Philip J. Siemens

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Philip John Siemens
Born(1943-11-13)November 13, 1943
Elgin, Illinois
DiedJune 23, 2023(2023-06-23) (aged 79)
Eugene, Oregon
Alma mater
Awards
Scientific career
FieldsTheoretical physics
Institutions
ThesisNew Statistical Theory of the Nuclear Surface
Hans Bethe

Philip John Siemens (November 13, 1943 – June 29, 2023) was a theoretical physicist who trained at MIT and Cornell, and who taught and conducted research at the Niels Bohr Institute, Lawrence Berkeley National Laboratory, Texas A&M University, Oak Ridge National Laboratory, and Oregon State University.

He was a fellow of both the American Physical Society and the American Association for the Advancement of Science.

Early life and education

Philip John Siemens, the eldest of Dorothea and Jacob J. Siemens' five children, was born November 13, 1943, in Elgin, Illinois. He attended Wheaton Academy and earned a National Merit scholarship[1] to study at the Massachusetts Institute of Technology, where he majored in physics.[2]

As a Cornell University graduate student, Siemens specialized in theoretical nuclear physics. He co-authored two publications prior to his dissertation: in 1967, "Shape of Heavy Nuclei",[3] and in 1969, "Nuclear-matter reaction matrix".[4]

His 1970 dissertation, New Statistical Theory of the Nuclear Surface, was advised by Nobel laureate Hans Bethe.[5]

Career

In the decade following completion of his doctorate, Siemens worked at the University of Copenhagen's Niels Bohr Institute. In 1975, he co-authored, "Linear response theory for dissipation in heavy-ion collisions" with Helmut Hofmann.[6]

While on leave from the Niels Bohr Institute in 1979, Siemens also co-authored three papers with Joseph I. Kapusta at Lawrence Berkeley National Laboratory: "Evidence for a Soft Nuclear-Matter Equation of State",[7] "Evidence for a Blast Wave from Compressed Nuclear Matter",[8] and "Evidence for a Soft Nuclear-Matter Equation of State".[7]

In the 1980s, Siemens was recruited to establish Texas A&M University's Physics Department and Cyclotron Institute faculty.[2] While there between 1983 and 1985, he authored and co-authored four studies: "Liquid–gas phase transition in nuclear matter",[9] "Nuclear fragmentation",[10] "Testing QCD Plasma Formation by Pion Correlations in Relativistic Nuclear Collisions",[11] and "Testing of QCD Plasma Formation by Dilepton Spectra in Relativistic Nuclear Collisions".[12]

Siemens was welcomed as a "distinguished scientist" at Oak Ridge National Laboratory in 1986.[13] The Knoxville News Sentinel reported Siemens was "recognized as one of the theoretical leaders in the physics of nuclei heated to very high temperatures stellar explosions and in high-energy collisions."[14] The Tomahawk in Mountain City called Siemens "a recognized leader in the theoretical interpretation of nuclear structures and collisions of energetic heavy nuclei produced by large particle accelerators".[15]

While at the University of Tennessee in the late 1980s, Siemens published two studies: "Bubbles and drops in superheated and supercooled nuclear matter,[16] and "Color correlations in QCD plasma".[17] He also co-authored the 1989 publication of "Relativistic transport theory of fluctuating fields for hadrons".[18]

Near the end of his career, wanting to be closer to his family in Oregon, he "convinced Oregon State University in Corvallis to hire him and increase its commitment to theoretical physics".[2] In 1990 he co-authored "Truncation of Schwinger-Dyson equations and the 1/𝑁 expansion in the O⁡(𝑁) model",[19] followed by two papers in 1991: "Vaporization of color-singlet pairs from a quark-gluon plasma",[20] and "Model solutions of regularized relativistic transport equations".[21] These papers were followed by three more: "Kaon pictures of QCD plasma droplets"[22] in 1992; "Crossing-symmetric two-particle reduction of four-point vertex"[23] in 1993; and "Self-consistent couplings of pions and Δ-hole states in nuclear matter"[24] in 1994.

Philip Siemens' retirement was acknowledged in the department newsletter in January 2007.[25] He died of leukemia in Eugene in January 2023.[2]

Books published

Siemens, Philip; Jensen, Asksel S. (1987). Elements Of Nuclei: Many-body Physics With The Strong Interaction. CRC Press: Taylor and Francis Group. doi:10.1201/9780429493904. ISBN 9780429493904.{{cite book}}: CS1 maint: publisher location (link)

Honors

  • 1984 Division of Nuclear Physics, Fellow of the American Physical Society, cited For important contributions to the theory of many-body systems as applied to nuclear physics.[26]

References

  1. "3 at Wheaton Academy Get Merit Honors". Chicago Tribune. 1961-03-16. p. 40. Retrieved 2026-06-22.
  2. "Philip John Siemens Obituary - Eugene Register-Guard". registerguard.com. 2023-11-09. Retrieved 2026-05-30.
  3. Siemens, Philip J.; Bethe, H. A. (1967-04-24). "Shape of Heavy Nuclei". Physical Review Letters. 18 (17): 704–706. doi:10.1103/PhysRevLett.18.704. ISSN 0031-9007. Archived from the original on 2024-08-12.
  4. Siemens, Philip J.; Bethe, H. A. (1967-04-24). "Shape of Heavy Nuclei". Physical Review Letters. 18 (17): 704–706. doi:10.1103/PhysRevLett.18.704. ISSN 0031-9007.
  5. Siemens, Philip J. (January 1970). "New Statistical Theory of the Nuclear Surface. I". Phys.Rev.C 1: 98–111. doi:10.1103/PhysRevC.1.98. Retrieved 2026-06-20.
  6. Hofmann, Helmut; Siemens, Philip J. (22 April 1975). "Linear response theory for dissipation in heavy-ion collisions". Nuclear Physics A. 257 (1): 165–188. doi:10.1016/0375-9474(76)90481-4.
  7. Siemens, Philip J.; Kapusta, Joseph I. (1979-11-12). "Evidence for a Soft Nuclear-Matter Equation of State". Physical Review Letters. 43 (20): 1486–1489. doi:10.1103/PhysRevLett.43.1486. ISSN 0031-9007. Archived from the original on 2026-03-10.
  8. Siemens, Philip J.; Rasmussen, John O. (1979-04-02). "Evidence for a Blast Wave from Compressed Nuclear Matter". Physical Review Letters. 42 (14): 880–883. doi:10.1103/PhysRevLett.42.880. ISSN 0031-9007. Archived from the original on 2025-11-21.
  9. Siemens, Philip J. (September 1983). "Liquid–gas phase transition in nuclear matter". Nature. 305 (5933): 410–412. doi:10.1038/305410a0. ISSN 1476-4687.
  10. Bertsch, G.; J. Siemens, Philip (June 1983). "Nuclear fragmentation". Physics Letters B. 126 (1–2): 9–12. doi:10.1016/0370-2693(83)90004-7. ISSN 0370-2693. Archived from the original on 2023-12-22.
  11. Lopez, Jorge A.; Parikh, Jitendra C.; Siemens, Philip J. (1984-09-24). "Testing QCD Plasma Formation by Pion Correlations in Relativistic Nuclear Collisions". Physical Review Letters. 53 (13): 1216–1218. doi:10.1103/PhysRevLett.53.1216. ISSN 0031-9007.
  12. Siemens, Philip J.; Chin, Siu A. (1985-09-16). "Testing of QCD Plasma Formation by Dilepton Spectra in Relativistic Nuclear Collisions". Physical Review Letters. 55 (12): 1266–1268. doi:10.1103/PhysRevLett.55.1266. ISSN 0031-9007.
  13. "A warm welcome". The Knoxville News-Sentinel. 1986-02-15. p. 6. Retrieved 2026-06-22.
  14. "3 scientists appointed to UT, ORNL". The Knoxville News-Sentinel. 1986-02-14. p. 26. Retrieved 2026-06-22.
  15. "Distinguished scientists join university staff". The Tomahawk. 1986-05-28. p. 11. Retrieved 2026-06-22.
  16. Li, Bao-An; Pratt, Scott; Siemens, Philip J. (1988-04-01). "Bubbles and drops in superheated and supercooled nuclear matter". Physical Review C. 37 (4): 1473–1477. doi:10.1103/PhysRevC.37.1473. ISSN 0556-2813.
  17. Parikh, Jitendra C.; Siemens, Philip J. (1988-06-01). "Color correlations in QCD plasma". Physical Review D. 37 (11): 3246–3251. doi:10.1103/PhysRevD.37.3246. ISSN 0556-2821.
  18. Siemens, Philip J.; Soyeur, Madeleine; White, Gary D.; Lantto, Lauri J.; Davies, K. Thomas R. (1989-12-01). "Relativistic transport theory of fluctuating fields for hadrons". Physical Review C. 40 (6): 2641–2671. doi:10.1103/PhysRevC.40.2641. ISSN 0556-2813. Archived from the original on 2024-04-19.
  19. Korpa, C. L.; Parikh, Jitendra C.; Siemens, Philip J. (1990-02-15). "Truncation of Schwinger-Dyson equations and the 1 N expansion in the O ( N ) model". Physical Review D. 41 (4): 1276–1279. doi:10.1103/PhysRevD.41.1276. ISSN 0556-2821.
  20. Vischer, Axel P.; Parikh, Jitendra C.; Siemens, Philip J. (1991-01-01). "Vaporization of color-singlet pairs from a quark-gluon plasma". Physical Review D. 43 (1): 271–273. doi:10.1103/PhysRevD.43.271. ISSN 0556-2821.
  21. Milana, Joseph P.; Siemens, Philip J. (1991-05-01). "Model solutions of regularized relativistic transport equations". Physical Review C. 43 (5): 2377–2392. doi:10.1103/PhysRevC.43.2377. ISSN 0556-2813. Archived from the original on 2022-03-01.
  22. Pratt, Scott; Siemens, Philip J.; Vischer, Axel P. (1992-02-24). "Kaon pictures of QCD plasma droplets". Physical Review Letters. 68 (8): 1109–1111. doi:10.1103/PhysRevLett.68.1109. ISSN 0031-9007.
  23. Korpa, C. L.; Siemens, Philip J. (1993-06-01). "Crossing-symmetric two-particle reduction of four-point vertex". Physical Review C. 47 (6): 2481–2484. doi:10.1103/PhysRevC.47.2481. ISSN 0556-2813.
  24. Xia, Linhua; Siemens, Philip J.; Soyeur, Madeleine (October 1994). "Self-consistent couplings of pions and Δ-hole states in nuclear matter". Nuclear Physics A. 578 (3–4): 493–510. doi:10.1016/0375-9474(94)90757-9.
  25. Jansen, Henri (January 2007). "Letter From the Chair" (PDF). OSU Physics Newsletter. Retrieved 24 June 2007.
  26. "APS Fellows Archive". 1984. Retrieved May 29, 2026.
  27. "OSU scientists honored". Corvallis Gazette-Times. 1991-03-13. p. 2. Retrieved 2026-06-22.