{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,12]],"date-time":"2025-10-12T03:00:58Z","timestamp":1760238058393,"version":"build-2065373602"},"reference-count":35,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2022,8,5]],"date-time":"2022-08-05T00:00:00Z","timestamp":1659657600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Entropy"],"abstract":"<jats:p>In view of a result recently published in the context of the deformation theory of linear Hamiltonian systems, we reconsider the eigenvalue problem associated with the angular equation arising after the separation of the Dirac equation in the Kerr metric, and we show how a quasilinear first order PDE for the angular eigenvalues can be derived efficiently. We also prove that it is not possible to obtain an ordinary differential equation for the eigenvalues when the role of the independent variable is played by the particle energy or the black hole mass. Finally, we construct new perturbative expansions for the eigenvalues in the Kerr case and obtain an asymptotic formula for the eigenvalues in the case of a Kerr naked singularity.<\/jats:p>","DOI":"10.3390\/e24081083","type":"journal-article","created":{"date-parts":[[2022,8,7]],"date-time":"2022-08-07T22:51:46Z","timestamp":1659912706000},"page":"1083","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["On the Eigenvalues of the Fermionic Angular Eigenfunctions in the Kerr Metric"],"prefix":"10.3390","volume":"24","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-7619-4900","authenticated-orcid":false,"given":"Davide","family":"Batic","sequence":"first","affiliation":[{"name":"Department of Mathematics, Khalifa University of Science and Technology, Main Campus, Abu Dhabi P.O. Box 127788, United Arab Emirates"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Suzan Hamad Abdul","family":"Karim","sequence":"additional","affiliation":[{"name":"Department of Mathematics, Khalifa University of Science and Technology, Main Campus, Abu Dhabi P.O. Box 127788, United Arab Emirates"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Marek","family":"Nowakowski","sequence":"additional","affiliation":[{"name":"Departamento de Fisica, Universidad de los Andes, Cra.1E No.18A-10, Bogota 111711, Colombia"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2022,8,5]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"571","DOI":"10.1098\/rspa.1976.0090","article-title":"The solution of Dirac\u2019s equation in Kerr geometry","volume":"349","author":"Chandrasekhar","year":"1976","journal-title":"Proc. R. Soc. Lond. 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