arXiv subjects

Joseph Seaward

Publications and source records attributed to Joseph Seaward.

3 recordsLinked to original sources

arXiv2023

Comparison of time profiles for the magnetic transport of cold atoms

We have compared different time profiles for the trajectory of the centre of a quadrupole magnetic trap designed for the transport of cold sodium atoms. Our experimental observations show that a smooth profile characterized by an analytical expression involving the error function minimizes the transport duration while limiting atom losses and heating of the trapped gas. Using numerical calculations of single atom classical trajectories within the trap, we show that this observation can be qualitatively interpreted as a trade-off between two types of losses: finite depth of the confinement and Majorana spin flips.

cond-mat.quant-gas↗

arXiv2022

Growth of the Wang-Casati-Prosen counter in an integrable billiard

This work is motivated by an article by Wang, Casati, and Prosen [Phys. Rev. E vol. 89, 042918 (2014)] devoted to a study of ergodicity in two-dimensional irrational right-triangular billiards. Numerical results presented there suggest that these billiards are generally not ergodic. However, they become ergodic when the billiard angle is equal to $π/2$ times a Liouvillian irrational, a Liouvillian irrational, a class of irrational numbers which are well approximated by rationals. In particular, Wang et al. study a special integer counter that reflects the irrational contribution to the velocity orientation; they conjecture that this counter is localized in the generic case, but grows in the Liouvillian case. We propose a generalization of the Wang-Casati-Prosen counter: this generalization allows to include rational billiards into consideration. We show that in the case of a $45^{\circ} \!\! : \! 45^{\circ} \!\! : \! 90^{\circ}$ billiard, the counter grows indefinitely, consistent with the Liouvillian scenario suggested by Wang et al.

nlin.CD↗

arXiv2019

Ergodicity in Golden Billiards

This comment is an analysis of the results presented by Wang et al. in their their 2014 paper on irrational right triangular billiards. They submit numerical evidence that these billiards are a novel kind of nonergodic, incompatible with KAM theory, at least in the "strongly irrational" case, typified by one of the angles being defined by the golden ratio. We offer an explanation of their results as well as a discussion of ergodicity. We suggest that the system is likely to be ergodic and offer a way to reconcile it with KAM theory if it is not.

math-ph↗