragmentation-induced localization and boundary charges in dimensions two and above

We study higher dimensional models with symmetric correlated hoppings, which generalize a one-dimensional model introduced in the context of dipole-conserving dynamics. We prove rigorously that whenever the local configuration space takes its smallest non-trivial value, these models exhibit localized behavior due to fragmentation, in any dimension. For the same class of models, we then construct a hierarchy of conserved quantities that are power-law localized at the boundary of the system with increasing powers. Combining these with Mazur's bound, we prove that boundary correlations are infinitely long lived, even when the bulk is not localized. We use our results to construct quantum Hamiltonians that exhibit the analogues of strong zero modes in two and higher dimensions.

cond-mat.stat-mech↗

arXiv2021

Dynamics in Systems with Modulated Symmetries

We extend the notions of multipole and subsystem symmetries to more general {\it spatially modulated} symmetries. We uncover two instances with exponential and (quasi)-periodic modulations, and provide simple microscopic models in one, two and three dimensions. Seeking to understand their effect in the long-time dynamics, we numerically study a stochastic cellular automaton evolution that obeys such symmetries. We prove that in one dimension, the periodically modulated symmetries lead to a diffusive scaling of correlations modulated by a finite microscopic momentum. In higher dimensions, these symmetries take the form of lines and surfaces of conserved momenta. These give rise to exotic forms of sub-diffusive behavior with a rich spatial structure influenced by lattice-scale features. Exponential modulation, on the other hand, can lead to correlations that are infinitely long-lived at the boundary, while decaying exponentially in the bulk.

cond-mat.stat-mech↗