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Modelling and analyzing strong-field effects in quantum plasma
Umeå University, Faculty of Science and Technology, Department of Physics.ORCID iD: 0000-0002-1555-7616
2023 (English)Doctoral thesis, comprehensive summary (Other academic)Alternative title
Modellering och analys av effekter från starka fält i kvantkinetiska plasmor (Swedish)
Abstract [en]

Under the extreme conditions that can be found around dense stars and in the accretion discs of black holes, several strong-field quantum phenomena dominate the dynamics of the plasma. This includes the creation of matter and anti-matter from the vacuum (Schwinger mechanism), radiation reaction and Landau quantization. Some of these strong field phenomena were presented theoretically a century ago but have never been verified in experiments due to the difficulty of creating the required extreme conditions in the lab. However, with the development of laser facilities in the past decades, it will be possible to observe several extreme physical phenomena in the near future. To conduct experiments on these extreme phenomena, theoretical simulations need to be constructed as a guide for optimizing experiments.

This thesis is concerned with developing and analyzing strong field phenomena in kinetic plasma models. The focus is to extend current kinetic models to include several physical phenomena that are relevant to future experiments on laser-plasma interaction. In particular, a kinetic theory based on the Wigner transformation of the Dirac equation has been analyzed in different regimes. This kinetic model is used to study the plasma dynamics at the Schwinger limit, where collective plasma effects and several quantum processes are studied.

Place, publisher, year, edition, pages
Umeå: Umeå University , 2023. , p. 69
Keywords [en]
Plasma physics, Strong-field physics, Kinetic theory, Quantum plasma
National Category
Fusion, Plasma and Space Physics
Research subject
Physics
Identifiers
URN: urn:nbn:se:umu:diva-208019ISBN: 978-91-8070-067-2 (print)ISBN: 978-91-8070-068-9 (electronic)OAI: oai:DiVA.org:umu-208019DiVA, id: diva2:1755417
Public defence
2023-06-01, NAT.D.450, Förvaltningshuset Hus D, 901 87, Umeå, 13:00 (English)
Opponent
Supervisors
Funder
Swedish Research Council, 2016-03806Available from: 2023-05-11 Created: 2023-05-08 Last updated: 2023-05-10Bibliographically approved
List of papers
1. Relativistic kinetic theory for spin-1/2 particles: Conservation laws, thermodynamics, and linear waves
Open this publication in new window or tab >>Relativistic kinetic theory for spin-1/2 particles: Conservation laws, thermodynamics, and linear waves
2019 (English)In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics: Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, ISSN 1063-651X, E-ISSN 1095-3787, Vol. 100, no 2, article id 023201Article in journal (Refereed) Published
Abstract [en]

We study a recently derived fully relativistic kinetic model for spin-1/2 particles. First, the full set of conservation laws for energy, momentum, and angular momentum are given together with an expression for the (nonsymmetric) stress-energy tensor. Next, the thermodynamic equilibrium distribution is given in different limiting cases. Furthermore, we address the analytical complexity that arises when the spin and momentum eigenfunctions are coupled in linear theory by calculating the linear dispersion relation for such a case. Finally, we discuss the model and give some context by comparing with potentially relevant phenomena that are not included, such as radiation reaction and vacuum polarization.

National Category
Fusion, Plasma and Space Physics
Research subject
Theoretical Physics
Identifiers
urn:nbn:se:umu:diva-162463 (URN)10.1103/PhysRevE.100.023201 (DOI)000479192700004 ()31574677 (PubMedID)2-s2.0-85070558937 (Scopus ID)
Available from: 2019-08-20 Created: 2019-08-20 Last updated: 2023-05-08Bibliographically approved
2. Kinetic theory for spin-1/2 particles in ultrastrong magnetic fields
Open this publication in new window or tab >>Kinetic theory for spin-1/2 particles in ultrastrong magnetic fields
2020 (English)In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics, ISSN 1539-3755, E-ISSN 1550-2376, Vol. 102, no 4, article id 043203Article in journal (Refereed) Published
Abstract [en]

When the Zecman energy approaches the characteristic kinetic energy of electrons, Landau quantization becomes important. In the vicinity of magnetars, the Zeeman energy can even be relativistic. We start from the Dirac equation and derive a kinetic equation for electrons, focusing on the phenomenon of Landau quantization in such ultrastrong but constant magnetic fields, neglecting short-scale quantum phenomena. It turns out that the usual relativistic gamma factor of the Vlasov equation is replaced by an energy operator, depending on the spin state, and also containing momentum derivatives. Furthermore, we show that the energy eigenstates in a magnetic field can be computed as eigenfunctions of this operator. The dispersion relation for electrostatic waves in a plasma is computed, and the significance of our results is discussed.

Place, publisher, year, edition, pages
American Physical Society, 2020
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:umu:diva-176304 (URN)10.1103/PhysRevE.102.043203 (DOI)000577084700005 ()33212646 (PubMedID)2-s2.0-85093365286 (Scopus ID)
Available from: 2020-11-04 Created: 2020-11-04 Last updated: 2023-05-08Bibliographically approved
3. Plasma dynamics and vacuum pair creation using the Dirac-Heisenberg-Wigner formalism
Open this publication in new window or tab >>Plasma dynamics and vacuum pair creation using the Dirac-Heisenberg-Wigner formalism
2021 (English)In: Physical review. E, ISSN 2470-0045, E-ISSN 2470-0053, Vol. 104, no 1, article id 015207Article in journal (Refereed) Published
Abstract [en]

We derive a system of coupled partial differential equations for the equal-time Wigner function in an arbitrary strong electromagnetic field using the Dirac-Heisenberg-Wigner formalism. In the electrostatic limit, we present a system of four coupled partial differential equations, which are completed by Ampères law. This electrostatic system is further studied for two different cases. In the first case, we consider linearized wave propagation in a plasma accounting for the nonzero vacuum expectation values. We then derive the dispersion relation and compare it with well-known limiting cases. In the second case, we consider Schwinger pair production using the local density approximation to allow for analytical treatment. The dependence of the pair production rate on the perpendicular momentum is investigated and it turns out that the spread of the produced pairs along with perpendicular momentum depends on the strength of the applied electric field.

Place, publisher, year, edition, pages
American Physical Society, 2021
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:umu:diva-186411 (URN)10.1103/PhysRevE.104.015207 (DOI)000674387800007 ()2-s2.0-85110430469 (Scopus ID)
Available from: 2021-07-29 Created: 2021-07-29 Last updated: 2023-05-08Bibliographically approved
4. Linear pair-creation damping of high-frequency plasma oscillation
Open this publication in new window or tab >>Linear pair-creation damping of high-frequency plasma oscillation
2022 (English)In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 29, no 4, article id 042106Article in journal (Refereed) Published
Abstract [en]

We have studied the linear dispersion relation for Langmuir waves in plasmas of very high density, based on the Dirac-Heisenberg-Wigner formalism. The vacuum contribution to the physical observables leads to ultraviolet divergences, which are removed by a charge renormalization. The remaining vacuum contribution is small and is in agreement with previously derived expressions for the time-dependent vacuum polarization. The main new feature of the theory is a damping mechanism similar to Landau damping, but where the plasmon energy gives rise to creation of electron-positron pairs. The dependence of the damping rate (pair-creation rate) on the wavenumber, temperature, and density is analyzed. Finally, the analytical results of linearized theory are compared with numerical solutions.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2022
National Category
Fusion, Plasma and Space Physics Condensed Matter Physics
Identifiers
urn:nbn:se:umu:diva-194333 (URN)10.1063/5.0087085 (DOI)000788793900002 ()2-s2.0-85128402117 (Scopus ID)
Available from: 2022-05-04 Created: 2022-05-04 Last updated: 2023-05-08Bibliographically approved
5. Radiation reaction effects in relativistic plasmas: the electrostatic limit
Open this publication in new window or tab >>Radiation reaction effects in relativistic plasmas: the electrostatic limit
2023 (English)In: Physical review. E, ISSN 2470-0045, E-ISSN 2470-0053, Vol. 107, no 3, article id 035203Article in journal (Refereed) Published
Abstract [en]

We study the evolution of electrostatic plasma waves, using the relativistic Vlasov equation extended by the Landau-Lifshitz radiation reaction, accounting for the back-reaction due to the emission of single particle Larmor radiation. In particular, the Langmuir wave damping is calculated as a function of wave number, initial temperature, and initial electric field amplitude. Moreover, the background distribution function loses energy in the process, and we calculate the cooling rate as a function of initial temperature and initial wave amplitude. Finally, we investigate how the relative magnitude of wave damping and background cooling varies with the initial parameters. In particular, it is found that the relative contribution to the energy loss associated with background cooling decreases slowly with the initial wave amplitude.

Place, publisher, year, edition, pages
American Physical Society, 2023
National Category
Fusion, Plasma and Space Physics
Research subject
Physics
Identifiers
urn:nbn:se:umu:diva-205904 (URN)10.1103/physreve.107.035203 (DOI)000954805400003 ()37072971 (PubMedID)2-s2.0-85151338611 (Scopus ID)
Available from: 2023-03-22 Created: 2023-03-22 Last updated: 2023-05-08Bibliographically approved
6. Plasma dynamics at the Schwinger limit and beyond
Open this publication in new window or tab >>Plasma dynamics at the Schwinger limit and beyond
Show others...
2023 (English)In: Physical review. E, ISSN 2470-0045, E-ISSN 2470-0053, Vol. 107, no 3, article id 035204Article in journal (Refereed) Published
Abstract [en]

Strong field physics close to or above the Schwinger limit are typically studied with vacuum as initial condition or by considering test particle dynamics. However, with a plasma present initially, quantum relativistic mechanisms such as Schwinger pair creation are complemented by classical plasma nonlinearities. In this work we use the Dirac-Heisenberg-Wigner formalism to study the interplay between classical and quantum mechanical mechanisms in the regime of ultrastrong electric fields. In particular, the effects of initial density and temperature on the plasma oscillation dynamics are determined. Finally, comparisons with competing mechanisms such as radiation reaction and Breit-Wheeler pair production are made.

Place, publisher, year, edition, pages
American Physical Society, 2023
National Category
Fusion, Plasma and Space Physics
Research subject
Physics
Identifiers
urn:nbn:se:umu:diva-205903 (URN)10.1103/physreve.107.035204 (DOI)000957776100003 ()37073070 (PubMedID)2-s2.0-85151329265 (Scopus ID)
Funder
Swedish Research Council, 2020-04327
Available from: 2023-03-22 Created: 2023-03-22 Last updated: 2023-05-08Bibliographically approved
7. Applicability of the Klein-Gordon equation for pair production in vacuum and plasma
Open this publication in new window or tab >>Applicability of the Klein-Gordon equation for pair production in vacuum and plasma
2023 (English)In: Physical review. E, ISSN 2470-0045, E-ISSN 2470-0053, Vol. 108, no 5, article id 055205Article in journal (Refereed) Published
Abstract [en]

In this paper, a phase-space description of electron-positron pair-creation will be applied, based on a Wigner transformation of the Klein-Gordon equation. The resulting theory is similar in many respects to the equations from the Dirac-Heisenberg-Wigner formalism. However, in the former case, all physics related to particle spin is neglected. In the present paper we compare the pair-production rate in vacuum and plasmas, with and without spin effects, in order to evaluate the accuracy and applicability of the spinless approximation. It is found that for modest frequencies of the electromagnetic field, the pair production rate of the Klein-Gordon theory is a good approximation to the Dirac theory, provided the matter density is small enough for Pauli blocking to be neglected, and a factor of two related to the difference in the vacuum energy density is compensated for.  

Place, publisher, year, edition, pages
American Physical Society, 2023
National Category
Fusion, Plasma and Space Physics
Research subject
Physics
Identifiers
urn:nbn:se:umu:diva-208015 (URN)10.1103/PhysRevE.108.055205 (DOI)2-s2.0-85177615325 (Scopus ID)
Funder
Knut and Alice Wallenberg Foundation
Note

Originally included in thesis in manuscript form. 

Available from: 2023-05-08 Created: 2023-05-08 Last updated: 2023-11-30Bibliographically approved

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Al-Naseri, Haidar

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