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Entanglement, partial set of measurements, and diagonality of the density matrix in the parton model

by Haowu Duan

Submission summary

As Contributors: Haowu Duan
Arxiv Link: (pdf)
Date submitted: 2021-07-23 02:46
Submitted by: Duan, Haowu
Submitted to: SciPost Physics Proceedings
Proceedings issue: DIS2021
Academic field: Physics
  • High-Energy Physics - Phenomenology
Approach: Phenomenological


To study quantum properties of the hadron wavefunction at small x, we derived the reduced density matrix for soft gluons in the CGC framework. We explicitly showed that the reduced density matrix is not diagonal in the particle number basis. The off-diagonal components are usually ignored in the conventional parton model. We thus defined the density matrix of ignorance by keeping only the part of the reduced density matrix which can be probed in a limited set of experimental measurements. We calculated Von Neumann entropy for both the reduced and ignorance density matrices. The entropy of ignorance is always greater than the entanglement entropy (computed drom the reduced density matrix) of gluons. Finally, we showed that the CGC reduced density matrix for soft gluons can be diagonalized in a thermal basis with Boltzmann weights suggesting thermalization of new quasi-particle states which we dubbed entangolons.

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Submission 2107.10812v1 on 23 July 2021

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